"""Implementation of JSONDecoder

"""

import re

import sys

import struct

from django.utils.simplejson.scanner import make_scanner

c_scanstring = None

__all__ = ['JSONDecoder']

FLAGS = re.VERBOSE | re.MULTILINE | re.DOTALL

def _floatconstants():

    _BYTES = '7FF80000000000007FF0000000000000'.decode('hex')

    if sys.byteorder != 'big':

        _BYTES = _BYTES[:8][::-1] + _BYTES[8:][::-1]

    nan, inf = struct.unpack('dd', _BYTES)

    return nan, inf, -inf

NaN, PosInf, NegInf = _floatconstants()

def linecol(doc, pos):

    lineno = doc.count('\n', 0, pos) + 1

    if lineno == 1:

        colno = pos

    else:

        colno = pos - doc.rindex('\n', 0, pos)

    return lineno, colno

def errmsg(msg, doc, pos, end=None):

    # Note that this function is called from _speedups

    lineno, colno = linecol(doc, pos)

    if end is None:

        return '%s: line %d column %d (char %d)' % (msg, lineno, colno, pos)

    endlineno, endcolno = linecol(doc, end)

    return '%s: line %d column %d - line %d column %d (char %d - %d)' % (

        msg, lineno, colno, endlineno, endcolno, pos, end)

_CONSTANTS = {

    '-Infinity': NegInf,

    'Infinity': PosInf,

    'NaN': NaN,

}

STRINGCHUNK = re.compile(r'(.*?)(["\\\x00-\x1f])', FLAGS)

BACKSLASH = {

    '"': u'"', '\\': u'\\', '/': u'/',

    'b': u'\b', 'f': u'\f', 'n': u'\n', 'r': u'\r', 't': u'\t',

}

DEFAULT_ENCODING = "utf-8"

def py_scanstring(s, end, encoding=None, strict=True, _b=BACKSLASH, _m=STRINGCHUNK.match):

    """Scan the string s for a JSON string. End is the index of the

    character in s after the quote that started the JSON string.

    Unescapes all valid JSON string escape sequences and raises ValueError

    on attempt to decode an invalid string. If strict is False then literal

    control characters are allowed in the string.

    Returns a tuple of the decoded string and the index of the character in s

    after the end quote."""

    if encoding is None:

        encoding = DEFAULT_ENCODING

    chunks = []

    _append = chunks.append

    begin = end - 1

    while 1:

        chunk = _m(s, end)

        if chunk is None:

            raise ValueError(

                errmsg("Unterminated string starting at", s, begin))

        end = chunk.end()

        content, terminator = chunk.groups()

        # Content is contains zero or more unescaped string characters

        if content:

            if not isinstance(content, unicode):

                content = unicode(content, encoding)

            _append(content)

        # Terminator is the end of string, a literal control character,

        # or a backslash denoting that an escape sequence follows

        if terminator == '"':

            break

        elif terminator != '\\':

            if strict:

                msg = "Invalid control character %r at" % (terminator,)

                raise ValueError(msg, s, end)

            else:

                _append(terminator)

                continue

        try:

            esc = s[end]

        except IndexError:

            raise ValueError(

                errmsg("Unterminated string starting at", s, begin))

        # If not a unicode escape sequence, must be in the lookup table

        if esc != 'u':

            try:

                char = _b[esc]

            except KeyError:

                raise ValueError(

                    errmsg("Invalid \\escape: %r" % (esc,), s, end))

            end += 1

        else:

            # Unicode escape sequence

            esc = s[end + 1:end + 5]

            next_end = end + 5

            if len(esc) != 4:

                msg = "Invalid \\uXXXX escape"

                raise ValueError(errmsg(msg, s, end))

            uni = int(esc, 16)

            # Check for surrogate pair on UCS-4 systems

            if 0xd800 <= uni <= 0xdbff and sys.maxunicode > 65535:

                msg = "Invalid \\uXXXX\\uXXXX surrogate pair"

                if not s[end + 5:end + 7] == '\\u':

                    raise ValueError(errmsg(msg, s, end))

                esc2 = s[end + 7:end + 11]

                if len(esc2) != 4:

                    raise ValueError(errmsg(msg, s, end))

                uni2 = int(esc2, 16)

                uni = 0x10000 + (((uni - 0xd800) << 10) | (uni2 - 0xdc00))

                next_end += 6

            char = unichr(uni)

            end = next_end

        # Append the unescaped character

        _append(char)

    return u''.join(chunks), end

# Use speedup if available

scanstring = c_scanstring or py_scanstring

WHITESPACE = re.compile(r'[ \t\n\r]*', FLAGS)

WHITESPACE_STR = ' \t\n\r'

def JSONObject((s, end), encoding, strict, scan_once, object_hook, _w=WHITESPACE.match, _ws=WHITESPACE_STR):

    pairs = {}

    # Use a slice to prevent IndexError from being raised, the following

    # check will raise a more specific ValueError if the string is empty

    nextchar = s[end:end + 1]

    # Normally we expect nextchar == '"'

    if nextchar != '"':

        if nextchar in _ws:

            end = _w(s, end).end()

            nextchar = s[end:end + 1]

        # Trivial empty object

        if nextchar == '}':

            return pairs, end + 1

        elif nextchar != '"':

            raise ValueError(errmsg("Expecting property name", s, end))

    end += 1

    while True:

        key, end = scanstring(s, end, encoding, strict)

        # To skip some function call overhead we optimize the fast paths where

        # the JSON key separator is ": " or just ":".

        if s[end:end + 1] != ':':

            end = _w(s, end).end()

            if s[end:end + 1] != ':':

                raise ValueError(errmsg("Expecting : delimiter", s, end))

        end += 1

        try:

            if s[end] in _ws:

                end += 1

                if s[end] in _ws:

                    end = _w(s, end + 1).end()

        except IndexError:

            pass

        try:

            value, end = scan_once(s, end)

        except StopIteration:

            raise ValueError(errmsg("Expecting object", s, end))

        pairs[key] = value

        try:

            nextchar = s[end]

            if nextchar in _ws:

                end = _w(s, end + 1).end()

                nextchar = s[end]

        except IndexError:

            nextchar = ''

        end += 1

        if nextchar == '}':

            break

        elif nextchar != ',':

            raise ValueError(errmsg("Expecting , delimiter", s, end - 1))

        try:

            nextchar = s[end]

            if nextchar in _ws:

                end += 1

                nextchar = s[end]

                if nextchar in _ws:

                    end = _w(s, end + 1).end()

                    nextchar = s[end]

        except IndexError:

            nextchar = ''

        end += 1

        if nextchar != '"':

            raise ValueError(errmsg("Expecting property name", s, end - 1))

    if object_hook is not None:

        pairs = object_hook(pairs)

    return pairs, end

def JSONArray((s, end), scan_once, _w=WHITESPACE.match, _ws=WHITESPACE_STR):

    values = []

    nextchar = s[end:end + 1]

    if nextchar in _ws:

        end = _w(s, end + 1).end()

        nextchar = s[end:end + 1]

    # Look-ahead for trivial empty array

    if nextchar == ']':

        return values, end + 1

    _append = values.append

    while True:

        try:

            value, end = scan_once(s, end)

        except StopIteration:

            raise ValueError(errmsg("Expecting object", s, end))

        _append(value)

        nextchar = s[end:end + 1]

        if nextchar in _ws:

            end = _w(s, end + 1).end()

            nextchar = s[end:end + 1]

        end += 1

        if nextchar == ']':

            break

        elif nextchar != ',':

            raise ValueError(errmsg("Expecting , delimiter", s, end))

        try:

            if s[end] in _ws:

                end += 1

                if s[end] in _ws:

                    end = _w(s, end + 1).end()

        except IndexError:

            pass

    return values, end

class JSONDecoder(object):

    """Simple JSON <http://json.org> decoder

    Performs the following translations in decoding by default:

    +---------------+-------------------+

    | JSON          | Python            |

    +===============+===================+

    | object        | dict              |

    +---------------+-------------------+

    | array         | list              |

    +---------------+-------------------+

    | string        | unicode           |

    +---------------+-------------------+

    | number (int)  | int, long         |

    +---------------+-------------------+

    | number (real) | float             |

    +---------------+-------------------+

    | true          | True              |

    +---------------+-------------------+

    | false         | False             |

    +---------------+-------------------+

    | null          | None              |

    +---------------+-------------------+

    It also understands ``NaN``, ``Infinity``, and ``-Infinity`` as

    their corresponding ``float`` values, which is outside the JSON spec.

    """

    def __init__(self, encoding=None, object_hook=None, parse_float=None,

            parse_int=None, parse_constant=None, strict=True):

        """``encoding`` determines the encoding used to interpret any ``str``

        objects decoded by this instance (utf-8 by default).  It has no

        effect when decoding ``unicode`` objects.

        Note that currently only encodings that are a superset of ASCII work,

        strings of other encodings should be passed in as ``unicode``.

        ``object_hook``, if specified, will be called with the result

        of every JSON object decoded and its return value will be used in

        place of the given ``dict``.  This can be used to provide custom

        deserializations (e.g. to support JSON-RPC class hinting).

        ``parse_float``, if specified, will be called with the string

        of every JSON float to be decoded. By default this is equivalent to

        float(num_str). This can be used to use another datatype or parser

        for JSON floats (e.g. decimal.Decimal).

        ``parse_int``, if specified, will be called with the string

        of every JSON int to be decoded. By default this is equivalent to

        int(num_str). This can be used to use another datatype or parser

        for JSON integers (e.g. float).

        ``parse_constant``, if specified, will be called with one of the

        following strings: -Infinity, Infinity, NaN.

        This can be used to raise an exception if invalid JSON numbers

        are encountered.

        """

        self.encoding = encoding

        self.object_hook = object_hook

        self.parse_float = parse_float or float

        self.parse_int = parse_int or int

        self.parse_constant = parse_constant or _CONSTANTS.__getitem__

        self.strict = strict

        self.parse_object = JSONObject

        self.parse_array = JSONArray

        self.parse_string = scanstring

        self.scan_once = make_scanner(self)

    def decode(self, s, _w=WHITESPACE.match):

        """Return the Python representation of ``s`` (a ``str`` or ``unicode``

        instance containing a JSON document)

        """

        obj, end = self.raw_decode(s, idx=_w(s, 0).end())

        end = _w(s, end).end()

        if end != len(s):

            raise ValueError(errmsg("Extra data", s, end, len(s)))

        return obj

    def raw_decode(self, s, idx=0):

        """Decode a JSON document from ``s`` (a ``str`` or ``unicode`` beginning

        with a JSON document) and return a 2-tuple of the Python

        representation and the index in ``s`` where the document ended.

        This can be used to decode a JSON document from a string that may

        have extraneous data at the end.

        """

        try:

            obj, end = self.scan_once(s, idx)

        except StopIteration:

            raise ValueError("No JSON object could be decoded")

        return obj, end