darcsweb - src/DarcsWeb/Config.hs

{-# LANGUAGE OverloadedStrings #-}

module DarcsWeb.Config
  ( parseConfigFile
  , CfgMap
  , cfgLookup
  , cfgLookupDefault
  ) where

import           Data.Char (isSpace)
import           Data.Map.Strict (Map)
import qualified Data.Map.Strict as Map

type CfgMap = Map String String

-- | Parse a simple key = value config file.
--   Blank lines and lines starting with # are ignored.
parseConfigFile :: FilePath -> IO CfgMap
parseConfigFile path = do
    contents <- readFile path
    let ls = filter meaningful (lines contents)
    return $ Map.fromList (map parseLine ls)
  where
    meaningful l =
      let stripped = dropWhile isSpace l
      in not (null stripped) && head stripped /= '#'

    parseLine l =
      case break (== '=') l of
        (key, '=':val) -> (trim key, trim val)
        (key, _)       -> (trim key, "")

    trim = reverse . dropWhile isSpace . reverse . dropWhile isSpace

cfgLookup :: String -> CfgMap -> Maybe String
cfgLookup = Map.lookup

cfgLookupDefault :: String -> String -> CfgMap -> String
cfgLookupDefault key def m = maybe def id (Map.lookup key m)