module PursLoader.Loader
  ( Effects()
  , loader
  , loaderFn
  ) where

import Prelude (Unit(), ($), (<>), (>>=), (<$>), (++), bind, flip, id, pure, return, unit)

import Control.Monad.Aff (Aff(), runAff)
import Control.Monad.Eff (Eff())
import Control.Monad.Eff.Class (liftEff)
import Control.Monad.Eff.Exception (error)

import Data.Array ((!!), concat)
import Data.Function (Fn2(), mkFn2)
import Data.Maybe (Maybe(..), fromMaybe, maybe)
import Data.String (joinWith)
import Data.String.Regex (match, noFlags, regex, test)

import PursLoader.ChildProcess (ChildProcess(), spawn)
import PursLoader.FS (FS(), writeFileUtf8, findFileUtf8)
import PursLoader.Glob (Glob(), globAll)
import PursLoader.LoaderRef (LoaderRef(), Loader(), async, cacheable, query, clearDependencies, addDependency, resourcePath)
import PursLoader.LoaderUtil (parseQuery)
import PursLoader.Options (loaderFFIOption, loaderSrcOption, pscOptions)

type Effects eff = (cp :: ChildProcess, fs :: FS, glob :: Glob, loader :: Loader | eff)

moduleRegex = regex "(?:^|\\n)module\\s+([\\w\\.]+)" noFlags { ignoreCase = true }

foreignRegex = regex "(?:^|\\n)\\s*foreign import\\s+" noFlags { ignoreCase = true }

pscCommand = "psc"

psciCommand = "psci"

psciFilename = ".psci"

(!!!) = flip (!!)

foreign import cwd :: String

foreign import relative :: String -> String -> String

mkPsci :: Array (Array String) -> Array (Array String) -> String
mkPsci srcs ffis = joinWith "\n" ((loadModule <$> concat srcs) <> (loadForeign <$> concat ffis))
  where
    loadModule :: String -> String
    loadModule a = ":m " ++ relative cwd a

    loadForeign :: String -> String
    loadForeign a = ":f " ++ relative cwd a

findFFI :: forall eff. Array (Array String) -> String -> Aff (fs :: FS | eff) (Maybe String)
findFFI ffiss name = findFileUtf8 re (concat ffiss)
  where
    re = regex ("(?:^|\\n)//\\s*module\\s*" ++ name ++ "\\s*\\n") noFlags

loader' :: forall eff. LoaderRef -> String -> Aff (Effects eff) (Maybe String)
loader' ref source = do
  liftEff $ cacheable ref

  let parsed = parseQuery $ query ref
      srcs = fromMaybe [] (loaderSrcOption parsed)
      ffis = fromMaybe [] (loaderFFIOption parsed)
      opts = pscOptions parsed

  spawn pscCommand (srcs <> opts)

  srcss <- globAll srcs
  ffiss <- globAll ffis

  let psciFile = mkPsci srcss ffiss

  writeFileUtf8 psciFilename psciFile

  let moduleName = match moduleRegex source >>= (!!!) 1 >>= id
      hasForeign = test foreignRegex source
      result = (\a -> "module.exports = require('" ++ a ++ "');") <$> moduleName

  liftEff (clearDependencies ref)
  liftEff (addDependency ref (resourcePath ref))

  foreignPath <- if hasForeign
                    then fromMaybe (pure Nothing) (findFFI ffiss <$> moduleName)
                    else pure Nothing

  fromMaybe (pure unit) ((\path -> liftEff (addDependency ref path)) <$> foreignPath)

  return result

loader :: forall eff. LoaderRef -> String -> Eff (Effects eff) Unit
loader ref source = do
  callback <- async ref
  runAff (\e -> callback (Just e) "")
         (maybe (callback (Just (error "Loader has failed to run")) "")
                (callback Nothing))
         (loader' ref source)

loaderFn :: forall eff. Fn2 LoaderRef String (Eff (Effects eff) Unit)
loaderFn = mkFn2 loader