# urllib3/poolmanager.py
# Copyright 2008-2012 Andrey Petrov and contributors (see CONTRIBUTORS.txt)
#
# This module is part of urllib3 and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php

import logging

from ._collections import RecentlyUsedContainer
from .connectionpool import HTTPConnectionPool, HTTPSConnectionPool
from .connectionpool import connection_from_url, port_by_scheme
from .request import RequestMethods
from .util import parse_url


__all__ = ['PoolManager', 'ProxyManager', 'proxy_from_url']


pool_classes_by_scheme = {
    'http': HTTPConnectionPool,
    'https': HTTPSConnectionPool,
}

log = logging.getLogger(__name__)


class PoolManager(RequestMethods):
    """
    Allows for arbitrary requests while transparently keeping track of
    necessary connection pools for you.

    :param num_pools:
        Number of connection pools to cache before discarding the least
        recently used pool.

    :param headers:
        Headers to include with all requests, unless other headers are given
        explicitly.

    :param \**connection_pool_kw:
        Additional parameters are used to create fresh
        :class:`urllib3.connectionpool.ConnectionPool` instances.

    Example: ::

        >>> manager = PoolManager(num_pools=2)
        >>> r = manager.request('GET', 'http://google.com/')
        >>> r = manager.request('GET', 'http://google.com/mail')
        >>> r = manager.request('GET', 'http://yahoo.com/')
        >>> len(manager.pools)
        2

    """

    def __init__(self, num_pools=10, headers=None, **connection_pool_kw):
        RequestMethods.__init__(self, headers)
        self.connection_pool_kw = connection_pool_kw
        self.pools = RecentlyUsedContainer(num_pools,
                                           dispose_func=lambda p: p.close())

    def _new_pool(self, scheme, host, port):
        """
        Create a new :class:`ConnectionPool` based on host, port and scheme.

        This method is used to actually create the connection pools handed out
        by :meth:`connection_from_url` and companion methods. It is intended
        to be overridden for customization.
        """
        pool_cls = pool_classes_by_scheme[scheme]
        return pool_cls(host, port, **self.connection_pool_kw)

    def clear(self):
        """
        Empty our store of pools and direct them all to close.

        This will not affect in-flight connections, but they will not be
        re-used after completion.
        """
        self.pools.clear()

    def connection_from_host(self, host, port=None, scheme='http'):
        """
        Get a :class:`ConnectionPool` based on the host, port, and scheme.

        If ``port`` isn't given, it will be derived from the ``scheme`` using
        ``urllib3.connectionpool.port_by_scheme``.
        """
        scheme = scheme or 'http'
        port = port or port_by_scheme.get(scheme, 80)

        pool_key = (scheme, host, port)

        # If the scheme, host, or port doesn't match existing open connections,
        # open a new ConnectionPool.
        pool = self.pools.get(pool_key)
        if pool:
            return pool

        # Make a fresh ConnectionPool of the desired type
        pool = self._new_pool(scheme, host, port)
        self.pools[pool_key] = pool
        return pool

    def connection_from_url(self, url):
        """
        Similar to :func:`urllib3.connectionpool.connection_from_url` but
        doesn't pass any additional parameters to the
        :class:`urllib3.connectionpool.ConnectionPool` constructor.

        Additional parameters are taken from the :class:`.PoolManager`
        constructor.
        """
        u = parse_url(url)
        return self.connection_from_host(u.host, port=u.port, scheme=u.scheme)

    def urlopen(self, method, url, redirect=True, **kw):
        """
        Same as :meth:`urllib3.connectionpool.HTTPConnectionPool.urlopen`
        with custom cross-host redirect logic and only sends the request-uri
        portion of the ``url``.

        The given ``url`` parameter must be absolute, such that an appropriate
        :class:`urllib3.connectionpool.ConnectionPool` can be chosen for it.
        """
        u = parse_url(url)
        conn = self.connection_from_host(u.host, port=u.port, scheme=u.scheme)

        kw['assert_same_host'] = False
        kw['redirect'] = False
        if 'headers' not in kw:
            kw['headers'] = self.headers

        response = conn.urlopen(method, u.request_uri, **kw)

        redirect_location = redirect and response.get_redirect_location()
        if not redirect_location:
            return response

        if response.status == 303:
            method = 'GET'

        log.info("Redirecting %s -> %s" % (url, redirect_location))
        kw['retries'] = kw.get('retries', 3) - 1  # Persist retries countdown
        return self.urlopen(method, redirect_location, **kw)


class ProxyManager(RequestMethods):
    """
    Given a ConnectionPool to a proxy, the ProxyManager's ``urlopen`` method
    will make requests to any url through the defined proxy. The ProxyManager
    class will automatically set the 'Host' header if it is not provided.
    """

    def __init__(self, proxy_pool):
        self.proxy_pool = proxy_pool

    def _set_proxy_headers(self, url, headers=None):
        """
        Sets headers needed by proxies: specifically, the Accept and Host
        headers. Only sets headers not provided by the user.
        """
        headers_ = {'Accept': '*/*'}

        host = parse_url(url).host
        if host:
            headers_['Host'] = host

        if headers:
            headers_.update(headers)

        return headers_

    def urlopen(self, method, url, **kw):
        "Same as HTTP(S)ConnectionPool.urlopen, ``url`` must be absolute."
        kw['assert_same_host'] = False
        kw['headers'] = self._set_proxy_headers(url, headers=kw.get('headers'))
        return self.proxy_pool.urlopen(method, url, **kw)


def proxy_from_url(url, **pool_kw):
    proxy_pool = connection_from_url(url, **pool_kw)
    return ProxyManager(proxy_pool)
