{- |
   Module      : Text.Pandoc.Writers.HTML 
   Copyright   : Copyright (C) 2006 John MacFarlane
   License     : GNU GPL, version 2 or above 

   Maintainer  : John MacFarlane <jgm at berkeley dot edu>
   Stability   : provisional
   Portability : portable

Conversion of 'Pandoc' documents to HTML.
-}
module Text.Pandoc.Writers.HTML ( 
                                 writeHtml
                                ) where
import Text.Pandoc.Definition
import Text.Pandoc.Shared
import Text.Html ( stringToHtmlString )
import Text.Regex ( mkRegex, matchRegex )
import Numeric ( showHex )
import Data.Char ( ord, toLower )
import Data.List ( isPrefixOf, partition )

-- | Convert Pandoc document to string in HTML format.
writeHtml :: WriterOptions -> Pandoc -> String
writeHtml options (Pandoc (Meta title authors date) blocks) = 
  let titlePrefix = writerTitlePrefix options in
  let topTitle = if not (null titlePrefix)
                    then [Str titlePrefix] ++ (if not (null title) 
                                                  then [Str " - "] ++ title
                                                  else [])
                    else title in
  let head = if (writerStandalone options)
                then htmlHeader options (Meta topTitle authors date)
                else "" 
      titleBlocks = if (writerStandalone options) && (not (null title)) && 
                    (not (writerS5 options))
                       then [RawHtml "<h1 class=\"title\">", Plain title, 
                             RawHtml "</h1>\n"]
                       else []
      foot = if (writerStandalone options) then "</body>\n</html>\n" else "" 
      blocks' = replaceReferenceLinks (titleBlocks ++ blocks)
      (noteBlocks, blocks'') = partition isNoteBlock blocks' 
      body = (writerIncludeBefore options) ++ 
             concatMap (blockToHtml options) blocks'' ++
             footnoteSection options noteBlocks ++
             (writerIncludeAfter options) in
  head ++ body ++ foot

-- | Convert list of Note blocks to a footnote <div>.
-- Assumes notes are sorted.
footnoteSection :: WriterOptions -> [Block] -> String
footnoteSection options notes =
  if null notes 
    then ""
    else "<div class=\"footnotes\">\n<hr />\n<ol>\n" ++
         concatMap (blockToHtml options) notes ++
         "</ol>\n</div>\n"  

-- | Obfuscate a "mailto:" link using Javascript.
obfuscateLink :: WriterOptions -> [Inline] -> String -> String
obfuscateLink options text src =
  let emailRegex = mkRegex "mailto:*([^@]*)@(.*)"
      text' = inlineListToHtml options text 
      src' = map toLower src in
  case (matchRegex emailRegex src') of
    (Just [name, domain]) ->
      let domain' = gsub "\\." " dot " domain
          at' = obfuscateChar '@' in
      let linkText = if src' == ("mailto:" ++ text')
                        then "e"
                        else "'" ++ text' ++ "'" 
          altText  = if src' == ("mailto:" ++ text')
                        then name ++ " at " ++ domain'
                        else text' ++ " (" ++ name ++ " at " ++ 
                             domain' ++ ")" in 
      "<script type=\"text/javascript\">\n<!--\nh='" ++ 
      obfuscateString domain ++ "';a='" ++ at' ++ "';n='" ++ 
      obfuscateString name ++ "';e=n+a+h;\n" ++
      "document.write('<a h'+'ref'+'=\"ma'+'ilto'+':'+e+'\">'+" ++ 
      linkText  ++ "+'<\\/'+'a'+'>');\n// -->\n</script><noscript>" ++ 
      obfuscateString altText ++ "</noscript>"
    _ -> "<a href=\"" ++ src ++ "\">" ++ text' ++ "</a>" -- malformed email

-- | Obfuscate character as entity.
obfuscateChar :: Char -> String
obfuscateChar char = 
  let num = ord char in
  let numstr = if even num then (show num) else ("x" ++ (showHex num "")) in
  "&#" ++ numstr ++ ";"

-- | Obfuscate string using entities.
obfuscateString :: String -> String
obfuscateString = concatMap obfuscateChar

-- | Escape string, preserving character entities and quote.
stringToHtml :: String -> String
stringToHtml str = escapePreservingRegex stringToHtmlString 
                   (mkRegex "\"|(&[[:alnum:]]*;)") str

-- | Escape string as in 'stringToHtml' but add smart typography filter.
stringToSmartHtml :: String -> String
stringToSmartHtml = 
  let escapeDoubleQuotes = 
        gsub "(\"|&quot;)" "&rdquo;" . -- rest are right quotes
        gsub "(\"|&quot;)(&r[sd]quo;)" "&rdquo;\\2" . 
             -- never left quo before right quo
        gsub "(&l[sd]quo;)(\"|&quot;)" "\\2&ldquo;" . 
             -- never right quo after left quo
        gsub "([ \t])(\"|&quot;)" "\\1&ldquo;" . 
             -- never right quo after space 
        gsub "(\"|&quot;)([^,.;:!?^) \t-])" "&ldquo;\\2" . -- "word left
        gsub "(\"|&quot;)('|`|&lsquo;)" "&rdquo;&rsquo;" . 
             -- right if it got through last filter
        gsub "(\"|&quot;)('|`|&lsquo;)([^,.;:!?^) \t-])" "&ldquo;&lsquo;\\3" .
             -- "'word left
        gsub "``" "&ldquo;" .
        gsub "''" "&rdquo;"
      escapeSingleQuotes =
        gsub "'" "&rsquo;"  . -- otherwise right
        gsub "'(&r[sd]quo;)" "&rsquo;\\1" . -- never left quo before right quo
        gsub "(&l[sd]quo;)'" "\\1&lsquo;" . -- never right quo after left quo
        gsub "([ \t])'" "\\1&lsquo;" . -- never right quo after space 
        gsub "`" "&lsquo;"  . -- ` is left
        gsub "([^,.;:!?^) \t-])'" "\\1&rsquo;" .  -- word' right
        gsub "^('|`)([^,.;:!?^) \t-])" "&lsquo;\\2" . -- 'word left 
        gsub "('|`)(\"|&quot;|&ldquo;|``)" "&lsquo;&ldquo;" .  -- '"word left
        gsub "([^,.;:!?^) \t-])'(s|S)" "\\1&rsquo;\\2" . -- possessive
        gsub "([[:space:]])'([^,.;:!?^) \t-])" "\\1&lsquo;\\2" . -- 'word left
        gsub "'([0-9][0-9](s|S))" "&rsquo;\\1"  -- '80s - decade abbrevs.
      escapeDashes = 
        gsub " ?-- ?" "&mdash;" .
        gsub " ?--- ?" "&mdash;" .
        gsub "([0-9])--?([0-9])" "\\1&ndash;\\2" 
      escapeEllipses = gsub "\\.\\.\\.|\\. \\. \\." "&hellip;" in
  escapeSingleQuotes . escapeDoubleQuotes . escapeDashes . 
  escapeEllipses . stringToHtml 

-- | Escape code string as needed for HTML.
codeStringToHtml :: String -> String
codeStringToHtml [] = []
codeStringToHtml (x:xs) = case x of
  '&' -> "&amp;" ++ codeStringToHtml xs
  '<' -> "&lt;"  ++ codeStringToHtml xs
  _   -> x:(codeStringToHtml xs) 

-- | Escape string to HTML appropriate for attributes
attributeStringToHtml :: String -> String
attributeStringToHtml = gsub "\"" "&quot;"

-- | Returns an HTML header with appropriate bibliographic information.
htmlHeader :: WriterOptions -> Meta -> String
htmlHeader options (Meta title authors date) = 
  let titletext = "<title>" ++ (inlineListToHtml options title) ++ 
                  "</title>\n"
      authortext = if (null authors) 
                      then "" 
                      else "<meta name=\"author\" content=\"" ++ 
                           (joinWithSep ", " (map stringToHtml authors)) ++ 
                           "\" />\n" 
      datetext = if (date == "")
                    then "" 
                    else "<meta name=\"date\" content=\"" ++ 
                         (stringToHtml date) ++ "\" />\n" in
  (writerHeader options) ++ authortext ++ datetext ++ titletext ++ 
  "</head>\n<body>\n"

-- | Convert Pandoc block element to HTML.
blockToHtml :: WriterOptions -> Block -> String
blockToHtml options Blank = "\n" 
blockToHtml options Null = ""
blockToHtml options (Plain lst) = inlineListToHtml options lst 
blockToHtml options (Para lst) = "<p>" ++ (inlineListToHtml options lst) ++ "</p>\n"
blockToHtml options (BlockQuote blocks) = 
  if (writerS5 options)
     then  -- in S5, treat list in blockquote specially
           -- if default is incremental, make it nonincremental; 
           -- otherwise incremental
           let inc = not (writerIncremental options) in
           case blocks of 
              [BulletList lst] -> blockToHtml (options {writerIncremental = 
                                                        inc}) (BulletList lst)
              [OrderedList lst] -> blockToHtml (options {writerIncremental =
                                                       inc}) (OrderedList lst)
              otherwise         -> "<blockquote>\n" ++ 
                                   (concatMap (blockToHtml options) blocks) ++
                                   "</blockquote>\n"
     else "<blockquote>\n" ++ (concatMap (blockToHtml options) blocks) ++ 
          "</blockquote>\n"
blockToHtml options (Note ref lst) = 
  let contents = (concatMap (blockToHtml options) lst) in
  "<li id=\"fn" ++ ref ++ "\">" ++ contents ++ " <a href=\"#fnref" ++ ref ++ 
  "\" class=\"footnoteBacklink\" title=\"Jump back to footnote " ++ ref ++ 
  "\">&#8617;</a></li>\n" 
blockToHtml options (Key _ _) = ""
blockToHtml options (CodeBlock str) = 
  "<pre><code>" ++ (codeStringToHtml str) ++ "\n</code></pre>\n"
blockToHtml options (RawHtml str) = str 
blockToHtml options (BulletList lst) = 
  let attribs = if (writerIncremental options)
                   then " class=\"incremental\"" 
                   else "" in
  "<ul" ++ attribs ++ ">\n" ++ (concatMap (listItemToHtml options) lst) ++ 
  "</ul>\n"
blockToHtml options (OrderedList lst) = 
  let attribs = if (writerIncremental options)
                   then " class=\"incremental\""
                   else "" in
  "<ol" ++ attribs ++ ">\n" ++ (concatMap (listItemToHtml options) lst) ++ 
  "</ol>\n"
blockToHtml options HorizontalRule = "<hr />\n"
blockToHtml options (Header level lst) = 
  let contents = inlineListToHtml options lst in
  let simplify = gsub "<[^>]*>" ""  . gsub " " "_" in
  if ((level > 0) && (level <= 6))
      then "<a id=\"" ++ simplify contents ++ "\"></a>\n" ++
           "<h" ++ (show level) ++ ">" ++ contents ++ 
           "</h" ++ (show level) ++ ">\n"
      else "<p>" ++ contents ++ "</p>\n"
listItemToHtml options list = 
  "<li>" ++ (concatMap (blockToHtml options) list) ++ "</li>\n"

-- | Convert list of Pandoc inline elements to HTML.
inlineListToHtml :: WriterOptions -> [Inline] -> String
inlineListToHtml options lst = 
  -- consolidate adjacent Str and Space elements for more intelligent 
  -- smart typography filtering
  let lst' = consolidateList lst in
  concatMap (inlineToHtml options) lst'

-- | Convert Pandoc inline element to HTML.
inlineToHtml :: WriterOptions -> Inline -> String
inlineToHtml options (Emph lst) = 
  "<em>" ++ (inlineListToHtml options lst) ++ "</em>"
inlineToHtml options (Strong lst) = 
  "<strong>" ++ (inlineListToHtml options lst) ++ "</strong>"
inlineToHtml options (Code str) =  
  "<code>" ++ (codeStringToHtml str) ++ "</code>"
inlineToHtml options (Str str) = 
  if (writerSmart options) then stringToSmartHtml str else stringToHtml str
inlineToHtml options (TeX str) = (codeStringToHtml str)
inlineToHtml options (HtmlInline str) = str
inlineToHtml options (LineBreak) = "<br />\n"
inlineToHtml options Space = " "
inlineToHtml options (Link text (Src src tit)) = 
  let title = attributeStringToHtml tit in
  if (isPrefixOf "mailto:" src)
     then obfuscateLink options text src 
     else "<a href=\"" ++ (codeStringToHtml src) ++ "\"" ++ 
          (if tit /= "" then " title=\"" ++ title  ++ "\">" else ">") ++ 
          (inlineListToHtml options text) ++ "</a>"
inlineToHtml options (Link text (Ref [])) = 
  "[" ++ (inlineListToHtml options text) ++ "]" 
inlineToHtml options (Link text (Ref ref)) = 
  "[" ++ (inlineListToHtml options text) ++ "][" ++ 
  (inlineListToHtml options ref) ++ "]"  
  -- this is what markdown does, for better or worse
inlineToHtml options (Image alt (Src source tit)) = 
  let title = attributeStringToHtml tit
      alternate = inlineListToHtml options alt in 
  "<img src=\"" ++ source ++ "\"" ++ 
  (if tit /= "" then " title=\"" ++ title ++ "\"" else "") ++ 
  (if alternate /= "" then " alt=\"" ++ alternate ++ "\"" else "") ++ ">"
inlineToHtml options (Image alternate (Ref [])) = 
  "![" ++ (inlineListToHtml options alternate) ++ "]"
inlineToHtml options (Image alternate (Ref ref)) = 
  "![" ++ (inlineListToHtml options alternate) ++ "][" ++ 
  (inlineListToHtml options ref) ++ "]"
inlineToHtml options (NoteRef ref) = 
  "<sup class=\"footnoteRef\" id=\"fnref" ++ ref ++ "\"><a href=\"#fn" ++ 
  ref ++ "\">" ++ ref ++ "</a></sup>"