{-# LANGUAGE TemplateHaskell #-}
module Text.HTML.Form.I18n(strings, i18n, stringsJSON) where

import Data.FileEmbed (embedDir, makeRelativeToProject)
import Data.Text.Encoding (decodeUtf8Lenient)
import Data.Text (unpack, pack)
import Data.ByteString (ByteString)

import qualified Data.Aeson.KeyMap as KM
import Data.Aeson.Key as K
import Data.Aeson (Value(String, Object))

import Data.List (isPrefixOf)
import Data.Maybe (fromMaybe)

files :: [(FilePath, ByteString)]
files = $(embedDir =<< makeRelativeToProject "i18n")
bs2str :: ByteString -> String
bs2str = unpack . decodeUtf8Lenient

strings :: String -> [(String, String)]
strings = fromMaybe [] . flip lookup [(k, parseKVs $ bs2str v) | (k, v) <- files]

i18n :: String -> String -> String
i18n lang key = fromMaybe key $ lookup key $ strings lang

stringsJSON :: String -> Value
stringsJSON = Object . KM.fromList . map inner . strings
  where inner (k, v) = (K.fromString k, String $ pack v)

------
--- Support
------

parseKVs :: String -> [(String, String)]
parseKVs = map inner . filter (isPrefixOf "#") . filter null . map strip . lines
  where inner line = let (key, val) = break (==':') line in (strip key, strip val)

-- | Removes any whitespace at the start or end of a string
strip :: String -> String
strip = lstrip . rstrip

-- | Same as 'strip', but applies only to the left side of the string.
lstrip :: String -> String
lstrip s = case s of
                  [] -> []
                  (x:xs) -> if elem x " \t\r\n"
                            then lstrip xs
                            else s

-- | Same as 'strip', but applies only to the right side of the string.
rstrip :: String -> String
rstrip = reverse . lstrip . reverse