vis: reject invalid register name when recording a macro

[vis.git] / vis-lua.c

/***
 * Lua Extension API for the [Vis Editor](https://github.com/martanne/vis).
 *
 * *WARNING:* there is no stability guarantee at this time, the API might
 * change without notice!
 *
 * This document might be out of date, run `make luadoc` to regenerate it.
 *
 * @module vis
 * @author Marc André Tanner
 * @license ISC
 * @release RELEASE
 */
#include <stddef.h>
#include <stdarg.h>
#include <stdio.h>
#include <string.h>
#include <limits.h>
#include <unistd.h>
#include <libgen.h>
#include <sys/types.h>
#include <pwd.h>

#include "vis-lua.h"
#include "vis-core.h"
#include "text-motions.h"
#include "util.h"

#ifndef VIS_PATH
#define VIS_PATH "/usr/local/share/vis"
#endif

#define VIS_LUA_TYPE_VIS "vis"
#define VIS_LUA_TYPE_FILE "file"
#define VIS_LUA_TYPE_TEXT "text"
#define VIS_LUA_TYPE_MARK "mark"
#define VIS_LUA_TYPE_MARKS "marks"
#define VIS_LUA_TYPE_WINDOW "window"
#define VIS_LUA_TYPE_CURSOR "cursor"
#define VIS_LUA_TYPE_CURSORS "cursors"
#define VIS_LUA_TYPE_UI "ui"
#define VIS_LUA_TYPE_REGISTERS "registers"
#define VIS_LUA_TYPE_KEYACTION "keyaction"

#ifndef DEBUG_LUA
#define DEBUG_LUA 0
#endif

#if DEBUG_LUA
#define debug(...) do { printf(__VA_ARGS__); fflush(stdout); } while (0)
#else
#define debug(...) do { } while (0)
#endif

static void window_status_update(Vis *vis, Win *win) {
        char left_parts[4][255] = { "", "", "", "" };
        char right_parts[4][32] = { "", "", "", "" };
        char left[sizeof(left_parts)+LENGTH(left_parts)*8];
        char right[sizeof(right_parts)+LENGTH(right_parts)*8];
        char status[sizeof(left)+sizeof(right)+1];
        size_t left_count = 0;
        size_t right_count = 0;

        View *view = win->view;
        File *file = win->file;
        Text *txt = file->text;
        int width = vis_window_width_get(win);
        enum UiOption options = view_options_get(view);
        bool focused = vis->win == win;
        const char *filename = file_name_get(file);
        const char *mode = vis->mode->status;

        if (focused && mode)
                strcpy(left_parts[left_count++], mode);

        snprintf(left_parts[left_count], sizeof(left_parts[left_count])-1, "%s%s%s",
                 filename ? filename : "[No Name]",
                 text_modified(txt) ? " [+]" : "",
                 vis_macro_recording(vis) ? " @": "");
        left_count++;

        int cursor_count = view_cursors_count(view);
        if (cursor_count > 1) {
                Cursor *c = view_cursors_primary_get(view);
                int cursor_number = view_cursors_number(c) + 1;
                snprintf(right_parts[right_count], sizeof(right_parts[right_count])-1,
                         "%d/%d", cursor_number, cursor_count);
                right_count++;
        }

        size_t size = text_size(txt);
        size_t pos = view_cursor_get(view);
        size_t percent = 0;
        if (size > 0) {
                double tmp = ((double)pos/(double)size)*100;
                percent = (size_t)(tmp+1);
        }
        snprintf(right_parts[right_count], sizeof(right_parts[right_count])-1,
                 "%zu%%", percent);
        right_count++;

        if (!(options & UI_OPTION_LARGE_FILE)) {
                Cursor *cur = view_cursors_primary_get(win->view);
                size_t line = view_cursors_line(cur);
                size_t col = view_cursors_col(cur);
                if (col > UI_LARGE_FILE_LINE_SIZE) {
                        options |= UI_OPTION_LARGE_FILE;
                        view_options_set(win->view, options);
                }
                snprintf(right_parts[right_count], sizeof(right_parts[right_count])-1,
                         "%zu, %zu", line, col);
                right_count++;
        }

        int left_len = snprintf(left, sizeof(left)-1, " %s%s%s%s%s%s%s",
                 left_parts[0],
                 left_parts[1][0] ? " » " : "",
                 left_parts[1],
                 left_parts[2][0] ? " » " : "",
                 left_parts[2],
                 left_parts[3][0] ? " » " : "",
                 left_parts[3]);

        int right_len = snprintf(right, sizeof(right)-1, "%s%s%s%s%s%s%s ",
                 right_parts[0],
                 right_parts[1][0] ? " « " : "",
                 right_parts[1],
                 right_parts[2][0] ? " « " : "",
                 right_parts[2],
                 right_parts[3][0] ? " « " : "",
                 right_parts[3]);

        if (left_len < 0 || right_len < 0)
                return;
        int left_width = text_string_width(left, left_len);
        int right_width = text_string_width(right, right_len);

        int spaces = width - left_width - right_width;
        if (spaces < 1)
                spaces = 1;

        snprintf(status, sizeof(status)-1, "%s%*s%s", left, spaces, " ", right);
        vis_window_status(win, status);
}

#if !CONFIG_LUA

bool vis_lua_path_add(Vis *vis, const char *path) { return true; }
bool vis_lua_paths_get(Vis *vis, char **lpath, char **cpath) { return false; }
void vis_lua_init(Vis *vis) { }
void vis_lua_start(Vis *vis) { }
void vis_lua_quit(Vis *vis) { }
void vis_lua_file_open(Vis *vis, File *file) { }
bool vis_lua_file_save_pre(Vis *vis, File *file, const char *path) { return true; }
void vis_lua_file_save_post(Vis *vis, File *file, const char *path) { }
void vis_lua_file_close(Vis *vis, File *file) { }
void vis_lua_win_open(Vis *vis, Win *win) { }
void vis_lua_win_close(Vis *vis, Win *win) { }
void vis_lua_win_highlight(Vis *vis, Win *win) { }
void vis_lua_win_status(Vis *vis, Win *win) { window_status_update(vis, win); }

#else

#if DEBUG_LUA
static void stack_dump_entry(lua_State *L, int i) {
        int t = lua_type(L, i);
        switch (t) {
        case LUA_TNIL:
                printf("nil");
                break;
        case LUA_TBOOLEAN:
                printf(lua_toboolean(L, i) ? "true" : "false");
                break;
        case LUA_TLIGHTUSERDATA:
                printf("lightuserdata(%p)", lua_touserdata(L, i));
                break;
        case LUA_TNUMBER:
                printf("%g", lua_tonumber(L, i));
                break;
        case LUA_TSTRING:
                printf("`%s'", lua_tostring(L, i));
                break;
        case LUA_TTABLE:
                printf("table[");
                lua_pushnil(L); /* first key */
                while (lua_next(L, i > 0 ? i : i - 1)) {
                        stack_dump_entry(L, -2);
                        printf("=");
                        stack_dump_entry(L, -1);
                        printf(",");
                        lua_pop(L, 1); /* remove value, keep key */
                }
                printf("]");
                break;
        case LUA_TUSERDATA:
                printf("userdata(%p)", lua_touserdata(L, i));
                break;
        default:  /* other values */
                printf("%s", lua_typename(L, t));
                break;
        }
}

static void stack_dump(lua_State *L, const char *format, ...) {
        va_list ap;
        va_start(ap, format);
        vprintf(format, ap);
        va_end(ap);
        int top = lua_gettop(L);
        for (int i = 1; i <= top; i++) {
                printf("%d: ", i);
                stack_dump_entry(L, i);
                printf("\n");
        }
        printf("\n\n");
        fflush(stdout);
}

#endif

static int panic_handler(lua_State *L) {
        void *ud = NULL;
        lua_getallocf(L, &ud);
        if (ud) {
                Vis *vis = ud;
                vis->lua = NULL;
                const char *msg = NULL;
                if (lua_type(L, -1) == LUA_TSTRING)
                        msg = lua_tostring(L, -1);
                vis_info_show(vis, "Fatal Lua error: %s", msg ? msg : "unknown reason");
                lua_close(L);
                if (vis->running)
                        siglongjmp(vis->sigbus_jmpbuf, 1);
        }
        return 0;
}

static int error_handler(lua_State *L) {
        Vis *vis = lua_touserdata(L, lua_upvalueindex(1));
        if (vis->errorhandler)
                return 1;
        vis->errorhandler = true;
        size_t len;
        const char *msg = lua_tostring(L, 1);
        if (msg)
                luaL_traceback(L, L, msg, 1);
        msg = lua_tolstring(L, 1, &len);
        vis_message_show(vis, msg);
        vis->errorhandler = false;
        return 1;
}

static int pcall(Vis *vis, lua_State *L, int nargs, int nresults) {
        /* insert a custom error function below all arguments */
        int msgh = lua_gettop(L) - nargs;
        lua_pushlightuserdata(L, vis);
        lua_pushcclosure(L, error_handler, 1);
        lua_insert(L, msgh);
        int ret = lua_pcall(L, nargs, nresults, msgh);
        lua_remove(L, msgh);
        return ret;
}

/* expects a lua function at stack position `narg` and stores a
 * reference to it in the registry. The return value can be used
 * to look it up.
 *
 *   registry["vis.functions"][(void*)(function)] = function
 */
static const void *func_ref_new(lua_State *L, int narg) {
        const void *addr = lua_topointer(L, narg);
        if (!lua_isfunction(L, narg) || !addr)
                luaL_argerror(L, narg, "function expected");
        lua_getfield(L, LUA_REGISTRYINDEX, "vis.functions");
        lua_pushlightuserdata(L, (void*)addr);
        lua_pushvalue(L, narg);
        lua_settable(L, -3);
        lua_pop(L, 1);
        return addr;
}

/* retrieve function from registry and place it at the top of the stack */
static bool func_ref_get(lua_State *L, const void *addr) {
        if (!addr)
                return false;
        lua_getfield(L, LUA_REGISTRYINDEX, "vis.functions");
        lua_pushlightuserdata(L, (void*)addr);
        lua_gettable(L, -2);
        lua_remove(L, -2);
        if (!lua_isfunction(L, -1)) {
                lua_pop(L, 1);
                return false;
        }
        return true;
}

/* creates a new metatable for a given type and stores a mapping:
 *
 *   registry["vis.types"][metatable] = type
 *
 * leaves the metatable at the top of the stack.
 */
static void obj_type_new(lua_State *L, const char *type) {
        luaL_newmetatable(L, type);
        lua_getglobal(L, "vis");
        if (!lua_isnil(L, -1)) {
                lua_getfield(L, -1, "types");
                lua_pushvalue(L, -3);
                lua_setfield(L, -2, type);
                lua_pop(L, 1);
        }
        lua_pop(L, 1);
        lua_getfield(L, LUA_REGISTRYINDEX, "vis.types");
        lua_pushvalue(L, -2);
        lua_pushstring(L, type);
        lua_settable(L, -3);
        lua_pop(L, 1);
}

/* get type of userdatum at the top of the stack:
 *
 *   return registry["vis.types"][getmetatable(userdata)]
 */
const char *obj_type_get(lua_State *L) {
        if (lua_isnil(L, -1))
                return "nil";
        lua_getfield(L, LUA_REGISTRYINDEX, "vis.types");
        lua_getmetatable(L, -2);
        lua_gettable(L, -2);
        // XXX: in theory string might become invalid when poped from stack
        const char *type = lua_tostring(L, -1);
        lua_pop(L, 2);
        return type;
}

static void *obj_new(lua_State *L, size_t size, const char *type) {
        void *obj = lua_newuserdata(L, size);
        luaL_getmetatable(L, type);
        lua_setmetatable(L, -2);
        lua_newtable(L);
        lua_setuservalue(L, -2);
        return obj;
}

/* returns registry["vis.objects"][addr] if it is of correct type */
static void *obj_ref_get(lua_State *L, void *addr, const char *type) {
        lua_getfield(L, LUA_REGISTRYINDEX, "vis.objects");
        lua_pushlightuserdata(L, addr);
        lua_gettable(L, -2);
        lua_remove(L, -2);
        if (lua_isnil(L, -1)) {
                debug("get: vis.objects[%p] = nil\n", addr);
                lua_pop(L, 1);
                return NULL;
        }
        if (DEBUG_LUA) {
                const char *actual_type = obj_type_get(L);
                if (strcmp(type, actual_type) != 0)
                        debug("get: vis.objects[%p] = %s (BUG: expected %s)\n", addr, actual_type, type);
                void **handle = luaL_checkudata(L, -1, type);
                if (!handle)
                        debug("get: vis.objects[%p] = %s (BUG: invalid handle)\n", addr, type);
                else if (*handle != addr)
                        debug("get: vis.objects[%p] = %s (BUG: handle mismatch %p)\n", addr, type, *handle);
        }
        return luaL_checkudata(L, -1, type);
}

/* expects a userdatum at the top of the stack and sets
 *
 *   registry["vis.objects"][addr] = userdata
 */
static void obj_ref_set(lua_State *L, void *addr) {
        //debug("set: vis.objects[%p] = %s\n", addr, obj_type_get(L));
        lua_getfield(L, LUA_REGISTRYINDEX, "vis.objects");
        lua_pushlightuserdata(L, addr);
        lua_pushvalue(L, -3);
        lua_settable(L, -3);
        lua_pop(L, 1);
}

/* invalidates an object reference
 *
 *   registry["vis.objects"][addr] = nil
 */
static void obj_ref_free(lua_State *L, void *addr) {
        if (DEBUG_LUA) {
                lua_getfield(L, LUA_REGISTRYINDEX, "vis.objects");
                lua_pushlightuserdata(L, addr);
                lua_gettable(L, -2);
                lua_remove(L, -2);
                if (lua_isnil(L, -1))
                        debug("free-unused: %p\n", addr);
                else
                        debug("free: vis.objects[%p] = %s\n", addr, obj_type_get(L));
                lua_pop(L, 1);
        }
        lua_pushnil(L);
        obj_ref_set(L, addr);
}

/* creates a new object reference of given type if it does not already exist in the registry:
 *
 *  if (registry["vis.types"][metatable(registry["vis.objects"][addr])] != type) {
 *      // XXX: should not happen
 *      registry["vis.objects"][addr] = new_obj(addr, type)
 *  }
 *  return registry["vis.objects"][addr];
 */
static void *obj_ref_new(lua_State *L, void *addr, const char *type) {
        if (!addr) {
                lua_pushnil(L);
                return NULL;
        }
        lua_getfield(L, LUA_REGISTRYINDEX, "vis.objects");
        lua_pushlightuserdata(L, addr);
        lua_gettable(L, -2);
        lua_remove(L, -2);
        const char *old_type = obj_type_get(L);
        if (strcmp(type, old_type) == 0) {
                debug("new: vis.objects[%p] = %s (returning existing object)\n", addr, old_type);
                void **handle = luaL_checkudata(L, -1, type);
                if (!handle)
                        debug("new: vis.objects[%p] = %s (BUG: invalid handle)\n", addr, old_type);
                else if (*handle != addr)
                        debug("new: vis.objects[%p] = %s (BUG: handle mismatch %p)\n", addr, old_type, *handle);
                return addr;
        }
        if (!lua_isnil(L, -1))
                debug("new: vis.objects[%p] = %s (WARNING: changing object type from %s)\n", addr, type, old_type);
        else
                debug("new: vis.objects[%p] = %s (creating new object)\n", addr, type);
        lua_pop(L, 1);
        void **handle = obj_new(L, sizeof(addr), type);
        obj_ref_set(L, addr);
        *handle = addr;
        return addr;
}

/* retrieve object stored in reference at stack location `idx' */
static void *obj_ref_check_get(lua_State *L, int idx, const char *type) {
        void **addr = luaL_checkudata(L, idx, type);
        if (!obj_ref_get(L, *addr, type))
                return NULL;
        return *addr;
}

/* (type) check validity of object reference at stack location `idx' */
static void *obj_ref_check(lua_State *L, int idx, const char *type) {
        void *obj = obj_ref_check_get(L, idx, type);
        if (obj)
                lua_pop(L, 1);
        else
                luaL_argerror(L, idx, "invalid object reference");
        return obj;
}

static void *obj_ref_check_containerof(lua_State *L, int idx, const char *type, size_t offset) {
        void *obj = obj_ref_check(L, idx, type);
        return obj ? ((char*)obj-offset) : obj;
}

static void *obj_lightref_new(lua_State *L, void *addr, const char *type) {
        if (!addr)
                return NULL;
        void **handle = obj_new(L, sizeof(addr), type);
        *handle = addr;
        return addr;
}

static void *obj_lightref_check(lua_State *L, int idx, const char *type) {
        void **addr = luaL_checkudata(L, idx, type);
        return *addr;
}

static int index_common(lua_State *L) {
        lua_getmetatable(L, 1);
        lua_pushvalue(L, 2);
        lua_gettable(L, -2);
        if (lua_isnil(L, -1)) {
                lua_getuservalue(L, 1);
                lua_pushvalue(L, 2);
                lua_gettable(L, -2);
        }
        return 1;
}

static int newindex_common(lua_State *L) {
        lua_getuservalue(L, 1);
        lua_pushvalue(L, 2);
        lua_pushvalue(L, 3);
        lua_settable(L, -3);
        return 0;
}

static size_t getpos(lua_State *L, int narg) {
        return lua_tounsigned(L, narg);
}

static size_t checkpos(lua_State *L, int narg) {
        lua_Number n = luaL_checknumber(L, narg);
        if (n >= 0 && n <= SIZE_MAX && n == (size_t)n)
                return n;
        return luaL_argerror(L, narg, "expected position, got number");
}

static void pushpos(lua_State *L, size_t pos) {
        if (pos == EPOS)
                lua_pushnil(L);
        else
                lua_pushunsigned(L, pos);
}

static void pushrange(lua_State *L, Filerange *r) {
        if (!text_range_valid(r)) {
                lua_pushnil(L);
                return;
        }
        lua_createtable(L, 0, 2);
        lua_pushstring(L, "start");
        lua_pushunsigned(L, r->start);
        lua_settable(L, -3);
        lua_pushstring(L, "finish");
        lua_pushunsigned(L, r->end);
        lua_settable(L, -3);
}

static Filerange getrange(lua_State *L, int index) {
        Filerange range = text_range_empty();
        if (lua_istable(L, index)) {
                lua_getfield(L, index, "start");
                range.start = checkpos(L, -1);
                lua_pop(L, 1);
                lua_getfield(L, index, "finish");
                range.end = checkpos(L, -1);
                lua_pop(L, 1);
        } else {
                range.start = checkpos(L, index);
                range.end = range.start + checkpos(L, index+1);
        }
        return range;
}

static const char *keymapping(Vis *vis, const char *keys, const Arg *arg) {
        lua_State *L = vis->lua;
        if (!func_ref_get(L, arg->v))
                return keys;
        lua_pushstring(L, keys);
        if (pcall(vis, L, 1, 1) != 0)
                return keys;
        if (lua_type(L, -1) != LUA_TNUMBER)
                return keys; /* invalid or no return value, assume zero */
        lua_Number number = lua_tonumber(L, -1);
        lua_Integer integer = lua_tointeger(L, -1);
        if (number != integer)
                return keys;
        if (integer < 0)
                return NULL; /* need more input */
        size_t len = integer;
        size_t max = strlen(keys);
        return (len <= max) ? keys+len : keys;
}

/***
 * The main editor object.
 * @type Vis
 */

/***
 * Version information.
 * @tfield string VERSION
 * version information in `git describe` format, same as reported by `vis -v`.
 */
/***
 * Lua API object types
 * @field types meta tables of userdata objects used for type checking
 * @local
 */
/***
 * User interface.
 * @tfield Ui ui the user interface being used
 */
/***
 * Mode constants.
 * @tfield modes modes
 */
/***
 * Events.
 * @tfield events events
 */
/***
 * Registers.
 * @field registers array to access the register by single letter name
 */
/***
 * Scintillua lexer module.
 * @field lexers might be `nil` if module is not found
 */
/***
 * LPeg lexer module.
 * @field lpeg might be `nil` if module is not found
 */
/***
 * Current count.
 * @tfield int count the specified count for the current command or `nil` if none was given
 */

/***
 * Create an iterator over all windows.
 * @function windows
 * @return the new iterator
 * @see win
 * @usage
 * for win in vis:windows() do
 *      -- do something with win
 * end
 */
static int windows_iter(lua_State *L);
static int windows(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        Win **handle = lua_newuserdata(L, sizeof *handle);
        *handle = vis->windows;
        lua_pushcclosure(L, windows_iter, 1);
        return 1;
}

static int windows_iter(lua_State *L) {
        Win **handle = lua_touserdata(L, lua_upvalueindex(1));
        if (!*handle)
                return 0;
        Win *win = obj_ref_new(L, *handle, VIS_LUA_TYPE_WINDOW);
        if (win)
                *handle = win->next;
        return 1;
}

/***
 * Create an iterator over all files.
 * @function files
 * @return the new iterator
 * @usage
 * for file in vis:files() do
 *      -- do something with file
 * end
 */
static int files_iter(lua_State *L);
static int files(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        File **handle = lua_newuserdata(L, sizeof *handle);
        *handle = vis->files;
        lua_pushcclosure(L, files_iter, 1);
        return 1;
}

static int files_iter(lua_State *L) {
        File **handle = lua_touserdata(L, lua_upvalueindex(1));
        if (!*handle)
                return 0;
        File *file = obj_ref_new(L, *handle, VIS_LUA_TYPE_FILE);
        if (file)
                *handle = file->next;
        return 1;
}

/***
 * Create an iterator over all mark names.
 * @function mark_names
 * @return the new iterator
 * @usage
 * local marks = vis.win.file.marks;
 * for mark in vis:mark_names() do
 *      local pos = marks[mark]
 *      if pos then
 *              -- do something with mark pos
 *      end
 * end
 */
static int mark_names_iter(lua_State *L);
static int mark_names(lua_State *L) {
        enum VisMark *handle = lua_newuserdata(L, sizeof *handle);
        *handle = 0;
        lua_pushcclosure(L, mark_names_iter, 1);
        return 1;
}

static int mark_names_iter(lua_State *L) {
        char mark = '\0';
        enum VisMark *handle = lua_touserdata(L, lua_upvalueindex(1));
        if (*handle < LENGTH(vis_marks))
                mark = vis_marks[*handle].name;
        else if (VIS_MARK_a <= *handle && *handle <= VIS_MARK_z)
                mark = 'a' + *handle - VIS_MARK_a;
        if (mark) {
                char name[2] = { mark, '\0' };
                lua_pushstring(L, name);
                (*handle)++;
                return 1;
        }
        return 0;
}

/***
 * Create an iterator over all register names.
 * @function register_names
 * @return the new iterator
 * @usage
 * for reg in vis:register_names() do
 *      local value = vis.registers[reg]
 *      if value then
 *              -- do something with register value
 *      end
 * end
 */
static int register_names_iter(lua_State *L);
static int register_names(lua_State *L) {
        enum VisRegister *handle = lua_newuserdata(L, sizeof *handle);
        *handle = 0;
        lua_pushcclosure(L, register_names_iter, 1);
        return 1;
}

static int register_names_iter(lua_State *L) {
        char reg = '\0';
        enum VisRegister *handle = lua_touserdata(L, lua_upvalueindex(1));
        if (*handle < LENGTH(vis_registers))
                reg = vis_registers[*handle].name;
        else if (VIS_REG_a <= *handle && *handle <= VIS_REG_z)
                reg = 'a' + *handle - VIS_REG_a;
        if (reg) {
                char name[2] = { reg, '\0' };
                lua_pushstring(L, name);
                (*handle)++;
                return 1;
        }
        return 0;
}

/***
 * Execute a `:`-command.
 * @function command
 * @tparam string command the command to execute
 * @treturn bool whether the command succeeded
 * @usage
 * vis:command("set number")
 */
static int command(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        const char *cmd = luaL_checkstring(L, 2);
        bool ret = vis_cmd(vis, cmd);
        lua_pushboolean(L, ret);
        return 1;
}

/***
 * Display a short message.
 *
 * The single line message will be displayed at the bottom of
 * the scren and automatically hidden once a key is pressed.
 *
 * @function info
 * @tparam string message the message to display
 */
static int info(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        const char *msg = luaL_checkstring(L, 2);
        vis_info_show(vis, "%s", msg);
        return 0;
}

/***
 * Display a multi line message.
 *
 * Opens a new window and displays an arbitrarily long message.
 *
 * @function message
 * @tparam string message the message to display
 */
static int message(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        const char *msg = luaL_checkstring(L, 2);
        vis_message_show(vis, msg);
        return 0;
}

/***
 * Register a Lua function as key action.
 * @function action_register
 * @tparam string name the name of the action, can be referred to in key bindings as `<name>` pseudo key
 * @tparam Function func the lua function implementing the key action (see @{keyhandler})
 * @tparam[opt] string help the single line help text as displayed in `:help`
 * @treturn KeyAction action the registered key action
 * @see Vis:map
 * @see Window:map
 */
static int action_register(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        const char *name = luaL_checkstring(L, 2);
        const void *func = func_ref_new(L, 3);
        const char *help = luaL_optstring(L, 4, NULL);
        KeyAction *action = vis_action_new(vis, name, help, keymapping, (Arg){ .v = func });
        if (!action)
                goto err;
        if (!vis_action_register(vis, action))
                goto err;
        obj_ref_new(L, action, VIS_LUA_TYPE_KEYACTION);
        return 1;
err:
        vis_action_free(vis, action);
        lua_pushnil(L);
        return 1;
}

static int keymap(lua_State *L, Vis *vis, Win *win) {
        int mode = luaL_checkint(L, 2);
        const char *key = luaL_checkstring(L, 3);
        const char *help = luaL_optstring(L, 5, NULL);
        KeyBinding *binding = vis_binding_new(vis);
        if (!binding)
                goto err;
        if (lua_isstring(L, 4)) {
                const char *alias = luaL_checkstring(L, 4);
                if (!(binding->alias = strdup(alias)))
                        goto err;
        } else if (lua_isfunction(L, 4)) {
                const void *func = func_ref_new(L, 4);
                if (!(binding->action = vis_action_new(vis, NULL, help, keymapping, (Arg){ .v = func })))
                        goto err;
        } else if (lua_isuserdata(L, 4)) {
                binding->action = obj_ref_check(L, 4, VIS_LUA_TYPE_KEYACTION);
        }

        if (win) {
                if (!vis_window_mode_map(win, mode, true, key, binding))
                        goto err;
        } else {
                if (!vis_mode_map(vis, mode, true, key, binding))
                        goto err;
        }

        lua_pushboolean(L, true);
        return 1;
err:
        vis_binding_free(vis, binding);
        lua_pushboolean(L, false);
        return 1;
}

/***
 * Map a key to a Lua function.
 *
 * Creates a new key mapping in a given mode.
 *
 * @function map
 * @tparam int mode the mode to which the mapping should be added
 * @tparam string key the key to map
 * @tparam function func the Lua function to handle the key mapping (see @{keyhandler})
 * @tparam[opt] string help the single line help text as displayed in `:help`
 * @treturn bool whether the mapping was successfully established
 * @see Window:map
 * @usage
 * vis:map(vis.modes.INSERT, "<C-k>", function(keys)
 *      if #keys < 2 then
 *              return -1 -- need more input
 *      end
 *      local digraph = keys:sub(1, 2)
 *      if digraph == "l*" then
 *              vis:feedkeys('λ')
 *              return 2 -- consume 2 bytes of input
 *      end
 * end, "Insert digraph")
 */
/***
 * Setup a key alias.
 *
 * This is equivalent to `vis:command('map! mode key alias')`.
 *
 * Mappings are always recursive!
 * @function map
 * @tparam int mode the mode to which the mapping should be added
 * @tparam string key the key to map
 * @tparam string alias the key to map to
 * @treturn bool whether the mapping was successfully established
 * @see Window:map
 * @usage
 * vis:map(vis.modes.NORMAL, "j", "k")
 */
/***
 * Map a key to a key action.
 *
 * @function map
 * @tparam int mode the mode to which the mapping should be added
 * @tparam string key the key to map
 * @param action the action to map
 * @treturn bool whether the mapping was successfully established
 * @see Window:map
 * @usage
 * local action = vis:action_register("info", function()
 *   vis:info("Mapping works!")
 * end, "Info message help text")
 * vis:map(vis.modes.NORMAL, "gh", action)
 * vis:map(vis.modes.NORMAL, "gl", action)
 */
static int map(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        return keymap(L, vis, NULL);
}

/***
 * Execute a motion.
 *
 * @function motion
 * @tparam int id the id of the motion to execute
 * @treturn bool whether the id was valid
 * @local
 */
static int motion(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        enum VisMotion id = luaL_checkunsigned(L, 2);
        // TODO handle var args?
        lua_pushboolean(L, vis && vis_motion(vis, id));
        return 1;
}

static size_t motion_lua(Vis *vis, Win *win, void *data, size_t pos) {
        lua_State *L = vis->lua;
        if (!L || !func_ref_get(L, data) || !obj_ref_new(L, win, VIS_LUA_TYPE_WINDOW))
                return EPOS;

        lua_pushunsigned(L, pos);
        if (pcall(vis, L, 2, 1) != 0)
                return EPOS;
        return getpos(L, -1);
}

/***
 * Register a custom motion.
 *
 * @function motion_register
 * @tparam function motion the Lua function implementing the motion
 * @treturn int the associated motion id, or `-1` on failure
 * @see motion, motion_new
 * @local
 * @usage
 * -- custom motion advancing to the next byte
 * local id = vis:motion_register(function(win, pos)
 *      return pos+1
 * end)
 */
static int motion_register(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        const void *func = func_ref_new(L, 2);
        int id = vis_motion_register(vis, 0, (void*)func, motion_lua);
        lua_pushinteger(L, id);
        return 1;
}

/***
 * Execute an operator.
 *
 * @function operator
 * @tparam int id the id of the operator to execute
 * @treturn bool whether the id was valid
 * @local
 */
static int operator(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        enum VisOperator id = luaL_checkunsigned(L, 2);
        // TODO handle var args?
        lua_pushboolean(L, vis && vis_operator(vis, id));
        return 1;
}

static size_t operator_lua(Vis *vis, Text *text, OperatorContext *c) {
        lua_State *L = vis->lua;
        if (!L || !func_ref_get(L, c->context))
                return EPOS;
        File *file = vis->files;
        while (file && (file->internal || file->text != text))
                file = file->next;
        if (!file || !obj_ref_new(L, file, VIS_LUA_TYPE_FILE))
                return EPOS;
        pushrange(L, &c->range);
        pushpos(L, c->pos);
        if (pcall(vis, L, 3, 1) != 0)
                return EPOS;
        return getpos(L, -1);
}

/***
 * Register a custom operator.
 *
 * @function operator_register
 * @tparam function operator the Lua function implementing the operator
 * @treturn int the associated operator id, or `-1` on failure
 * @see operator, operator_new
 * @local
 * @usage
 * -- custom operator replacing every 'a' with 'b'
 * local id = vis:operator_register(function(file, range, pos)
 *      local data = file:content(range)
 *      data = data:gsub("a", "b")
 *      file:delete(range)
 *      file:insert(range.start, data)
 *      return range.start -- new cursor location
 * end)
 */
static int operator_register(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        const void *func = func_ref_new(L, 2);
        int id = vis_operator_register(vis, operator_lua, (void*)func);
        lua_pushinteger(L, id);
        return 1;
}

/***
 * Execute a text object.
 *
 * @function textobject
 * @tparam int id the id of the text object to execute
 * @treturn bool whether the id was valid
 * @see textobject_register, textobject_new
 * @local
 */
static int textobject(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        enum VisTextObject id = luaL_checkunsigned(L, 2);
        lua_pushboolean(L, vis_textobject(vis, id));
        return 1;
}

static Filerange textobject_lua(Vis *vis, Win *win, void *data, size_t pos) {
        lua_State *L = vis->lua;
        if (!L || !func_ref_get(L, data) || !obj_ref_new(L, win, VIS_LUA_TYPE_WINDOW))
                return text_range_empty();
        lua_pushunsigned(L, pos);
        if (pcall(vis, L, 2, 2) != 0 || lua_isnil(L, -1))
                return text_range_empty();
        return text_range_new(getpos(L, -2), getpos(L, -1));
}

/***
 * Register a custom text object.
 *
 * @function textobject_register
 * @tparam function textobject the Lua function implementing the text object
 * @treturn int the associated text object id, or `-1` on failure
 * @see textobject, textobject_new
 * @local
 * @usage
 * -- custom text object covering the next byte
 * local id = vis:textobject_register(function(win, pos)
 *      return pos, pos+1
 * end)
 */
static int textobject_register(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        const void *func = func_ref_new(L, 2);
        int id = vis_textobject_register(vis, 0, (void*)func, textobject_lua);
        lua_pushinteger(L, id);
        return 1;
}

static bool option_lua(Vis *vis, Win *win, void *context, bool toggle,
                       enum VisOption flags, const char *name, Arg *value) {
        lua_State *L = vis->lua;
        if (!L || !func_ref_get(L, context))
                return false;
        if (flags & VIS_OPTION_TYPE_BOOL)
                lua_pushboolean(L, value->b);
        else if (flags & VIS_OPTION_TYPE_STRING)
                lua_pushstring(L, value->s);
        else if (flags & VIS_OPTION_TYPE_NUMBER)
                lua_pushnumber(L, value->i);
        else
                return false;
        lua_pushboolean(L, toggle);
        return pcall(vis, L, 2, 2) == 0 && (!lua_isboolean(L, -1) || lua_toboolean(L, -1));
}

/***
 * Register a custom `:set` option.
 *
 * @function option_register
 * @tparam string name the option name
 * @tparam string type the option type (`bool`, `string` or `number`)
 * @tparam function handler the Lua function being called when the option is changed
 * @tparam[opt] string help the single line help text as displayed in `:help`
 * @treturn bool whether the option was successfully registered
 * @usage
 * vis:option_register("foo", "bool", function(value, toogle)
 *      if not vis.win then return false end
 *      vis.win.foo = toogle and not vis.win.foo or value
 *      vis:info("Option foo = " .. tostring(vis.win.foo))
 *      return true
 * end, "Foo enables superpowers")
 */
static int option_register(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        const char *name = luaL_checkstring(L, 2);
        const char *type = luaL_checkstring(L, 3);
        const void *func = func_ref_new(L, 4);
        const char *help = luaL_optstring(L, 5, NULL);
        const char *names[] = { name, NULL };
        enum VisOption flags = 0;
        if (strcmp(type, "string") == 0)
                flags |= VIS_OPTION_TYPE_STRING;
        else if (strcmp(type, "number") == 0)
                flags |= VIS_OPTION_TYPE_NUMBER;
        else
                flags |= VIS_OPTION_TYPE_BOOL;
        bool ret = vis_option_register(vis, names, flags, option_lua, (void*)func, help);
        lua_pushboolean(L, ret);
        return 1;
}

/***
 * Unregister a `:set` option.
 *
 * @function option_unregister
 * @tparam string name the option name
 * @treturn bool whether the option was successfully unregistered
 */
static int option_unregister(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        const char *name = luaL_checkstring(L, 2);
        bool ret = vis_option_unregister(vis, name);
        lua_pushboolean(L, ret);
        return 1;
}

static bool command_lua(Vis *vis, Win *win, void *data, bool force, const char *argv[], Cursor *cur, Filerange *range) {
        lua_State *L = vis->lua;
        if (!L || !func_ref_get(L, data))
                return false;
        lua_newtable(L);
        for (size_t i = 0; argv[i]; i++) {
                lua_pushunsigned(L, i);
                lua_pushstring(L, argv[i]);
                lua_settable(L, -3);
        }
        lua_pushboolean(L, force);
        if (!obj_ref_new(L, win, VIS_LUA_TYPE_WINDOW))
                return false;
        if (!cur)
                cur = view_cursors_primary_get(win->view);
        if (!obj_lightref_new(L, cur, VIS_LUA_TYPE_CURSOR))
                return false;
        pushrange(L, range);
        if (pcall(vis, L, 5, 1) != 0)
                return false;
        return lua_toboolean(L, -1);
}

/***
 * Register a custom `:`-command.
 *
 * @function command_register
 * @tparam string name the command name
 * @tparam function command the Lua function implementing the command
 * @tparam[opt] string help the single line help text as displayed in `:help`
 * @treturn bool whether the command has been successfully registered
 * @usage
 * vis:command_register("foo", function(argv, force, win, cursor, range)
 *       for i,arg in ipairs(argv) do
 *               print(i..": "..arg)
 *       end
 *       print("was command forced with ! "..(force and "yes" or "no"))
 *       print(win.file.name)
 *       print(cursor.pos)
 *       print(range ~= nil and ('['..range.start..', '..range.finish..']') or "invalid range")
 *       return true;
 * end)
 */
static int command_register(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        const char *name = luaL_checkstring(L, 2);
        const void *func = func_ref_new(L, 3);
        const char *help = luaL_optstring(L, 4, "");
        bool ret = vis_cmd_register(vis, name, help, (void*)func, command_lua);
        lua_pushboolean(L, ret);
        return 1;
}

/***
 * Push keys to input queue and interpret them.
 *
 * The keys are processed as if they were read from the keyboard.
 *
 * @function feedkeys
 * @tparam string keys the keys to interpret
 */
static int feedkeys(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        const char *keys = luaL_checkstring(L, 2);
        vis_keys_feed(vis, keys);
        return 0;
}

/***
 * Insert keys at all cursor positions of active window.
 *
 * This function behaves as if the keys were entered in insert mode,
 * but in contrast to @{Vis:feedkeys} it bypasses the input queue,
 * meaning mappings do not apply and the keys will not be recorded in macros.
 *
 * @function insert
 * @tparam string keys the keys to insert
 * @see Vis:feedkeys
 */
static int insert(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        size_t len;
        const char *keys = luaL_checklstring(L, 2, &len);
        vis_insert_key(vis, keys, len);
        return 0;
}

/***
 * Replace keys at all cursor positions of active window.
 *
 * This function behaves as if the keys were entered in replace mode,
 * but in contrast to @{Vis:feedkeys} it bypasses the input queue,
 * meaning mappings do not apply and the keys will not be recorded in macros.
 *
 * @function replace
 * @tparam string keys the keys to insert
 * @see Vis:feedkeys
 */
static int replace(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        size_t len;
        const char *keys = luaL_checklstring(L, 2, &len);
        vis_replace_key(vis, keys, len);
        return 0;
}

/***
 * Terminate editor process.
 *
 * Termination happens upon the next iteration of the main event loop.
 * This means the calling Lua code will be executed further until it
 * eventually hands over control to the editor core. The exit status
 * of the most recent call is used.
 *
 * All unsaved chanes will be lost!
 *
 * @function exit
 * @tparam int code the exit status returned to the operating system
 */
static int exit_func(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        int code = luaL_checkint(L, 2);
        vis_exit(vis, code);
        return 0;
}

/***
 * Pipe file range to external process and collect output.
 *
 * The editor core will be blocked while the external process is running.
 *
 * @function pipe
 * @tparam File file the file to which the range applies
 * @tparam Range range the range to pipe
 * @tparam string command the command to execute
 * @treturn int code the exit status of the executed command
 * @treturn string stdout the data written to stdout
 * @treturn string stderr the data written to stderr
 */
static int pipe_func(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        File *file = obj_ref_check(L, 2, VIS_LUA_TYPE_FILE);
        Filerange range = getrange(L, 3);
        const char *cmd = luaL_checkstring(L, 4);
        char *out = NULL, *err = NULL;
        int status = vis_pipe_collect(vis, file, &range, (const char*[]){ cmd, NULL }, &out, &err);
        lua_pushinteger(L, status);
        if (out)
                lua_pushstring(L, out);
        else
                lua_pushnil(L);
        free(out);
        if (err)
                lua_pushstring(L, err);
        else
                lua_pushnil(L);
        free(err);
        vis_draw(vis);
        return 3;
}
/***
 * Currently active window.
 * @tfield Window win
 * @see windows
 */
/***
 * Currently active mode.
 * @tfield modes mode
 */
/***
 * Whether a macro is being recorded.
 * @tfield bool recording
 */
static int vis_index(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");

        if (lua_isstring(L, 2)) {
                const char *key = lua_tostring(L, 2);
                if (strcmp(key, "win") == 0) {
                        if (vis->win)
                                obj_ref_new(L, vis->win, VIS_LUA_TYPE_WINDOW);
                        else
                                lua_pushnil(L);
                        return 1;
                }

                if (strcmp(key, "mode") == 0) {
                        lua_pushunsigned(L, vis->mode->id);
                        return 1;
                }

                if (strcmp(key, "recording") == 0) {
                        lua_pushboolean(L, vis_macro_recording(vis));
                        return 1;
                }

                if (strcmp(key, "count") == 0) {
                        int count = vis_count_get(vis);
                        if (count == VIS_COUNT_UNKNOWN)
                                lua_pushnil(L);
                        else
                                lua_pushunsigned(L, count);
                        return 1;
                }

                if (strcmp(key, "registers") == 0) {
                        obj_ref_new(L, vis->ui, VIS_LUA_TYPE_REGISTERS);
                        return 1;
                }

                if (strcmp(key, "ui") == 0) {
                        obj_ref_new(L, vis->ui, VIS_LUA_TYPE_UI);
                        return 1;
                }
        }

        return index_common(L);
}

static int vis_newindex(lua_State *L) {
        Vis *vis = obj_ref_check(L, 1, "vis");
        if (lua_isstring(L, 2)) {
                const char *key = lua_tostring(L, 2);
                if (strcmp(key, "mode") == 0) {
                        enum VisMode mode = luaL_checkunsigned(L, 3);
                        vis_mode_switch(vis, mode);
                        return 0;
                }

                if (strcmp(key, "count") == 0) {
                        int count;
                        if (lua_isnil(L, 3))
                                count = VIS_COUNT_UNKNOWN;
                        else
                                count = luaL_checkunsigned(L, 3);
                        vis_count_set(vis, count);
                        return 0;
                }

                if (strcmp(key, "win") == 0) {
                        vis_window_focus(obj_ref_check(L, 3, VIS_LUA_TYPE_WINDOW));
                        return 0;
                }
        }
        return newindex_common(L);
}

static const struct luaL_Reg vis_lua[] = {
        { "files", files },
        { "windows", windows },
        { "mark_names", mark_names },
        { "register_names", register_names },
        { "command", command },
        { "info", info },
        { "message", message },
        { "map", map },
        { "operator", operator },
        { "operator_register", operator_register },
        { "motion", motion },
        { "motion_register", motion_register },
        { "textobject", textobject },
        { "textobject_register", textobject_register },
        { "option_register", option_register },
        { "option_unregister", option_unregister },
        { "command_register", command_register },
        { "feedkeys", feedkeys },
        { "insert", insert },
        { "replace", replace },
        { "action_register", action_register },
        { "exit", exit_func },
        { "pipe", pipe_func },
        { "__index", vis_index },
        { "__newindex", vis_newindex },
        { NULL, NULL },
};

static const struct luaL_Reg ui_funcs[] = {
        { "__index", index_common },
        { NULL, NULL },
};

static int registers_index(lua_State *L) {
        Vis *vis = lua_touserdata(L, lua_upvalueindex(1));
        const char *symbol = luaL_checkstring(L, 2);
        if (strlen(symbol) != 1)
                goto err;
        enum VisRegister reg = vis_register_from(vis, symbol[0]);
        if (reg >= VIS_REG_INVALID)
                goto err;
        size_t len;
        const char *value = vis_register_get(vis, reg, &len);
        lua_pushlstring(L, value ? value : "" , len);
        return 1;
err:
        lua_pushnil(L);
        return 1;
}

static int registers_newindex(lua_State *L) {
        Vis *vis = lua_touserdata(L, lua_upvalueindex(1));
        const char *symbol = luaL_checkstring(L, 2);
        if (strlen(symbol) != 1)
                return 0;
        enum VisRegister reg = vis_register_from(vis, symbol[0]);
        if (reg >= VIS_REG_INVALID)
                return 0;
        size_t len;
        const char *value = luaL_checklstring(L, 3, &len);
        register_put(vis, &vis->registers[reg], value, len+1);
        return 0;
}

static int registers_len(lua_State *L) {
        Vis *vis = lua_touserdata(L, lua_upvalueindex(1));
        lua_pushunsigned(L, LENGTH(vis->registers));
        return 1;
}

static const struct luaL_Reg registers_funcs[] = {
        { "__index", registers_index },
        { "__newindex", registers_newindex },
        { "__len", registers_len },
        { NULL, NULL },
};

/***
 * A window object.
 * @type Window
 */

/***
 * Viewport currently being displayed.
 * @tfield Range viewport
 */
/***
 * The window width.
 * @tfield int width
 */
/***
 * The window height.
 * @tfield int height
 */
/***
 * The file being displayed in this window.
 * @tfield File file
 */
/***
 * The primary cursor of this window.
 * @tfield Cursor cursor
 */
/***
 * The cursors of this window.
 * @tfield Array(Cursor) cursors
 */
static int window_index(lua_State *L) {
        Win *win = obj_ref_check(L, 1, VIS_LUA_TYPE_WINDOW);

        if (lua_isstring(L, 2)) {
                const char *key = lua_tostring(L, 2);

                if (strcmp(key, "viewport") == 0) {
                        Filerange r = view_viewport_get(win->view);
                        pushrange(L, &r);
                        return 1;
                }

                if (strcmp(key, "width") == 0) {
                        lua_pushunsigned(L, vis_window_width_get(win));
                        return 1;
                }

                if (strcmp(key, "height") == 0) {
                        lua_pushunsigned(L, vis_window_height_get(win));
                        return 1;
                }

                if (strcmp(key, "file") == 0) {
                        obj_ref_new(L, win->file, VIS_LUA_TYPE_FILE);
                        return 1;
                }

                if (strcmp(key, "cursor") == 0) {
                        Cursor *cur = view_cursors_primary_get(win->view);
                        obj_lightref_new(L, cur, VIS_LUA_TYPE_CURSOR);
                        return 1;
                }

                if (strcmp(key, "cursors") == 0) {
                        obj_ref_new(L, win->view, VIS_LUA_TYPE_CURSORS);
                        return 1;
                }
        }

        return index_common(L);
}

static int window_cursors_iterator_next(lua_State *L) {
        Cursor **handle = lua_touserdata(L, lua_upvalueindex(1));
        if (!*handle)
                return 0;
        Cursor *cur = obj_lightref_new(L, *handle, VIS_LUA_TYPE_CURSOR);
        if (!cur)
                return 0;
        *handle = view_cursors_next(cur);
        return 1;
}

/***
 * Create an iterator over all cursors of this window.
 * @function cursors_iterator
 * @return the new iterator
 */
static int window_cursors_iterator(lua_State *L) {
        Win *win = obj_ref_check(L, 1, VIS_LUA_TYPE_WINDOW);
        Cursor **handle = lua_newuserdata(L, sizeof *handle);
        *handle = view_cursors(win->view);
        lua_pushcclosure(L, window_cursors_iterator_next, 1);
        return 1;
}

/***
 * Set up a window local key mapping.
 * The function signatures are the same as for @{Vis:map}.
 * @function map
 * @param ...
 * @see Vis:map
 */
static int window_map(lua_State *L) {
        Win *win = obj_ref_check(L, 1, VIS_LUA_TYPE_WINDOW);
        return keymap(L, win->vis, win);
}

/***
 * Define a display style.
 * @function style_define
 * @tparam int id the style id to use
 * @tparam string style the style definition 
 * @treturn bool whether the style definition has been successfully
 *  associated with the given id
 * @see style
 * @usage
 * win:style_define(win.STYLE_DEFAULT, "fore:red")
 */
static int window_style_define(lua_State *L) {
        Win *win = obj_ref_check(L, 1, VIS_LUA_TYPE_WINDOW);
        enum UiStyle id = luaL_checkunsigned(L, 2);
        const char *style = luaL_checkstring(L, 3);
        bool ret = view_style_define(win->view, id, style);
        lua_pushboolean(L, ret);
        return 1;
}

/***
 * Style a window range.
 *
 * The style will be cleared after every window redraw.
 * @function style
 * @tparam int id the display style as registered with @{style_define}
 * @tparam int start the absolute file position in bytes
 * @tparam int len the length in bytes to style
 * @see style_define
 * @usage
 * win:style(win.STYLE_DEFAULT, 0, 10)
 */
static int window_style(lua_State *L) {
        Win *win = obj_ref_check(L, 1, VIS_LUA_TYPE_WINDOW);
        enum UiStyle style = luaL_checkunsigned(L, 2);
        size_t start = checkpos(L, 3);
        size_t end = checkpos(L, 4);
        view_style(win->view, style, start, end);
        return 0;
}

/***
 * Set window status line.
 *
 * @function status
 * @tparam string left the left aligned part of the status line
 * @tparam[opt] string right the right aligned part of the status line
 */
static int window_status(lua_State *L) {
        Win *win = obj_ref_check(L, 1, VIS_LUA_TYPE_WINDOW);
        char status[1024] = "";
        int width = vis_window_width_get(win);
        const char *left = luaL_checkstring(L, 2);
        const char *right = luaL_optstring(L, 3, "");
        int left_width = text_string_width(left, strlen(left));
        int right_width = text_string_width(right, strlen(right));
        int spaces = width - left_width - right_width;
        if (spaces < 1)
                spaces = 1;
        snprintf(status, sizeof(status)-1, "%s%*s%s", left, spaces, " ", right);
        vis_window_status(win, status);
        return 0;
}

/***
 * Redraw window content.
 *
 * @function draw
 */
static int window_draw(lua_State *L) {
        Win *win = obj_ref_check(L, 1, VIS_LUA_TYPE_WINDOW);
        view_draw(win->view);
        return 0;
}

static const struct luaL_Reg window_funcs[] = {
        { "__index", window_index },
        { "__newindex", newindex_common },
        { "cursors_iterator", window_cursors_iterator },
        { "map", window_map },
        { "style_define", window_style_define },
        { "style", window_style },
        { "status", window_status },
        { "draw", window_draw },
        { NULL, NULL },
};

static int window_cursors_index(lua_State *L) {
        View *view = obj_ref_check(L, 1, VIS_LUA_TYPE_CURSORS);
        size_t index = luaL_checkunsigned(L, 2);
        size_t count = view_cursors_count(view);
        if (index == 0 || index > count)
                goto err;
        for (Cursor *c = view_cursors(view); c; c = view_cursors_next(c)) {
                if (!--index) {
                        obj_lightref_new(L, c, VIS_LUA_TYPE_CURSOR);
                        return 1;
                }
        }
err:
        lua_pushnil(L);
        return 1;
}

static int window_cursors_len(lua_State *L) {
        View *view = obj_ref_check(L, 1, VIS_LUA_TYPE_CURSORS);
        lua_pushunsigned(L, view_cursors_count(view));
        return 1;
}

static const struct luaL_Reg window_cursors_funcs[] = {
        { "__index", window_cursors_index },
        { "__len", window_cursors_len },
        { NULL, NULL },
};

/***
 * A cursor object.
 *
 * Cursors are represented as absolute byte offsets from the start of the file.
 * Valid cursor placements are within the closed interval `[0, file.size]`.
 * Cursors are currently implemented using character marks into the underlying
 * persistent [text management data structure](https://github.com/martanne/vis/wiki/Text-management-using-a-piece-chain).
 * This has a few consequences you should be aware of:
 *
 *  - A cursor becomes invalid when the underlying text range it is referencing
 *    is deleted:
 *
 *        -- leaves cursor in an invalid state
 *        win.file:delete(win.cursor.pos, 1)
 *        assert(win.cursor.pos == nil)
 *
 *    Like a regular mark it will become valid again when the text is reverted
 *    to the state before the deletion.
 *
 *  - Inserts after the cursor position (`> cursor.pos`) will not affect the
 *    cursor postion.
 *
 *        local pos = win.cursor.pos
 *        win.file:insert(pos+1, "-")
 *        assert(win.cursor.pos == pos)
 *
 *  - Non-cached inserts before the cursor position (`<= cursor.pos`) will
 *    affect the mark and adjust the cursor postion by the number of bytes
 *    which were inserted.
 *
 *        local pos = win.cursor.pos
 *        win.file:insert(pos, "-")
 *        assert(win.cursor.pos == pos+1)
 *
 *  - Cached inserts before the cursor position (`<= cursor.pos`) will
 *    not affect the cursor position because the underlying text is replaced
 *    inplace.
 *
 * For these reasons it is generally recommended to update the cursor position
 * after a modification. The general procedure amounts to:
 *
 * 1. Read out the current cursor position
 * 2. Perform text modifications
 * 3. Update the cursor postion
 *
 * This is what @{Vis:insert} and @{Vis:replace} do internally.
 *
 * @type Cursor
 * @usage
 * local data = "new text"
 * local pos = win.cursor.pos
 * win.file:insert(pos, data)
 * win.cursor.pos = pos + #data
 */

/***
 * The zero based byte position in the file.
 *
 * Might be `nil` if the cursor is in an invalid state.
 * Setting this field will move the cursor to the given position.
 * @tfield int pos
 */
/***
 * The 1-based line the cursor resides on.
 *
 * @tfield int line
 * @see to
 */
/***
 * The 1-based column position the cursor resides on.
 * @tfield int col
 * @see to
 */
/***
 * The 1-based cursor index.
 * @tfield int number
 */
/***
 * The selection associated with this cursor.
 * @tfield Range selection the selection or `nil` if not in visual mode
 */
static int window_cursor_index(lua_State *L) {
        Cursor *cur = obj_lightref_check(L, 1, VIS_LUA_TYPE_CURSOR);
        if (!cur) {
                lua_pushnil(L);
                return 1;
        }

        if (lua_isstring(L, 2)) {
                const char *key = lua_tostring(L, 2);
                if (strcmp(key, "pos") == 0) {
                        pushpos(L, view_cursors_pos(cur));
                        return 1;
                }

                if (strcmp(key, "line") == 0) {
                        lua_pushunsigned(L, view_cursors_line(cur));
                        return 1;
                }

                if (strcmp(key, "col") == 0) {
                        lua_pushunsigned(L, view_cursors_col(cur));
                        return 1;
                }

                if (strcmp(key, "number") == 0) {
                        lua_pushunsigned(L, view_cursors_number(cur)+1);
                        return 1;
                }

                if (strcmp(key, "selection") == 0) {
                        Filerange sel = view_cursors_selection_get(cur);
                        pushrange(L, &sel);
                        return 1;
                }
        }

        return index_common(L);
}

static int window_cursor_newindex(lua_State *L) {
        Cursor *cur = obj_lightref_check(L, 1, VIS_LUA_TYPE_CURSOR);
        if (!cur)
                return 0;
        if (lua_isstring(L, 2)) {
                const char *key = lua_tostring(L, 2);
                if (strcmp(key, "pos") == 0) {
                        size_t pos = checkpos(L, 3);
                        view_cursors_to(cur, pos);
                        return 0;
                }

                if (strcmp(key, "selection") == 0) {
                        Filerange sel = getrange(L, 3);
                        if (text_range_valid(&sel))
                                view_cursors_selection_set(cur, &sel);
                        else
                                view_cursors_selection_clear(cur);
                        return 0;
                }
        }
        return newindex_common(L);
}

/***
 * Move cursor.
 * @function to
 * @tparam int line the 1-based line number
 * @tparam int col the 1-based column number
 */
static int window_cursor_to(lua_State *L) {
        Cursor *cur = obj_lightref_check(L, 1, VIS_LUA_TYPE_CURSOR);
        if (cur) {
                size_t line = checkpos(L, 2);
                size_t col = checkpos(L, 3);
                view_cursors_place(cur, line, col);
        }
        return 0;
}

static const struct luaL_Reg window_cursor_funcs[] = {
        { "__index", window_cursor_index },
        { "__newindex", window_cursor_newindex },
        { "to", window_cursor_to },
        { NULL, NULL },
};

/***
 * A file object.
 * @type File
 */
/***
 * File name.
 * @tfield string name the file name relative to current working directory or `nil` if not yet named
 */
/***
 * File path.
 * @tfield string path the absolute file path or `nil` if not yet named
 */
/***
 * File content by logical lines.
 *
 * Assigning to array element `0` (`#lines+1`) will insert a new line at
 * the beginning (end) of the file.
 * @tfield Array(string) lines the file content accessible as 1-based array
 * @see content
 * @usage
 * local lines = vis.win.file.lines
 * for i=1, #lines do
 *      lines[i] = i .. ": " .. lines[i]
 * end
 */
/***
 * File size in bytes.
 * @tfield int size the current file size in bytes
 */
/***
 * File state.
 * @tfield bool modified whether the file contains unsaved changes
 */
/***
 * File marks.
 * @field marks array to access the marks of this file by single letter name
 */
static int file_index(lua_State *L) {
        File *file = obj_ref_check(L, 1, VIS_LUA_TYPE_FILE);

        if (lua_isstring(L, 2)) {
                const char *key = lua_tostring(L, 2);
                if (strcmp(key, "name") == 0) {
                        lua_pushstring(L, file_name_get(file));
                        return 1;
                }

                if (strcmp(key, "path") == 0) {
                        lua_pushstring(L, file->name);
                        return 1;
                }

                if (strcmp(key, "lines") == 0) {
                        obj_ref_new(L, file->text, VIS_LUA_TYPE_TEXT);
                        return 1;
                }

                if (strcmp(key, "size") == 0) {
                        lua_pushunsigned(L, text_size(file->text));
                        return 1;
                }

                if (strcmp(key, "modified") == 0) {
                        lua_pushboolean(L, text_modified(file->text));
                        return 1;
                }

                if (strcmp(key, "marks") == 0) {
                        obj_ref_new(L, file->marks, VIS_LUA_TYPE_MARKS);
                        return 1;
                }
        }

        return index_common(L);
}

/***
 * Insert data at position.
 * @function insert
 * @tparam int pos the 0-based file position in bytes
 * @tparam string data the data to insert
 * @treturn bool whether the file content was successfully changed
 */
static int file_insert(lua_State *L) {
        File *file = obj_ref_check(L, 1, VIS_LUA_TYPE_FILE);
        size_t pos = checkpos(L, 2);
        size_t len;
        luaL_checkstring(L, 3);
        const char *data = lua_tolstring(L, 3, &len);
        lua_pushboolean(L, text_insert(file->text, pos, data, len));
        return 1;
}

/***
 * Delete data at position.
 *
 * @function delete
 * @tparam int pos the 0-based file position in bytes
 * @tparam int len the length in bytes to delete
 * @treturn bool whether the file content was successfully changed
 */
/***
 * Delete file range.
 *
 * @function delete
 * @tparam Range range the range to delete
 * @treturn bool whether the file content was successfully changed
 */
static int file_delete(lua_State *L) {
        File *file = obj_ref_check(L, 1, VIS_LUA_TYPE_FILE);
        Filerange range = getrange(L, 2);
        lua_pushboolean(L, text_delete_range(file->text, &range));
        return 1;
}

/***
 * Create an iterator over all lines of the file.
 *
 * For large files this is probably faster than @{lines}.
 * @function lines_iterator
 * @return the new iterator
 * @see lines
 * @usage
 * for line in file:lines_iterator() do
 *      -- do something with line
 * end
 */
static int file_lines_iterator_it(lua_State *L);
static int file_lines_iterator(lua_State *L) {
        /* need to check second parameter first, because obj_ref_check_get
         * modifies the stack */
        size_t line = luaL_optunsigned(L, 2, 1);
        File *file = obj_ref_check_get(L, 1, VIS_LUA_TYPE_FILE);
        size_t *pos = lua_newuserdata(L, sizeof *pos);
        *pos = text_pos_by_lineno(file->text, line);
        lua_pushcclosure(L, file_lines_iterator_it, 2);
        return 1;
}

static int file_lines_iterator_it(lua_State *L) {
        File *file = *(File**)lua_touserdata(L, lua_upvalueindex(1));
        size_t *start = lua_touserdata(L, lua_upvalueindex(2));
        if (*start == text_size(file->text))
                return 0;
        size_t end = text_line_end(file->text, *start);
        size_t len = end - *start;
        char *buf = malloc(len);
        if (!buf && len)
                return 0;
        len = text_bytes_get(file->text, *start, len, buf);
        lua_pushlstring(L, buf, len);
        free(buf);
        *start = text_line_next(file->text, end);
        return 1;
}

/***
 * Get file content of position and length.
 *
 * @function content
 * @tparam int pos the 0-based file position in bytes
 * @tparam int len the length in bytes to read
 * @treturn string the file content corresponding to the range
 * @see lines
 * @usage
 * local file = vis.win.file
 * local text = file:content(0, file.size)
 */
/***
 * Get file content of range.
 *
 * @function content
 * @tparam Range range the range to read
 * @treturn string the file content corresponding to the range
 */
static int file_content(lua_State *L) {
        File *file = obj_ref_check(L, 1, VIS_LUA_TYPE_FILE);
        Filerange range = getrange(L, 2);
        if (!text_range_valid(&range))
                goto err;
        size_t len = text_range_size(&range);
        char *data = malloc(len);
        if (!data)
                goto err;
        len = text_bytes_get(file->text, range.start, len, data);
        lua_pushlstring(L, data, len);
        free(data);
        return 1;
err:
        lua_pushnil(L);
        return 1;
}

/***
 * Set mark.
 * @function mark_set
 * @tparam int pos the position to set the mark to, must be in [0, file.size]
 * @treturn Mark mark the mark which can be looked up later
 */
static int file_mark_set(lua_State *L) {
        File *file = obj_ref_check(L, 1, VIS_LUA_TYPE_FILE);
        size_t pos = checkpos(L, 2);
        Mark mark = text_mark_set(file->text, pos);
        if (mark)
                obj_lightref_new(L, (void*)mark, VIS_LUA_TYPE_MARK);
        else
                lua_pushnil(L);
        return 1;
}

/***
 * Get position of mark.
 * @function mark_get
 * @tparam Mark mark the mark to look up
 * @treturn int pos the position of the mark, or `nil` if invalid
 */
static int file_mark_get(lua_State *L) {
        File *file = obj_ref_check(L, 1, VIS_LUA_TYPE_FILE);
        Mark mark = (Mark)obj_lightref_check(L, 2, VIS_LUA_TYPE_MARK);
        size_t pos = text_mark_get(file->text, mark);
        if (pos == EPOS)
                lua_pushnil(L);
        else
                lua_pushunsigned(L, pos);
        return 1;
}

/***
 * Word text object.
 *
 * @function text_object_word
 * @tparam int pos the position which must be part of the word
 * @treturn Range range the range
 */

static int file_text_object(lua_State *L) {
        Filerange range = text_range_empty();
        File *file = obj_ref_check(L, 1, VIS_LUA_TYPE_FILE);
        size_t pos = checkpos(L, 2);
        size_t idx = lua_tointeger(L, lua_upvalueindex(1));
        if (idx < LENGTH(vis_textobjects)) {
                const TextObject *txtobj = &vis_textobjects[idx];
                if (txtobj->txt)
                        range = txtobj->txt(file->text, pos);
        }
        pushrange(L, &range);
        return 1;
}

static const struct luaL_Reg file_funcs[] = {
        { "__index", file_index },
        { "__newindex", newindex_common },
        { "insert", file_insert },
        { "delete", file_delete },
        { "lines_iterator", file_lines_iterator },
        { "content", file_content },
        { "mark_set", file_mark_set },
        { "mark_get", file_mark_get },
        { NULL, NULL },
};

static int file_lines_index(lua_State *L) {
        Text *txt = obj_ref_check(L, 1, VIS_LUA_TYPE_TEXT);
        size_t line = luaL_checkunsigned(L, 2);
        size_t start = text_pos_by_lineno(txt, line);
        size_t end = text_line_end(txt, start);
        if (start != EPOS && end != EPOS) {
                size_t size = end - start;
                char *data = malloc(size);
                if (!data && size)
                        goto err;
                size = text_bytes_get(txt, start, size, data);
                lua_pushlstring(L, data, size);
                free(data);
                return 1;
        }
err:
        lua_pushnil(L);
        return 1;
}

static int file_lines_newindex(lua_State *L) {
        Text *txt = obj_ref_check(L, 1, VIS_LUA_TYPE_TEXT);
        size_t line = luaL_checkunsigned(L, 2);
        size_t size;
        const char *data = luaL_checklstring(L, 3, &size);
        if (line == 0) {
                text_insert(txt, 0, data, size);
                text_insert_newline(txt, size);
                return 0;
        }
        size_t start = text_pos_by_lineno(txt, line);
        size_t end = text_line_end(txt, start);
        if (start != EPOS && end != EPOS) {
                text_delete(txt, start, end - start);
                text_insert(txt, start, data, size);
                if (text_size(txt) == start + size)
                        text_insert_newline(txt, text_size(txt));
        }
        return 0;
}

static int file_lines_len(lua_State *L) {
        Text *txt = obj_ref_check(L, 1, VIS_LUA_TYPE_TEXT);
        size_t lines = 0;
        char lastchar;
        size_t size = text_size(txt);
        if (size > 0)
                lines = text_lineno_by_pos(txt, size);
        if (lines > 1 && text_byte_get(txt, size-1, &lastchar) && lastchar == '\n')
                lines--;
        lua_pushunsigned(L, lines);
        return 1;
}

static const struct luaL_Reg file_lines_funcs[] = {
        { "__index", file_lines_index },
        { "__newindex", file_lines_newindex },
        { "__len", file_lines_len },
        { NULL, NULL },
};

static int file_marks_index(lua_State *L) {
        size_t pos = EPOS;
        Vis *vis = lua_touserdata(L, lua_upvalueindex(1));
        File *file = obj_ref_check_containerof(L, 1, VIS_LUA_TYPE_MARKS, offsetof(File, marks));
        if (!file)
                goto err;
        const char *symbol = luaL_checkstring(L, 2);
        if (strlen(symbol) != 1)
                goto err;
        enum VisMark mark = vis_mark_from(vis, symbol[0]);
        if (mark == VIS_MARK_INVALID)
                goto err;
        pos = text_mark_get(file->text, file->marks[mark]);
err:
        pushpos(L, pos);
        return 1;
}

static int file_marks_newindex(lua_State *L) {
        Vis *vis = lua_touserdata(L, lua_upvalueindex(1));
        File *file = obj_ref_check_containerof(L, 1, VIS_LUA_TYPE_MARKS, offsetof(File, marks));
        if (!file)
                return 0;
        const char *symbol = luaL_checkstring(L, 2);
        if (strlen(symbol) != 1)
                return 0;
        enum VisMark mark = vis_mark_from(vis, symbol[0]);
        size_t pos = luaL_checkunsigned(L, 3);
        if (mark < LENGTH(file->marks))
                file->marks[mark] = text_mark_set(file->text, pos);
        return 0;
}

static int file_marks_len(lua_State *L) {
        File *file = obj_ref_check_containerof(L, 1, VIS_LUA_TYPE_MARKS, offsetof(File, marks));
        lua_pushunsigned(L, file ? LENGTH(file->marks) : 0);
        return 1;
}

static const struct luaL_Reg file_marks_funcs[] = {
        { "__index", file_marks_index },
        { "__newindex", file_marks_newindex },
        { "__len", file_marks_len },
        { NULL, NULL },
};

/***
 * The user interface.
 *
 * @type Ui
 */
/***
 * Number of available colors.
 * @tfield int colors
 */

/***
 * A file range.
 *
 * For a valid range `start <= finish` holds.
 * An invalid range is represented as `nil`.
 * @type Range
 */
/***
 * The being of the range.
 * @tfield int start
 */
/***
 * The end of the range.
 * @tfield int finish
 */

/***
 * Modes.
 * @section Modes
 */

/***
 * Mode constants.
 * @table modes
 * @tfield int NORMAL
 * @tfield int OPERATOR_PENDING
 * @tfield int INSERT
 * @tfield int REPLACE
 * @tfield int VISUAL
 * @tfield int VISUAL_LINE
 * @see Vis:map
 * @see Window:map
 */

/***
 * Key Handling.
 *
 * This section describes the contract between the editor core and Lua
 * key handling functions mapped to symbolic keys using either @{Vis:map}
 * or @{Window:map}.
 *
 * @section Key_Handling
 */

/***
 * Example of a key handling function.
 *
 * The keyhandler is invoked with the pending content of the input queue
 * given as argument. This might be the empty string if no further input
 * is available.
 *
 * The function is expected to return the number of *bytes* it has
 * consumed from the passed input keys. A negative return value is
 * interpreted as an indication that not enough input was available. The
 * function will be called again once the user has provided more input. A
 * missing return value (i.e. `nil`) is interpreted as zero, meaning
 * no further input was consumed but the function completed successfully.
 *
 * @function keyhandler
 * @tparam string keys the keys following the mapping
 * @treturn int the number of *bytes* being consumed by the function (see above)
 * @see Vis:action_register
 * @see Vis:map
 * @see Window:map
 * @usage
 * vis:map(vis.modes.INSERT, "<C-k>", function(keys)
 *      if #keys < 2 then
 *              return -1 -- need more input
 *      end
 *      local digraph = keys:sub(1, 2)
 *      if digraph == "l*" then
 *              vis:feedkeys('λ')
 *              return 2 -- consume 2 bytes of input
 *      end
 * end, "Insert digraph")
 */

/***
 * Core Events.
 *
 * These events are invoked from the editor core.
 * The following functions are invoked if they are registered in the
 * `vis.events` table. Users scripts should generally use the [Events](#events)
 * mechanism instead which multiplexes these core events.
 *
 * @section Core_Events
 */

static void vis_lua_event_get(lua_State *L, const char *name) {
        lua_getglobal(L, "vis");
        lua_getfield(L, -1, "events");
        if (lua_istable(L, -1)) {
                lua_getfield(L, -1, name);
        }
        lua_remove(L, -2);
}

static void vis_lua_event_call(Vis *vis, const char *name) {
        lua_State *L = vis->lua;
        vis_lua_event_get(L, name);
        if (lua_isfunction(L, -1))
                pcall(vis, L, 0, 0);
        lua_pop(L, 1);
}

static bool vis_lua_path_strip(Vis *vis) {
        lua_State *L = vis->lua;
        lua_getglobal(L, "package");

        for (const char **var = (const char*[]){ "path", "cpath", NULL }; *var; var++) {

                lua_getfield(L, -1, *var);
                const char *path = lua_tostring(L, -1);
                lua_pop(L, 1);
                if (!path)
                        return false;

                char *copy = strdup(path), *stripped = calloc(1, strlen(path)+2);
                if (!copy || !stripped) {
                        free(copy);
                        free(stripped);
                        return false;
                }

                for (char *elem = copy, *stripped_elem = stripped, *next; elem; elem = next) {
                        if ((next = strstr(elem, ";")))
                                *next++ = '\0';
                        if (strstr(elem, "./"))
                                continue; /* skip relative path entries */
                        stripped_elem += sprintf(stripped_elem, "%s;", elem);
                }

                lua_pushstring(L, stripped);
                lua_setfield(L, -2, *var);

                free(copy);
                free(stripped);
        }

        lua_pop(L, 1); /* package */
        return true;
}

bool vis_lua_path_add(Vis *vis, const char *path) {
        lua_State *L = vis->lua;
        if (!L || !path)
                return false;
        lua_getglobal(L, "package");
        lua_pushstring(L, path);
        lua_pushstring(L, "/?.lua;");
        lua_getfield(L, -3, "path");
        lua_concat(L, 3);
        lua_setfield(L, -2, "path");
        lua_pop(L, 1); /* package */
        return true;
}

bool vis_lua_paths_get(Vis *vis, char **lpath, char **cpath) {
        lua_State *L = vis->lua;
        if (!L)
                return false;
        const char *s;
        lua_getglobal(L, "package");
        lua_getfield(L, -1, "path");
        s = lua_tostring(L, -1);
        *lpath = s ? strdup(s) : NULL;
        lua_getfield(L, -2, "cpath");
        s = lua_tostring(L, -1);
        *cpath = s ? strdup(s) : NULL;
        return true;
}

static bool package_exist(Vis *vis, lua_State *L, const char *name) {
        const char lua[] =
                "local name = ...\n"
                "for _, searcher in ipairs(package.searchers or package.loaders) do\n"
                        "local loader = searcher(name)\n"
                        "if type(loader) == 'function' then\n"
                                "return true\n"
                        "end\n"
                "end\n"
                "return false\n";
        if (luaL_loadstring(L, lua) != LUA_OK)
                return false;
        lua_pushstring(L, name);
        /* an error indicates package exists */
        bool ret = lua_pcall(L, 1, 1, 0) != LUA_OK || lua_toboolean(L, -1);
        lua_pop(L, 1);
        return ret;
}

static void *alloc_lua(void *ud, void *ptr, size_t osize, size_t nsize) {
        if (nsize == 0) {
                free(ptr);
                return NULL;
        } else {
                return realloc(ptr, nsize);
        }
}

/***
 * Editor initialization completed.
 * This event is emitted immediately after `visrc.lua` has been sourced, but
 * before any other events have occured, in particular the command line arguments
 * have not yet been processed.
 *
 * Can be used to set *global* configuration options.
 * @function init
 */
void vis_lua_init(Vis *vis) {
        lua_State *L = lua_newstate(alloc_lua, vis);
        if (!L)
                return;
        vis->lua = L;
        lua_atpanic(L, &panic_handler);

        luaL_openlibs(L);

#if CONFIG_LPEG
        extern int luaopen_lpeg(lua_State *L);
        lua_getglobal(L, "package");
        lua_getfield(L, -1, "preload");
        lua_pushcfunction(L, luaopen_lpeg);
        lua_setfield(L, -2, "lpeg");
        lua_pop(L, 2);
#endif

        /* remove any relative paths from lua's default package.path */
        vis_lua_path_strip(vis);

        /* extends lua's package.path with:
         * - $VIS_PATH
         * - ./lua (relative path to the binary location)
         * - $XDG_CONFIG_HOME/vis (defaulting to $HOME/.config/vis)
         * - /etc/vis (for system-wide configuration provided by administrator)
         * - /usr/(local/)?share/vis (or whatever is specified during ./configure)
         * - package.path (standard lua search path)
         */
        char path[PATH_MAX];

        vis_lua_path_add(vis, VIS_PATH);

        /* try to get users home directory */
        const char *home = getenv("HOME");
        if (!home || !*home) {
                struct passwd *pw = getpwuid(getuid());
                if (pw)
                        home = pw->pw_dir;
        }

        vis_lua_path_add(vis, "/etc/vis");

        const char *xdg_config = getenv("XDG_CONFIG_HOME");
        if (xdg_config) {
                snprintf(path, sizeof path, "%s/vis", xdg_config);
                vis_lua_path_add(vis, path);
        } else if (home && *home) {
                snprintf(path, sizeof path, "%s/.config/vis", home);
                vis_lua_path_add(vis, path);
        }

        ssize_t len = readlink("/proc/self/exe", path, sizeof(path)-1);
        if (len > 0) {
                path[len] = '\0';
                /* some idotic dirname(3) implementations return pointers to statically
                 * allocated memory, hence we use memmove to copy it back */
                char *dir = dirname(path);
                if (dir) {
                        size_t len = strlen(dir)+1;
                        if (len < sizeof(path) - sizeof("/lua")) {
                                memmove(path, dir, len);
                                strcat(path, "/lua");
                                vis_lua_path_add(vis, path);
                        }
                }
        }

        vis_lua_path_add(vis, getenv("VIS_PATH"));

        /* table in registry to lookup object type, stores metatable -> type mapping */
        lua_newtable(L);
        lua_setfield(L, LUA_REGISTRYINDEX, "vis.types");
        /* table in registry to track lifetimes of C objects */
        lua_newtable(L);
        lua_setfield(L, LUA_REGISTRYINDEX, "vis.objects");
        /* table in registry to store references to Lua functions */
        lua_newtable(L);
        lua_setfield(L, LUA_REGISTRYINDEX, "vis.functions");
        /* metatable used to type check user data */
        obj_type_new(L, VIS_LUA_TYPE_VIS);
        luaL_setfuncs(L, vis_lua, 0);
        lua_newtable(L);
        lua_setfield(L, -2, "types");
        /* create reference to main vis object, such that the further
         * calls to obj_type_new can register the type meta tables in
         * vis.types[name] */
        obj_ref_new(L, vis, "vis");
        lua_setglobal(L, "vis");

        obj_type_new(L, VIS_LUA_TYPE_FILE);

        const struct {
                enum VisTextObject id;
                const char *name;
        } textobjects[] = {
                { VIS_TEXTOBJECT_INNER_WORD, "text_object_word" },
        };

        for (size_t i = 0; i < LENGTH(textobjects); i++) {
                lua_pushunsigned(L, textobjects[i].id);
                lua_pushcclosure(L, file_text_object, 1);
                lua_setfield(L, -2, textobjects[i].name);
        }

        luaL_setfuncs(L, file_funcs, 0);

        obj_type_new(L, VIS_LUA_TYPE_TEXT);
        luaL_setfuncs(L, file_lines_funcs, 0);
        obj_type_new(L, VIS_LUA_TYPE_WINDOW);
        luaL_setfuncs(L, window_funcs, 0);

        const struct {
                enum UiStyle id;
                const char *name;
        } styles[] = {
                { UI_STYLE_DEFAULT,        "STYLE_DEFAULT"        },
                { UI_STYLE_CURSOR,         "STYLE_CURSOR"         },
                { UI_STYLE_CURSOR_PRIMARY, "STYLE_CURSOR_PRIMARY" },
                { UI_STYLE_CURSOR_LINE,    "STYLE_CURSOR_LINE"    },
                { UI_STYLE_SELECTION,      "STYLE_SELECTION"      },
                { UI_STYLE_LINENUMBER,     "STYLE_LINENUMBER"     },
                { UI_STYLE_COLOR_COLUMN,   "STYLE_COLOR_COLUMN"   },
                { UI_STYLE_STATUS,         "STYLE_STATUS"         },
                { UI_STYLE_STATUS_FOCUSED, "STYLE_STATUS_FOCUSED" },
                { UI_STYLE_SEPARATOR,      "STYLE_SEPARATOR"      },
                { UI_STYLE_INFO,           "STYLE_INFO"           },
                { UI_STYLE_EOF,            "STYLE_EOF"            },
        };

        for (size_t i = 0; i < LENGTH(styles); i++) {
                lua_pushunsigned(L, styles[i].id);
                lua_setfield(L, -2, styles[i].name);
        }

        obj_type_new(L, VIS_LUA_TYPE_MARK);
        obj_type_new(L, VIS_LUA_TYPE_MARKS);
        lua_pushlightuserdata(L, vis);
        luaL_setfuncs(L, file_marks_funcs, 1);

        obj_type_new(L, VIS_LUA_TYPE_CURSOR);
        luaL_setfuncs(L, window_cursor_funcs, 0);
        obj_type_new(L, VIS_LUA_TYPE_CURSORS);
        luaL_setfuncs(L, window_cursors_funcs, 0);

        obj_type_new(L, VIS_LUA_TYPE_UI);
        luaL_setfuncs(L, ui_funcs, 0);
        lua_pushunsigned(L, vis->ui->colors(vis->ui));
        lua_setfield(L, -2, "colors");

        obj_type_new(L, VIS_LUA_TYPE_REGISTERS);
        lua_pushlightuserdata(L, vis);
        luaL_setfuncs(L, registers_funcs, 1);

        obj_type_new(L, VIS_LUA_TYPE_KEYACTION);

        lua_getglobal(L, "vis");
        lua_getmetatable(L, -1);

        lua_pushstring(L, VERSION);
        lua_setfield(L, -2, "VERSION");

        lua_newtable(L);

        static const struct {
                enum VisMode id;
                const char *name;
        } modes[] = {
                { VIS_MODE_NORMAL,           "NORMAL"           },
                { VIS_MODE_OPERATOR_PENDING, "OPERATOR_PENDING" },
                { VIS_MODE_VISUAL,           "VISUAL"           },
                { VIS_MODE_VISUAL_LINE,      "VISUAL_LINE"      },
                { VIS_MODE_INSERT,           "INSERT"           },
                { VIS_MODE_REPLACE,          "REPLACE"          },
        };

        for (size_t i = 0; i < LENGTH(modes); i++) {
                lua_pushunsigned(L, modes[i].id);
                lua_setfield(L, -2, modes[i].name);
        }

        lua_setfield(L, -2, "modes");

        if (!package_exist(vis, L, "visrc")) {
                vis_info_show(vis, "WARNING: failed to load visrc.lua");
        } else {
                lua_getglobal(L, "require");
                lua_pushstring(L, "visrc");
                pcall(vis, L, 1, 0);
                vis_lua_event_call(vis, "init");
        }
}

/***
 * Editor startup completed.
 * This event is emitted immediately before the main loop starts.
 * At this point all files are loaded and corresponding windows are created.
 * We are about to process interactive keyboard input.
 * @function start
 */
void vis_lua_start(Vis *vis) {
        vis_lua_event_call(vis, "start");
}

/**
 * Editor is about to terminate.
 * @function quit
 */
void vis_lua_quit(Vis *vis) {
        if (!vis->lua)
                return;
        vis_lua_event_call(vis, "quit");
        lua_close(vis->lua);
        vis->lua = NULL;
}

/***
 * Input key event in either input or replace mode.
 * @function input
 * @tparam string key
 * @treturn bool whether the key was cosumed or not
 */
static bool vis_lua_input(Vis *vis, const char *key, size_t len) {
        lua_State *L = vis->lua;
        if (!L || vis->win->file->internal)
                return false;
        bool ret = false;
        vis_lua_event_get(L, "input");
        if (lua_isfunction(L, -1)) {
                lua_pushlstring(L, key, len);
                if (pcall(vis, L, 1, 1) == 0) {
                        ret = lua_isboolean(L, -1) && lua_toboolean(L, -1);
                        lua_pop(L, 1);
                }
        }
        lua_pop(L, 1);
        return ret;
}

void vis_lua_mode_insert_input(Vis *vis, const char *key, size_t len) {
        if (!vis_lua_input(vis, key, len))
                vis_insert_key(vis, key, len);
}

void vis_lua_mode_replace_input(Vis *vis, const char *key, size_t len) {
        if (!vis_lua_input(vis, key, len))
                vis_replace_key(vis, key, len);
}

/***
 * File open.
 * @function file_open
 * @tparam File file the file to be opened
 */
void vis_lua_file_open(Vis *vis, File *file) {
        debug("event: file-open: %s %p %p\n", file->name ? file->name : "unnamed", (void*)file, (void*)file->text);
        lua_State *L = vis->lua;
        if (!L)
                return;
        vis_lua_event_get(L, "file_open");
        if (lua_isfunction(L, -1)) {
                obj_ref_new(L, file, VIS_LUA_TYPE_FILE);
                pcall(vis, L, 1, 0);
        }
        lua_pop(L, 1);
}

/***
 * File pre save.
 * Triggered *before* the file is being written.
 * @function file_save_pre
 * @tparam File file the file being written
 * @tparam string path the absolute path to which the file will be written, `nil` if standard output
 * @treturn bool whether the write operation should be proceeded
 */
bool vis_lua_file_save_pre(Vis *vis, File *file, const char *path) {
        lua_State *L = vis->lua;
        if (!L)
                return true;
        vis_lua_event_get(L, "file_save_pre");
        if (lua_isfunction(L, -1)) {
                obj_ref_new(L, file, VIS_LUA_TYPE_FILE);
                lua_pushstring(L, path);
                if (pcall(vis, L, 2, 1) != 0)
                        return false;
                return !lua_isboolean(L, -1) || lua_toboolean(L, -1);
        }
        lua_pop(L, 1);
        return true;
}

/***
 * File post save.
 * Triggered *after* a successfull write operation.
 * @function file_save_post
 * @tparam File file the file which was written
 * @tparam string path the absolute path to which it was written, `nil` if standard output
 */
void vis_lua_file_save_post(Vis *vis, File *file, const char *path) {
        lua_State *L = vis->lua;
        if (!L)
                return;
        vis_lua_event_get(L, "file_save_post");
        if (lua_isfunction(L, -1)) {
                obj_ref_new(L, file, VIS_LUA_TYPE_FILE);
                lua_pushstring(L, path);
                pcall(vis, L, 2, 0);
        }
        lua_pop(L, 1);
}

/***
 * File close.
 * The last window displaying the file has been closed.
 * @function file_close
 * @tparam File file the file being closed
 */
void vis_lua_file_close(Vis *vis, File *file) {
        debug("event: file-close: %s %p %p\n", file->name ? file->name : "unnamed", (void*)file, (void*)file->text);
        lua_State *L = vis->lua;
        if (!L)
                return;
        vis_lua_event_get(L, "file_close");
        if (lua_isfunction(L, -1)) {
                obj_ref_new(L, file, VIS_LUA_TYPE_FILE);
                pcall(vis, L, 1, 0);
        }
        obj_ref_free(L, file->marks);
        obj_ref_free(L, file->text);
        obj_ref_free(L, file);
        lua_pop(L, 1);
}

/***
 * Window open.
 * A new window has been created.
 * @function win_open
 * @tparam Window win the window being opened
 */
void vis_lua_win_open(Vis *vis, Win *win) {
        debug("event: win-open: %s %p %p\n", win->file->name ? win->file->name : "unnamed", (void*)win, (void*)win->view);
        lua_State *L = vis->lua;
        if (!L)
                return;
        vis_lua_event_get(L, "win_open");
        if (lua_isfunction(L, -1)) {
                obj_ref_new(L, win, VIS_LUA_TYPE_WINDOW);
                pcall(vis, L, 1, 0);
        }
        lua_pop(L, 1);
}

/***
 * Window close.
 * An window is being closed.
 * @function win_close
 * @tparam Window win the window being closed
 */
void vis_lua_win_close(Vis *vis, Win *win) {
        debug("event: win-close: %s %p %p\n", win->file->name ? win->file->name : "unnamed", (void*)win, (void*)win->view);
        lua_State *L = vis->lua;
        if (!L)
                return;
        vis_lua_event_get(L, "win_close");
        if (lua_isfunction(L, -1)) {
                obj_ref_new(L, win, VIS_LUA_TYPE_WINDOW);
                pcall(vis, L, 1, 0);
        }
        obj_ref_free(L, win->view);
        obj_ref_free(L, win);
        lua_pop(L, 1);
}

/**
 * Window highlight.
 * The window has been redrawn and the syntax highlighting needs to be performed.
 * @function win_highlight
 * @tparam Window win the window being redrawn
 * @see style
 */
void vis_lua_win_highlight(Vis *vis, Win *win) {
        lua_State *L = vis->lua;
        if (!L)
                return;
        vis_lua_event_get(L, "win_highlight");
        if (lua_isfunction(L, -1)) {
                obj_ref_new(L, win, VIS_LUA_TYPE_WINDOW);
                pcall(vis, L, 1, 0);
        }
        lua_pop(L, 1);
}

/***
 * Window status bar redraw.
 * @function win_status
 * @tparam Window win the affected window
 * @see status
 */
void vis_lua_win_status(Vis *vis, Win *win) {
        lua_State *L = vis->lua;
        if (!L || win->file->internal) {
                window_status_update(vis, win);
                return;
        }
        vis_lua_event_get(L, "win_status");
        if (lua_isfunction(L, -1)) {
                obj_ref_new(L, win, VIS_LUA_TYPE_WINDOW);
                pcall(vis, L, 1, 0);
        } else {
                window_status_update(vis, win);
        }
        lua_pop(L, 1);
}

#endif