"""Implementation of JSONDecoder
"""
import re

from json import scanner

# JSONDecodeError is exported for backwards compatibility
__all__ = ['JSONDecoder', 'JSONDecodeError']

JSONDecodeError = scanner.JSONDecodeError

_CONSTANTS = {
    '-Infinity': float('-inf'),
    'Infinity': float('inf'),
    'NaN': float('nan'),
}

WHITESPACE = re.compile(r'[ \t\n\r]*',
                        (re.VERBOSE | re.MULTILINE | re.DOTALL))


class JSONDecoder(object):
    """Simple JSON <http://json.org> decoder
    Performs the following translations in decoding by default:
    +---------------+-------------------+
    | JSON          | Python            |
    +===============+===================+
    | object        | dict              |
    +---------------+-------------------+
    | array         | list              |
    +---------------+-------------------+
    | string        | str               |
    +---------------+-------------------+
    | number (int)  | int               |
    +---------------+-------------------+
    | 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, *, parse_object=None, parse_ordered_object=None,
                 parse_string=None, parse_key=None, parse_array=None,
                 parse_float=None, parse_int=None, parse_constant=None,
                 strict=True, **kw):
        """``parse_object``, 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_ordered_object``, if specified will be called with the result of
        every JSON object decoded with an ordered list of pairs.  The return
        value of ``object_pairs_hook`` will be used instead of the ``dict``.
        This feature can be used to implement custom decoders that rely on the
        order that the key and value pairs are decoded (for example,
        collections.OrderedDict will remember the order of insertion). If
        ``parse_object`` is also defined, the ``parse_ordered_object`` takes
        priority.
        ``parse_key``, if specified, will be called with the string of every
        JSON object's key to be decoded.
        ``parse_string``, if specified, will be called with the string of every
        JSON object's value to be decoded.
        ``parse_Array``, if specified, will be called with the list of every
        JSON array decoded and its return will be used in place of the given
        ``list``. This feature can be used to provide custom decoders (for
        example, ``tuple``).
        ``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.
        If ``strict`` is false (true is the default), then control
        characters will be allowed inside strings.  Control characters in
        this context are those with character codes in the 0-31 range,
        including ``'\\t'`` (tab), ``'\\n'``, ``'\\r'`` and ``'\\0'``.
        """
        # Backwards compatibility
        parse_object = kw.get('object_hook', parse_object)
        parse_ordered_object = kw.get('object_pairs_hook', parse_ordered_object)

        self.parse_ordered_object = parse_ordered_object
        self.parse_object = parse_object
        self.parse_key = parse_key
        self.parse_array = parse_array
        self.parse_string = parse_string
        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.memo = {}
        self.scan_once = scanner.make_scanner(self)

    def decode(self, s, _w=WHITESPACE.match):
        """Return the Python representation of ``s`` (a ``str`` 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 JSONDecodeError("Extra data", s, end)
        return obj

    def raw_decode(self, s, idx=0):
        """Decode a JSON document from ``s`` (a ``str`` 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 as err:
            raise JSONDecodeError("Expecting value", s, err.value) from None
        return obj, end