{-|
Module      : Web.App.Main
Copyright   : (c) Nathaniel Symer, 2015
License     : MIT
Maintainer  : nate@symer.io
Stability   : experimental
Portability : POSIX

Main functions for running webapps. They provide a CLI interface
to the Web.App.HTTP module. They are designed to be used like

@
module Main where

import Web.App

routes :: (WebAppState s, MonadIO m) => [Route s m]
routes = [] -- routes go here

main :: IO ()
main = webappMain' routes []
@

-}

{-# LANGUAGE TupleSections #-}

module Web.App.Main
(
  webappMain,
  webappMain',
  webappMainIO,
  webappMainIO',
  webappMainSimple,
)
where

import Web.App.RouteT
import Web.App.State
import Web.App.HTTP

import Network.Wai (Middleware, Response)

import Data.Maybe
import Data.Monoid
import Control.Monad
import Control.Monad.IO.Class

import Control.Applicative
import Options.Applicative
import System.Posix
import System.Exit
import System.Environment
import System.IO

import GHC.IO.Handle

import Text.Read

data Options = Options {
  _optionsDaemonize :: Maybe FilePath,
  _optionsPort :: Int,
  _optionsHTTPSSLCert :: Maybe FilePath,
  _optionsHTTPSSLKey :: Maybe FilePath,
  _optionsOutputPath :: Maybe FilePath,
  _optionsErrorPath :: Maybe FilePath
}

webappMainSimple :: (WebAppState s) => [Route s IO] -> IO ()
webappMainSimple = flip webappMainIO' []

-- |Like 'webappMainIO' without the CLI extension arguments.
webappMainIO' :: (WebAppState s)
              => [Route s IO] -- ^ routes
              -> [Middleware] -- ^ middlewares
              -> IO ()
webappMainIO' a m = webappMainIO a m Nothing (const $ return ())
  
-- |Run a webapp based on IO.
webappMainIO :: (WebAppState s)
             => [Route s IO] -- ^ routes
             -> [Middleware] -- ^ middlewares
             -> Maybe (Parser a) -- ^ extra CLI parser (available under @util@ subcommand)
             -> (a -> IO ()) -- ^ action to apply to parse result of 'utilParser'
             -> IO ()
webappMainIO = webappMain id

-- |Like 'webappMain' without the CLI extension arguments.
webappMain' :: (WebAppState s, MonadIO m)
            => (m (Maybe Response) -> IO (Maybe Response)) -- ^ action to eval a monadic computation in @m@ in @IO@
            -> [Route s m] -- ^ routes
            -> [Middleware] -- ^ middlewares
            -> IO ()
webappMain' f a m = webappMain f a m Nothing (const $ return ())

-- | Read commandline arguments and start webapp accordingly. When passing an
-- additional CLI parser, it is made available under the @util@ subcommand.
webappMain :: (WebAppState s, MonadIO m)
           => (m (Maybe Response) -> IO (Maybe Response)) -- ^ action to eval a monadic computation in @m@ in @IO@
           -> [Route s m] -- ^ routes
           -> [Middleware] -- ^ middlewares
           -> Maybe (Parser a) -- ^ extra CLI parser, parsed after the built-in parser
           -> (a -> IO ()) -- ^ action to apply the result of 'extraParser'
           -> IO ()
webappMain runToIO app mws extraParser extraf = parseArgs extraParser >>= either extraf f
  where
    f (Options Nothing p c k o e) = start p c k o e
    f (Options (Just pidFile) p c k o e) = do
      forkProcess $ do
        createSession
        forkProcess $ do
          getProcessID >>= writeFile pidFile . show
          redirectHandle stdout $ fromMaybe "/dev/null" o
          redirectHandle stderr $ fromMaybe "/dev/null" e
          redirectHandle stdin "/dev/null"
          installHandler sigHUP Ignore Nothing
          start p c k Nothing Nothing
        exitImmediately ExitSuccess
      exitImmediately ExitSuccess
    start port cert key out err = runServer ((,) <$> cert <*> key) port pre teardown wai
      where (wai, teardown) = toApplication runToIO app mws
            pre = do
              -- drop privileges after binding to a port
              getRealGroupID >>= setEffectiveGroupID
              getRealUserID >>= setEffectiveUserID
              -- redirect I/O
              maybe (return ()) (redirectHandle stdout) out
              maybe (return ()) (redirectHandle stderr) err
    redirectHandle hdl pth = do
      exists <- fileExist pth
      when (not exists) $ writeFile pth ""
      h <- openFile pth WriteMode
      hDuplicateTo h hdl
      hClose h
      hSetBuffering hdl NoBuffering
      
parseArgs :: Maybe (Parser a) -> IO (Either a Options)
parseArgs extra = do
  defaultPort <- ((=<<) readMaybe) <$> lookupEnv "PORT"
  customExecParser pprefs $ info (helper <*> parser defaultPort) fullDesc
  where
    pprefs = ParserPrefs "" False False True True 80
    parser port = (Right <$> parseStart port) <|> (maybe empty (fmap Left) extra)--  <|> (Right <$> showHelp)
    parseStart port = Options
      <$> (optional $ strOption $ long "daemonize"  <> short 'd' <> metavar "FILEPATH" <> help "Daemonize server and write its pid to FILEPATH.")
      <*> (option auto $          long "port"       <> short 'p' <> metavar "PORT"     <> help "Run server on PORT." <> value (fromMaybe 3000 port))
      <*> (optional $ strOption $ long "ssl-cert"   <> short 'c' <> metavar "FILEPATH" <> help "SSL certificate file. If a certificate and key are provided, the server will be run secure.")
      <*> (optional $ strOption $ long "ssl-key"    <> short 'k' <> metavar "FILEPATH" <> help "SSL private key file. If a certificate and key are provided, the server will be run secure.")
      <*> (optional $ strOption $ long "output-log" <> short 'o' <> metavar "FILEPATH" <> help "Redirect output to FILEPATH.")
      <*> (optional $ strOption $ long "error-log"  <> short 'e' <> metavar "FILEPATH" <> help "Redirect error to FILEPATH.")