{-# LANGUAGE TemplateHaskell, QuasiQuotes, ScopedTypeVariables #-}
-- | A generator is executed at compile time to load a list of entries
-- to embed into the subsite.  This module contains several basic generators,
-- but the design of generators and entries is such that it is straightforward
-- to make custom generators for your own specific purposes, see <#g:4 this section>.
module Yesod.EmbeddedStatic.Generators (
  -- * Generators
    Location
  , embedFile
  , embedFileAt
  , embedDir
  , embedDirAt
  , concatFiles
  , concatFilesWith

  -- * Compression options for 'concatFilesWith'
  , jasmine
  , uglifyJs
  , yuiJavascript
  , yuiCSS
  , closureJs
  , compressTool
  , tryCompressTools

  -- * Util
  , pathToName

  -- * Custom Generators

  -- $example
) where

import Control.Applicative as A ((<$>), (<*>))
import Control.Exception (try, SomeException)
import Control.Monad (forM, when)
import Data.Char (isDigit, isLower)
import Data.Default (def)
import Data.Maybe (isNothing)
import Language.Haskell.TH
import Network.Mime (defaultMimeLookup)
import System.Directory (doesDirectoryExist, getDirectoryContents, findExecutable)
import System.FilePath ((</>))
import Text.Jasmine (minifym)
import qualified Data.ByteString as BS
import qualified Data.ByteString.Lazy as BL
import Conduit
import qualified Data.Text as T
import qualified System.Process as Proc
import System.Exit (ExitCode (ExitSuccess))
import Control.Concurrent.Async (Concurrently (..))
import System.IO (hClose)

import Yesod.EmbeddedStatic.Types

-- | Embed a single file.  Equivalent to passing the same string twice to 'embedFileAt'.
embedFile :: FilePath -> Generator
embedFile f = embedFileAt f f

-- | Embed a single file at a given location within the static subsite and generate a
--   route variable based on the location via 'pathToName'.  The @FilePath@ must be a relative
--   path to the directory in which you run @cabal build@.  During development, the file located
--   at this filepath will be reloaded on every request.  When compiling for production, the contents
--   of the file will be embedded into the executable and so the file does not need to be
--   distributed along with the executable.
embedFileAt :: Location -> FilePath -> Generator
embedFileAt loc f = do
    let mime = defaultMimeLookup $ T.pack f
    let entry = def {
                    ebHaskellName = Just $ pathToName loc
                  , ebLocation = loc
                  , ebMimeType = mime
                  , ebProductionContent = fmap BL.fromStrict (BS.readFile f)
                  , ebDevelReload = [| fmap BL.fromStrict
                                       (BS.readFile $(litE $ stringL f)) |]
                  }
    return [entry]

-- | List all files recursively in a directory
getRecursiveContents :: Location -- ^ The directory to search
                     -> FilePath   -- ^ The prefix to add to the filenames
                     -> IO [(Location,FilePath)]
getRecursiveContents prefix topdir = do
  names <- getDirectoryContents topdir
  let properNames = filter (`notElem` [".", ".."]) names
  paths <- forM properNames $ \name -> do
    let path = topdir </> name
    let loc = if null prefix then name else prefix ++ "/" ++ name
    isDirectory <- doesDirectoryExist path
    if isDirectory
      then getRecursiveContents loc path
      else return [(loc, path)]
  return (concat paths)

-- | Embed all files in a directory into the static subsite.
-- 
-- Equivalent to passing the empty string as the location to 'embedDirAt',
-- so the directory path itself is not part of the resource locations (and so
-- also not part of the generated route variable names).
embedDir :: FilePath -> Generator
embedDir = embedDirAt ""

-- | Embed all files in a directory to a given location within the static subsite.
--
-- The directory tree rooted at the 'FilePath' (which must be relative to the directory in
-- which you run @cabal build@) is embedded into the static subsite at the given
-- location.  Also, route variables will be created based on the final location
-- of each file.  For example, if a directory \"static\" contains the files
--
-- * css/bootstrap.css
--
-- * js/jquery.js
--
-- * js/bootstrap.js
-- 
-- then @embedDirAt \"somefolder\" \"static\"@ will
--
-- * Make the file @static\/css\/bootstrap.css@ available at the location
--   @somefolder\/css\/bootstrap.css@ within the static subsite and similarly
--   for the other two files.
--
-- * Create variables @somefolder_css_bootstrap_css@, @somefolder_js_jquery_js@,
--   @somefolder_js_bootstrap_js@ all of type @Route EmbeddedStatic@.
--
-- * During development, the files will be reloaded on every request.  During
--   production, the contents of all files will be embedded into the executable.
--
-- * During development, files that are added to the directory while the server
--   is running will not be detected.  You need to recompile the module which
--   contains the call to @mkEmbeddedStatic@.  This will also generate new route
--   variables for the new files.
embedDirAt :: Location -> FilePath -> Generator
embedDirAt loc dir = do
    files <- runIO $ getRecursiveContents loc dir
    concat <$> mapM (uncurry embedFileAt) files

-- | Concatinate a list of files and embed it at the location.  Equivalent to passing @return@ to
--   'concatFilesWith'.
concatFiles :: Location -> [FilePath] -> Generator
concatFiles loc files = concatFilesWith loc return files

-- | Concatinate a list of files into a single 'BL.ByteString', run the resulting content through the given
--   function, embed it at the given location, and create a haskell variable name for the route based on
--   the location.
--
--   The processing function is only run when compiling for production, and the processing function is
--   executed at compile time.  During development, on every request the files listed are reloaded,
--   concatenated, and served as a single resource at the given location without being processed.
concatFilesWith :: Location -> (BL.ByteString -> IO BL.ByteString) -> [FilePath] -> Generator
concatFilesWith loc process files = do
    let load = do putStrLn $ "Creating " ++ loc
                  BL.concat <$> mapM BL.readFile files >>= process
        expFiles = listE $ map (litE . stringL) files
        expCt = [| BL.concat <$> mapM BL.readFile $expFiles |]
        mime = defaultMimeLookup $ T.pack loc
    return [def { ebHaskellName = Just $ pathToName loc
                , ebLocation = loc
                , ebMimeType = mime
                , ebProductionContent = load
                , ebDevelReload = expCt
                }]

-- | Convienient rexport of 'minifym' with a type signature to work with 'concatFilesWith'.
jasmine :: BL.ByteString -> IO BL.ByteString
jasmine ct = return $ either (const ct) id $ minifym ct

-- | Use <https://github.com/mishoo/UglifyJS2 UglifyJS2> to compress javascript.
-- Assumes @uglifyjs@ is located in the path and uses options @[\"-m\", \"-c\"]@
-- to both mangle and compress and the option \"-\" to cause uglifyjs to read from
-- standard input.
uglifyJs :: BL.ByteString -> IO BL.ByteString
uglifyJs = compressTool "uglifyjs" ["-", "-m", "-c"]

-- | Use <http://yui.github.io/yuicompressor/ YUI Compressor> to compress javascript.
-- Assumes a script @yuicompressor@ is located in the path.  If not, you can still
-- use something like
--
-- > compressTool "java" ["-jar", "/path/to/yuicompressor.jar", "--type", "js"]
yuiJavascript :: BL.ByteString -> IO BL.ByteString
yuiJavascript = compressTool "yuicompressor" ["--type", "js"]

-- | Use <http://yui.github.io/yuicompressor/ YUI Compressor> to compress CSS.
-- Assumes a script @yuicompressor@ is located in the path.
yuiCSS :: BL.ByteString -> IO BL.ByteString
yuiCSS = compressTool "yuicompressor" ["--type", "css"]

-- | Use <https://developers.google.com/closure/compiler/ Closure> to compress
-- javascript using the default options.  Assumes a script @closure@ is located in
-- the path. If not, you can still run using
--
-- > compressTool "java" ["-jar", "/path/to/compiler.jar"]
closureJs :: BL.ByteString -> IO BL.ByteString
closureJs = compressTool "closure" []

-- | Helper to convert a process into a compression function.  The process
-- should be set up to take input from standard input and write to standard output.
compressTool :: FilePath -- ^ program
             -> [String] -- ^ options
             -> BL.ByteString -> IO BL.ByteString
compressTool f opts ct = do
    mpath <- findExecutable f
    when (isNothing mpath) $
        fail $ "Unable to find " ++ f
    let p = (Proc.proc f opts)
                { Proc.std_in = Proc.CreatePipe
                , Proc.std_out = Proc.CreatePipe
                }
    (Just hin, Just hout, _, ph) <- Proc.createProcess p
    (compressed, (), code) <- runConcurrently $ (,,)
        A.<$> Concurrently (runConduit $ sourceHandle hout .| sinkLazy)
        A.<*> Concurrently (BL.hPut hin ct >> hClose hin)
        A.<*> Concurrently (Proc.waitForProcess ph)
    if code == ExitSuccess
        then do
            putStrLn $ "Compressed successfully with " ++ f
            return compressed
        else error $ "compressTool: compression failed with " ++ f


-- | Try a list of processing functions (like the compressions above) one by one until
-- one succeeds (does not raise an exception).  Once a processing function succeeds,
-- none of the remaining functions are used.  If none succeeds, the input is just
-- returned unprocessed.  This is helpful if you are distributing
-- code on hackage and do not know what compressors the user will have installed.  You
-- can list several and they will be tried in order until one succeeds.
tryCompressTools :: [BL.ByteString -> IO BL.ByteString] -> BL.ByteString -> IO BL.ByteString
tryCompressTools [] x = return x
tryCompressTools (p:ps) x = do
    mres <- try $ p x
    case mres of
        Left (err :: SomeException) -> do
            putStrLn $ show err
            tryCompressTools ps x
        Right res -> return res

-- | Clean up a path to make it a valid haskell name by replacing all non-letters
--   and non-numbers by underscores.  In addition, if the path starts with a capital
--   letter or number add an initial underscore.
pathToName :: FilePath -> Name
pathToName f = routeName
    where
      replace c
        | 'A' <= c && c <= 'Z' = c
        | 'a' <= c && c <= 'z' = c
        | '0' <= c && c <= '9' = c
        | otherwise = '_'
      name = map replace f
      routeName = mkName $
            case () of
                ()
                    | null name -> error "null-named file"
                    | isDigit (head name) -> '_' : name
                    | isLower (head name) -> name
                    | otherwise -> '_' : name


-- $example
-- Here is an example of creating your own custom generator.
-- Because of template haskell stage restrictions, you must define generators in a
-- different module from where you use them.  The following generator will embed a
-- JSON document that contains the compile time.
--
-- >{-# LANGUAGE TemplateHaskell, QuasiQuotes, OverloadedStrings #-}
-- >module CompileTime where
-- >
-- >import Data.Aeson
-- >import Data.Default
-- >import Data.Time
-- >import Yesod.EmbeddedStatic.Generators
-- >import Yesod.EmbeddedStatic.Types
-- >import qualified Data.ByteString.Lazy as BL
-- >
-- >getTime :: IO BL.ByteString
-- >getTime = do
-- >    t <- getCurrentTime
-- >    return $ encode $
-- >        object [ "compile_time" .= show t ]
-- >
-- >timeGenerator :: Location -> Generator
-- >timeGenerator loc =
-- >    return $ [def
-- >        { ebHaskellName = Just $ pathToName loc
-- >        , ebLocation    = loc
-- >        , ebMimeType    = "application/json"
-- >        , ebProductionContent = getTime
-- >        , ebDevelReload = [| getTime |]
-- >        }]
--
-- Notice how the @getTime@ action is given as both 'ebProductionContent' and
-- 'ebDevelReload'.  The result is that during development, the @getTime@ action
-- will be re-executed on every request so the time returned will be different
-- for each reload.  When compiling for production, the @getTime@ action will
-- be executed once at compile time to produce the content to embed and never
-- called at runtime.
--
-- Here is a small example yesod program using this generator.  Try toggling
-- the development argument to @mkEmbeddedStatic@.
-- 
-- >{-# LANGUAGE TemplateHaskell, QuasiQuotes, TypeFamilies #-}
-- >module Main where
-- >
-- >import Yesod
-- >import Yesod.EmbeddedStatic
-- >import CompileTime (timeGenerator)
-- >
-- >mkEmbeddedStatic True "eStatic" [timeGenerator "compile-time.json"]
-- >
-- >-- The above will generate variables
-- >-- eStatic :: EmbeddedStatic
-- >-- compile_time_json :: Route EmbeddedStatic
-- >
-- >data MyApp = MyApp { getStatic :: EmbeddedStatic }
-- >
-- >mkYesod "MyApp" [parseRoutes|
-- >/ HomeR GET
-- >/static StaticR EmbeddedStatic getStatic
-- >|]
-- >
-- >instance Yesod MyApp
-- >
-- >getHomeR :: Handler Html
-- >getHomeR = defaultLayout $ [whamlet|
-- ><h1>Hello
-- ><p>Check the 
-- >    <a href=@{StaticR compile_time_json}>compile time
-- >|]
-- >
-- >main :: IO ()
-- >main = warp 3000 $ MyApp eStatic
