-- | This is the main Hakyll module, exporting the important @hakyl@ function.
--
--   Most configurations would use this @hakyll@ function more or less as the
--   main function:
--
--   > main = hakyll $ do
--   >     directory css "css"
--   >     directory static "images"
--
module Text.Hakyll
    ( defaultHakyllConfiguration
    , hakyll
    , hakyllWithConfiguration
    ) where

import Control.Monad.Reader (runReaderT, liftIO, ask)
import Control.Concurrent (forkIO, threadDelay)
import Control.Monad (when)
import qualified Data.Map as M
import System.Environment (getArgs, getProgName)
import System.Directory (doesDirectoryExist, removeDirectoryRecursive)
import System.Time (getClockTime)

import Network.Hakyll.SimpleServer (simpleServer)
import Text.Hakyll.HakyllMonad
import Text.Hakyll.File

-- | The default hakyll configuration.
defaultHakyllConfiguration :: HakyllConfiguration
defaultHakyllConfiguration = HakyllConfiguration
    { absoluteUrl       = ""
    , additionalContext = M.empty
    , siteDirectory     = "_site"
    , cacheDirectory    = "_cache"
    , enableIndexUrl    = False
    , previewPollDelay  = 1000000
    }

-- | Main function to run Hakyll with the default configuration. The
--   absolute URL is only used in certain cases, for example RSS feeds et
--   cetera.
hakyll :: String    -- ^ Absolute URL of your site. Used in certain cases.
       -> Hakyll () -- ^ You code.
       -> IO ()
hakyll absolute = hakyllWithConfiguration configuration
  where
    configuration = defaultHakyllConfiguration { absoluteUrl = absolute }

-- | Main function to run hakyll with a custom configuration.
hakyllWithConfiguration :: HakyllConfiguration -> Hakyll () -> IO ()
hakyllWithConfiguration configuration buildFunction = do
    args <- getArgs
    let f = case args of ["build"]      -> buildFunction
                         ["clean"]      -> clean
                         ["preview", p] -> preview buildFunction (read p)
                         ["preview"]    -> preview buildFunction 8000
                         ["rebuild"]    -> clean >> buildFunction
                         ["server", p]  -> server (read p)
                         ["server"]     -> server 8000
                         _              -> help
    runReaderT f configuration

-- | Clean up directories.
clean :: Hakyll ()
clean = do askHakyll siteDirectory >>= remove'
           askHakyll cacheDirectory >>= remove'
  where
    remove' dir = liftIO $ do putStrLn $ "Removing " ++ dir ++ "..."
                              exists <- doesDirectoryExist dir
                              when exists $ removeDirectoryRecursive dir

-- | Autocompile mode.
preview :: Hakyll () -> Integer -> Hakyll ()
preview buildFunction port = do
    buildFunction
    _ <- startServer
    liftIO getClockTime >>= run
  where
    startServer = do configuration <- ask
                     liftIO $ forkIO $ runReaderT (server port) configuration
    run time = do delay <- askHakyll previewPollDelay
                  liftIO $ threadDelay delay
                  contents <- getRecursiveContents "."
                  valid <- isMoreRecent time contents
                  if valid then run time
                           else do buildFunction
                                   liftIO getClockTime >>= run

-- | Show usage information.
help :: Hakyll ()
help = liftIO $ do
    name <- getProgName
    putStrLn $  "This is a Hakyll site generator program. You should always\n"
             ++ "run it from the project root directory.\n"
             ++ "\n"
             ++ "Usage:\n"
             ++ name ++ " build           Generate the site.\n"
             ++ name ++ " clean           Clean up and remove cache.\n"
             ++ name ++ " help            Show this message.\n"
             ++ name ++ " preview [port]  Run a server and autocompile.\n"
             ++ name ++ " rebuild         Clean up and build again.\n"
             ++ name ++ " server [port]   Run a local test server.\n"

-- | Start a server at the given port number.
server :: Integer -> Hakyll ()
server p = askHakyll siteDirectory >>= liftIO . simpleServer (fromIntegral p)