potrero/src/Potrero/Opts.hs

module Potrero.Opts
  ( Config(..)
  , Mode(..)
  , getConfig

  , usage
  , version
  ) where

import qualified System.Console.GetOpt as Opt

data Mode
  = ShowHelp
  | ShowVersion
  | REPL
    deriving (Eq, Show)

data Config = Config
  { configFiles     :: [FilePath]
  , configShowRolls :: Bool
  , configMode      :: Mode
  } deriving (Eq, Show)

defaultConfig :: Config
defaultConfig = Config
  { configFiles     = []
  , configShowRolls = False
  , configMode      = REPL
  }

opts :: [Opt.OptDescr (Config -> Config)]
opts =
  [ Opt.Option ['s'] ["show-rolls"]
    (Opt.NoArg (\ conf -> conf { configShowRolls = True }))
    "show the exact roll results"
  , Opt.Option ['h'] ["help"]
    (Opt.NoArg (\ conf -> conf { configMode = ShowHelp }))
    "show this help text"
  , Opt.Option ['v'] ["version"]
    (Opt.NoArg (\ conf -> conf { configMode = ShowVersion }))
    "show the version"
  ]

usage :: String
usage = Opt.usageInfo "potrero" opts

version :: String
version = "potrero, version 0.1"

getConfig :: [String] -> Either String Config
getConfig args =
  let (fs, files, errors) = Opt.getOpt Opt.Permute opts args
      conf = foldr ($) defaultConfig fs
  in case errors of
    [] -> pure conf { configFiles = files }
    _  -> Left (unlines errors)