{-# LANGUAGE FlexibleInstances    #-}
{-# LANGUAGE ScopedTypeVariables  #-}
{-# LANGUAGE TypeSynonymInstances #-}

module Development.Shake.ATS ( -- * Shake Rules
                               cgen
                             , cgenPretty
                             , cleanATS
                             , atsBin
                             , lexAts
                             -- * Actions
                             , patsHome
                             -- Types
                             , Version (..)
                             ) where

import           Control.Monad
import           Control.Monad.IO.Class
import           Data.Either                (fromRight)
import           Data.Maybe                 (fromMaybe)
import           Data.Semigroup             (Semigroup (..))
import           Development.Shake
import           Development.Shake.FilePath
import           Language.ATS
import           System.Directory           (copyFile, createDirectoryIfMissing)
import           System.Exit                (ExitCode (ExitSuccess))

newtype Version = Version [Integer]

instance Show Version where
    show (Version [])     = ""
    show (Version [x])    = show x
    show (Version (x:xs)) = show x ++ "." ++ show (Version xs)

patsHome :: Version -> Action String
patsHome v = fromMaybe "/usr/local/lib/ats2-postiats-0.3.9" <$> mh
    where mh = fmap (++ ("/.atspkg/" ++ show v ++ "/")) <$> getEnv "HOME"

-- TODO install the whole compiler?
atsCommand :: CmdResult r => Version -> Version -> String -> String -> Action r
atsCommand v v' sourceFile out = do
    h <- patsHome v'
    let home = h ++ "lib/ats2-postiats-" ++ show v
    let atsArgs = [EchoStderr False, AddEnv "PATSHOME" home]
        patsc = "patsopt"
    command atsArgs patsc ["--output", out, "-dd", sourceFile, "-cc"]

gcFlag :: Bool -> String
gcFlag False = "-DATS_MEMALLOC_LIBC"
gcFlag True  = "-DATS_MEMALLOC_GCBDW"

copySources :: Version -> Version -> [FilePath] -> Action ()
copySources v v' sources =
    forM_ sources $ \dep -> do
        h <- patsHome v'
        let home = h ++ "lib/ats2-postiats-" ++ show v
        liftIO $ createDirectoryIfMissing True (home ++ "/" ++ takeDirectory dep)
        liftIO $ copyFile dep (home ++ "/" ++ dep)

-- TODO musl?
atsBin :: Version -> Version -> Bool -> [String] -> String -> String -> Rules ()
atsBin v v' gc libs sourceFile out =

    out %> \_ -> do
        sources <- transitiveDeps [sourceFile]
        h <- patsHome v'
        let home = h ++ "lib/ats2-postiats-" ++ show v
        need sources
        copySources v v' sources
        cmd_ ["mkdir", "-p", dropDirectory1 out]

        let toLibs = fmap ("-l" <>)
        command
            [EchoStderr False, AddEnv "PATSHOME" home]
            (home ++ "/bin/patscc")
            ([sourceFile, "-atsccomp", "gcc -flto -I" ++ h ++ "/ccomp/runtime/ -I" ++ h, gcFlag gc, "-o", out, "-cleanaft", "-O2", "-mtune=native", "-flto"] <> toLibs libs)

    -- | Build a @.lats@ file.
lexAts :: Rules ()
lexAts = priority 0.5 $
    "*.dats" %> \out -> do
        lats <- liftIO $ readFile (out -<.> "lats")
        (Stdout contents) <- command [Stdin lats] "atslex" []
        liftIO $ writeFile out contents

cleanATS :: Rules ()
cleanATS =

    "clean" ~> do
        cmd_ ["sn", "c"]
        removeFilesAfter "." ["//*.c", "//tags"]
        removeFilesAfter ".shake" ["//*"]
        removeFilesAfter ".atspkg" ["//*"]
        removeFilesAfter "ats-deps" ["//*"]

handleSource :: Version -> Version -> FilePath -> Action ()
handleSource v v' sourceFile = do
        sources <- transitiveDeps [sourceFile]
        need sources
        copySources v v' sources

-- | This provides rules for generating C code from ATS source files in the
-- @ats-src@ directory.
cgen :: Version -> FilePath -> Rules ()
cgen v dir =

    "//*.c" %> \out -> do
        let sourceFile = dir ++ "/" ++ (dropDirectory1 out -<.> "dats")
        handleSource v v sourceFile
        atsCommand v v sourceFile out

trim :: String -> String
trim = init . drop 1

transitiveDeps :: [FilePath] -> Action [FilePath]
transitiveDeps [] = pure []
transitiveDeps ps = fmap join $ forM ps $ \p -> do
    contents <- liftIO $ readFile p
    let ats = fromRight mempty . parseATS . lexATS $ contents
    deps <- filterM doesFileExist $ trim <$> getDependencies ats
    deps' <- transitiveDeps deps
    pure $ (p:deps) ++ deps'

-- | This uses @pats-filter@ to prettify the errors.
cgenPretty :: Version -> FilePath -> Rules ()
cgenPretty v dir =

    "//*.c" %> \out -> do

        let sourceFile = dir ++ "/" ++ (dropDirectory1 out -<.> "dats")
        handleSource v v sourceFile
        (Exit c, Stderr err) :: (Exit, Stderr String) <- atsCommand v v sourceFile out
        cmd_ [Stdin err] Shell "pats-filter"
        if c /= ExitSuccess
            then error "patscc failure"
            else pure ()