"""

Implementation of JSONEncoder

"""

import re

ESCAPE = re.compile(r'[\x00-\x19\\"\b\f\n\r\t]')

ESCAPE_ASCII = re.compile(r'([\\"/]|[^\ -~])')

ESCAPE_DCT = {

    # escape all forward slashes to prevent </script> attack

    '/': '\\/',

    '\\': '\\\\',

    '"': '\\"',

    '\b': '\\b',

    '\f': '\\f',

    '\n': '\\n',

    '\r': '\\r',

    '\t': '\\t',

}

for i in range(0x20):

    ESCAPE_DCT.setdefault(chr(i), '\\u%04x' % (i,))

# assume this produces an infinity on all machines (probably not guaranteed)

INFINITY = float('1e66666')

def floatstr(o, allow_nan=True):

    # Check for specials.  Note that this type of test is processor- and/or

    # platform-specific, so do tests which don't depend on the internals.

    if o != o:

        text = 'NaN'

    elif o == INFINITY:

        text = 'Infinity'

    elif o == -INFINITY:

        text = '-Infinity'

    else:

        return str(o)

    if not allow_nan:

        raise ValueError("Out of range float values are not JSON compliant: %r"

            % (o,))

    return text

def encode_basestring(s):

    """

    Return a JSON representation of a Python string

    """

    def replace(match):

        return ESCAPE_DCT[match.group(0)]

    return '"' + ESCAPE.sub(replace, s) + '"'

def encode_basestring_ascii(s):

    def replace(match):

        s = match.group(0)

        try:

            return ESCAPE_DCT[s]

        except KeyError:

            return '\\u%04x' % (ord(s),)

    return '"' + str(ESCAPE_ASCII.sub(replace, s)) + '"'

class JSONEncoder(object):

    """

    Extensible JSON <http://json.org> encoder for Python data structures.

    Supports the following objects and types by default:

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

    | Python            | JSON          |

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

    | dict              | object        |

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

    | list, tuple       | array         |

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

    | str, unicode      | string        |

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

    | int, long, float  | number        |

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

    | True              | true          |

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

    | False             | false         |

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

    | None              | null          |

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

    To extend this to recognize other objects, subclass and implement a

    ``.default()`` method with another method that returns a serializable

    object for ``o`` if possible, otherwise it should call the superclass

    implementation (to raise ``TypeError``).

    """

    __all__ = ['__init__', 'default', 'encode', 'iterencode']

    item_separator = ', '

    key_separator = ': '

    def __init__(self, skipkeys=False, ensure_ascii=True,

            check_circular=True, allow_nan=True, sort_keys=False,

            indent=None, separators=None):

        """

        Constructor for JSONEncoder, with sensible defaults.

        If skipkeys is False, then it is a TypeError to attempt

        encoding of keys that are not str, int, long, float or None.  If

        skipkeys is True, such items are simply skipped.

        If ensure_ascii is True, the output is guaranteed to be str

        objects with all incoming unicode characters escaped.  If

        ensure_ascii is false, the output will be unicode object.

        If check_circular is True, then lists, dicts, and custom encoded

        objects will be checked for circular references during encoding to

        prevent an infinite recursion (which would cause an OverflowError).

        Otherwise, no such check takes place.

        If allow_nan is True, then NaN, Infinity, and -Infinity will be

        encoded as such.  This behavior is not JSON specification compliant,

        but is consistent with most JavaScript based encoders and decoders.

        Otherwise, it will be a ValueError to encode such floats.

        If sort_keys is True, then the output of dictionaries will be

        sorted by key; this is useful for regression tests to ensure

        that JSON serializations can be compared on a day-to-day basis.

        If indent is a non-negative integer, then JSON array

        elements and object members will be pretty-printed with that

        indent level.  An indent level of 0 will only insert newlines.

        None is the most compact representation.

        If specified, separators should be a (item_separator, key_separator)

        tuple. The default is (', ', ': '). To get the most compact JSON

        representation you should specify (',', ':') to eliminate whitespace.

        """

        self.skipkeys = skipkeys

        self.ensure_ascii = ensure_ascii

        self.check_circular = check_circular

        self.allow_nan = allow_nan

        self.sort_keys = sort_keys

        self.indent = indent

        self.current_indent_level = 0

        if separators is not None:

            self.item_separator, self.key_separator = separators

    def _newline_indent(self):

        return '\n' + (' ' * (self.indent * self.current_indent_level))

    def _iterencode_list(self, lst, markers=None):

        if not lst:

            yield '[]'

            return

        if markers is not None:

            markerid = id(lst)

            if markerid in markers:

                raise ValueError("Circular reference detected")

            markers[markerid] = lst

        yield '['

        if self.indent is not None:

            self.current_indent_level += 1

            newline_indent = self._newline_indent()

            separator = self.item_separator + newline_indent

            yield newline_indent

        else:

            newline_indent = None

            separator = self.item_separator

        first = True

        for value in lst:

            if first:

                first = False

            else:

                yield separator

            for chunk in self._iterencode(value, markers):

                yield chunk

        if newline_indent is not None:

            self.current_indent_level -= 1

            yield self._newline_indent()

        yield ']'

        if markers is not None:

            del markers[markerid]

    def _iterencode_dict(self, dct, markers=None):

        if not dct:

            yield '{}'

            return

        if markers is not None:

            markerid = id(dct)

            if markerid in markers:

                raise ValueError("Circular reference detected")

            markers[markerid] = dct

        yield '{'

        key_separator = self.key_separator

        if self.indent is not None:

            self.current_indent_level += 1

            newline_indent = self._newline_indent()

            item_separator = self.item_separator + newline_indent

            yield newline_indent

        else:

            newline_indent = None

            item_separator = self.item_separator

        first = True

        if self.ensure_ascii:

            encoder = encode_basestring_ascii

        else:

            encoder = encode_basestring

        allow_nan = self.allow_nan

        if self.sort_keys:

            keys = dct.keys()

            keys.sort()

            items = [(k, dct[k]) for k in keys]

        else:

            items = dct.iteritems()

        for key, value in items:

            if isinstance(key, basestring):

                pass

            # JavaScript is weakly typed for these, so it makes sense to

            # also allow them.  Many encoders seem to do something like this.

            elif isinstance(key, float):

                key = floatstr(key, allow_nan)

            elif isinstance(key, (int, long)):

                key = str(key)

            elif key is True:

                key = 'true'

            elif key is False:

                key = 'false'

            elif key is None:

                key = 'null'

            elif self.skipkeys:

                continue

            else:

                raise TypeError("key %r is not a string" % (key,))

            if first:

                first = False

            else:

                yield item_separator

            yield encoder(key)

            yield key_separator

            for chunk in self._iterencode(value, markers):

                yield chunk

        if newline_indent is not None:

            self.current_indent_level -= 1

            yield self._newline_indent()

        yield '}'

        if markers is not None:

            del markers[markerid]

    def _iterencode(self, o, markers=None):

        if isinstance(o, basestring):

            if self.ensure_ascii:

                encoder = encode_basestring_ascii

            else:

                encoder = encode_basestring

            yield encoder(o)

        elif o is None:

            yield 'null'

        elif o is True:

            yield 'true'

        elif o is False:

            yield 'false'

        elif isinstance(o, (int, long)):

            yield str(o)

        elif isinstance(o, float):

            yield floatstr(o, self.allow_nan)

        elif isinstance(o, (list, tuple)):

            for chunk in self._iterencode_list(o, markers):

                yield chunk

        elif isinstance(o, dict):

            for chunk in self._iterencode_dict(o, markers):

                yield chunk

        else:

            if markers is not None:

                markerid = id(o)

                if markerid in markers:

                    raise ValueError("Circular reference detected")

                markers[markerid] = o

            for chunk in self._iterencode_default(o, markers):

                yield chunk

            if markers is not None:

                del markers[markerid]

    def _iterencode_default(self, o, markers=None):

        newobj = self.default(o)

        return self._iterencode(newobj, markers)

    def default(self, o):

        """

        Implement this method in a subclass such that it returns

        a serializable object for ``o``, or calls the base implementation

        (to raise a ``TypeError``).

        For example, to support arbitrary iterators, you could

        implement default like this::

            def default(self, o):

                try:

                    iterable = iter(o)

                except TypeError:

                    pass

                else:

                    return list(iterable)

                return JSONEncoder.default(self, o)

        """

        raise TypeError("%r is not JSON serializable" % (o,))

    def encode(self, o):

        """

        Return a JSON string representation of a Python data structure.

        >>> JSONEncoder().encode({"foo": ["bar", "baz"]})

        '{"foo":["bar", "baz"]}'

        """

        # This doesn't pass the iterator directly to ''.join() because it

        # sucks at reporting exceptions.  It's going to do this internally

        # anyway because it uses PySequence_Fast or similar.

        chunks = list(self.iterencode(o))

        return ''.join(chunks)

    def iterencode(self, o):

        """

        Encode the given object and yield each string

        representation as available.

        For example::

            for chunk in JSONEncoder().iterencode(bigobject):

                mysocket.write(chunk)

        """

        if self.check_circular:

            markers = {}

        else:

            markers = None

        return self._iterencode(o, markers)

__all__ = ['JSONEncoder']