Main.hs

module Rattletrap.Main where

import Rattletrap.Json ()
import Rattletrap.Replay
import Rattletrap.Version

import qualified Data.Aeson as Aeson
import qualified Data.Binary.Get as Binary
import qualified Data.Binary.Put as Binary
import qualified Data.ByteString.Lazy as ByteString
import qualified Data.Version as Version
import qualified System.Environment as Environment

-- | Gets command-line arguments and passes them to 'mainWithArgs'.
main :: IO ()
main = do
  args <- Environment.getArgs
  mainWithArgs args

-- | Runs the main command-line interface. Can be used in one of three modes:
--
-- 1. @mainWithArgs ["version"]@: Prints out the version number and exits.
--    Mostly useful for debugging.
-- 2. @mainWithArgs ["decode"]@: Parses a raw replay into JSON. By default
--    this reads from STDIN and writes to STDOUT. To read from a file, pass a
--    second argument like @mainWithArgs ["decode", "input.replay"]@. To write
--    to a file, pass a third argument like
--    @mainWithArgs ["decode", "input.replay", "output.json"]@.
-- 3. @mainWithArgs ["encode"]@: Generates a raw replay from JSON. The
--    handling of input and output is the same as decoding.
mainWithArgs :: [String] -> IO ()
mainWithArgs args =
  case args of
    ["version"] -> putStrLn (Version.showVersion version)
    "decode":files -> do
      (getInput, putOutput) <- getIO files
      input <- getInput
      let replay = Binary.runGet getReplay input
      let output = Aeson.encode replay
      putOutput output
    "encode":files -> do
      (getInput, putOutput) <- getIO files
      input <- getInput
      case Aeson.eitherDecode input of
        Left message -> fail ("could not parse JSON: " ++ message)
        Right replay -> do
          let output = Binary.runPut (putReplay replay)
          putOutput output
    _ -> fail ("unexpected arguments " ++ show args)

getIO :: [FilePath]
      -> IO (IO ByteString.ByteString, ByteString.ByteString -> IO ())
getIO files =
  case files of
    [] -> pure (ByteString.getContents, ByteString.putStr)
    [i] -> pure (ByteString.readFile i, ByteString.putStr)
    [i, o] -> pure (ByteString.readFile i, ByteString.writeFile o)
    _ -> fail ("unexpected arguments " ++ show files)