Update: Translations from eints

[openttd-github.git] / src / engine.cpp

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file engine.cpp Base for all engine handling. */

#include "stdafx.h"
#include "company_func.h"
#include "command_func.h"
#include "news_func.h"
#include "aircraft.h"
#include "newgrf.h"
#include "newgrf_engine.h"
#include "strings_func.h"
#include "core/random_func.hpp"
#include "window_func.h"
#include "autoreplace_gui.h"
#include "string_func.h"
#include "ai/ai.hpp"
#include "core/pool_func.hpp"
#include "engine_gui.h"
#include "engine_func.h"
#include "engine_base.h"
#include "company_base.h"
#include "vehicle_func.h"
#include "articulated_vehicles.h"
#include "error.h"
#include "engine_base.h"
#include "timer/timer.h"
#include "timer/timer_game_tick.h"
#include "timer/timer_game_calendar.h"

#include "table/strings.h"
#include "table/engines.h"

#include "safeguards.h"

EnginePool _engine_pool("Engine");
INSTANTIATE_POOL_METHODS(Engine)

EngineOverrideManager _engine_mngr;

/**
 * Year that engine aging stops. Engines will not reduce in reliability
 * and no more engines will be introduced
 */
static TimerGameCalendar::Year _year_engine_aging_stops;

/** Number of engines of each vehicle type in original engine data */
const uint8_t _engine_counts[4] = {
        lengthof(_orig_rail_vehicle_info),
        lengthof(_orig_road_vehicle_info),
        lengthof(_orig_ship_vehicle_info),
        lengthof(_orig_aircraft_vehicle_info),
};

/** Offset of the first engine of each vehicle type in original engine data */
const uint8_t _engine_offsets[4] = {
        0,
        lengthof(_orig_rail_vehicle_info),
        lengthof(_orig_rail_vehicle_info) + lengthof(_orig_road_vehicle_info),
        lengthof(_orig_rail_vehicle_info) + lengthof(_orig_road_vehicle_info) + lengthof(_orig_ship_vehicle_info),
};

static_assert(lengthof(_orig_rail_vehicle_info) + lengthof(_orig_road_vehicle_info) + lengthof(_orig_ship_vehicle_info) + lengthof(_orig_aircraft_vehicle_info) == lengthof(_orig_engine_info));

const uint EngineOverrideManager::NUM_DEFAULT_ENGINES = _engine_counts[VEH_TRAIN] + _engine_counts[VEH_ROAD] + _engine_counts[VEH_SHIP] + _engine_counts[VEH_AIRCRAFT];

Engine::Engine(VehicleType type, EngineID base)
{
        this->type = type;
        this->grf_prop.local_id = base;
        this->list_position = base;
        this->preview_company = INVALID_COMPANY;
        this->display_last_variant = INVALID_ENGINE;

        /* Check if this base engine is within the original engine data range */
        if (base >= _engine_counts[type]) {
                /* 'power' defaults to zero, so we also have to default to 'wagon' */
                if (type == VEH_TRAIN) this->u.rail.railveh_type = RAILVEH_WAGON;
                /* Set model life to maximum to make wagons available */
                this->info.base_life = 0xFF;
                /* Set road vehicle tractive effort to the default value */
                if (type == VEH_ROAD) this->u.road.tractive_effort = 0x4C;
                /* Aircraft must have INVALID_CARGO as default, as there is no property */
                if (type == VEH_AIRCRAFT) this->info.cargo_type = INVALID_CARGO;
                /* Ships must have a non-zero acceleration. */
                if (type == VEH_SHIP) this->u.ship.acceleration = 1;
                /* Set visual effect to the default value */
                switch (type) {
                        case VEH_TRAIN: this->u.rail.visual_effect = VE_DEFAULT; break;
                        case VEH_ROAD:  this->u.road.visual_effect = VE_DEFAULT; break;
                        case VEH_SHIP:  this->u.ship.visual_effect = VE_DEFAULT; break;
                        default: break; // The aircraft, disasters and especially visual effects have no NewGRF configured visual effects
                }
                /* Set cargo aging period to the default value. */
                this->info.cargo_age_period = Ticks::CARGO_AGING_TICKS;
                /* Not a variant */
                this->info.variant_id = INVALID_ENGINE;
                return;
        }

        /* Copy the original engine info for this slot */
        this->info = _orig_engine_info[_engine_offsets[type] + base];

        /* Copy the original engine data for this slot */
        switch (type) {
                default: NOT_REACHED();

                case VEH_TRAIN:
                        this->u.rail = _orig_rail_vehicle_info[base];
                        this->original_image_index = this->u.rail.image_index;
                        this->info.string_id = STR_VEHICLE_NAME_TRAIN_ENGINE_RAIL_KIRBY_PAUL_TANK_STEAM + base;

                        /* Set the default model life of original wagons to "infinite" */
                        if (this->u.rail.railveh_type == RAILVEH_WAGON) this->info.base_life = 0xFF;

                        break;

                case VEH_ROAD:
                        this->u.road = _orig_road_vehicle_info[base];
                        this->original_image_index = this->u.road.image_index;
                        this->info.string_id = STR_VEHICLE_NAME_ROAD_VEHICLE_MPS_REGAL_BUS + base;
                        break;

                case VEH_SHIP:
                        this->u.ship = _orig_ship_vehicle_info[base];
                        this->original_image_index = this->u.ship.image_index;
                        this->info.string_id = STR_VEHICLE_NAME_SHIP_MPS_OIL_TANKER + base;
                        break;

                case VEH_AIRCRAFT:
                        this->u.air = _orig_aircraft_vehicle_info[base];
                        this->original_image_index = this->u.air.image_index;
                        this->info.string_id = STR_VEHICLE_NAME_AIRCRAFT_SAMPSON_U52 + base;
                        break;
        }
}

/**
 * Checks whether the engine is a valid (non-articulated part of an) engine.
 * @return true if enabled
 */
bool Engine::IsEnabled() const
{
        return this->info.string_id != STR_NEWGRF_INVALID_ENGINE && HasBit(this->info.climates, _settings_game.game_creation.landscape);
}

/**
 * Retrieve the GRF ID of the NewGRF the engine is tied to.
 * This is the GRF providing the Action 3.
 * @return GRF ID of the associated NewGRF.
 */
uint32_t Engine::GetGRFID() const
{
        const GRFFile *file = this->GetGRF();
        return file == nullptr ? 0 : file->grfid;
}

/**
 * Determines whether an engine can carry something.
 * A vehicle cannot carry anything if its capacity is zero, or none of the possible cargoes is available in the climate.
 * @return true if the vehicle can carry something.
 */
bool Engine::CanCarryCargo() const
{
        /* For engines that can appear in a consist (i.e. rail vehicles and (articulated) road vehicles), a capacity
         * of zero is a special case, to define the vehicle to not carry anything. The default cargotype is still used
         * for livery selection etc.
         * Note: Only the property is tested. A capacity callback returning 0 does not have the same effect.
         */
        switch (this->type) {
                case VEH_TRAIN:
                        if (this->u.rail.capacity == 0) return false;
                        break;

                case VEH_ROAD:
                        if (this->u.road.capacity == 0) return false;
                        break;

                case VEH_SHIP:
                case VEH_AIRCRAFT:
                        break;

                default: NOT_REACHED();
        }
        return IsValidCargoID(this->GetDefaultCargoType());
}


/**
 * Determines capacity of a given vehicle from scratch.
 * For aircraft the main capacity is determined. Mail might be present as well.
 * @param v Vehicle of interest; nullptr in purchase list
 * @param mail_capacity returns secondary cargo (mail) capacity of aircraft
 * @return Capacity
 */
uint Engine::DetermineCapacity(const Vehicle *v, uint16_t *mail_capacity) const
{
        assert(v == nullptr || this->index == v->engine_type);
        if (mail_capacity != nullptr) *mail_capacity = 0;

        if (!this->CanCarryCargo()) return 0;

        bool new_multipliers = HasBit(this->info.misc_flags, EF_NO_DEFAULT_CARGO_MULTIPLIER);
        CargoID default_cargo = this->GetDefaultCargoType();
        CargoID cargo_type = (v != nullptr) ? v->cargo_type : default_cargo;

        if (mail_capacity != nullptr && this->type == VEH_AIRCRAFT && IsCargoInClass(cargo_type, CC_PASSENGERS)) {
                *mail_capacity = GetEngineProperty(this->index, PROP_AIRCRAFT_MAIL_CAPACITY, this->u.air.mail_capacity, v);
        }

        /* Check the refit capacity callback if we are not in the default configuration, or if we are using the new multiplier algorithm. */
        if (HasBit(this->info.callback_mask, CBM_VEHICLE_REFIT_CAPACITY) &&
                        (new_multipliers || default_cargo != cargo_type || (v != nullptr && v->cargo_subtype != 0))) {
                uint16_t callback = GetVehicleCallback(CBID_VEHICLE_REFIT_CAPACITY, 0, 0, this->index, v);
                if (callback != CALLBACK_FAILED) return callback;
        }

        /* Get capacity according to property resp. CB */
        uint capacity;
        uint extra_mail_cap = 0;
        switch (this->type) {
                case VEH_TRAIN:
                        capacity = GetEngineProperty(this->index, PROP_TRAIN_CARGO_CAPACITY,        this->u.rail.capacity, v);

                        /* In purchase list add the capacity of the second head. Always use the plain property for this. */
                        if (v == nullptr && this->u.rail.railveh_type == RAILVEH_MULTIHEAD) capacity += this->u.rail.capacity;
                        break;

                case VEH_ROAD:
                        capacity = GetEngineProperty(this->index, PROP_ROADVEH_CARGO_CAPACITY,      this->u.road.capacity, v);
                        break;

                case VEH_SHIP:
                        capacity = GetEngineProperty(this->index, PROP_SHIP_CARGO_CAPACITY,         this->u.ship.capacity, v);
                        break;

                case VEH_AIRCRAFT:
                        capacity = GetEngineProperty(this->index, PROP_AIRCRAFT_PASSENGER_CAPACITY, this->u.air.passenger_capacity, v);
                        if (!IsCargoInClass(cargo_type, CC_PASSENGERS)) {
                                extra_mail_cap = GetEngineProperty(this->index, PROP_AIRCRAFT_MAIL_CAPACITY, this->u.air.mail_capacity, v);
                        }
                        if (IsValidCargoID(GetCargoIDByLabel(CT_MAIL))) {
                                if (!new_multipliers && cargo_type == GetCargoIDByLabel(CT_MAIL)) return capacity + extra_mail_cap;
                        }
                        default_cargo = GetCargoIDByLabel(CT_PASSENGERS); // Always use 'passengers' wrt. cargo multipliers
                        break;

                default: NOT_REACHED();
        }

        if (!new_multipliers) {
                /* Use the passenger multiplier for mail as well */
                capacity += extra_mail_cap;
                extra_mail_cap = 0;
        }

        /* Apply multipliers depending on cargo- and vehicletype. */
        if (new_multipliers || (this->type != VEH_SHIP && default_cargo != cargo_type)) {
                uint16_t default_multiplier = new_multipliers ? 0x100 : CargoSpec::Get(default_cargo)->multiplier;
                uint16_t cargo_multiplier = CargoSpec::Get(cargo_type)->multiplier;
                capacity *= cargo_multiplier;
                if (extra_mail_cap > 0 && IsValidCargoID(GetCargoIDByLabel(CT_MAIL))) {
                        uint mail_multiplier = CargoSpec::Get(GetCargoIDByLabel(CT_MAIL))->multiplier;
                        capacity += (default_multiplier * extra_mail_cap * cargo_multiplier + mail_multiplier / 2) / mail_multiplier;
                }
                capacity = (capacity + default_multiplier / 2) / default_multiplier;
        }

        return capacity;
}

/**
 * Return how much the running costs of this engine are.
 * @return Yearly running cost of the engine.
 */
Money Engine::GetRunningCost() const
{
        Price base_price;
        uint cost_factor;
        switch (this->type) {
                case VEH_ROAD:
                        base_price = this->u.road.running_cost_class;
                        if (base_price == INVALID_PRICE) return 0;
                        cost_factor = GetEngineProperty(this->index, PROP_ROADVEH_RUNNING_COST_FACTOR, this->u.road.running_cost);
                        break;

                case VEH_TRAIN:
                        base_price = this->u.rail.running_cost_class;
                        if (base_price == INVALID_PRICE) return 0;
                        cost_factor = GetEngineProperty(this->index, PROP_TRAIN_RUNNING_COST_FACTOR, this->u.rail.running_cost);
                        break;

                case VEH_SHIP:
                        base_price = PR_RUNNING_SHIP;
                        cost_factor = GetEngineProperty(this->index, PROP_SHIP_RUNNING_COST_FACTOR, this->u.ship.running_cost);
                        break;

                case VEH_AIRCRAFT:
                        base_price = PR_RUNNING_AIRCRAFT;
                        cost_factor = GetEngineProperty(this->index, PROP_AIRCRAFT_RUNNING_COST_FACTOR, this->u.air.running_cost);
                        break;

                default: NOT_REACHED();
        }

        return GetPrice(base_price, cost_factor, this->GetGRF(), -8);
}

/**
 * Return how much a new engine costs.
 * @return Cost of the engine.
 */
Money Engine::GetCost() const
{
        Price base_price;
        uint cost_factor;
        switch (this->type) {
                case VEH_ROAD:
                        base_price = PR_BUILD_VEHICLE_ROAD;
                        cost_factor = GetEngineProperty(this->index, PROP_ROADVEH_COST_FACTOR, this->u.road.cost_factor);
                        break;

                case VEH_TRAIN:
                        if (this->u.rail.railveh_type == RAILVEH_WAGON) {
                                base_price = PR_BUILD_VEHICLE_WAGON;
                                cost_factor = GetEngineProperty(this->index, PROP_TRAIN_COST_FACTOR, this->u.rail.cost_factor);
                        } else {
                                base_price = PR_BUILD_VEHICLE_TRAIN;
                                cost_factor = GetEngineProperty(this->index, PROP_TRAIN_COST_FACTOR, this->u.rail.cost_factor);
                        }
                        break;

                case VEH_SHIP:
                        base_price = PR_BUILD_VEHICLE_SHIP;
                        cost_factor = GetEngineProperty(this->index, PROP_SHIP_COST_FACTOR, this->u.ship.cost_factor);
                        break;

                case VEH_AIRCRAFT:
                        base_price = PR_BUILD_VEHICLE_AIRCRAFT;
                        cost_factor = GetEngineProperty(this->index, PROP_AIRCRAFT_COST_FACTOR, this->u.air.cost_factor);
                        break;

                default: NOT_REACHED();
        }

        return GetPrice(base_price, cost_factor, this->GetGRF(), -8);
}

/**
 * Returns max speed of the engine for display purposes
 * @return max speed in km-ish/h
 */
uint Engine::GetDisplayMaxSpeed() const
{
        switch (this->type) {
                case VEH_TRAIN:
                        return GetEngineProperty(this->index, PROP_TRAIN_SPEED, this->u.rail.max_speed);

                case VEH_ROAD: {
                        uint max_speed = GetEngineProperty(this->index, PROP_ROADVEH_SPEED, 0);
                        return (max_speed != 0) ? max_speed * 2 : this->u.road.max_speed / 2;
                }

                case VEH_SHIP:
                        return GetEngineProperty(this->index, PROP_SHIP_SPEED, this->u.ship.max_speed) / 2;

                case VEH_AIRCRAFT: {
                        uint max_speed = GetEngineProperty(this->index, PROP_AIRCRAFT_SPEED, 0);
                        if (max_speed != 0) {
                                return (max_speed * 128) / 10;
                        }
                        return this->u.air.max_speed;
                }

                default: NOT_REACHED();
        }
}

/**
 * Returns the power of the engine for display
 * and sorting purposes.
 * Only trains and road vehicles have power
 * @return power in display units hp
 */
uint Engine::GetPower() const
{
        /* Only trains and road vehicles have 'power'. */
        switch (this->type) {
                case VEH_TRAIN:
                        return GetEngineProperty(this->index, PROP_TRAIN_POWER, this->u.rail.power);
                case VEH_ROAD:
                        return GetEngineProperty(this->index, PROP_ROADVEH_POWER, this->u.road.power) * 10;

                default: NOT_REACHED();
        }
}

/**
 * Returns the weight of the engine for display purposes.
 * For dual-headed train-engines this is the weight of both heads
 * @return weight in display units metric tons
 */
uint Engine::GetDisplayWeight() const
{
        /* Only trains and road vehicles have 'weight'. */
        switch (this->type) {
                case VEH_TRAIN:
                        return GetEngineProperty(this->index, PROP_TRAIN_WEIGHT, this->u.rail.weight) << (this->u.rail.railveh_type == RAILVEH_MULTIHEAD ? 1 : 0);
                case VEH_ROAD:
                        return GetEngineProperty(this->index, PROP_ROADVEH_WEIGHT, this->u.road.weight) / 4;

                default: NOT_REACHED();
        }
}

/**
 * Returns the tractive effort of the engine for display purposes.
 * For dual-headed train-engines this is the tractive effort of both heads
 * @return tractive effort in display units kN
 */
uint Engine::GetDisplayMaxTractiveEffort() const
{
        /* Only trains and road vehicles have 'tractive effort'. */
        switch (this->type) {
                case VEH_TRAIN:
                        return (GROUND_ACCELERATION * this->GetDisplayWeight() * GetEngineProperty(this->index, PROP_TRAIN_TRACTIVE_EFFORT, this->u.rail.tractive_effort)) / 256;
                case VEH_ROAD:
                        return (GROUND_ACCELERATION * this->GetDisplayWeight() * GetEngineProperty(this->index, PROP_ROADVEH_TRACTIVE_EFFORT, this->u.road.tractive_effort)) / 256;

                default: NOT_REACHED();
        }
}

/**
 * Returns the vehicle's (not model's!) life length in days.
 * @return the life length
 */
TimerGameCalendar::Date Engine::GetLifeLengthInDays() const
{
        /* Assume leap years; this gives the player a bit more than the given amount of years, but never less. */
        return (this->info.lifelength + _settings_game.vehicle.extend_vehicle_life).base() * CalendarTime::DAYS_IN_LEAP_YEAR;
}

/**
 * Get the range of an aircraft type.
 * @return Range of the aircraft type in tiles or 0 if unlimited range.
 */
uint16_t Engine::GetRange() const
{
        switch (this->type) {
                case VEH_AIRCRAFT:
                        return GetEngineProperty(this->index, PROP_AIRCRAFT_RANGE, this->u.air.max_range);

                default: NOT_REACHED();
        }
}

/**
 * Get the name of the aircraft type for display purposes.
 * @return Aircraft type string.
 */
StringID Engine::GetAircraftTypeText() const
{
        switch (this->type) {
                case VEH_AIRCRAFT:
                        switch (this->u.air.subtype) {
                                case AIR_HELI: return STR_LIVERY_HELICOPTER;
                                case AIR_CTOL: return STR_LIVERY_SMALL_PLANE;
                                case AIR_CTOL | AIR_FAST: return STR_LIVERY_LARGE_PLANE;
                                default: NOT_REACHED();
                        }

                default: NOT_REACHED();
        }
}

/**
 * Check whether the engine variant chain is hidden in the GUI for the given company.
 * @param c Company to check.
 * @return \c true iff the engine variant chain is hidden in the GUI for the given company.
 */
bool Engine::IsVariantHidden(CompanyID c) const
{
        /* In case company is spectator. */
        if (c >= MAX_COMPANIES) return false;

        /* Shortcut if this engine is explicitly hidden. */
        if (this->IsHidden(c)) return true;

        /* Check for hidden parent variants. This is a bit convoluted as we must check hidden status of
         * the last display variant rather than the actual parent variant. */
        const Engine *re = this;
        const Engine *ve = re->GetDisplayVariant();
        while (!(ve->IsHidden(c)) && re->info.variant_id != INVALID_ENGINE) {
                re = Engine::Get(re->info.variant_id);
                ve = re->GetDisplayVariant();
        }
        return ve->IsHidden(c);
}

/**
 * Initializes the #EngineOverrideManager with the default engines.
 */
void EngineOverrideManager::ResetToDefaultMapping()
{
        this->clear();
        for (VehicleType type = VEH_TRAIN; type <= VEH_AIRCRAFT; type++) {
                for (uint internal_id = 0; internal_id < _engine_counts[type]; internal_id++) {
                        EngineIDMapping &eid = this->emplace_back();
                        eid.type            = type;
                        eid.grfid           = INVALID_GRFID;
                        eid.internal_id     = internal_id;
                        eid.substitute_id   = internal_id;
                }
        }
}

/**
 * Looks up an EngineID in the EngineOverrideManager
 * @param type Vehicle type
 * @param grf_local_id The local id in the newgrf
 * @param grfid The GrfID that defines the scope of grf_local_id.
 *              If a newgrf overrides the engines of another newgrf, the "scope grfid" is the ID of the overridden newgrf.
 *              If dynnamic_engines is disabled, all newgrf share the same ID scope identified by INVALID_GRFID.
 * @return The engine ID if present, or INVALID_ENGINE if not.
 */
EngineID EngineOverrideManager::GetID(VehicleType type, uint16_t grf_local_id, uint32_t grfid)
{
        EngineID index = 0;
        for (const EngineIDMapping &eid : *this) {
                if (eid.type == type && eid.grfid == grfid && eid.internal_id == grf_local_id) {
                        return index;
                }
                index++;
        }
        return INVALID_ENGINE;
}

/**
 * Tries to reset the engine mapping to match the current NewGRF configuration.
 * This is only possible when there are currently no vehicles in the game.
 * @return false if resetting failed due to present vehicles.
 */
bool EngineOverrideManager::ResetToCurrentNewGRFConfig()
{
        for (const Vehicle *v : Vehicle::Iterate()) {
                if (IsCompanyBuildableVehicleType(v)) return false;
        }

        /* Reset the engines, they will get new EngineIDs */
        _engine_mngr.ResetToDefaultMapping();
        ReloadNewGRFData();

        return true;
}

/**
 * Initialise the engine pool with the data from the original vehicles.
 */
void SetupEngines()
{
        CloseWindowByClass(WC_ENGINE_PREVIEW);
        _engine_pool.CleanPool();

        assert(_engine_mngr.size() >= _engine_mngr.NUM_DEFAULT_ENGINES);
        [[maybe_unused]] uint index = 0;
        for (const EngineIDMapping &eid : _engine_mngr) {
                /* Assert is safe; there won't be more than 256 original vehicles
                 * in any case, and we just cleaned the pool. */
                assert(Engine::CanAllocateItem());
                [[maybe_unused]] const Engine *e = new Engine(eid.type, eid.internal_id);
                assert(e->index == index);
                index++;
        }
}

void ShowEnginePreviewWindow(EngineID engine);

/**
 * Determine whether an engine type is a wagon (and not a loco).
 * @param index %Engine getting queried.
 * @return Whether the queried engine is a wagon.
 */
static bool IsWagon(EngineID index)
{
        const Engine *e = Engine::Get(index);
        return e->type == VEH_TRAIN && e->u.rail.railveh_type == RAILVEH_WAGON;
}

/**
 * Ensure engine is not set as the last used variant for any other engine.
 * @param engine_id Engine being removed.
 * @param type      Type of engine.
 */
static void ClearLastVariant(EngineID engine_id, VehicleType type)
{
        for (Engine *e : Engine::IterateType(type)) {
                if (e->display_last_variant == engine_id) e->display_last_variant = INVALID_ENGINE;
        }
}

/**
 * Update #Engine::reliability and (if needed) update the engine GUIs.
 * @param e %Engine to update.
 */
void CalcEngineReliability(Engine *e, bool new_month)
{
        /* Get source engine for reliability age. This is normally our engine unless variant reliability syncing is requested. */
        Engine *re = e;
        while (re->info.variant_id != INVALID_ENGINE && HasFlag(re->info.extra_flags, ExtraEngineFlags::SyncReliability)) {
                re = Engine::Get(re->info.variant_id);
        }

        uint32_t age = re->age;
        if (new_month && re->index > e->index && age != INT32_MAX) age++; /* parent variant's age has not yet updated. */

        /* Check for early retirement */
        if (e->company_avail != 0 && !_settings_game.vehicle.never_expire_vehicles && e->info.base_life != 0xFF) {
                int retire_early = e->info.retire_early;
                uint retire_early_max_age = std::max(0, e->duration_phase_1 + e->duration_phase_2 - retire_early * 12);
                if (retire_early != 0 && age >= retire_early_max_age) {
                        /* Early retirement is enabled and we're past the date... */
                        e->company_avail = 0;
                        ClearLastVariant(e->index, e->type);
                        AddRemoveEngineFromAutoreplaceAndBuildWindows(e->type);
                }
        }

        if (age < e->duration_phase_1) {
                uint start = e->reliability_start;
                e->reliability = age * (e->reliability_max - start) / e->duration_phase_1 + start;
        } else if ((age -= e->duration_phase_1) < e->duration_phase_2 || _settings_game.vehicle.never_expire_vehicles || e->info.base_life == 0xFF) {
                /* We are at the peak of this engines life. It will have max reliability.
                 * This is also true if the engines never expire. They will not go bad over time */
                e->reliability = e->reliability_max;
        } else if ((age -= e->duration_phase_2) < e->duration_phase_3) {
                uint max = e->reliability_max;
                e->reliability = (int)age * (int)(e->reliability_final - max) / e->duration_phase_3 + max;
        } else {
                /* time's up for this engine.
                 * We will now completely retire this design */
                e->company_avail = 0;
                e->reliability = e->reliability_final;
                /* Kick this engine out of the lists */
                ClearLastVariant(e->index, e->type);
                AddRemoveEngineFromAutoreplaceAndBuildWindows(e->type);
        }

}

/** Compute the value for #_year_engine_aging_stops. */
void SetYearEngineAgingStops()
{
        /* Determine last engine aging year, default to 2050 as previously. */
        _year_engine_aging_stops = 2050;

        for (const Engine *e : Engine::Iterate()) {
                const EngineInfo *ei = &e->info;

                /* Exclude certain engines */
                if (!HasBit(ei->climates, _settings_game.game_creation.landscape)) continue;
                if (e->type == VEH_TRAIN && e->u.rail.railveh_type == RAILVEH_WAGON) continue;

                /* Base year ending date on half the model life */
                TimerGameCalendar::YearMonthDay ymd = TimerGameCalendar::ConvertDateToYMD(ei->base_intro + (ei->lifelength.base() * CalendarTime::DAYS_IN_LEAP_YEAR) / 2);

                _year_engine_aging_stops = std::max(_year_engine_aging_stops, ymd.year);
        }
}

/**
 * Start/initialise one engine.
 * @param e The engine to initialise.
 * @param aging_date The date used for age calculations.
 * @param seed Random seed.
 */
void StartupOneEngine(Engine *e, const TimerGameCalendar::YearMonthDay &aging_ymd, uint32_t seed)
{
        const EngineInfo *ei = &e->info;

        e->age = 0;
        e->flags = 0;
        e->company_avail = 0;
        e->company_hidden = 0;

        /* Vehicles with the same base_intro date shall be introduced at the same time.
         * Make sure they use the same randomisation of the date. */
        SavedRandomSeeds saved_seeds;
        SaveRandomSeeds(&saved_seeds);
        SetRandomSeed(_settings_game.game_creation.generation_seed ^ seed ^
                      ei->base_intro.base() ^
                      e->type ^
                      e->GetGRFID());
        uint32_t r = Random();

        /* Don't randomise the start-date in the first two years after gamestart to ensure availability
         * of engines in early starting games.
         * Note: TTDP uses fixed 1922 */
        e->intro_date = ei->base_intro <= TimerGameCalendar::ConvertYMDToDate(_settings_game.game_creation.starting_year + 2, 0, 1) ? ei->base_intro : (TimerGameCalendar::Date)GB(r, 0, 9) + ei->base_intro;
        if (e->intro_date <= TimerGameCalendar::date) {
                TimerGameCalendar::YearMonthDay intro_ymd = TimerGameCalendar::ConvertDateToYMD(e->intro_date);
                int aging_months = aging_ymd.year.base() * 12 + aging_ymd.month;
                int intro_months = intro_ymd.year.base() * 12 + intro_ymd.month;
                if (intro_ymd.day > 1) intro_months++; // Engines are introduced at the first month start at/after intro date.
                e->age = aging_months - intro_months;
                e->company_avail = MAX_UVALUE(CompanyMask);
                e->flags |= ENGINE_AVAILABLE;
        }

        /* Get parent variant index for syncing reliability via random seed. */
        const Engine *re = e;
        while (re->info.variant_id != INVALID_ENGINE && HasFlag(re->info.extra_flags, ExtraEngineFlags::SyncReliability)) {
                re = Engine::Get(re->info.variant_id);
        }

        SetRandomSeed(_settings_game.game_creation.generation_seed ^ seed ^
                      (re->index << 16) ^ (re->info.base_intro.base() << 12) ^ (re->info.decay_speed << 8) ^
                      (re->info.lifelength.base() << 4) ^ re->info.retire_early ^
                      e->type ^
                      e->GetGRFID());

        /* Base reliability defined as a percentage of UINT16_MAX. */
        const uint16_t RELIABILITY_START = UINT16_MAX * 48 / 100;
        const uint16_t RELIABILITY_MAX   = UINT16_MAX * 75 / 100;
        const uint16_t RELIABILITY_FINAL = UINT16_MAX * 25 / 100;

        static_assert(RELIABILITY_START == 0x7AE0);
        static_assert(RELIABILITY_MAX   == 0xBFFF);
        static_assert(RELIABILITY_FINAL == 0x3FFF);

        r = Random();
        /* 14 bits gives a value between 0 and 16383, which is up to an additional 25%p reliability on top of the base reliability. */
        e->reliability_start = GB(r, 16, 14) + RELIABILITY_START;
        e->reliability_max   = GB(r,  0, 14) + RELIABILITY_MAX;

        r = Random();
        e->reliability_final = GB(r, 16, 14) + RELIABILITY_FINAL;

        e->duration_phase_1 = GB(r, 0, 5) + 7;
        e->duration_phase_2 = std::max(0, int(GB(r, 5, 4)) + ei->base_life.base() * 12 - 96);
        e->duration_phase_3 = GB(r, 9, 7) + 120;

        RestoreRandomSeeds(saved_seeds);

        e->reliability_spd_dec = ei->decay_speed << 2;

        /* prevent certain engines from ever appearing. */
        if (!HasBit(ei->climates, _settings_game.game_creation.landscape)) {
                e->flags |= ENGINE_AVAILABLE;
                e->company_avail = 0;
        }
}

/**
 * Start/initialise all our engines. Must be called whenever there are changes
 * to the NewGRF config.
 */
void StartupEngines()
{
        /* Aging of vehicles stops, so account for that when starting late */
        const TimerGameCalendar::Date aging_date = std::min(TimerGameCalendar::date, TimerGameCalendar::ConvertYMDToDate(_year_engine_aging_stops, 0, 1));
        TimerGameCalendar::YearMonthDay aging_ymd = TimerGameCalendar::ConvertDateToYMD(aging_date);
        uint32_t seed = Random();

        for (Engine *e : Engine::Iterate()) {
                StartupOneEngine(e, aging_ymd, seed);
        }
        for (Engine *e : Engine::Iterate()) {
                CalcEngineReliability(e, false);
        }

        /* Update the bitmasks for the vehicle lists */
        for (Company *c : Company::Iterate()) {
                c->avail_railtypes = GetCompanyRailTypes(c->index);
                c->avail_roadtypes = GetCompanyRoadTypes(c->index);
        }

        /* Invalidate any open purchase lists */
        InvalidateWindowClassesData(WC_BUILD_VEHICLE);

        SetWindowClassesDirty(WC_BUILD_VEHICLE);
        SetWindowClassesDirty(WC_REPLACE_VEHICLE);
}

/**
 * Allows engine \a eid to be used by a company \a company.
 * @param eid The engine to enable.
 * @param company The company to allow using the engine.
 */
static void EnableEngineForCompany(EngineID eid, CompanyID company)
{
        Engine *e = Engine::Get(eid);
        Company *c = Company::Get(company);

        SetBit(e->company_avail, company);
        if (e->type == VEH_TRAIN) {
                c->avail_railtypes = GetCompanyRailTypes(c->index);
        } else if (e->type == VEH_ROAD) {
                c->avail_roadtypes = GetCompanyRoadTypes(c->index);
        }

        if (company == _local_company) {
                AddRemoveEngineFromAutoreplaceAndBuildWindows(e->type);

                /* Update the toolbar. */
                InvalidateWindowData(WC_MAIN_TOOLBAR, 0);
                if (e->type == VEH_ROAD) InvalidateWindowData(WC_BUILD_TOOLBAR, TRANSPORT_ROAD);
                if (e->type == VEH_SHIP) InvalidateWindowData(WC_BUILD_TOOLBAR, TRANSPORT_WATER);
                if (e->type == VEH_AIRCRAFT) InvalidateWindowData(WC_BUILD_TOOLBAR, TRANSPORT_AIR);
        }
}

/**
 * Forbids engine \a eid to be used by a company \a company.
 * @param eid The engine to disable.
 * @param company The company to forbid using the engine.
 */
static void DisableEngineForCompany(EngineID eid, CompanyID company)
{
        Engine *e = Engine::Get(eid);
        Company *c = Company::Get(company);

        ClrBit(e->company_avail, company);
        if (e->type == VEH_TRAIN) {
                c->avail_railtypes = GetCompanyRailTypes(c->index);
        } else if (e->type == VEH_ROAD) {
                c->avail_roadtypes = GetCompanyRoadTypes(c->index);
        }

        if (company == _local_company) {
                ClearLastVariant(e->index, e->type);
                AddRemoveEngineFromAutoreplaceAndBuildWindows(e->type);
        }
}

/**
 * Company \a company accepts engine \a eid for preview.
 * @param eid Engine being accepted (is under preview).
 * @param company Current company previewing the engine.
 * @param recursion_depth Recursion depth to avoid infinite loop.
 */
static void AcceptEnginePreview(EngineID eid, CompanyID company, int recursion_depth = 0)
{
        Engine *e = Engine::Get(eid);

        e->preview_company = INVALID_COMPANY;
        e->preview_asked = MAX_UVALUE(CompanyMask);

        EnableEngineForCompany(eid, company);

        /* Notify preview window, that it might want to close.
         * Note: We cannot directly close the window.
         *       In singleplayer this function is called from the preview window, so
         *       we have to use the GUI-scope scheduling of InvalidateWindowData.
         */
        InvalidateWindowData(WC_ENGINE_PREVIEW, eid);

        /* Don't search for variants to include if we are 10 levels deep already. */
        if (recursion_depth >= 10) return;

        /* Find variants to be included in preview. */
        for (Engine *ve : Engine::IterateType(e->type)) {
                if (ve->index != eid && ve->info.variant_id == eid && HasFlag(ve->info.extra_flags, ExtraEngineFlags::JoinPreview)) {
                        AcceptEnginePreview(ve->index, company, recursion_depth + 1);
                }
        }
}

/**
 * Get the best company for an engine preview.
 * @param e Engine to preview.
 * @return Best company if it exists, #INVALID_COMPANY otherwise.
 */
static CompanyID GetPreviewCompany(Engine *e)
{
        CompanyID best_company = INVALID_COMPANY;

        /* For trains the cargomask has no useful meaning, since you can attach other wagons */
        CargoTypes cargomask = e->type != VEH_TRAIN ? GetUnionOfArticulatedRefitMasks(e->index, true) : ALL_CARGOTYPES;

        int32_t best_hist = -1;
        for (const Company *c : Company::Iterate()) {
                if (c->block_preview == 0 && !HasBit(e->preview_asked, c->index) &&
                                c->old_economy[0].performance_history > best_hist) {

                        /* Check whether the company uses similar vehicles */
                        for (const Vehicle *v : Vehicle::Iterate()) {
                                if (v->owner != c->index || v->type != e->type) continue;
                                if (!v->GetEngine()->CanCarryCargo() || !HasBit(cargomask, v->cargo_type)) continue;

                                best_hist = c->old_economy[0].performance_history;
                                best_company = c->index;
                                break;
                        }
                }
        }

        return best_company;
}

/**
 * Checks if a vehicle type is disabled for all/ai companies.
 * @param type The vehicle type which shall be checked.
 * @param ai If true, check if the type is disabled for AI companies, otherwise check if
 *           the vehicle type is disabled for human companies.
 * @return Whether or not a vehicle type is disabled.
 */
static bool IsVehicleTypeDisabled(VehicleType type, bool ai)
{
        switch (type) {
                case VEH_TRAIN:    return _settings_game.vehicle.max_trains == 0   || (ai && _settings_game.ai.ai_disable_veh_train);
                case VEH_ROAD:     return _settings_game.vehicle.max_roadveh == 0  || (ai && _settings_game.ai.ai_disable_veh_roadveh);
                case VEH_SHIP:     return _settings_game.vehicle.max_ships == 0    || (ai && _settings_game.ai.ai_disable_veh_ship);
                case VEH_AIRCRAFT: return _settings_game.vehicle.max_aircraft == 0 || (ai && _settings_game.ai.ai_disable_veh_aircraft);

                default: NOT_REACHED();
        }
}

/** Daily check to offer an exclusive engine preview to the companies. */
static IntervalTimer<TimerGameCalendar> _calendar_engines_daily({TimerGameCalendar::DAY, TimerGameCalendar::Priority::ENGINE}, [](auto)
{
        for (Company *c : Company::Iterate()) {
                c->avail_railtypes = AddDateIntroducedRailTypes(c->avail_railtypes, TimerGameCalendar::date);
                c->avail_roadtypes = AddDateIntroducedRoadTypes(c->avail_roadtypes, TimerGameCalendar::date);
        }

        if (TimerGameCalendar::year >= _year_engine_aging_stops) return;

        for (Engine *e : Engine::Iterate()) {
                EngineID i = e->index;
                if (e->flags & ENGINE_EXCLUSIVE_PREVIEW) {
                        if (e->preview_company != INVALID_COMPANY) {
                                if (!--e->preview_wait) {
                                        CloseWindowById(WC_ENGINE_PREVIEW, i);
                                        e->preview_company = INVALID_COMPANY;
                                }
                        } else if (CountBits(e->preview_asked) < MAX_COMPANIES) {
                                e->preview_company = GetPreviewCompany(e);

                                if (e->preview_company == INVALID_COMPANY) {
                                        e->preview_asked = MAX_UVALUE(CompanyMask);
                                        continue;
                                }

                                SetBit(e->preview_asked, e->preview_company);
                                e->preview_wait = 20;
                                /* AIs are intentionally not skipped for preview even if they cannot build a certain
                                 * vehicle type. This is done to not give poor performing human companies an "unfair"
                                 * boost that they wouldn't have gotten against other human companies. The check on
                                 * the line below is just to make AIs not notice that they have a preview if they
                                 * cannot build the vehicle. */
                                if (!IsVehicleTypeDisabled(e->type, true)) AI::NewEvent(e->preview_company, new ScriptEventEnginePreview(i));
                                if (IsInteractiveCompany(e->preview_company)) ShowEnginePreviewWindow(i);
                        }
                }
        }
});

/**
 * Clear the 'hidden' flag for all engines of a new company.
 * @param cid Company being created.
 */
void ClearEnginesHiddenFlagOfCompany(CompanyID cid)
{
        for (Engine *e : Engine::Iterate()) {
                SB(e->company_hidden, cid, 1, 0);
        }
}

/**
 * Set the visibility of an engine.
 * @param flags Operation to perform.
 * @param engine_id Engine id..
 * @param hide Set for hidden, unset for visible.
 * @return The cost of this operation or an error.
 */
CommandCost CmdSetVehicleVisibility(DoCommandFlag flags, EngineID engine_id, bool hide)
{
        Engine *e = Engine::GetIfValid(engine_id);
        if (e == nullptr || _current_company >= MAX_COMPANIES) return CMD_ERROR;
        if (!IsEngineBuildable(e->index, e->type, _current_company)) return CMD_ERROR;

        if ((flags & DC_EXEC) != 0) {
                AssignBit(e->company_hidden, _current_company, hide);
                AddRemoveEngineFromAutoreplaceAndBuildWindows(e->type);
        }

        return CommandCost();
}

/**
 * Accept an engine prototype. XXX - it is possible that the top-company
 * changes while you are waiting to accept the offer? Then it becomes invalid
 * @param flags operation to perform
 * @param engine_id engine-prototype offered
 * @return the cost of this operation or an error
 */
CommandCost CmdWantEnginePreview(DoCommandFlag flags, EngineID engine_id)
{
        Engine *e = Engine::GetIfValid(engine_id);
        if (e == nullptr || !(e->flags & ENGINE_EXCLUSIVE_PREVIEW) || e->preview_company != _current_company) return CMD_ERROR;

        if (flags & DC_EXEC) AcceptEnginePreview(engine_id, _current_company);

        return CommandCost();
}

/**
 * Allow or forbid a specific company to use an engine
 * @param flags operation to perform
 * @param engine_id engine id
 * @param company_id Company to allow/forbid the use of an engine.
 * @param allow false to forbid, true to allow.
 * @return the cost of this operation or an error
 */
CommandCost CmdEngineCtrl(DoCommandFlag flags, EngineID engine_id, CompanyID company_id, bool allow)
{
        if (_current_company != OWNER_DEITY) return CMD_ERROR;

        if (!Engine::IsValidID(engine_id) || !Company::IsValidID(company_id)) return CMD_ERROR;

        if (flags & DC_EXEC) {
                if (allow) {
                        EnableEngineForCompany(engine_id, company_id);
                } else {
                        DisableEngineForCompany(engine_id, company_id);
                }
        }

        return CommandCost();
}

/**
 * An engine has become available for general use.
 * Also handle the exclusive engine preview contract.
 * @param e Engine generally available as of now.
 */
static void NewVehicleAvailable(Engine *e)
{
        EngineID index = e->index;

        /* In case the company didn't build the vehicle during the intro period,
         * prevent that company from getting future intro periods for a while. */
        if (e->flags & ENGINE_EXCLUSIVE_PREVIEW) {
                for (Company *c : Company::Iterate()) {
                        uint block_preview = c->block_preview;

                        if (!HasBit(e->company_avail, c->index)) continue;

                        /* We assume the user did NOT build it.. prove me wrong ;) */
                        c->block_preview = 20;

                        for (const Vehicle *v : Vehicle::Iterate()) {
                                if (v->type == VEH_TRAIN || v->type == VEH_ROAD || v->type == VEH_SHIP ||
                                                (v->type == VEH_AIRCRAFT && Aircraft::From(v)->IsNormalAircraft())) {
                                        if (v->owner == c->index && v->engine_type == index) {
                                                /* The user did prove me wrong, so restore old value */
                                                c->block_preview = block_preview;
                                                break;
                                        }
                                }
                        }
                }
        }

        e->flags = (e->flags & ~ENGINE_EXCLUSIVE_PREVIEW) | ENGINE_AVAILABLE;
        AddRemoveEngineFromAutoreplaceAndBuildWindows(e->type);

        /* Now available for all companies */
        e->company_avail = MAX_UVALUE(CompanyMask);

        /* Do not introduce new rail wagons */
        if (IsWagon(index)) return;

        if (e->type == VEH_TRAIN) {
                /* maybe make another rail type available */
                assert(e->u.rail.railtype < RAILTYPE_END);
                for (Company *c : Company::Iterate()) c->avail_railtypes = AddDateIntroducedRailTypes(c->avail_railtypes | GetRailTypeInfo(e->u.rail.railtype)->introduces_railtypes, TimerGameCalendar::date);
        } else if (e->type == VEH_ROAD) {
                /* maybe make another road type available */
                assert(e->u.road.roadtype < ROADTYPE_END);
                for (Company *c : Company::Iterate()) c->avail_roadtypes = AddDateIntroducedRoadTypes(c->avail_roadtypes | GetRoadTypeInfo(e->u.road.roadtype)->introduces_roadtypes, TimerGameCalendar::date);
        }

        /* Only broadcast event if AIs are able to build this vehicle type. */
        if (!IsVehicleTypeDisabled(e->type, true)) AI::BroadcastNewEvent(new ScriptEventEngineAvailable(index));

        /* Only provide the "New Vehicle available" news paper entry, if engine can be built. */
        if (!IsVehicleTypeDisabled(e->type, false) && !HasFlag(e->info.extra_flags, ExtraEngineFlags::NoNews)) {
                SetDParam(0, GetEngineCategoryName(index));
                SetDParam(1, PackEngineNameDParam(index, EngineNameContext::PreviewNews));
                AddNewsItem(STR_NEWS_NEW_VEHICLE_NOW_AVAILABLE_WITH_TYPE, NT_NEW_VEHICLES, NF_VEHICLE, NR_ENGINE, index);
        }

        /* Update the toolbar. */
        if (e->type == VEH_ROAD) InvalidateWindowData(WC_BUILD_TOOLBAR, TRANSPORT_ROAD);
        if (e->type == VEH_SHIP) InvalidateWindowData(WC_BUILD_TOOLBAR, TRANSPORT_WATER);
        if (e->type == VEH_AIRCRAFT) InvalidateWindowData(WC_BUILD_TOOLBAR, TRANSPORT_AIR);

        /* Close pending preview windows */
        CloseWindowById(WC_ENGINE_PREVIEW, index);
}

/** Monthly update of the availability, reliability, and preview offers of the engines. */
void CalendarEnginesMonthlyLoop()
{
        if (TimerGameCalendar::year < _year_engine_aging_stops) {
                bool refresh = false;
                for (Engine *e : Engine::Iterate()) {
                        /* Age the vehicle */
                        if ((e->flags & ENGINE_AVAILABLE) && e->age != INT32_MAX) {
                                e->age++;
                                CalcEngineReliability(e, true);
                                refresh = true;
                        }

                        /* Do not introduce invalid engines */
                        if (!e->IsEnabled()) continue;

                        if (!(e->flags & ENGINE_AVAILABLE) && TimerGameCalendar::date >= (e->intro_date + CalendarTime::DAYS_IN_YEAR)) {
                                /* Introduce it to all companies */
                                NewVehicleAvailable(e);
                        } else if (!(e->flags & (ENGINE_AVAILABLE | ENGINE_EXCLUSIVE_PREVIEW)) && TimerGameCalendar::date >= e->intro_date) {
                                /* Introduction date has passed...
                                 * Check if it is allowed to build this vehicle type at all
                                 * based on the current game settings. If not, it does not
                                 * make sense to show the preview dialog to any company. */
                                if (IsVehicleTypeDisabled(e->type, false)) continue;

                                /* Do not introduce new rail wagons */
                                if (IsWagon(e->index)) continue;

                                /* Engine has no preview */
                                if (HasFlag(e->info.extra_flags, ExtraEngineFlags::NoPreview)) continue;

                                /* Show preview dialog to one of the companies. */
                                e->flags |= ENGINE_EXCLUSIVE_PREVIEW;
                                e->preview_company = INVALID_COMPANY;
                                e->preview_asked = 0;
                        }
                }

                InvalidateWindowClassesData(WC_BUILD_VEHICLE); // rebuild the purchase list (esp. when sorted by reliability)

                if (refresh) {
                        SetWindowClassesDirty(WC_BUILD_VEHICLE);
                        SetWindowClassesDirty(WC_REPLACE_VEHICLE);
                }
        }
}

static IntervalTimer<TimerGameCalendar> _calendar_engines_monthly({TimerGameCalendar::MONTH, TimerGameCalendar::Priority::ENGINE}, [](auto)
{
        CalendarEnginesMonthlyLoop();
});

/**
 * Is \a name still free as name for an engine?
 * @param name New name of an engine.
 * @return \c false if the name is being used already, else \c true.
 */
static bool IsUniqueEngineName(const std::string &name)
{
        for (const Engine *e : Engine::Iterate()) {
                if (!e->name.empty() && e->name == name) return false;
        }

        return true;
}

/**
 * Rename an engine.
 * @param flags operation to perform
 * @param engine_id engine ID to rename
 * @param text the new name or an empty string when resetting to the default
 * @return the cost of this operation or an error
 */
CommandCost CmdRenameEngine(DoCommandFlag flags, EngineID engine_id, const std::string &text)
{
        Engine *e = Engine::GetIfValid(engine_id);
        if (e == nullptr) return CMD_ERROR;

        bool reset = text.empty();

        if (!reset) {
                if (Utf8StringLength(text) >= MAX_LENGTH_ENGINE_NAME_CHARS) return CMD_ERROR;
                if (!IsUniqueEngineName(text)) return_cmd_error(STR_ERROR_NAME_MUST_BE_UNIQUE);
        }

        if (flags & DC_EXEC) {
                if (reset) {
                        e->name.clear();
                } else {
                        e->name = text;
                }

                MarkWholeScreenDirty();
        }

        return CommandCost();
}


/**
 * Check if an engine is buildable.
 * @param engine  index of the engine to check.
 * @param type    the type the engine should be.
 * @param company index of the company.
 * @return True if an engine is valid, of the specified type, and buildable by
 *              the given company.
 */
bool IsEngineBuildable(EngineID engine, VehicleType type, CompanyID company)
{
        const Engine *e = Engine::GetIfValid(engine);

        /* check if it's an engine that is in the engine array */
        if (e == nullptr) return false;

        /* check if it's an engine of specified type */
        if (e->type != type) return false;

        /* check if it's available ... */
        if (company == OWNER_DEITY) {
                /* ... for any company (preview does not count) */
                if (!(e->flags & ENGINE_AVAILABLE) || e->company_avail == 0) return false;
        } else {
                /* ... for this company */
                if (!HasBit(e->company_avail, company)) return false;
        }

        if (!e->IsEnabled()) return false;

        if (type == VEH_TRAIN && company != OWNER_DEITY) {
                /* Check if the rail type is available to this company */
                const Company *c = Company::Get(company);
                if (((GetRailTypeInfo(e->u.rail.railtype))->compatible_railtypes & c->avail_railtypes) == 0) return false;
        }
        if (type == VEH_ROAD && company != OWNER_DEITY) {
                /* Check if the road type is available to this company */
                const Company *c = Company::Get(company);
                if ((GetRoadTypeInfo(e->u.road.roadtype)->powered_roadtypes & c->avail_roadtypes) == ROADTYPES_NONE) return false;
        }

        return true;
}

/**
 * Check if an engine is refittable.
 * Note: Likely you want to use IsArticulatedVehicleRefittable().
 * @param engine index of the engine to check.
 * @return true if the engine is refittable.
 */
bool IsEngineRefittable(EngineID engine)
{
        const Engine *e = Engine::GetIfValid(engine);

        /* check if it's an engine that is in the engine array */
        if (e == nullptr) return false;

        if (!e->CanCarryCargo()) return false;

        const EngineInfo *ei = &e->info;
        if (ei->refit_mask == 0) return false;

        /* Are there suffixes?
         * Note: This does not mean the suffixes are actually available for every consist at any time. */
        if (HasBit(ei->callback_mask, CBM_VEHICLE_CARGO_SUFFIX)) return true;

        /* Is there any cargo except the default cargo? */
        CargoID default_cargo = e->GetDefaultCargoType();
        CargoTypes default_cargo_mask = 0;
        SetBit(default_cargo_mask, default_cargo);
        return IsValidCargoID(default_cargo) && ei->refit_mask != default_cargo_mask;
}

/**
 * Check for engines that have an appropriate availability.
 */
void CheckEngines()
{
        TimerGameCalendar::Date min_date = INT32_MAX;

        for (const Engine *e : Engine::Iterate()) {
                if (!e->IsEnabled()) continue;

                /* Don't consider train wagons, we need a powered engine available. */
                if (e->type == VEH_TRAIN && e->u.rail.railveh_type == RAILVEH_WAGON) continue;

                /* We have an available engine... yay! */
                if ((e->flags & ENGINE_AVAILABLE) != 0 && e->company_avail != 0) return;

                /* Okay, try to find the earliest date. */
                min_date = std::min(min_date, e->info.base_intro);
        }

        if (min_date < INT32_MAX) {
                SetDParam(0, min_date);
                ShowErrorMessage(STR_ERROR_NO_VEHICLES_AVAILABLE_YET, STR_ERROR_NO_VEHICLES_AVAILABLE_YET_EXPLANATION, WL_WARNING);
        } else {
                ShowErrorMessage(STR_ERROR_NO_VEHICLES_AVAILABLE_AT_ALL, STR_ERROR_NO_VEHICLES_AVAILABLE_AT_ALL_EXPLANATION, WL_WARNING);
        }
}