'''Utilities for patching in cassettes'''
import functools
import itertools

import contextlib2
import mock

from .stubs import VCRHTTPConnection, VCRHTTPSConnection
from six.moves import http_client as httplib


# Save some of the original types for the purposes of unpatching
_HTTPConnection = httplib.HTTPConnection
_HTTPSConnection = httplib.HTTPSConnection


# Try to save the original types for requests
try:
    import requests.packages.urllib3.connectionpool as cpool
except ImportError:  # pragma: no cover
    pass
else:
    _VerifiedHTTPSConnection = cpool.VerifiedHTTPSConnection
    _cpoolHTTPConnection = cpool.HTTPConnection
    _cpoolHTTPSConnection = cpool.HTTPSConnection


# Try to save the original types for urllib3
try:
    import urllib3
except ImportError:  # pragma: no cover
    pass
else:
    _VerifiedHTTPSConnection = urllib3.connectionpool.VerifiedHTTPSConnection


# Try to save the original types for httplib2
try:
    import httplib2
except ImportError:  # pragma: no cover
    pass
else:
    _HTTPConnectionWithTimeout = httplib2.HTTPConnectionWithTimeout
    _HTTPSConnectionWithTimeout = httplib2.HTTPSConnectionWithTimeout
    _SCHEME_TO_CONNECTION = httplib2.SCHEME_TO_CONNECTION


# Try to save the original types for boto
try:
    import boto.https_connection
except ImportError:  # pragma: no cover
    pass
else:
    _CertValidatingHTTPSConnection = boto.https_connection.CertValidatingHTTPSConnection


class CassettePatcherBuilder(object):

    def _build_patchers_from_mock_triples_decorator(function):
        @functools.wraps(function)
        def wrapped(self, *args, **kwargs):
            return self._build_patchers_from_mock_triples(
                function(self, *args, **kwargs)
            )
        return wrapped

    def __init__(self, cassette):
        self._cassette = cassette
        self._class_to_cassette_subclass = {}

    def build(self):
        return itertools.chain(
            self._httplib(), self._requests(), self._urllib3(), self._httplib2(),
            self._boto(), self._build_patchers_from_mock_triples(
                self._cassette.custom_patches
            )
        )

    def _build_patchers_from_mock_triples(self, mock_triples):
        for args in mock_triples:
            patcher = self._build_patcher(*args)
            if patcher:
                yield patcher

    def _build_patcher(self, obj, patched_attribute, replacement_class):
        if not hasattr(obj, patched_attribute):
            return

        return mock.patch.object(obj, patched_attribute,
                                 self._recursively_apply_get_cassette_subclass(
                                     replacement_class))

    def _recursively_apply_get_cassette_subclass(self, replacement_dict_or_obj):
        """One of the subtleties of this class is that it does not directly
        replace HTTPSConnection with VCRRequestsHTTPSConnection, but a
        subclass of this class that has cassette assigned to the
        appropriate value. This behavior is necessary to properly
        support nested cassette contexts

        This function exists to ensure that we use the same class
        object (reference) to patch everything that replaces
        VCRRequestHTTP[S]Connection, but that we can talk about
        patching them with the raw references instead.
        """
        if isinstance(replacement_dict_or_obj, dict):
            for key, replacement_obj  in replacement_dict_or_obj.items():
                replacement_obj = self._recursively_apply_get_cassette_subclass(
                    replacement_obj)
                replacement_dict_or_obj[key] = replacement_obj
            return replacement_dict_or_obj
        if hasattr(replacement_dict_or_obj, 'cassette'):
            replacement_dict_or_obj =  self._get_cassette_subclass(
                replacement_dict_or_obj)
        return replacement_dict_or_obj

    def _get_cassette_subclass(self, klass):
        if klass.cassette is not None:
            return klass
        if klass not in self._class_to_cassette_subclass:
            subclass = self._build_cassette_subclass(klass)
            self._class_to_cassette_subclass[klass] = subclass
        return self._class_to_cassette_subclass[klass]

    def _build_cassette_subclass(self, base_class):
        bases = (base_class,)
        if not issubclass(base_class, object): # Check for old style class
            bases += (object,)
        return type('{0}{1}'.format(base_class.__name__, self._cassette._path),
                    bases, dict(cassette=self._cassette))

    @_build_patchers_from_mock_triples_decorator
    def _httplib(self):
        yield httplib, 'HTTPConnection', VCRHTTPConnection
        yield httplib, 'HTTPSConnection', VCRHTTPSConnection

    def _requests(self):
        try:
            import requests.packages.urllib3.connectionpool as cpool
        except ImportError:  # pragma: no cover
            return ()
        from .stubs.requests_stubs import VCRRequestsHTTPConnection, VCRRequestsHTTPSConnection
        http_connection_remover = ConnectionRemover(
            self._get_cassette_subclass(VCRRequestsHTTPConnection)
        )
        https_connection_remover = ConnectionRemover(
            self._get_cassette_subclass(VCRRequestsHTTPSConnection)
        )
        mock_triples = (
            (cpool, 'VerifiedHTTPSConnection', VCRRequestsHTTPSConnection),
            (cpool, 'VerifiedHTTPSConnection', VCRRequestsHTTPSConnection),
            (cpool, 'HTTPConnection', VCRRequestsHTTPConnection),
            (cpool, 'HTTPSConnection', VCRRequestsHTTPSConnection),
            (cpool, 'is_connection_dropped', mock.Mock(return_value=False)),  # Needed on Windows only
            (cpool.HTTPConnectionPool, 'ConnectionCls', VCRRequestsHTTPConnection),
            (cpool.HTTPSConnectionPool, 'ConnectionCls', VCRRequestsHTTPSConnection),
        )
        # These handle making sure that sessions only use the
        # connections of the appropriate type.
        mock_triples += ((cpool.HTTPConnectionPool, '_get_conn',
                          self._patched_get_conn(cpool.HTTPConnectionPool,
                                                 lambda : cpool.HTTPConnection)),
                         (cpool.HTTPSConnectionPool, '_get_conn',
                          self._patched_get_conn(cpool.HTTPSConnectionPool,
                                                 lambda : cpool.HTTPSConnection)),
                         (cpool.HTTPConnectionPool, '_new_conn',
                          self._patched_new_conn(cpool.HTTPConnectionPool,
                                                 http_connection_remover)),
                         (cpool.HTTPSConnectionPool, '_new_conn',
                          self._patched_new_conn(cpool.HTTPSConnectionPool,
                                                 https_connection_remover)))

        return itertools.chain(self._build_patchers_from_mock_triples(mock_triples),
                               (http_connection_remover, https_connection_remover))

    def _patched_get_conn(self, connection_pool_class, connection_class_getter):
        get_conn = connection_pool_class._get_conn
        @functools.wraps(get_conn)
        def patched_get_conn(pool, timeout=None):
            connection = get_conn(pool, timeout)
            connection_class = pool.ConnectionCls if hasattr(pool, 'ConnectionCls') \
                               else connection_class_getter()
            while not isinstance(connection, connection_class):
                connection = get_conn(pool, timeout)
            return connection
        return patched_get_conn

    def _patched_new_conn(self, connection_pool_class, connection_remover):
        new_conn = connection_pool_class._new_conn
        @functools.wraps(new_conn)
        def patched_new_conn(pool):
            new_connection = new_conn(pool)
            connection_remover.add_connection_to_pool_entry(pool, new_connection)
            return new_connection
        return patched_new_conn

    @_build_patchers_from_mock_triples_decorator
    def _urllib3(self):
        try:
            import urllib3.connectionpool as cpool
        except ImportError:  # pragma: no cover
            pass
        else:
            from .stubs.urllib3_stubs import VCRVerifiedHTTPSConnection

            yield cpool, 'VerifiedHTTPSConnection', VCRVerifiedHTTPSConnection
            yield cpool, 'HTTPConnection', VCRHTTPConnection

    @_build_patchers_from_mock_triples_decorator
    def _httplib2(self):
        try:
            import httplib2 as cpool
        except ImportError:  # pragma: no cover
            pass
        else:
            from .stubs.httplib2_stubs import VCRHTTPConnectionWithTimeout
            from .stubs.httplib2_stubs import VCRHTTPSConnectionWithTimeout

            yield cpool, 'HTTPConnectionWithTimeout', VCRHTTPConnectionWithTimeout
            yield cpool, 'HTTPSConnectionWithTimeout', VCRHTTPSConnectionWithTimeout
            yield cpool, 'SCHEME_TO_CONNECTION', {'http': VCRHTTPConnectionWithTimeout,
                                                  'https': VCRHTTPSConnectionWithTimeout}

    @_build_patchers_from_mock_triples_decorator
    def _boto(self):
        try:
            import boto.https_connection as cpool
        except ImportError:  # pragma: no cover
            pass
        else:
            from .stubs.boto_stubs import VCRCertValidatingHTTPSConnection
            yield cpool, 'CertValidatingHTTPSConnection', VCRCertValidatingHTTPSConnection


class ConnectionRemover(object):

    def __init__(self, connection_class):
        self._connection_class = connection_class
        self._connection_pool_to_connections = {}

    def add_connection_to_pool_entry(self, pool, connection):
        if isinstance(connection, self._connection_class):
            self._connection_pool_to_connections.setdefault(pool, set()).add(connection)

    def remove_connection_to_pool_entry(self, pool, connection):
        if isinstance(connection, self._connection_class):
            self._connection_pool_to_connections[self._connection_class].remove(connection)

    def __enter__(self):
        return self

    def __exit__(self, *args):
        for pool, connections in self._connection_pool_to_connections.items():
            readd_connections = []
            while pool.pool and not pool.pool.empty() and connections:
                connection = pool.pool.get()
                if isinstance(connection, self._connection_class):
                    connections.remove(connection)
                else:
                    readd_connections.append(connection)
            for connection in readd_connections:
                pool._put_conn(connection)


def reset_patchers():
    yield mock.patch.object(httplib, 'HTTPConnection', _HTTPConnection)
    yield mock.patch.object(httplib, 'HTTPSConnection', _HTTPSConnection)
    try:
        import requests.packages.urllib3.connectionpool as cpool
    except ImportError:  # pragma: no cover
        pass
    else:
        # unpatch requests v1.x
        yield mock.patch.object(cpool, 'VerifiedHTTPSConnection', _VerifiedHTTPSConnection)
        yield mock.patch.object(cpool, 'HTTPConnection', _cpoolHTTPConnection)
        # unpatch requests v2.x
        if hasattr(cpool.HTTPConnectionPool, 'ConnectionCls'):
            yield mock.patch.object(cpool.HTTPConnectionPool, 'ConnectionCls',
                                    _cpoolHTTPConnection)
            yield mock.patch.object(cpool.HTTPSConnectionPool, 'ConnectionCls',
                                    _cpoolHTTPSConnection)

        if hasattr(cpool, 'HTTPSConnection'):
            yield mock.patch.object(cpool, 'HTTPSConnection', _cpoolHTTPSConnection)

    try:
        import urllib3.connectionpool as cpool
    except ImportError:  # pragma: no cover
        pass
    else:
        yield mock.patch.object(cpool, 'VerifiedHTTPSConnection', _VerifiedHTTPSConnection)
        yield mock.patch.object(cpool, 'HTTPConnection', _HTTPConnection)
        yield mock.patch.object(cpool, 'HTTPSConnection', _HTTPSConnection)
        if hasattr(cpool.HTTPConnectionPool, 'ConnectionCls'):
            yield mock.patch.object(cpool.HTTPConnectionPool, 'ConnectionCls', _HTTPConnection)
            yield mock.patch.object(cpool.HTTPSConnectionPool, 'ConnectionCls', _HTTPSConnection)

    try:
        import httplib2 as cpool
    except ImportError:  # pragma: no cover
        pass
    else:
        yield mock.patch.object(cpool, 'HTTPConnectionWithTimeout', _HTTPConnectionWithTimeout)
        yield mock.patch.object(cpool, 'HTTPSConnectionWithTimeout', _HTTPSConnectionWithTimeout)
        yield mock.patch.object(cpool, 'SCHEME_TO_CONNECTION', _SCHEME_TO_CONNECTION)

    try:
        import boto.https_connection as cpool
    except ImportError:  # pragma: no cover
        pass
    else:
        yield mock.patch.object(cpool, 'CertValidatingHTTPSConnection',
                                _CertValidatingHTTPSConnection)


@contextlib2.contextmanager
def force_reset():
    with contextlib2.ExitStack() as exit_stack:
        for patcher in reset_patchers():
            exit_stack.enter_context(patcher)
        yield