{-# LANGUAGE LambdaCase      #-}
{-# LANGUAGE TemplateHaskell #-}

module Main where

import           Data.Default.Class        (def)
import           Data.List                 (intersperse)
import           Data.Monoid               ((<>))
import qualified Data.Text                 as T

import           System.Environment        (getArgs)
import           System.Directory          (doesFileExist)
import           System.IO.Temp            (writeSystemTempFile)

import           Text.Pandoc.Filter.Pyplot (plotTransformWithConfig, configuration, SaveFormat(..))
import           Text.Pandoc.JSON          (toJSONFilter)

import           Web.Browser               (openBrowser)

import qualified Data.Version              as V
import           Paths_pandoc_pyplot       (version)

import           ManPage                   (embedManualHtml)

supportedSaveFormats :: [SaveFormat]
supportedSaveFormats = enumFromTo minBound maxBound

manualHtml :: T.Text
manualHtml = T.pack $(embedManualHtml)

data Flag = Help
          | Version
          | Formats
          | Manual
    deriving (Eq)

parseFlag :: [String] -> Maybe Flag
parseFlag s
    | head s `elem` ["-h", "--help"]       = Just Help
    | head s `elem` ["-v", "--version"]    = Just Version
    | head s `elem` ["-f", "--formats"]    = Just Formats
    | head s `elem` ["-m", "--manual"]     = Just Manual
    | otherwise                            = Nothing -- This is the regular input from pandoc

flagAction :: Flag -> IO ()
flagAction f
    | f == Help    = showHelp
    | f == Version = showVersion
    | f == Formats = showFormats
    | f == Manual  = showManual
    | otherwise    = error "Unknown flag"
    where   
        showHelp    = putStrLn help
        showVersion = putStrLn (V.showVersion version)
        showFormats = putStrLn . mconcat . intersperse ", " . fmap show $ supportedSaveFormats
        showManual  = writeSystemTempFile "pandoc-pyplot-manual.html" (T.unpack manualHtml) 
                        >>= \fp -> openBrowser ("file:///" <> fp) >> return ()

help :: String
help =
    "\n\
    \\n\
    \   usage: pandoc-pyplot [-h, --help] [-v, --version] [-f, --formats] [-m, --manual]\n\
    \\n\
    \   This pandoc filter generates plots from Python code blocks using Matplotlib.\n\
    \   This allows to keep documentation and figures in perfect synchronicity.\n\
    \\n\
    \   Optional arguments:\n\
    \       -h, --help       Show this help message and exit.\n\
    \       -v, --version    Show version number and exit.\n\
    \       -f, --formats    Show supported output figure formats and exit.\n\
    \       -m, --manual     Open the manual page in the default web browser and exit.\n\
    \\n\
    \   Example usage with pandoc: \n\
    \\n\
    \       > pandoc --filter pandoc-pyplot input.md --output output.html\n\
    \\n\
    \   If you use pandoc-pyplot in combination with other filters, you probably want\n\
    \   to run pandoc-pyplot first. Here is an example with pandoc-crossref: \n\
    \\n\
    \       > pandoc --filter pandoc-pyplot --filter pandoc-crossref -i input.md -o output.pdf\n\
    \\n\
    \   More information can be found via the manual (pandoc-pyplot --manual) or the\n\ 
    \   repository README, located at \n\
    \       https://github.com/LaurentRDC/pandoc-pyplot\n"

main :: IO ()
main = do
    configExists <- doesFileExist ".pandoc-pyplot.yml"
    config <- if configExists
                then configuration ".pandoc-pyplot.yml"
                else def

    getArgs >>= \args -> case parseFlag args of
        Just f  -> flagAction f
        Nothing -> toJSONFilter (plotTransformWithConfig config)