    module Text.XML.HXT.RelaxNG.DataTypes
    where

    import Text.XML.HXT.DOM.TypeDefs

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

    relaxSchemaFile :: String
    relaxSchemaFile = "Text/XML/HXT/RelaxNG/SpecificationSchema.rng"

    relaxSchemaGrammarFile :: String
    relaxSchemaGrammarFile = "Text/XML/HXT/RelaxNG/SpecificationSchemaGrammar.rng"

    -- ------------------------------------------------------------
    -- datatypes for the simplification process

    a_numberOfErrors,
     a_relaxSimplificationChanges,
     defineOrigName :: String

    a_numberOfErrors             = "numberOfErrors"
    a_relaxSimplificationChanges = "relaxSimplificationChanges"
    defineOrigName               = "RelaxDefineOriginalName"

    type Env = [(String, XmlTree)]

    -- | Start of a context attribute value
    -- (see also: 'Text.XML.HXT.RelaxNG.Simplification.simplificationStep1')
    --
    -- The value is always followed by the original attribute name and value

    contextAttributes :: String
    contextAttributes = "RelaxContext:"

    -- | Start of base uri attribute value
    -- (see also: 'simplificationStep1' in "Text.XML.HXT.RelaxNG.Simplification")

    contextBaseAttr :: String
    contextBaseAttr = "RelaxContextBaseURI"

    -- see simplificationStep5 in Text.XML.HXT.RelaxNG.Simplification

    type OldName = String
    type NewName = String
    type NamePair = (OldName, NewName)
    type RefList = [NamePair]

    -- ------------------------------------------------------------
    -- datatype library handling

    -- | Type of all datatype libraries functions that tests whether
    -- a XML instance value matches a value-pattern.
    --
    -- Returns Just \"errorMessage\" in case of an error else Nothing.

    type DatatypeEqual  = DatatypeName -> String -> Context -> String -> Context -> Maybe String

    -- | Type of all datatype libraries functions that tests whether
    -- a XML instance value matches a data-pattern.
    --
    -- Returns Just \"errorMessage\" in case of an error else Nothing.

    type DatatypeAllows = DatatypeName -> ParamList -> String -> Context -> Maybe String

    -- | List of all supported datatype libraries

    type DatatypeLibraries = [DatatypeLibrary]

    -- | Each datatype library is identified by a URI.

    type DatatypeLibrary   = (Uri, DatatypeCheck)

    type DatatypeName      = String

    type ParamName         = String

    -- | List of all supported params for a datatype

    type AllowedParams     = [ParamName]

    -- | List of all supported datatypes and there allowed params

    type AllowedDatatypes  = [(DatatypeName, AllowedParams)]

    -- | The Constructor exports the list of supported datatypes for a library.
    -- It also exports the specialized datatype library functions to validate
    -- a XML instance value with respect to a datatype.

    data DatatypeCheck
      = DTC { dtAllowsFct    :: DatatypeAllows -- ^ function to test whether a value matches a data-pattern
            , dtEqualFct     :: DatatypeEqual -- ^ function to test whether a value matches a value-pattern
            , dtAllowedTypes :: AllowedDatatypes -- ^ list of all supported params for a datatype
            }

    -- ------------------------------------------------------------
    -- datatypes for the validation process

    type Uri = String

    type LocalName = String

    -- | List of parameters; each parameter is a pair consisting of a local name and a value.

    type ParamList = [(LocalName, String)]

    type Prefix = String

    -- | A Context represents the context of an XML element.
    -- It consists of a base URI and a mapping from prefixes to namespace URIs.

    type Context = (Uri, [(Prefix, Uri)])

    -- | A Datatype identifies a datatype by a datatype library name and a local name.

    type Datatype = (Uri, LocalName)

    showDatatype    :: Datatype -> String
    showDatatype (u, ln)
             | null u       = ln
             | otherwise    = "{" ++ u ++ "}" ++ ln

    -- | Represents a name class

    data NameClass = AnyName
                   | AnyNameExcept NameClass
                   | Name Uri LocalName
                   | NsName Uri
                   | NsNameExcept Uri NameClass
                   | NameClassChoice NameClass NameClass
                   | NCError String
                   deriving Eq

    instance Show NameClass
        where
        show AnyName        = "AnyName"
        show (AnyNameExcept nameClass)
                            = "AnyNameExcept: " ++ show nameClass
        show (Name uri localName)
            | null uri      = localName
            | otherwise     = "{" ++ uri ++ "}" ++ localName
        show (NsName uri)   = "{" ++ uri ++ "}AnyName"
        show (NsNameExcept uri nameClass)
                            = "NsNameExcept: {" ++ uri ++ "}" ++ show nameClass
        show (NameClassChoice nameClass1 nameClass2)
                            = "NameClassChoice: " ++ show nameClass1 ++ "|" ++ show nameClass2
        show (NCError string)
                             = "NCError: " ++ string

    -- | Represents a pattern after simplification

    data Pattern = Empty
                 | NotAllowed ErrMessage
                 | Text
                 | Choice Pattern Pattern
                 | Interleave Pattern Pattern
                 | Group Pattern Pattern
                 | OneOrMore Pattern
                 | List Pattern
                 | Data Datatype ParamList
                 | DataExcept Datatype ParamList Pattern
                 | Value Datatype String Context
                 | Attribute NameClass Pattern
                 | Element NameClass Pattern
                 | After Pattern Pattern

    instance Show Pattern where
        show Empty                  = "empty"
        show (NotAllowed e)         = show e
        show Text                   = "text"
        show (Choice p1 p2)         = "( " ++ show p1 ++ " | " ++ show p2 ++ " )"
        show (Interleave p1 p2)     = "( " ++ show p1 ++ " & " ++ show p2 ++ " )"
        show (Group p1 p2)          = "( " ++ show p1 ++ " , " ++ show p2 ++ " )"
        show (OneOrMore p)          = show p ++ "+"
        show (List p)               = "list { " ++ show p ++ " }"
        show (Data dt pl)           = showDatatype dt ++ showPL pl
                                      where
                                      showPL []     = ""
                                      showPL l      = " {" ++ concatMap showP l ++ " }"
                                      showP (ln, v) = " " ++ ln ++ " = " ++ show v
        show (DataExcept dt pl p)   = show (Data dt pl) ++ " - (" ++ show p ++ " )"
        show (Value dt v _cx)       = showDatatype dt ++ " " ++ show v
        show (Attribute nc p)       = "attribute " ++ show nc ++ " { " ++ show p ++ " }"
        show (Element nc p)         = "element "   ++ show nc ++ " { " ++ show p ++ " }"
        show (After p1 p2)          =  "( " ++ show p1 ++ " ; " ++ show p2 ++ " )"

    data ErrMessage = ErrMsg ErrLevel [String]
                      -- deriving Show

    instance Show ErrMessage where
        show (ErrMsg _lev es) = foldr1 (\ x y -> x ++ "\n" ++ y) es

    type ErrLevel   = Int

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

    -- smart constructor funtions for Pattern

    -- | smart constructor for NotAllowed

    notAllowed      :: String -> Pattern
    notAllowed      = notAllowedN 0

    notAllowed1     :: String -> Pattern
    notAllowed1     = notAllowedN 1

    notAllowed2     :: String -> Pattern
    notAllowed2     = notAllowedN 2

    notAllowedN     :: ErrLevel -> String -> Pattern
    notAllowedN l s = NotAllowed (ErrMsg l [s])

    -- | merge error messages
    --
    -- If error levels are different, the more important is taken,
    -- if level is 2 (max level) both error messages are taken
    -- else the 1. error mesage is taken

    mergeNotAllowed :: Pattern -> Pattern -> Pattern
    mergeNotAllowed p1@(NotAllowed (ErrMsg l1 s1)) p2@(NotAllowed (ErrMsg l2 s2))
        | l1 < l2   = p2
        | l1 > l2   = p1
        | l1 == 2   = NotAllowed $ ErrMsg 2 (s1 ++ s2)
        | otherwise = p1

    -- TODO : weird error when collecting error messages errors are duplicated

    mergeNotAllowed _p1 _p2
        = notAllowed2 "mergeNotAllowed with wrong patterns"

    -- | smart constructor for Choice

    choice :: Pattern -> Pattern -> Pattern
    choice p1@(NotAllowed _) p2@(NotAllowed _)      = mergeNotAllowed p1 p2
    choice p1                   (NotAllowed _)      = p1
    choice (NotAllowed _)    p2                     = p2
    choice p1                p2                     = Choice p1 p2

    -- | smart constructor for Group

    group :: Pattern -> Pattern -> Pattern
    group p1@(NotAllowed _)  p2@(NotAllowed _)      = mergeNotAllowed p1 p2
    group _                   n@(NotAllowed _)      = n
    group   n@(NotAllowed _)  _                     = n
    group p                  Empty                  = p
    group Empty              p                      = p
    group p1                 p2                     = Group p1 p2

    -- | smart constructor for OneOrMore

    oneOrMore :: Pattern -> Pattern
    oneOrMore n@(NotAllowed _) = n
    oneOrMore p                = OneOrMore p

    -- | smart constructor for Interleave

    interleave :: Pattern -> Pattern -> Pattern
    interleave p1@(NotAllowed _) p2@(NotAllowed _)  = mergeNotAllowed p1 p2
    interleave _                 p2@(NotAllowed _)  = p2
    interleave p1@(NotAllowed _) _                  = p1
    interleave p1                Empty              = p1
    interleave Empty             p2                 = p2
    interleave p1                p2                 = Interleave p1 p2

    -- | smart constructor for After

    after :: Pattern -> Pattern -> Pattern
    after p1@(NotAllowed _) p2@(NotAllowed _)       = mergeNotAllowed p1 p2
    after _                 p2@(NotAllowed _)       = p2
    after p1@(NotAllowed _) _                       = p1
    after p1                p2                      = After p1 p2

    -- | Possible content types of a Relax NG pattern.
    -- (see also chapter 7.2 in Relax NG specification)

    data ContentType = CTEmpty
                     | CTComplex
                     | CTSimple
                     | CTNone
         deriving (Show, Eq, Ord)

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