module CSVReader2 where
import Control.Monad.State
import CSV
----------------------------------------------
-- Keep track of lines and columns in the state
-- part of the monad
-- Define a function for each type
-- Separate reading a line from reading a file.
-- data State s a = State (s -> (a,s))
type Line a = State (Int,Int,[String]) a
report l c message =
 error ("\n at line: "++show l++", column: "++show c++"\n "++message)
bool:: Line Bool
bool = (state f)
 where f (l,c,"True" : ss) = (True,(l,c+1,ss))
 f (l,c,"False" : ss) = (False,(l,c+1,ss))
 f (l,c,x:xs) = report l c ("Non Bool in reader bool: "++x)
 f (l,c,[]) = report l c "No more strings to read a 'Bool' from"
string:: Line String
string = state f
 where f (l,c,s:ss) = (s,(l,c+1,ss))
 f (l,c,[]) = report l c "No more strings to read a 'String' from"
 
int:: Line Int
int = mapState f (return ())
 where f ((),(l,c,s:ss)) = (read s,(l,c+1,ss))
 f ((),(l,c,[])) = report l c "No more strings to read an 'Int' from"
 
skip:: Line ()
skip = state f
 where f (l,c,s:ss) = ( (), (l,c+1,ss))
 f (l,c,[]) = report l c "No more strings to 'skip' over"
list:: Int -> Line a -> Line [a]
list 0 r = return []
list n r = do { x <- r; xs <- list (n-1) r; return(x:xs)} blank:: Line a -> Line(Maybe a)
blank m = state f 
 where f (l,c,"":xs) = (Nothing, (l,c+1,xs))
 f xs = case runState m xs of
 (y,ys) -> (Just y,ys)
-------------------------------------------
-- Reading a whole file of Comma Separated Values
-- which is represented by [[String]]
type Reader a = State (Int,[[String]]) a
lineToReader:: Line a -> Reader a
lineToReader l1 = mapState f (return ())
 where f ((),(l,line:lines)) = (evalState l1 (l,1,line),(l+1,lines))
getN :: Int -> Line a -> Reader [a]
getN 0 line = return []
getN n line =
 do { x <- lineToReader line ; xs <- getN (n-1) line ; return(x:xs) } importCSV :: Reader a -> String -> IO a
importCSV reader file = 
 do { r <- parseCSVFromFile file; (f r)} where f (Left err) = error ("Error reading from file: "++ file++"\n"++show err) f (Right xs) = return(evalState reader (1,xs)) -------------------------------------------- -- Generic Monad operations infixr 3 `x` x :: Monad m => m b -> m c -> m(b,c) 
r1 `x` r2 = do { a <- r1; b <- r2; return(a,b) } many :: Monad m => Int -> m c -> m [c]
many n r = sequence (replicate n r)
 where -- sequence is in the Prelude but we provide
 -- a definition here because it is interesting
 sequence [] = return []
 sequence (c:cs) = do { x <- c ; xs <- sequence cs ; return(x:xs)} row:: (a -> b) -> Line a -> Reader b
row f line1 = lineToReader line2
 where line2 = do { x <- line1; return(f x) }
get3DieEx2 :: Reader ([[Char]],[([Char],[Maybe Int])])
get3DieEx2 = (row snd (skip `x` list 3 string)) 
 `x` (many 18 (row id cols2_18))
 where cols2_18 = (string `x` list 4 (blank int))
test2 = importCSV get3DieEx2 "roll3Die.csv" 
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