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

    {- |
       Module     : Text.XML.HXT.DOM.MimeTypes
       Copyright  : Copyright (C) 2008 Uwe Schmidt
       License    : MIT

       Maintainer : Uwe Schmidt (uwe@fh-wedel.de)
       Stability  : experimental
       Portability: portable

       mime type related data and functions

    -}

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

    module Text.XML.HXT.DOM.MimeTypes
    where

    import           Control.Monad          ( mplus )

    import qualified Data.ByteString        as B
    import qualified Data.ByteString.Char8  as C

    import           Data.Char
    import           Data.List
    import qualified Data.Map               as M
    import           Data.Maybe

    import           Text.XML.HXT.DOM.MimeTypeDefaults

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

    type MimeTypeTable      = M.Map String String

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

    -- mime types
    --
    -- see RFC \"http:\/\/www.rfc-editor.org\/rfc\/rfc3023.txt\"

    application_xhtml,
     application_xml,
     application_xml_external_parsed_entity,
     application_xml_dtd,
     text_html,
     text_pdf,
     text_plain,
     text_xdtd,
     text_xml,
     text_xml_external_parsed_entity        :: String

    application_xhtml                       = "application/xhtml+xml"
    application_xml                         = "application/xml"
    application_xml_external_parsed_entity  = "application/xml-external-parsed-entity"
    application_xml_dtd                     = "application/xml-dtd"

    text_html                               = "text/html"
    text_pdf                                = "text/pdf"
    text_plain                              = "text/plain"
    text_xdtd                               = "text/x-dtd"
    text_xml                                = "text/xml"
    text_xml_external_parsed_entity         = "text/xml-external-parsed-entity"

    isTextMimeType                          :: String -> Bool
    isTextMimeType                          = ("text/" `isPrefixOf`)

    isHtmlMimeType                          :: String -> Bool
    isHtmlMimeType t                        = t == text_html

    isXmlMimeType                           :: String -> Bool
    isXmlMimeType t                         = ( t `elem` [ application_xhtml
                                                         , application_xml
                                                         , application_xml_external_parsed_entity
                                                         , application_xml_dtd
                                                         , text_xml
                                                         , text_xml_external_parsed_entity
                                                         , text_xdtd
                                                         ]
                                                ||
                                                "+xml" `isSuffixOf` t               -- application/mathml+xml
                                              )                                     -- or image/svg+xml

    defaultMimeTypeTable                    :: MimeTypeTable
    defaultMimeTypeTable                    = M.fromList mimeTypeDefaults

    extensionToMimeType                     :: String -> MimeTypeTable -> String
    extensionToMimeType e                   = fromMaybe "" . lookupMime
        where
        lookupMime t                        = M.lookup e t                  -- try exact match
                                              `mplus`
                                              M.lookup (map toLower e) t    -- else try lowercase match
                                              `mplus`
                                              M.lookup (map toUpper e) t    -- else try uppercase match

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

    readMimeTypeTable                       :: FilePath -> IO MimeTypeTable
    readMimeTypeTable inp                   = do
                                              cb <- B.readFile inp
                                              return . M.fromList . parseMimeTypeTable . C.unpack $ cb

    parseMimeTypeTable                      :: String -> [(String, String)]
    parseMimeTypeTable                      = concat
                                              . map buildPairs
                                              . map words
                                              . filter (not . ("#" `isPrefixOf`))
                                              . filter (not . all (isSpace))
                                              . lines
        where
        buildPairs                          :: [String] -> [(String, String)]
        buildPairs  []                      = []
        buildPairs  (mt:exts)               = map (\ x -> (x, mt)) $ exts

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