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

    {- |
       Module     : Text.XML.HXT.Arrow.DocumentInput
       Copyright  : Copyright (C) 2005 Uwe Schmidt
       License    : MIT

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

       State arrows for document input
    -}

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

    module Text.XML.HXT.Arrow.DocumentInput
        ( getXmlContents
        , getXmlEntityContents
        , getEncoding
        , getTextEncoding
        , decodeDocument
        , addInputError
        )
    where

    import           Control.Arrow
    import           Control.Arrow.ArrowIf
    import           Control.Arrow.ArrowIO
    import           Control.Arrow.ArrowList
    import           Control.Arrow.ArrowTree
    import           Control.Arrow.ListArrow

    import           Data.List                            (isPrefixOf)
    import           Data.String.Unicode                  (getDecodingFct,
                                                           guessEncoding,
                                                           normalizeNL)

    import           System.FilePath                      (takeExtension)

    import qualified Text.XML.HXT.IO.GetFILE              as FILE

    import           Text.XML.HXT.DOM.Interface

    import           Text.XML.HXT.Arrow.ParserInterface   (parseXmlDocEncodingSpec, parseXmlEntityEncodingSpec,
                                                           removeEncodingSpec)
    import           Text.XML.HXT.Arrow.XmlArrow
    import           Text.XML.HXT.Arrow.XmlState
    import           Text.XML.HXT.Arrow.XmlState.TypeDefs

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

    protocolHandlers        :: AssocList String (IOStateArrow s XmlTree XmlTree)
    protocolHandlers
        = [ ("file",        getFileContents)
          , ("http",        getHttpContents)
          , ("https",       getHttpContents)
          , ("stdin",       getStdinContents)
          ]

    getProtocolHandler      :: IOStateArrow s String (IOStateArrow s XmlTree XmlTree)
    getProtocolHandler
        = arr (\ s -> lookupDef getUnsupported s protocolHandlers)

    getUnsupported          :: IOStateArrow s XmlTree XmlTree
    getUnsupported
        = perform ( getAttrValue a_source
                    >>>
                    arr (("unsupported protocol in URI " ++) . show)
                    >>>
                    applyA (arr issueFatal)
                  )
          >>>
          setDocumentStatusFromSystemState "accessing documents"

    getStringContents               :: IOStateArrow s XmlTree XmlTree
    getStringContents
        = setCont $< getAttrValue a_source
          >>>
          addAttr transferMessage "OK"
          >>>
          addAttr transferStatus "200"
        where
        setCont contents
            = replaceChildren (txt contents')
              >>>
              addAttr transferURI (take 7 contents)                 -- the "string:" prefix is stored, this is required by setBaseURIFromDoc
              >>>
              addAttr a_source (show . prefix 48 $ contents')       -- a quoted prefix of the content, max 48 chars is taken as source name
            where
            contents'  = drop (length stringProtocol) contents
            prefix l s
                | length s' > l = take (l - 3) s' ++ "..."
                | otherwise     = s'
                where
                s' = take (l + 1) s

    getFileContents         :: IOStateArrow s XmlTree XmlTree
    getFileContents
        = applyA ( ( getSysVar theStrictInput
                     &&&
                     ( getAttrValue transferURI
                       >>>
                       getPathFromURI
                     )
                   )
                   >>>
                   traceValue 2 (\ (b, f) -> "read file " ++ show f ++ " (strict input = " ++ show b ++ ")")
                   >>>
                   arrIO (uncurry FILE.getCont)
                   >>>
                   ( arr (uncurry addInputError) -- io error occured
                     |||
                     arr addTxtContent      -- content read
                   )
                 )
          >>>
          addMimeType

    getStdinContents                :: IOStateArrow s XmlTree XmlTree
    getStdinContents
        = applyA (  getSysVar theStrictInput
                    >>>
                    arrIO FILE.getStdinCont
                   >>>
                   ( arr (uncurry addInputError) -- io error occured
                     |||
                     arr addTxtContent           -- content read
                   )
                 )

    addInputError                :: Attributes -> String -> IOStateArrow s XmlTree XmlTree
    addInputError al e
        = issueFatal e
          >>>
          seqA (map (uncurry addAttr) al)
          >>>
          setDocumentStatusFromSystemState "accessing documents"

    addMimeType     :: IOStateArrow s XmlTree XmlTree
    addMimeType
        = addMime $< ( ( getSysVar theFileMimeType
                         >>>
                         isA (not . null)
                       )
                       `orElse`
                       ( getAttrValue transferURI
                         >>>
                         ( uriToMime $< getMimeTypeTable )
                       )
                     )
        where
        addMime mt
            = addAttr transferMimeType mt
        uriToMime mtt
            = arr $ ( \ uri -> extensionToMimeType (drop 1 . takeExtension $ uri) mtt )

    addTxtContent   :: Blob -> IOStateArrow s XmlTree XmlTree
    addTxtContent bc
        = replaceChildren (blb bc)
          >>>
          addAttr transferMessage "OK"
          >>>
          addAttr transferStatus "200"

    getHttpContents         :: IOStateArrow s XmlTree XmlTree
    getHttpContents
        = withoutUserState $ applyA $ getSysVar theHttpHandler

    getContentsFromString   :: IOStateArrow s XmlTree XmlTree
    getContentsFromString
        = ( getAttrValue a_source
            >>>
            isA (isPrefixOf stringProtocol)
          )
          `guards`
          getStringContents

    getContentsFromDoc      :: IOStateArrow s XmlTree XmlTree
    getContentsFromDoc
        = ( ( addTransferURI $< getBaseURI
              >>>
              getCont
            )
            `when`
            ( setAbsURI $< ( getAttrValue a_source
                             >>^
                             ( \ src-> (if null src then "stdin:" else src) )   -- empty document name -> read from stdin
                           )
            )
          )
          >>>
          setDocumentStatusFromSystemState "getContentsFromDoc"
        where
        setAbsURI src
            = ifA ( constA src >>> changeBaseURI )
              this
              ( issueFatal ("illegal URI : " ++ show src) )

        addTransferURI uri
            = addAttr transferURI uri

        getCont
            = applyA ( getBaseURI                           -- compute the handler and call it
                       >>>
                       traceValue 2 (("getContentsFromDoc: reading " ++) . show)
                       >>>
                       getSchemeFromURI
                       >>>
                       getProtocolHandler
                     )
              `orElse`
              this                                          -- don't change tree, when no handler can be found

    setBaseURIFromDoc       :: IOStateArrow s XmlTree XmlTree
    setBaseURIFromDoc
        = perform ( getAttrValue transferURI
                    >>>
                    isA (isPrefixOf stringProtocol)         -- do not change base URI when reading from a string
                    >>>
                    setBaseURI
                  )

    {- |
       Read the content of a document.

       This routine is usually called from 'Text.XML.HXT.Arrow.ProcessDocument.getDocumentContents'.

       The input must be a root node (constructed with 'Text.XML.HXT.Arrow.XmlArrow.root'), usually without children.
       The attribute list contains all input parameters, e.g. URI or source file name, encoding preferences, ...
       If the source name is empty, the input is read from standard input.

       The source is transformed into an absolute URI. If the source is a relative URI, or a file name,
       it is expanded into an absolut URI with respect to the current base URI.
       The default base URI is of protocol \"file\" and points to the current working directory.

       The currently supported protocols are \"http\", \"file\", \"stdin\" and \"string\".

       The latter two are internal protocols. An uri of the form \"stdin:\" stands for the content of
       the standard input stream.

       \"string:some text\" means, that \"some text\" is taken as input.
       This internal protocol is used for reading from normal 'String' values.

    -}

    getXmlContents          :: IOStateArrow s XmlTree XmlTree
    getXmlContents
        = getXmlContents' parseXmlDocEncodingSpec
          >>>
          setBaseURIFromDoc

    getXmlEntityContents            :: IOStateArrow s XmlTree XmlTree
    getXmlEntityContents
        = traceMsg 2 "getXmlEntityContents"
          >>>
          addAttr transferMimeType text_xml_external_parsed_entity  -- the default transfer mimetype
          >>>
          getXmlContents' parseXmlEntityEncodingSpec
          >>>
          addAttr transferMimeType text_xml_external_parsed_entity
          >>>
          processChildren
          ( removeEncodingSpec
            >>>
            changeText normalizeNL                  -- newline normalization must be done here
          )                                         -- the following calls of the parsers don't do this
          >>>
          setBaseURIFromDoc
          >>>
          traceMsg 2 "getXmlEntityContents done"

    getXmlContents'         :: IOStateArrow s XmlTree XmlTree -> IOStateArrow s XmlTree XmlTree
    getXmlContents' parseEncodingSpec
        = ( getContentsFromString    -- no decoding done for string: protocol
            `orElse`
            ( getContentsFromDoc
              >>>
              choiceA
              [ isXmlHtmlDoc  :-> ( parseEncodingSpec
                                    >>>
                                    filterErrorMsg
                                    >>>
                                    decodeDocument
                                  )
              , isTextDoc     :-> decodeDocument
              , this          :-> this
              ]
              >>>
              perform ( getAttrValue transferURI
                        >>>
                        traceValue 1 (("getXmlContents: content read and decoded for " ++) . show)
                      )
              >>>
              traceDoc "getXmlContents'"
            )
          )
          `when`
          isRoot

    isMimeDoc               :: (String -> Bool) -> IOStateArrow s XmlTree XmlTree
    isMimeDoc isMT          = fromLA $
                              ( ( getAttrValue transferMimeType >>^ stringToLower )
                                >>>
                                isA (\ t -> null t || isMT t)
                              )
                              `guards` this

    isTextDoc, isXmlHtmlDoc :: IOStateArrow s XmlTree XmlTree

    isTextDoc               = isMimeDoc isTextMimeType

    isXmlHtmlDoc            = isMimeDoc (\ mt -> isHtmlMimeType mt || isXmlMimeType mt)

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

    getEncoding     :: IOStateArrow s XmlTree String
    getEncoding
        = catA [ xshow getChildren                  -- 1. guess: guess encoding by looking at the first few bytes
                 >>>
                 arr guessEncoding
               , getAttrValue transferEncoding      -- 2. guess: take the transfer encoding
               , getAttrValue a_encoding            -- 3. guess: take encoding parameter in root node
               , getSysVar  theInputEncoding        -- 4. guess: take encoding parameter in global state
               , constA utf8                        -- default : utf8
               ]
          >. (head . filter (not . null))           -- make the filter deterministic: take 1. entry from list of guesses

    getTextEncoding :: IOStateArrow s XmlTree String
    getTextEncoding
        = catA [ getAttrValue transferEncoding      -- 1. guess: take the transfer encoding
               , getAttrValue a_encoding            -- 2. guess: take encoding parameter in root node
               , getSysVar theInputEncoding         -- 3. guess: take encoding parameter in global state
               , constA isoLatin1                   -- default : no encoding
               ]
          >. (head . filter (not . null))           -- make the filter deterministic: take 1. entry from list of guesses

    decodeDocument  :: IOStateArrow s XmlTree XmlTree
    decodeDocument
        = choiceA
          [ ( isRoot >>> isXmlHtmlDoc )   :-> ( decodeX   $< getSysVar theExpat)
          , ( isRoot >>> isTextDoc )      :-> ( decodeArr $< getTextEncoding )
          , this                          :-> this
          ]
        where
        decodeX             :: Bool -> IOStateArrow s XmlTree XmlTree
        decodeX False       = decodeArr $< getEncoding
        decodeX True        = noDecode  $< getEncoding         -- parse with expat

        noDecode enc        = traceMsg 2 ("no decoding (done by expat): encoding is " ++ show enc)
                              >>>
                              addAttr transferEncoding enc

        decodeArr   :: String -> IOStateArrow s XmlTree XmlTree
        decodeArr enc
            = maybe notFound found . getDecodingFct $ enc
            where
            found df
                = traceMsg 2 ("decodeDocument: encoding is " ++ show enc)
                  >>>
                  ( decodeText df $< getSysVar theEncodingErrors )
                  >>>
                  addAttr transferEncoding enc

            notFound
                = issueFatal ("encoding scheme not supported: " ++ show enc)
                  >>>
                  setDocumentStatusFromSystemState "decoding document"

    {- just for performance test
            decodeText _ _ = this
    -}
            decodeText df withEncErrors
                = processChildren
                  ( getText                                                 -- get the document content
                    -- the following 3 lines
                    -- don't seem to raise the space problem in decodeText
                    -- space is allocated in blobToString and in parsec
                    >>> arr df                                              -- decode the text, result is (string, [errMsg])
                    >>> ( ( fst ^>> mkText )                                -- take decoded string and build text node
                          <+>
                          ( if withEncErrors
                            then
                            ( arrL snd                                      -- take the error messages
                              >>>
                              arr ((enc ++) . (" encoding error" ++))       -- prefix with enc error
                              >>>
                              applyA (arr issueErr)                         -- build issueErr arrow and apply
                              >>>
                              none                                          -- neccessary for type match with <+>
                            )
                            else none
                          )
                        )
                  )

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