{-# LANGUAGE CPP #-}
{-# LANGUAGE OverloadedStrings #-}
-- | Some next-gen helper functions for the scaffolding's configuration system.
module Yesod.Default.Config2
    ( -- * Locally defined
      configSettingsYml
    , getDevSettings
    , develMainHelper
    , makeYesodLogger
      -- * Re-exports from Data.Yaml.Config
    , applyCurrentEnv
    , getCurrentEnv
    , applyEnvValue
    , loadYamlSettings
    , loadYamlSettingsArgs
    , EnvUsage
    , ignoreEnv
    , useEnv
    , requireEnv
    , useCustomEnv
    , requireCustomEnv
      -- * For backwards compatibility
    , MergedValue (..)
    , loadAppSettings
    , loadAppSettingsArgs
    ) where


import Data.Yaml.Config

import Data.Semigroup
import Data.Aeson
import qualified Data.HashMap.Strict as H
import System.Environment (getEnvironment)
import Network.Wai (Application)
import Network.Wai.Handler.Warp
import Text.Read (readMaybe)
import Data.Maybe (fromMaybe)
import Control.Concurrent (forkIO, threadDelay)
import System.Exit (exitSuccess)
import System.Directory (doesFileExist)
import Network.Wai.Logger (clockDateCacher)
import Yesod.Core.Types (Logger (Logger))
import System.Log.FastLogger (LoggerSet)

#ifndef mingw32_HOST_OS
import System.Posix.Signals (installHandler, sigINT, Handler(Catch))
#endif

newtype MergedValue = MergedValue { getMergedValue :: Value }

instance Semigroup MergedValue where
    MergedValue x <> MergedValue y = MergedValue $ mergeValues x y

-- | Left biased
mergeValues :: Value -> Value -> Value
mergeValues (Object x) (Object y) = Object $ H.unionWith mergeValues x y
mergeValues x _ = x

-- | Load the settings from the following three sources:
--
-- * Run time config files
--
-- * Run time environment variables
--
-- * The default compile time config file
loadAppSettings
    :: FromJSON settings
    => [FilePath] -- ^ run time config files to use, earlier files have precedence
    -> [Value] -- ^ any other values to use, usually from compile time config. overridden by files
    -> EnvUsage
    -> IO settings
loadAppSettings = loadYamlSettings
{-# DEPRECATED loadAppSettings "Use loadYamlSettings" #-}

-- | Same as @loadAppSettings@, but get the list of runtime config files from
-- the command line arguments.
loadAppSettingsArgs
    :: FromJSON settings
    => [Value] -- ^ any other values to use, usually from compile time config. overridden by files
    -> EnvUsage -- ^ use environment variables
    -> IO settings
loadAppSettingsArgs = loadYamlSettingsArgs
{-# DEPRECATED loadAppSettingsArgs "Use loadYamlSettingsArgs" #-}

-- | Location of the default config file.
configSettingsYml :: FilePath
configSettingsYml = "config/settings.yml"

-- | Helper for getApplicationDev in the scaffolding. Looks up PORT and
-- DISPLAY_PORT and prints appropriate messages.
getDevSettings :: Settings -> IO Settings
getDevSettings settings = do
    env <- getEnvironment
    let p = fromMaybe (getPort settings) $ lookup "PORT" env >>= readMaybe
        pdisplay = fromMaybe p $ lookup "DISPLAY_PORT" env >>= readMaybe
    putStrLn $ "Devel application launched: http://localhost:" ++ show pdisplay
    return $ setPort p settings

-- | Helper for develMain in the scaffolding.
develMainHelper :: IO (Settings, Application) -> IO ()
develMainHelper getSettingsApp = do
#ifndef mingw32_HOST_OS
    _ <- installHandler sigINT (Catch $ return ()) Nothing
#endif

    putStrLn "Starting devel application"
    (settings, app) <- getSettingsApp
    _ <- forkIO $ runSettings settings app
    loop
  where
    loop :: IO ()
    loop = do
        threadDelay 100000
        e <- doesFileExist "yesod-devel/devel-terminate"
        if e then terminateDevel else loop

    terminateDevel :: IO ()
    terminateDevel = exitSuccess

-- | Create a 'Logger' value (from yesod-core) out of a 'LoggerSet' (from
-- fast-logger).
makeYesodLogger :: LoggerSet -> IO Logger
makeYesodLogger loggerSet' = do
    (getter, _) <- clockDateCacher
    return $! Yesod.Core.Types.Logger loggerSet' getter
