content: {-# LANGUAGE PatternGuards, OverloadedStrings #-}
  {-|
      This module converts a list of 'Tag' back into a string.
  -}
  
  module Text.HTML.TagSoup.Render
      (
      renderTags, renderTagsOptions, escapeHTML,
      RenderOptions(..), renderOptions
      ) where
  
  import Text.HTML.TagSoup.Entity
  import Text.HTML.TagSoup.Type
  import Text.StringLike
  
  
  -- | These options control how 'renderTags' works.
  --
  --   The strange quirk of only minimizing @\<br\>@ tags is due to Internet Explorer treating
  --   @\<br\>\<\/br\>@ as @\<br\>\<br\>@.
  data RenderOptions str = RenderOptions
      {optEscape :: str -> str        -- ^ Escape a piece of text (default = escape the four characters @&\"\<\>@)
      ,optMinimize :: str -> Bool     -- ^ Minimise \<b\>\<\/b\> -> \<b/\> (default = minimise only @\<br\>@ tags)
      ,optRawTag :: str -> Bool      -- ^ Should a tag be output with no escaping (default = true only for @script@)
      }
  
  
  -- | Replace the four characters @&\"\<\>@ with their HTML entities ('escapeXML' lifted to 'StringLike').
  escapeHTML :: StringLike str => str -> str
  escapeHTML = fromString . escapeXML . toString
  
  -- | The default render options value, described in 'RenderOptions'.
  renderOptions :: StringLike str => RenderOptions str
  renderOptions = RenderOptions escapeHTML (\x -> toString x == "br") (\x -> toString x == "script")
  
  
  -- | Show a list of tags, as they might have been parsed, using the default settings given in
  --   'RenderOptions'.
  --
  -- > renderTags [TagOpen "hello" [],TagText "my&",TagClose "world"] == "<hello>my&amp;</world>"
  renderTags :: StringLike str => [Tag str] -> str
  renderTags = renderTagsOptions renderOptions
  
  
  -- | Show a list of tags using settings supplied by the 'RenderOptions' parameter,
  --   eg. to avoid escaping any characters one could do:
  --
  -- > renderTagsOptions renderOptions{optEscape = id} [TagText "my&"] == "my&"
  renderTagsOptions :: StringLike str => RenderOptions str -> [Tag str] -> str
  renderTagsOptions opts = strConcat . tags
      where
          ss x = [x]
  
          tags (TagOpen name atts:TagClose name2:xs)
              | name == name2 && optMinimize opts name = open name atts " /" ++ tags xs
          tags (TagOpen name atts:xs)
              | Just ('?',_) <- uncons name = open name atts " ?" ++ tags xs
              | optRawTag opts name =
                  let (a,b) = break (== TagClose name) (TagOpen name atts:xs)
                  in concatMap (\x -> case x of TagText s -> [s]; _ -> tag x) a ++ tags b
          tags (x:xs) = tag x ++ tags xs
          tags [] = []
  
          tag (TagOpen name atts) = open name atts ""
          tag (TagClose name) = ["</", name, ">"]
          tag (TagText text) = [txt text]
          tag (TagComment text) = ss "<!--" ++ com text ++ ss "-->"
          tag _ = ss ""
  
          txt = optEscape opts
          open name atts shut = ["<",name] ++ concatMap att atts ++ [shut,">"]
          att ("","") = [" \"\""]
          att (x ,"") = [" ", x]
          att ("", y) = [" \"",txt y,"\""]
          att (x , y) = [" ",x,"=\"",txt y,"\""]
  
          com xs | Just ('-',xs) <- uncons xs, Just ('-',xs) <- uncons xs, Just ('>',xs) <- uncons xs = "-- >" : com xs
          com xs = case uncons xs of
              Nothing -> []
              Just (x,xs) -> fromChar x : com xs
  