{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE FlexibleContexts #-}
module SJW.Compiler (
    main
  ) where

import SJW.Source (Source(..), HasSource, Path)
import Control.Monad.IO.Class (MonadIO(..))
import Control.Monad.RWS (ask, gets)
import Data.Map ((!))
import qualified Data.Map as Map (member)
import Data.Text (Text, cons)
import qualified Data.Text as Text (null, unlines)
import SJW.Dependencies as Dependencies (Failable, solve)
import SJW.Module (Environment, Log, Module(..), Modules(..))
import qualified SJW.Module as Module (parse, register)
import SJW.Module.File (File(..), variables)
import qualified SJW.Module.File as File (header, footer)

type Compiler m = (HasSource m, Log m, Environment m, MonadIO m, Failable m)

indent :: [Text] -> [Text]
indent = fmap indentLine
  where
    indentLine t
      | Text.null t = t
      | otherwise = cons '\t' t

include :: Environment m => Path -> m [Text]
include path = do
  File {isMain, imports, payload} <- gets (file . (! path) . modules)
  let (names, values) = unzip $ variables imports
  return $ File.header isMain path names : indent payload ++ File.footer values

scan :: Compiler m => Bool -> Path -> m ()
scan isMain modulePath = do
  alreadyLoaded <- gets (Map.member modulePath . modules)
  if alreadyLoaded then return () else load
  where
    load :: Compiler m => m ()
    load = do
      newModule <- Module.parse isMain modulePath
      Module.register modulePath newModule
      mapM_ (scan False) $ dependencies newModule

body :: Compiler m => m [Text]
body = do
  sortedPath <- Dependencies.solve =<< dependenciesGraph
  includes <- concat <$> mapM include sortedPath
  return $ "var modules = {};" : includes
  where
    dependenciesGraph = gets (fmap dependencies . modules)

main :: Compiler m => m Text
main = do
  Source {mainModule} <- ask
  scan True mainModule
  codeBody <- body
  return . Text.unlines $ openOnLoad : indent codeBody ++ [closeOnLoad]
  where
    openOnLoad = "window.addEventListener('load', function() {"
    closeOnLoad = "});"