CLIArgs.hs

-- |
-- Copyright: (c) 2019 Lucas David Traverso
-- License: MPL-2.0
-- Maintainer: Lucas David Traverso <lucas6246@gmail.com>
-- Stability: stable
-- Portability: portable
--
-- Command line arguments based source
module Conferer.Source.CLIArgs where

import Data.Text (Text)
import qualified Data.Text as Text
import Data.Maybe (mapMaybe)
import System.Environment (getArgs)

import Conferer.Source
import qualified Conferer.Source.InMemory as InMemory


-- | This source provides keys from the command line arguments passed into
-- the program. It only accepts arguments with @--@ and an equals, for
-- example: @./awesomeapp --warp.port=5000@
data CLIArgsSource =
  CLIArgsSource
  { originalCliArgs :: RawCLIArgs
  , innerSource :: Source
  } deriving (Show)

-- | Type alias for cli args
type RawCLIArgs = [String]

instance IsSource CLIArgsSource where
  getKeyInSource CLIArgsSource{..} key = do
    getKeyInSource innerSource key
  getSubkeysInSource CLIArgsSource{..} key = do
    getSubkeysInSource innerSource key


-- | Create a 'SourceCreator' using 'fromEnv'
fromConfig :: SourceCreator
fromConfig = \_config ->
  fromEnv

-- | Create a 'Source' using 'fromArgs' but using real cli args
fromEnv :: IO Source
fromEnv = do
  args <- getArgs
  return $ fromArgs args

-- | Create a 'Source' using cli args passed as parameter
fromArgs :: RawCLIArgs -> Source
fromArgs originalCliArgs =
  let configMap = parseArgsIntoKeyValue originalCliArgs
      innerSource = InMemory.fromAssociations configMap
  in Source $ CLIArgsSource {..}

-- | Parse an argument list into a dictionary suitable for a 'Source'
parseArgsIntoKeyValue :: [String] -> [(Key, Text)]
parseArgsIntoKeyValue =
  fmap (\s ->
    let (k, rawValue) = Text.breakOn "=" s
    in case Text.uncons rawValue of
         Nothing -> (fromText k, "true")
         (Just ('=', v)) -> (fromText k, v)
         -- Since rawValue comes from breaking on "=" the first character
         -- should always be '=' or none at all
         (Just (_, _)) ->
            error $ unlines
              [ "'"
              , Text.unpack rawValue
              , "' should always start with '='"
              ]
    ) .
  mapMaybe (Text.stripPrefix "--") .
  takeWhile (/= "--") .
  fmap Text.pack