{-# LANGUAGE OverloadedStrings #-}
module Text.HTML.Form.WebApp (renderPage, Form(..)) where

import Data.ByteString as BS
import Data.Text as Txt
import Data.Text.Encoding as Txt
import Text.Read (readMaybe)
import Network.URI (unEscapeString)

import Text.HTML.Form (Form(..), Input(..))
import Text.HTML.Form.WebApp.Ginger (template)
import Text.HTML.Form.Query (renderQueryString)

renderPage :: Form -> [Text] -> [(ByteString, Maybe ByteString)] -> IO (Maybe Text)
renderPage form (n:path) query
    | Just ix <- readMaybe $ Txt.unpack n, ix < Prelude.length (inputs form) =
        renderInput form ix (inputs form !! ix) path query
renderPage form [] _ = return $ Just $ Txt.concat [
    "<a href='/0?", Txt.pack $ renderQueryString form, "/'>Start!</a>"]
renderPage _ _ _ = return Nothing

renderInput :: Form -> Int -> Input -> [Text] -> [(ByteString, Maybe ByteString)] ->
    IO (Maybe Text)
renderInput form ix input [""] qs = renderInput form ix input [] qs
renderInput form ix input@Input { multiple = True } [p] qs
    | '=':v' <- Txt.unpack p,
            (utf8 $ inputName input, Just $ utf8' v') `Prelude.elem` qs =
        renderInput form ix input [] $
            unset (inputName input) (Txt.pack $ unEscapeString v') qs
    | '=':v' <- Txt.unpack p = renderInput form ix input [] $
        (utf8 $ inputName input, Just $ utf8' $ unEscapeString v'):qs
renderInput form ix input [p] qs
    | '=':v' <- Txt.unpack p = renderInput form ix input [] $
        set (inputName input) (Txt.pack $ unEscapeString v') qs
renderInput form ix input@Input {inputType="checkbox", inputName=k', value=v'} [] qs
    | (utf8 k', Just $ utf8 v') `Prelude.elem` qs =
        template "checkbox.html" form ix input $ unset k' v' qs
    | v' == "", (utf8 k', Nothing) `Prelude.elem` qs =
        template "checkbox.html" form ix input [
            q | q@(k, v) <- qs, not (k == utf8 k' && v == Nothing)]
    | otherwise =
        template "checkbox.html" form ix input $ (utf8 k', Just $ utf8 v'):qs
renderInput form ix input@Input {inputType="radio", inputName=k', value=v'} [] qs =
    template "checkbox.html" form ix input $ set k' v' qs
renderInput form ix input@Input { inputType="<select>" } [] qs =
    template "select.html" form ix input qs
renderInput _ _ input _ _ =
    return $ Just $ Txt.concat ["Unknown input type: ", inputType input]

utf8 :: Text -> ByteString
utf8 = Txt.encodeUtf8
utf8' :: String -> ByteString
utf8' = utf8 . Txt.pack
set :: Text -> Text -> [(ByteString, Maybe ByteString)]
    -> [(ByteString, Maybe ByteString)]
set k' v' qs = (utf8 k', Just $ utf8 v'):[q | q@(k, _) <- qs, k /= utf8 k']
unset :: Text -> Text -> [(ByteString, Maybe ByteString)]
    -> [(ByteString, Maybe ByteString)]
unset k' v' qs = [q | q@(k, v) <- qs, not (k == utf8 k' && v == Just (utf8 v'))]