"""Implementation of JSONDecoder
"""
import re

from json import scanner
try:
 from _json import scanstring as c_scanstring
except ImportError:
 c_scanstring = None

__all__ = ['JSONDecoder', 'JSONDecodeError']

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

NaN = float('nan')
PosInf = float('inf')
NegInf = float('-inf')


class JSONDecodeError(ValueError):
 """Subclass of ValueError with the following additional properties:

 msg: The unformatted error message
 doc: The JSON document being parsed
 pos: The start index of doc where parsing failed
 lineno: The line corresponding to pos
 colno: The column corresponding to pos

 """
 # Note that this exception is used from _json
 def __init__(self, msg, doc, pos):
 lineno = doc.count('\n', 0, pos) + 1
 colno = pos - doc.rfind('\n', 0, pos)
 errmsg = '%s: line %d column %d (char %d)' % (msg, lineno, colno, pos)
 ValueError.__init__(self, errmsg)
 self.msg = msg
 self.doc = doc
 self.pos = pos
 self.lineno = lineno
 self.colno = colno

 def __reduce__(self):
 return self.__class__, (self.msg, self.doc, self.pos)


_CONSTANTS = {
 '-Infinity': NegInf,
 'Infinity': PosInf,
 'NaN': NaN,
}


STRINGCHUNK = re.compile(r'(.*?)(["\\\x00-\x1f])', FLAGS)
BACKSLASH = {
 '"': '"', '\\': '\\', '/': '/',
 'b': '\b', 'f': '\f', 'n': '\n', 'r': '\r', 't': '\t',
}

def _decode_uXXXX(s, pos):
 esc = s[pos + 1:pos + 5]
 if len(esc) == 4 and esc[1] not in 'xX':
 try:
 return int(esc, 16)
 except ValueError:
 pass
 msg = "Invalid \\uXXXX escape"
 raise JSONDecodeError(msg, s, pos)

def py_scanstring(s, end, 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."""
 chunks = []
 _append = chunks.append
 begin = end - 1
 while 1:
 chunk = _m(s, end)
 if chunk is None:
 raise JSONDecodeError("Unterminated string starting at", s, begin)
 end = chunk.end()
 content, terminator = chunk.groups()
 # Content is contains zero or more unescaped string characters
 if content:
 _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,)
 msg = "Invalid control character {0!r} at".format(terminator)
 raise JSONDecodeError(msg, s, end)
 else:
 _append(terminator)
 continue
 try:
 esc = s[end]
 except IndexError:
 raise JSONDecodeError("Unterminated string starting at",
 s, begin) from None
 # If not a unicode escape sequence, must be in the lookup table
 if esc != 'u':
 try:
 char = _b[esc]
 except KeyError:
 msg = "Invalid \\escape: {0!r}".format(esc)
 raise JSONDecodeError(msg, s, end)
 end += 1
 else:
 uni = _decode_uXXXX(s, end)
 end += 5
 if 0xd800 <= uni <= 0xdbff and s[end:end + 2] == '\\u':
 uni2 = _decode_uXXXX(s, end + 1)
 if 0xdc00 <= uni2 <= 0xdfff:
 uni = 0x10000 + (((uni - 0xd800) << 10) | (uni2 - 0xdc00))
 end += 6
 char = chr(uni)
 _append(char)
 return ''.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_and_end, strict, scan_once, object_hook, object_pairs_hook,
 memo=None, _w=WHITESPACE.match, _ws=WHITESPACE_STR):
 s, end = s_and_end
 pairs = []
 pairs_append = pairs.append
 # Backwards compatibility
 if memo is None:
 memo = {}
 memo_get = memo.setdefault
 # 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 == '}':
 if object_pairs_hook is not None:
 result = object_pairs_hook(pairs)
 return result, end + 1
 pairs = {}
 if object_hook is not None:
 pairs = object_hook(pairs)
 return pairs, end + 1
 elif nextchar != '"':
 raise JSONDecodeError(
 "Expecting property name enclosed in double quotes", s, end)
 end += 1
 while True:
 key, end = scanstring(s, end, strict)
 key = memo_get(key, key)
 # 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 JSONDecodeError("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 as err:
 raise JSONDecodeError("Expecting value", s, err.value) from None
 pairs_append((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 JSONDecodeError("Expecting ',' delimiter", s, end - 1)
 end = _w(s, end).end()
 nextchar = s[end:end + 1]
 end += 1
 if nextchar != '"':
 raise JSONDecodeError(
 "Expecting property name enclosed in double quotes", s, end - 1)
 if object_pairs_hook is not None:
 result = object_pairs_hook(pairs)
 return result, end
 pairs = dict(pairs)
 if object_hook is not None:
 pairs = object_hook(pairs)
 return pairs, end

def JSONArray(s_and_end, scan_once, _w=WHITESPACE.match, _ws=WHITESPACE_STR):
 s, end = s_and_end
 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 as err:
 raise JSONDecodeError("Expecting value", s, err.value) from None
 _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 JSONDecodeError("Expecting ',' delimiter", s, end - 1)
 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 | 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, *, object_hook=None, parse_float=None,
 parse_int=None, parse_constant=None, strict=True,
 object_pairs_hook=None):
 """``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).

 ``object_pairs_hook``, 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.
 If ``object_hook`` is also defined, the ``object_pairs_hook`` takes
 priority.

 ``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'``.
 """
 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.object_pairs_hook = object_pairs_hook
 self.parse_object = JSONObject
 self.parse_array = JSONArray
 self.parse_string = scanstring
 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