{-# LANGUAGE NoImplicitPrelude #-}

{-# LANGUAGE OverloadedStrings #-}

-- | Parsing of stack command line arguments

module Data.Attoparsec.Args

( EscapingMode(..)

, argsParser

, parseArgs

, parseArgsFromString

) where

import Data.Attoparsec.Text ((<?>))

import qualified Data.Attoparsec.Text as P

import qualified Data.Text as T

import Stack.Prelude

-- | Mode for parsing escape characters.

data EscapingMode

= Escaping

| NoEscaping

deriving (Show,Eq,Enum)

-- | Parse arguments using 'argsParser'.

parseArgs :: EscapingMode -> Text -> Either String [String]

parseArgs mode = P.parseOnly (argsParser mode)

-- | Parse using 'argsParser' from a string.

parseArgsFromString :: EscapingMode -> String -> Either String [String]

parseArgsFromString mode = P.parseOnly (argsParser mode) . T.pack

-- | A basic argument parser. It supports space-separated text, and

-- string quotation with identity escaping: \x -> x.

argsParser :: EscapingMode -> P.Parser [String]

argsParser mode = many (P.skipSpace *> (quoted <|> unquoted)) <*

P.skipSpace <* (P.endOfInput <?> "unterminated string")

where

unquoted = P.many1 naked

quoted = P.char '"' *> string <* P.char '"'

string = many (case mode of

Escaping -> escaped <|> nonquote

NoEscaping -> nonquote)

escaped = P.char '\\' *> P.anyChar

nonquote = P.satisfy (/= '"')

naked = P.satisfy (not . flip elem ("\" " :: String))