"""JSON token scanner
"""
import re
try:
 from _json import make_scanner as c_make_scanner
except ImportError:
 c_make_scanner = None

__all__ = ['make_scanner']

NUMBER_RE = re.compile(
 r'(-?(?:0|[1-9]\d*))(\.\d+)?([eE][-+]?\d+)?',
 (re.VERBOSE | re.MULTILINE | re.DOTALL))

def py_make_scanner(context):
 parse_object = context.parse_object
 parse_array = context.parse_array
 parse_string = context.parse_string
 match_number = NUMBER_RE.match
 strict = context.strict
 parse_float = context.parse_float
 parse_int = context.parse_int
 parse_constant = context.parse_constant
 object_hook = context.object_hook
 object_pairs_hook = context.object_pairs_hook
 memo = context.memo

 def _scan_once(string, idx):
 try:
 nextchar = string[idx]
 except IndexError:
 raise StopIteration(idx) from None

 if nextchar == '"':
 return parse_string(string, idx + 1, strict)
 elif nextchar == '{':
 return parse_object((string, idx + 1), strict,
 _scan_once, object_hook, object_pairs_hook, memo)
 elif nextchar == '[':
 return parse_array((string, idx + 1), _scan_once)
 elif nextchar == 'n' and string[idx:idx + 4] == 'null':
 return None, idx + 4
 elif nextchar == 't' and string[idx:idx + 4] == 'true':
 return True, idx + 4
 elif nextchar == 'f' and string[idx:idx + 5] == 'false':
 return False, idx + 5

 m = match_number(string, idx)
 if m is not None:
 integer, frac, exp = m.groups()
 if frac or exp:
 res = parse_float(integer + (frac or '') + (exp or ''))
 else:
 res = parse_int(integer)
 return res, m.end()
 elif nextchar == 'N' and string[idx:idx + 3] == 'NaN':
 return parse_constant('NaN'), idx + 3
 elif nextchar == 'I' and string[idx:idx + 8] == 'Infinity':
 return parse_constant('Infinity'), idx + 8
 elif nextchar == '-' and string[idx:idx + 9] == '-Infinity':
 return parse_constant('-Infinity'), idx + 9
 else:
 raise StopIteration(idx)

 def scan_once(string, idx):
 try:
 return _scan_once(string, idx)
 finally:
 memo.clear()

 return scan_once

make_scanner = c_make_scanner or py_make_scanner