module Main where

import System.Environment
import System.Exit
import System.IO

import qualified Language.Tandem.Collection as Collection
import qualified Language.Tandem.Rule as Rule
import qualified Language.Tandem.Parser as Parser
import qualified Language.Tandem.Pragma as Pragma
import qualified Language.Tandem.Eval as Eval


main = do
    args <- getArgs
    case args of
        ["parse", fileName] -> do
            (_, rule) <- loadSource fileName
            putStrLn $ show rule
        ["eval", fileName] -> do
            (_, rule) <- loadSource fileName
            case Eval.rewrite rule Collection.empty of
                Just c -> do
                    putStr $ Collection.depict c
                Nothing -> do
                    return ()
        ["showeval", fileName] -> do
            (_, rule) <- loadSource fileName
            putStrLn $ show $ Eval.rewrite rule Collection.empty
        ["run", fileName] -> do
            (pragmas, rule) <- loadSource fileName
            initState <- setUpPragmas pragmas Collection.empty
            case Eval.rewrite rule initState of
                Just result -> tearDownPragmas pragmas result
                Nothing -> exitWith $ ExitFailure 1
        _ -> do
            abortWith "Usage: tandem (parse|eval|run) <input-filename>"

loadSource fileName = do
    handle <- openFile fileName ReadMode
    -- hSetEncoding handle utf8
    text <- hGetContents handle
    case Parser.parseTandem text of
        Right (pragmas, rule) -> do
            return (pragmas, rule)
        Left error ->
            abortWith $ show error

abortWith msg = do
    hPutStrLn stderr msg
    exitWith $ ExitFailure 1

setUpPragmas [] state = do
    return state

setUpPragmas (Pragma.BatchIO inputLabel outputLabel:rest) state = do
    input <- getContents
    setUpPragmas rest $ Collection.put inputLabel input state

setUpPragmas (_:rest) state = do
    setUpPragmas rest state

tearDownPragmas [] state = do
    return ()

tearDownPragmas (Pragma.BatchIO inputLabel outputLabel:rest) state = do
    putStrLn $ reverse $ Collection.get outputLabel state
    tearDownPragmas rest state

tearDownPragmas (_:rest) state = do
    tearDownPragmas rest state