# This module implements the RFCs 3490 (IDNA) and 3491 (Nameprep)

import stringprep, re, codecs

from unicodedata import ucd_3_2_0 as unicodedata

# IDNA section 3.1

dots = re.compile(u"[\u002E\u3002\uFF0E\uFF61]")

# IDNA section 5

ace_prefix = "xn--"

uace_prefix = unicode(ace_prefix, "ascii")

# This assumes query strings, so AllowUnassigned is true

def nameprep(label):

    # Map

    newlabel = []

    for c in label:

        if stringprep.in_table_b1(c):

            # Map to nothing

            continue

        newlabel.append(stringprep.map_table_b2(c))

    label = u"".join(newlabel)

    # Normalize

    label = unicodedata.normalize("NFKC", label)

    # Prohibit

    for c in label:

        if stringprep.in_table_c12(c) or \

           stringprep.in_table_c22(c) or \

           stringprep.in_table_c3(c) or \

           stringprep.in_table_c4(c) or \

           stringprep.in_table_c5(c) or \

           stringprep.in_table_c6(c) or \

           stringprep.in_table_c7(c) or \

           stringprep.in_table_c8(c) or \

           stringprep.in_table_c9(c):

            raise UnicodeError("Invalid character %r" % c)

    # Check bidi

    RandAL = map(stringprep.in_table_d1, label)

    for c in RandAL:

        if c:

            # There is a RandAL char in the string. Must perform further

            # tests:

            # 1) The characters in section 5.8 MUST be prohibited.

            # This is table C.8, which was already checked

            # 2) If a string contains any RandALCat character, the string

            # MUST NOT contain any LCat character.

            if filter(stringprep.in_table_d2, label):

                raise UnicodeError("Violation of BIDI requirement 2")

            # 3) If a string contains any RandALCat character, a

            # RandALCat character MUST be the first character of the

            # string, and a RandALCat character MUST be the last

            # character of the string.

            if not RandAL[0] or not RandAL[-1]:

                raise UnicodeError("Violation of BIDI requirement 3")

    return label

def ToASCII(label):

    try:

        # Step 1: try ASCII

        label = label.encode("ascii")

    except UnicodeError:

        pass

    else:

        # Skip to step 3: UseSTD3ASCIIRules is false, so

        # Skip to step 8.

        if 0 < len(label) < 64:

            return label

        raise UnicodeError("label empty or too long")

    # Step 2: nameprep

    label = nameprep(label)

    # Step 3: UseSTD3ASCIIRules is false

    # Step 4: try ASCII

    try:

        label = label.encode("ascii")

    except UnicodeError:

        pass

    else:

        # Skip to step 8.

        if 0 < len(label) < 64:

            return label

        raise UnicodeError("label empty or too long")

    # Step 5: Check ACE prefix

    if label.startswith(uace_prefix):

        raise UnicodeError("Label starts with ACE prefix")

    # Step 6: Encode with PUNYCODE

    label = label.encode("punycode")

    # Step 7: Prepend ACE prefix

    label = ace_prefix + label

    # Step 8: Check size

    if 0 < len(label) < 64:

        return label

    raise UnicodeError("label empty or too long")

def ToUnicode(label):

    # Step 1: Check for ASCII

    if isinstance(label, str):

        pure_ascii = True

    else:

        try:

            label = label.encode("ascii")

            pure_ascii = True

        except UnicodeError:

            pure_ascii = False

    if not pure_ascii:

        # Step 2: Perform nameprep

        label = nameprep(label)

        # It doesn't say this, but apparently, it should be ASCII now

        try:

            label = label.encode("ascii")

        except UnicodeError:

            raise UnicodeError("Invalid character in IDN label")

    # Step 3: Check for ACE prefix

    if not label.startswith(ace_prefix):

        return unicode(label, "ascii")

    # Step 4: Remove ACE prefix

    label1 = label[len(ace_prefix):]

    # Step 5: Decode using PUNYCODE

    result = label1.decode("punycode")

    # Step 6: Apply ToASCII

    label2 = ToASCII(result)

    # Step 7: Compare the result of step 6 with the one of step 3

    # label2 will already be in lower case.

    if label.lower() != label2:

        raise UnicodeError("IDNA does not round-trip", label, label2)

    # Step 8: return the result of step 5

    return result

### Codec APIs

class Codec(codecs.Codec):

    def encode(self,input,errors='strict'):

        if errors != 'strict':

            # IDNA is quite clear that implementations must be strict

            raise UnicodeError("unsupported error handling "+errors)

        if not input:

            return "", 0

        result = []

        labels = dots.split(input)

        if labels and len(labels[-1])==0:

            trailing_dot = '.'

            del labels[-1]

        else:

            trailing_dot = ''

        for label in labels:

            result.append(ToASCII(label))

        # Join with U+002E

        return ".".join(result)+trailing_dot, len(input)

    def decode(self,input,errors='strict'):

        if errors != 'strict':

            raise UnicodeError("Unsupported error handling "+errors)

        if not input:

            return u"", 0

        # IDNA allows decoding to operate on Unicode strings, too.

        if isinstance(input, unicode):

            labels = dots.split(input)

        else:

            # Must be ASCII string

            input = str(input)

            unicode(input, "ascii")

            labels = input.split(".")

        if labels and len(labels[-1]) == 0:

            trailing_dot = u'.'

            del labels[-1]

        else:

            trailing_dot = u''

        result = []

        for label in labels:

            result.append(ToUnicode(label))

        return u".".join(result)+trailing_dot, len(input)

class IncrementalEncoder(codecs.BufferedIncrementalEncoder):

    def _buffer_encode(self, input, errors, final):

        if errors != 'strict':

            # IDNA is quite clear that implementations must be strict

            raise UnicodeError("unsupported error handling "+errors)

        if not input:

            return ("", 0)

        labels = dots.split(input)

        trailing_dot = u''

        if labels:

            if not labels[-1]:

                trailing_dot = '.'

                del labels[-1]

            elif not final:

                # Keep potentially unfinished label until the next call

                del labels[-1]

                if labels:

                    trailing_dot = '.'

        result = []

        size = 0

        for label in labels:

            result.append(ToASCII(label))

            if size:

                size += 1

            size += len(label)

        # Join with U+002E

        result = ".".join(result) + trailing_dot

        size += len(trailing_dot)

        return (result, size)

class IncrementalDecoder(codecs.BufferedIncrementalDecoder):

    def _buffer_decode(self, input, errors, final):

        if errors != 'strict':

            raise UnicodeError("Unsupported error handling "+errors)

        if not input:

            return (u"", 0)

        # IDNA allows decoding to operate on Unicode strings, too.

        if isinstance(input, unicode):

            labels = dots.split(input)

        else:

            # Must be ASCII string

            input = str(input)

            unicode(input, "ascii")

            labels = input.split(".")

        trailing_dot = u''

        if labels:

            if not labels[-1]:

                trailing_dot = u'.'

                del labels[-1]

            elif not final:

                # Keep potentially unfinished label until the next call

                del labels[-1]

                if labels:

                    trailing_dot = u'.'

        result = []

        size = 0

        for label in labels:

            result.append(ToUnicode(label))

            if size:

                size += 1

            size += len(label)

        result = u".".join(result) + trailing_dot

        size += len(trailing_dot)

        return (result, size)

class StreamWriter(Codec,codecs.StreamWriter):

    pass

class StreamReader(Codec,codecs.StreamReader):

    pass

### encodings module API

def getregentry():

    return codecs.CodecInfo(

        name='idna',

        encode=Codec().encode,

        decode=Codec().decode,

        incrementalencoder=IncrementalEncoder,

        incrementaldecoder=IncrementalDecoder,

        streamwriter=StreamWriter,

        streamreader=StreamReader,

    )