# -*- coding: utf-8 -*-

"""
requests.session
~~~~~~~~~~~~~~~~

This module provides a Session object to manage and persist settings across
requests (cookies, auth, proxies).
"""
import os
import sys
import time
from datetime import timedelta

from .auth import _basic_auth_str
from .compat import cookielib, is_py3, OrderedDict, urljoin, urlparse, Mapping
from .cookies import (
    cookiejar_from_dict, extract_cookies_to_jar, RequestsCookieJar, merge_cookies)
from .models import Request, PreparedRequest, DEFAULT_REDIRECT_LIMIT
from .hooks import default_hooks, dispatch_hook
from ._internal_utils import to_native_string
from .utils import to_key_val_list, default_headers, DEFAULT_PORTS
from .exceptions import (
    TooManyRedirects, InvalidSchema, ChunkedEncodingError, ContentDecodingError)

from .structures import CaseInsensitiveDict
from .adapters import HTTPAdapter

from .utils import (
    requote_uri, get_environ_proxies, get_netrc_auth, should_bypass_proxies,
    get_auth_from_url, rewind_body
)

from .status_codes import codes

# formerly defined here, reexposed here for backward compatibility
from .models import REDIRECT_STATI

# Preferred clock, based on which one is more accurate on a given system.
if sys.platform == 'win32':
    try:  # Python 3.4+
        preferred_clock = time.perf_counter
    except AttributeError:  # Earlier than Python 3.
        preferred_clock = time.clock
else:
    preferred_clock = time.time


def merge_setting(request_setting, session_setting, dict_class=OrderedDict):
    """Determines appropriate setting for a given request, taking into account
    the explicit setting on that request, and the setting in the session. If a
    setting is a dictionary, they will be merged together using `dict_class`
    """

    if session_setting is None:
        return request_setting

    if request_setting is None:
        return session_setting

    # Bypass if not a dictionary (e.g. verify)
    if not (
            isinstance(session_setting, Mapping) and
            isinstance(request_setting, Mapping)
    ):
        return request_setting

    merged_setting = dict_class(to_key_val_list(session_setting))
    merged_setting.update(to_key_val_list(request_setting))

    # Remove keys that are set to None. Extract keys first to avoid altering
    # the dictionary during iteration.
    none_keys = [k for (k, v) in merged_setting.items() if v is None]
    for key in none_keys:
        del merged_setting[key]

    return merged_setting


def merge_hooks(request_hooks, session_hooks, dict_class=OrderedDict):
    """Properly merges both requests and session hooks.

    This is necessary because when request_hooks == {'response': []}, the
    merge breaks Session hooks entirely.
    """
    if session_hooks is None or session_hooks.get('response') == []:
        return request_hooks

    if request_hooks is None or request_hooks.get('response') == []:
        return session_hooks

    return merge_setting(request_hooks, session_hooks, dict_class)


class SessionRedirectMixin(object):

    def get_redirect_target(self, resp):
        """Receives a Response. Returns a redirect URI or ``None``"""
        # Due to the nature of how requests processes redirects this method will
        # be called at least once upon the original response and at least twice
        # on each subsequent redirect response (if any).
        # If a custom mixin is used to handle this logic, it may be advantageous
        # to cache the redirect location onto the response object as a private
        # attribute.
        if resp.is_redirect:
            location = resp.headers['location']
            # Currently the underlying http module on py3 decode headers
            # in latin1, but empirical evidence suggests that latin1 is very
            # rarely used with non-ASCII characters in HTTP headers.
            # It is more likely to get UTF8 header rather than latin1.
            # This causes incorrect handling of UTF8 encoded location headers.
            # To solve this, we re-encode the location in latin1.
            if is_py3:
                location = location.encode('latin1')
            return to_native_string(location, 'utf8')
        return None

    def should_strip_auth(self, old_url, new_url):
        """Decide whether Authorization header should be removed when redirecting"""
        old_parsed = urlparse(old_url)
        new_parsed = urlparse(new_url)
        if old_parsed.hostname != new_parsed.hostname:
            return True
        # Special case: allow http -> https redirect when using the standard
        # ports. This isn't specified by RFC 7235, but is kept to avoid
        # breaking backwards compatibility with older versions of requests
        # that allowed any redirects on the same host.
        if (old_parsed.scheme == 'http' and old_parsed.port in (80, None)
                and new_parsed.scheme == 'https' and new_parsed.port in (443, None)):
            return False

        # Handle default port usage corresponding to scheme.
        changed_port = old_parsed.port != new_parsed.port
        changed_scheme = old_parsed.scheme != new_parsed.scheme
        default_port = (DEFAULT_PORTS.get(old_parsed.scheme, None), None)
        if (not changed_scheme and old_parsed.port in default_port
                and new_parsed.port in default_port):
            return False

        # Standard case: root URI must match
        return changed_port or changed_scheme

    def resolve_redirects(self, resp, req, stream=False, timeout=None,
                          verify=True, cert=None, proxies=None, yield_requests=False, **adapter_kwargs):
        """Receives a Response. Returns a generator of Responses or Requests."""

        hist = []  # keep track of history

        url = self.get_redirect_target(resp)
        previous_fragment = urlparse(req.url).fragment
        while url:
            prepared_request = req.copy()

            # Update history and keep track of redirects.
            # resp.history must ignore the original request in this loop
            hist.append(resp)
            resp.history = hist[1:]

            try:
                resp.content  # Consume socket so it can be released
            except (ChunkedEncodingError, ContentDecodingError, RuntimeError):
                resp.raw.read(decode_content=False)

            if len(resp.history) >= self.max_redirects:
                raise TooManyRedirects('Exceeded %s redirects.' % self.max_redirects, response=resp)

            # Release the connection back into the pool.
            resp.close()

            # Handle redirection without scheme (see: RFC 1808 Section 4)
            if url.startswith('//'):
                parsed_rurl = urlparse(resp.url)
                url = '%s:%s' % (to_native_string(parsed_rurl.scheme), url)

            # Normalize url case and attach previous fragment if needed (RFC 7231 7.1.2)
            parsed = urlparse(url)
            if parsed.fragment == '' and previous_fragment:
                parsed = parsed._replace(fragment=previous_fragment)
            elif parsed.fragment:
                previous_fragment = parsed.fragment
            url = parsed.geturl()

            # Facilitate relative 'location' headers, as allowed by RFC 7231.
            # (e.g. '/path/to/resource' instead of 'http://domain.tld/path/to/resource')
            # Compliant with RFC3986, we percent encode the url.
            if not parsed.netloc:
                url = urljoin(resp.url, requote_uri(url))
            else:
                url = requote_uri(url)

            prepared_request.url = to_native_string(url)

            self.rebuild_method(prepared_request, resp)

            # https://github.com/requests/requests/issues/1084
            if resp.status_code not in (codes.temporary_redirect, codes.permanent_redirect):
                # https://github.com/requests/requests/issues/3490
                purged_headers = ('Content-Length', 'Content-Type', 'Transfer-Encoding')
                for header in purged_headers:
                    prepared_request.headers.pop(header, None)
                prepared_request.body = None

            headers = prepared_request.headers
            try:
                del headers['Cookie']
            except KeyError:
                pass

            # Extract any cookies sent on the response to the cookiejar
            # in the new request. Because we've mutated our copied prepared
            # request, use the old one that we haven't yet touched.
            extract_cookies_to_jar(prepared_request._cookies, req, resp.raw)
            merge_cookies(prepared_request._cookies, self.cookies)
            prepared_request.prepare_cookies(prepared_request._cookies)

            # Rebuild auth and proxy information.
            proxies = self.rebuild_proxies(prepared_request, proxies)
            self.rebuild_auth(prepared_request, resp)

            # A failed tell() sets `_body_position` to `object()`. This non-None
            # value ensures `rewindable` will be True, allowing us to raise an
            # UnrewindableBodyError, instead of hanging the connection.
            rewindable = (
                prepared_request._body_position is not None and
                ('Content-Length' in headers or 'Transfer-Encoding' in headers)
            )

            # Attempt to rewind consumed file-like object.
            if rewindable:
                rewind_body(prepared_request)

            # Override the original request.
            req = prepared_request

            if yield_requests:
                yield req
            else:

                resp = self.send(
                    req,
                    stream=stream,
                    timeout=timeout,
                    verify=verify,
                    cert=cert,
                    proxies=proxies,
                    allow_redirects=False,
                    **adapter_kwargs
                )

                extract_cookies_to_jar(self.cookies, prepared_request, resp.raw)

                # extract redirect url, if any, for the next loop
                url = self.get_redirect_target(resp)
                yield resp

    def rebuild_auth(self, prepared_request, response):
        """When being redirected we may want to strip authentication from the
        request to avoid leaking credentials. This method intelligently removes
        and reapplies authentication where possible to avoid credential loss.
        """
        headers = prepared_request.headers
        url = prepared_request.url

        if 'Authorization' in headers and self.should_strip_auth(response.request.url, url):
            # If we get redirected to a new host, we should strip out any
            # authentication headers.
            del headers['Authorization']

        # .netrc might have more auth for us on our new host.
        new_auth = get_netrc_auth(url) if self.trust_env else None
        if new_auth is not None:
            prepared_request.prepare_auth(new_auth)

        return

    def rebuild_proxies(self, prepared_request, proxies):
        """This method re-evaluates the proxy configuration by considering the
        environment variables. If we are redirected to a URL covered by
        NO_PROXY, we strip the proxy configuration. Otherwise, we set missing
        proxy keys for this URL (in case they were stripped by a previous
        redirect).

        This method also replaces the Proxy-Authorization header where
        necessary.

        :rtype: dict
        """
        proxies = proxies if proxies is not None else {}
        headers = prepared_request.headers
        url = prepared_request.url
        scheme = urlparse(url).scheme
        new_proxies = proxies.copy()
        no_proxy = proxies.get('no_proxy')

        bypass_proxy = should_bypass_proxies(url, no_proxy=no_proxy)
        if self.trust_env and not bypass_proxy:
            environ_proxies = get_environ_proxies(url, no_proxy=no_proxy)

            proxy = environ_proxies.get(scheme, environ_proxies.get('all'))

            if proxy:
                new_proxies.setdefault(scheme, proxy)

        if 'Proxy-Authorization' in headers:
            del headers['Proxy-Authorization']

        try:
            username, password = get_auth_from_url(new_proxies[scheme])
        except KeyError:
            username, password = None, None

        if username and password:
            headers['Proxy-Authorization'] = _basic_auth_str(username, password)

        return new_proxies

    def rebuild_method(self, prepared_request, response):
        """When being redirected we may want to change the method of the request
        based on certain specs or browser behavior.
        """
        method = prepared_request.method

        # https://tools.ietf.org/html/rfc7231#section-6.4.4
        if response.status_code == codes.see_other and method != 'HEAD':
            method = 'GET'

        # Do what the browsers do, despite standards...
        # First, turn 302s into GETs.
        if response.status_code == codes.found and method != 'HEAD':
            method = 'GET'

        # Second, if a POST is responded to with a 301, turn it into a GET.
        # This bizarre behaviour is explained in Issue 1704.
        if response.status_code == codes.moved and method == 'POST':
            method = 'GET'

        prepared_request.method = method


class Session(SessionRedirectMixin):
    """A Requests session.

    Provides cookie persistence, connection-pooling, and configuration.

    Basic Usage::