"""
This module implements the Request class which is used to represent HTTP
requests in Scrapy.

See documentation in docs/topics/request-response.rst
"""
import six
from w3lib.url import safe_url_string

from scrapy.http.headers import Headers
from scrapy.utils.python import to_bytes
from scrapy.utils.trackref import object_ref
from scrapy.utils.url import escape_ajax
from scrapy.http.common import obsolete_setter


class Request(object_ref):

    def __init__(self, url, callback=None, method='GET', headers=None, body=None,
                 cookies=None, meta=None, encoding='utf-8', priority=0,
                 dont_filter=False, errback=None, flags=None, cb_kwargs=None):

        self._encoding = encoding  # this one has to be set first
        self.method = str(method).upper()
        self._set_url(url)
        self._set_body(body)
        assert isinstance(priority, int), "Request priority not an integer: %r" % priority
        self.priority = priority

        if callback is not None and not callable(callback):
            raise TypeError('callback must be a callable, got %s' % type(callback).__name__)
        if errback is not None and not callable(errback):
            raise TypeError('errback must be a callable, got %s' % type(errback).__name__)
        assert callback or not errback, "Cannot use errback without a callback"
        self.callback = callback
        self.errback = errback

        self.cookies = cookies or {}
        self.headers = Headers(headers or {}, encoding=encoding)
        self.dont_filter = dont_filter

        self._meta = dict(meta) if meta else None
        self._cb_kwargs = dict(cb_kwargs) if cb_kwargs else None
        self.flags = [] if flags is None else list(flags)

    @property
    def cb_kwargs(self):
        if self._cb_kwargs is None:
            self._cb_kwargs = {}
        return self._cb_kwargs

    @property
    def meta(self):
        if self._meta is None:
            self._meta = {}
        return self._meta

    def _get_url(self):
        return self._url

    def _set_url(self, url):
        if not isinstance(url, six.string_types):
            raise TypeError('Request url must be str or unicode, got %s:' % type(url).__name__)

        s = safe_url_string(url, self.encoding)
        self._url = escape_ajax(s)

        if ':' not in self._url:
            raise ValueError('Missing scheme in request url: %s' % self._url)

    url = property(_get_url, obsolete_setter(_set_url, 'url'))

    def _get_body(self):
        return self._body

    def _set_body(self, body):
        if body is None:
            self._body = b''
        else:
            self._body = to_bytes(body, self.encoding)

    body = property(_get_body, obsolete_setter(_set_body, 'body'))

    @property
    def encoding(self):
        return self._encoding

    def __str__(self):
        return "<%s %s>" % (self.method, self.url)

    __repr__ = __str__

    def copy(self):
        """Return a copy of this Request"""
        return self.replace()

    def replace(self, *args, **kwargs):
        """Create a new Request with the same attributes except for those
        given new values.
        """
        for x in ['url', 'method', 'headers', 'body', 'cookies', 'meta', 'flags',
                  'encoding', 'priority', 'dont_filter', 'callback', 'errback', 'cb_kwargs']:
            kwargs.setdefault(x, getattr(self, x))
        cls = kwargs.pop('cls', self.__class__)
        return cls(*args, **kwargs)
