-- This file is part of Hoppy.
--
-- Copyright 2015-2018 Bryan Gardiner <bog@khumba.net>
--
-- This program is free software: you can redistribute it and/or modify
-- it under the terms of the GNU Affero General Public License as published by
-- the Free Software Foundation, either version 3 of the License, or
-- (at your option) any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-- GNU Affero General Public License for more details.
--
-- You should have received a copy of the GNU Affero General Public License
-- along with this program.  If not, see <http://www.gnu.org/licenses/>.

{-# LANGUAGE CPP #-}

-- | A driver for a command-line interface to a generator.
--
-- A simple @Main.hs@ for a generator can simply be:
--
-- @
-- import "Foreign.Hoppy.Generator.Main" ('defaultMain')
-- import "Foreign.Hoppy.Generator.Spec" ('ErrorMsg', 'Interface', 'interface')
--
-- interfaceResult :: Either 'ErrorMsg' 'Interface'
-- interfaceResult = 'interface' ...
--
-- main :: IO ()
-- main = 'defaultMain' interfaceResult
-- @
module Foreign.Hoppy.Generator.Main (
  Action (..),
  defaultMain,
  defaultMain',
  run,
  ) where

#if !MIN_VERSION_base(4,8,0)
import Control.Applicative ((<$>))
#endif
import Control.Arrow ((&&&))
import Control.Concurrent.MVar (MVar, modifyMVar, modifyMVar_, newMVar, readMVar)
import Control.Monad ((<=<), forM, unless, when)
import Data.Foldable (forM_)
import Data.List (intercalate)
import qualified Data.Map as M
import Data.Map (Map)
import Data.Maybe (fromMaybe)
import Foreign.Hoppy.Generator.Common (writeFileIfDifferent)
import qualified Foreign.Hoppy.Generator.Language.Cpp.Internal as Cpp
import qualified Foreign.Hoppy.Generator.Language.Haskell.Internal as Haskell
import Foreign.Hoppy.Generator.Spec
import System.Directory (createDirectoryIfMissing, doesDirectoryExist)
import System.Environment (getArgs)
import System.Exit (exitFailure, exitSuccess)
import System.FilePath ((</>), takeDirectory)
import System.IO (hPutStrLn, stderr)

-- | Actions that can be requested of the program.
data Action =
    SelectInterface String
    -- ^ Sets the interface that will be used for subsequent actions.
  | ListInterfaces
    -- ^ Lists the interfaces compiled into the generator.
  | ListCppFiles
    -- ^ Lists the generated files in C++ bindings.
  | ListHsFiles
    -- ^ Lists the generated files in Haskell bindings.
  | GenCpp FilePath
    -- ^ Generates C++ wrappers for an interface in the given location.
  | GenHaskell FilePath
    -- ^ Generates Haskell bindings for an interface in the given location.

data AppState = AppState
  { appInterfaces :: Map String Interface
  , appCurrentInterface :: Interface
  , appCaches :: Caches
  }

initialAppState :: [Interface] -> AppState
initialAppState ifaces = AppState
  { appInterfaces = M.fromList $ map (interfaceName &&& id) ifaces
  , appCurrentInterface = head ifaces
  , appCaches = M.empty
  }

type Caches = Map String InterfaceCache

data InterfaceCache = InterfaceCache
  { cacheInterface :: Interface
  , generatedCpp :: Maybe Cpp.Generation
  , generatedHaskell :: Maybe Haskell.Generation
  }

emptyCache :: Interface -> InterfaceCache
emptyCache iface = InterfaceCache iface Nothing Nothing

getGeneratedCpp :: InterfaceCache -> IO (InterfaceCache, Either String Cpp.Generation)
getGeneratedCpp cache = case generatedCpp cache of
  Just gen -> return (cache, Right gen)
  _ -> case Cpp.generate $ cacheInterface cache of
    l@(Left _) -> return (cache, l)
    r@(Right gen) -> return (cache { generatedCpp = Just gen }, r)

getGeneratedHaskell :: InterfaceCache -> IO (InterfaceCache, Either String Haskell.Generation)
getGeneratedHaskell cache = case generatedHaskell cache of
  Just gen -> return (cache, Right gen)
  _ -> case Haskell.generate $ cacheInterface cache of
    l@(Left _) -> return (cache, l)
    r@(Right gen) -> return (cache { generatedHaskell = Just gen }, r)

-- | This provides a simple @main@ function for a generator.  Define your @main@
-- as:
--
-- @
-- main = defaultMain $ 'interface' ...
-- @
--
-- Refer to 'run' for how to use the command-line interface.  Use 'defaultMain''
-- if you want to include multiple interfaces in your generator.
defaultMain :: Either String Interface -> IO ()
defaultMain interfaceResult = defaultMain' [interfaceResult]

-- | This is a version of 'defaultMain' that accepts multiple interfaces.
defaultMain' :: [Either String Interface] -> IO ()
defaultMain' interfaceResults = do
  interfaces <- forM interfaceResults $ \interfaceResult -> case interfaceResult of
    Left errorMsg -> do
      hPutStrLn stderr $ "Error initializing interface: " ++ errorMsg
      exitFailure
    Right iface -> return iface

  args <- getArgs
  _ <- run interfaces args
  return ()

-- | @run interfaces args@ runs the driver with the command-line arguments from
-- @args@ against the listed interfaces, and returns the list of actions
-- performed.
--
-- The recognized arguments are listed below.  The exact forms shown are
-- required; the @--long-arg=value@ style is not supported.
--
-- - __@--help@:__ Displays a menu listing the valid commands.
--
-- - __@--list-interfaces@:__ Lists the interfaces compiled into the generator.
--
-- - __@--interface \<iface\>@:__ Sets the interface that will be used for
--   subsequent arguments.
--
-- - __@--gen-cpp \<outdir\>@:__ Generates C++ bindings in the given directory.
--
-- - __@--gen-hs \<outdir\>@:__ Generates Haskell bindings under the given
--   top-level source directory.
run :: [Interface] -> [String] -> IO [Action]
run interfaces args = do
  stateVar <- newMVar $ initialAppState interfaces
  when (null args) $ do
    putStrLn "This is a Hoppy interface generator.  Use --help for options."
    putStrLn ""
    putStrLn $ "Interfaces: " ++ unwords (map interfaceName interfaces)
    exitSuccess
  when ("--help" `elem` args) $ usage stateVar >> exitSuccess
  processArgs stateVar args

usage :: MVar AppState -> IO ()
usage stateVar = do
  interfaceNames <- map interfaceName <$> getInterfaces stateVar
  mapM_ putStrLn
    [ "Hoppy binding generator"
    , ""
    , "Interfaces: " ++ intercalate ", " interfaceNames
    , ""
    , "Supported options:"
    , "  --help                      Displays this menu."
    , "  --interface <iface>         Sets the interface used for subsequent options."
    , "  --list-interfaces           Lists the interfaces compiled into this binary."
    , "  --list-cpp-files            Lists generated file paths in C++ bindings."
    , "  --list-hs-files             Lists generated file paths in Haskell bindings."
    , "  --gen-cpp <outdir>          Generate C++ bindings in a directory."
    , "  --gen-hs <outdir>           Generate Haskell bindings under the given"
    , "                              top-level source directory."
    ]

processArgs :: MVar AppState -> [String] -> IO [Action]
processArgs stateVar args =
  case args of
    [] -> return []

    "--interface":name:rest -> do
      modifyMVar_ stateVar $ \state ->
        case M.lookup name $ appInterfaces state of
          Nothing -> do
            hPutStrLn stderr $
              "--interface: Interface '" ++ name ++ "' doesn't exist in this generator."
            _ <- exitFailure
            return state
          Just iface -> return state { appCurrentInterface = iface }
      (SelectInterface name:) <$> processArgs stateVar rest

    "--list-interfaces":rest -> do
      listInterfaces stateVar
      (ListInterfaces:) <$> processArgs stateVar rest

    "--list-cpp-files":rest -> do
      genResult <- withCurrentCache stateVar getGeneratedCpp
      case genResult of
        Left errorMsg -> do
          hPutStrLn stderr $ "--list-cpp-files: Failed to generate: " ++ errorMsg
          exitFailure
        Right gen -> do
          mapM_ putStrLn $ M.keys $ Cpp.generatedFiles gen
          (ListCppFiles:) <$> processArgs stateVar rest

    "--list-hs-files":rest -> do
      genResult <- withCurrentCache stateVar getGeneratedHaskell
      case genResult of
        Left errorMsg -> do
          hPutStrLn stderr $ "--list-hs-files: Failed to generate: " ++ errorMsg
          exitFailure
        Right gen -> do
          mapM_ putStrLn $ M.keys $ Haskell.generatedFiles gen
          (ListHsFiles:) <$> processArgs stateVar rest

    "--gen-cpp":baseDir:rest -> do
      baseDirExists <- doesDirectoryExist baseDir
      unless baseDirExists $ do
        hPutStrLn stderr $
          "--gen-cpp: Please create this directory so that I can generate files in it: " ++
          baseDir
        exitFailure
      genResult <- withCurrentCache stateVar getGeneratedCpp
      case genResult of
        Left errorMsg -> do
          hPutStrLn stderr $ "--gen-cpp: Failed to generate: " ++ errorMsg
          exitFailure
        Right gen -> do
          forM_ (M.toList $ Cpp.generatedFiles gen) $
            uncurry $ writeGeneratedFile baseDir
          (GenCpp baseDir:) <$> processArgs stateVar rest

    "--gen-hs":baseDir:rest -> do
      baseDirExists <- doesDirectoryExist baseDir
      unless baseDirExists $ do
        hPutStrLn stderr $
          "--gen-hs: Please create this directory so that I can generate files in it: " ++
          baseDir
        exitFailure
      genResult <- withCurrentCache stateVar getGeneratedHaskell
      case genResult of
        Left errorMsg -> do
          hPutStrLn stderr $ "--gen-hs: Failed to generate: " ++ errorMsg
          exitFailure
        Right gen -> do
          forM_ (M.toList $ Haskell.generatedFiles gen) $
            uncurry $ writeGeneratedFile baseDir
          (GenHaskell baseDir:) <$> processArgs stateVar rest

    arg:_ -> do
      hPutStrLn stderr $ "Invalid option or missing argument for '" ++ arg ++ "'."
      exitFailure

writeGeneratedFile :: FilePath -> FilePath -> String -> IO ()
writeGeneratedFile baseDir subpath contents = do
  let path = baseDir </> subpath
  createDirectoryIfMissing True $ takeDirectory path
  writeFileIfDifferent path contents

withCurrentCache :: MVar AppState -> (InterfaceCache -> IO (InterfaceCache, a)) -> IO a
withCurrentCache stateVar fn = modifyMVar stateVar $ \state -> do
  let currentInterface = appCurrentInterface state
      name = interfaceName currentInterface
  (cache, result) <- fn $
                     fromMaybe (emptyCache currentInterface) $
                     M.lookup name $
                     appCaches state
  return (state { appCaches = M.insert name cache $ appCaches state }, result)

listInterfaces :: MVar AppState -> IO ()
listInterfaces = mapM_ (putStrLn . interfaceName) <=< getInterfaces

getInterfaces :: MVar AppState -> IO [Interface]
getInterfaces = fmap (M.elems . appInterfaces) . readMVar