From 998d9a085e9323c561d62b03ff791a20079f8d12 Mon Sep 17 00:00:00 2001
From: Sergey Alirzaev <zl29ah@gmail.com>
Date: Mon, 21 Dec 2009 06:24:01 +0300
Subject: [PATCH] some beautiful error messages

---
 laziness.hs | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/laziness.hs b/laziness.hs
index 0a6200c..683531c 100644
--- a/laziness.hs
+++ b/laziness.hs
@@ -2,10 +2,6 @@
  - laziness: a tool to memoize your Earth-seizure plans
  - by Sergey 'L29Ah' Alirzaev, <zl29ah@gmail.com>
  -
- - Synopsis:
- - laziness dig <id> <depth> -- make laziness print todo graph starting at 
- - 'id' up to 'depth' jumps into
- -
  - File format:
  - <id>\t<description>\t<importance>\t<start timestamp>\t<end timestamp>
  - [\t<dependency>[\t<dependency>...]]\n<id>\t...
@@ -16,6 +12,8 @@ import Data.List.Split
 import Data.Maybe
 import Data.DateTime
 
+import Control.Monad
+
 import System
 
 data Todo = Todo {
@@ -59,13 +57,19 @@ _dig :: M.Map String Todo -> String -> Int -> Int -> [(Int, Todo)]
 _dig _ _ _ 0 = []
 _dig db id curdepth maxdepth = (curdepth, node) : 
 	(concatMap (\x -> _dig db x (curdepth + 1) (maxdepth - 1)) $ deps node)
-      			where node = fromJust $ M.lookup id db
+      			where node = fromMaybe (error $ "No node named \"" ++ id ++ "\" in the database!") $ M.lookup id db
 
+-- TODO: use getOpt
 main = do
-	(action:args) <- getArgs
+	args <- getArgs
+	when (length args == 0) $ error usage
+	let (action:cmdargs) = args
 	f <- readFile ".todo"
 	let db = M.fromList $ catMaybes $ map parseLine $ lines f
 	putStr $ case action of
-		"dig" -> dig db (args!!0) (read $ args!!1)
-		otherwise -> "Usage! ;-)\n"
+		"dig" -> dig db (cmdargs!!0) (read $ cmdargs!!1)
+		otherwise -> error usage
+
+usage = "Usage:\n" ++
+        "laziness dig <id> <depth> -- make laziness print todo graph starting at 'id' up to 'depth' jumps into\n"
 
-- 
2.11.4.GIT