From 5bdaa1e4ffe40add10f000ee993e6b500c419a37 Mon Sep 17 00:00:00 2001
From: Joe Zhao <ztuowen@gmail.com>
Date: Sat, 9 Aug 2014 10:58:03 +0800
Subject: add files from home for previous chapters and sandboxes

---
 todo.hs | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100644 todo.hs

(limited to 'todo.hs')

diff --git a/todo.hs b/todo.hs
new file mode 100644
index 0000000..2cb21c1
--- /dev/null
+++ b/todo.hs
@@ -0,0 +1,52 @@
+import System.Environment
+import System.Directory
+import System.IO
+import Data.List
+import Control.Exception
+import Control.Monad(when)
+
+fileName = "todo.txt"
+
+dispatch :: String -> String -> IO ()
+dispatch file "add" = add file
+dispatch file "view" = view file
+dispatch file "rm" = remove file
+dispatch file _ = do
+    putStrLn "Operations supported:\nadd - Append Item\nview - Inspect Item\nrm - Remove Item"
+
+view file = do
+    contents <- readFile file
+    let todoTasks = lines contents
+    putStr $ unlines $ number todoTasks
+
+add file = do
+    todoItem <- getLine
+    when (not $ null todoItem) (do
+        appendFile file todoItem)
+
+remove file = do
+    contents <- readFile file
+    numberString <- getLine
+    let todoTasks = lines contents
+        number = read numberString
+        newTodoList = unlines $ delete (todoTasks !! number) todoTasks
+    bracketOnError (openTempFile "." "temp") 
+        (\(tempName,tempHandle) -> do
+            hClose tempHandle
+            removeFile tempName)
+        (\(tempName,tempHandle) -> do
+            hPutStr tempHandle newTodoList
+            hClose tempHandle
+            removeFile file
+            renameFile tempName file)
+
+
+number task = zipWith (\n line -> show n ++ " - " ++ line) [0..] task
+
+main = do
+    line <- getLine
+    if null line then return ()
+        else (do
+            dispatch fileName line
+            main)
+
-- 
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