module Main where

import Text.ParserCombinators.ReadP
import Control.Monad
import Control.Applicative

type HeaderLevel = Int

newtype URL = URL {getUrl :: String}
newtype ImgPath = ImgPath {getPath :: String}

data MdToken = Header HeaderLevel MdToken
             | Para [MdToken]
             | Linebreak
             | HorizontalRule
             | Blockquote MdToken
             | UnordList [MdToken]
             | OrdList [MdToken]
             | Code String
             | Codeblock String
             | Link [MdToken] URL
             | Image [MdToken] ImgPath
             | Bold [MdToken]
             | Italic [MdToken]
             | Strikethrough [MdToken]
             | Unit String

-- Deriving Show for MdToken
instance Show MdToken where
    show (Header level token) = "<h" ++ show level ++ ">" ++ show token ++ "</h" ++ show level ++ ">"
    show (Para tokens) = concat(map show tokens)
    show Linebreak = "\n"
    show HorizontalRule = "---------"
    show (Blockquote token) = "BLOCK" ++ show token
    show (UnordList tokens) = "UNORD" ++ concat(map show tokens)
    show (OrdList tokens) = "ORD" ++ concat(map show tokens)
    show (Code code) = concat(map show code)
    show (Codeblock code) = concat(map show code)
    show (Link txt url) = "<a href=" ++ (getUrl url) ++ ">" ++ concat(map show txt) ++ "</a>"
    show (Image txt path) = "<img src=" ++ (getPath path) ++ ">" ++ concat(map show txt) ++ "</img>"
    show (Bold tokens) = "<b>" ++ concat(map show tokens) ++ "</b>"
    show (Italic tokens) = "<i>" ++ concat(map show tokens) ++ "</i>"
    show (Strikethrough tokens) = "<s>" ++ concat (map show tokens) ++ "</s>"
    show (Unit unit) = show unit



-- ---------------
-- Helpers
mustBeHash :: ReadP Char
mustBeHash = satisfy (\x -> x == '#')




-- ---------------

parseHeader :: ReadP MdToken
parseHeader = do
        headers <- many1 mustBeHash
        when ((length headers) > 6)
            pfail
        _ <- string " "
        text <- munch1 (const True) -- Parse until EOL
        return (Header (length headers) text)
                
parseBold :: ReadP MdToken
parseBold = do
        _ <- string "__" <|> string "**"
        text <- munch1 (\x -> x /= '_' && x /= '*') -- Parse until first asterisk/underscore
        _ <- char '_' <|> char '*' -- Throw away the second asterisk/underscore
        return (Bold text)


parseMain :: String -> []MdToken

parseMain 
            

main :: IO ()
main = putStrLn "Hello, Haskell!"