import os
import sys
import threading
import select
import socket
import errno

from django.conf import settings
from django.db import connections, DEFAULT_DB_ALIAS
from django.core.management import call_command
from django.core.exceptions import ImproperlyConfigured
from django.contrib.staticfiles.handlers import StaticFilesHandler
from django.core.handlers.wsgi import WSGIHandler
from django.core.servers.basehttp import (WSGIRequestHandler, WSGIServer,
    WSGIServerException)
from django.views.static import serve

from django.test.testcases import TransactionTestCase


""" LiveServerTestCase extracted from Django 1.4 alpha source """


class _ImprovedEvent(threading._Event):
    """
    Does the same as `threading.Event` except it overrides the wait() method
    with some code borrowed from Python 2.7 to return the set state of the
    event (see: http://hg.python.org/cpython/rev/b5aa8aa78c0f/). This allows
    to know whether the wait() method exited normally or because of the
    timeout. This class can be removed when Django supports only Python >= 2.7.
    """

    def wait(self, timeout=None):
        self._Event__cond.acquire()
        try:
            if not self._Event__flag:
                self._Event__cond.wait(timeout)
            return self._Event__flag
        finally:
            self._Event__cond.release()


class QuietWSGIRequestHandler(WSGIRequestHandler):
    """
    Just a regular WSGIRequestHandler except it doesn't log to the standard
    output any of the requests received, so as to not clutter the output for
    the tests' results.
    """
    def log_message(*args):
        pass


class StoppableWSGIServer(WSGIServer):
    """
    The code in this class is borrowed from the `SocketServer.BaseServer` class
    in Python 2.6. The important functionality here is that the server is non-
    blocking and that it can be shut down at any moment. This is made possible
    by the server regularly polling the socket and checking if it has been
    asked to stop.
    Note for the future: Once Django stops supporting Python 2.6, this class
    can be removed as `WSGIServer` will have this ability to shutdown on
    demand and will not require the use of the _ImprovedEvent class whose code
    is borrowed from Python 2.7.
    """

    def __init__(self, *args, **kwargs):
        WSGIServer.__init__(self, *args, **kwargs)
        self.__is_shut_down = _ImprovedEvent()
        self.__serving = False

    def serve_forever(self, poll_interval=0.5):
        """
        Handle one request at a time until shutdown.

        Polls for shutdown every poll_interval seconds.
        """
        self.__serving = True
        self.__is_shut_down.clear()
        while self.__serving:
            r, w, e = select.select([self], [], [], poll_interval)
            if r:
                self._handle_request_noblock()
        self.__is_shut_down.set()

    def shutdown(self):
        """
        Stops the serve_forever loop.

        Blocks until the loop has finished. This must be called while
        serve_forever() is running in another thread, or it will
        deadlock.
        """
        self.__serving = False
        if not self.__is_shut_down.wait(2):
            raise RuntimeError(
                "Failed to shutdown the live test server in 2 seconds. The "
                "server might be stuck or generating a slow response.")

    def handle_request(self):
        """Handle one request, possibly blocking.
        """
        fd_sets = select.select([self], [], [], None)
        if not fd_sets[0]:
            return
        self._handle_request_noblock()

    def _handle_request_noblock(self):
        """
        Handle one request, without blocking.

        I assume that select.select has returned that the socket is
        readable before this function was called, so there should be
        no risk of blocking in get_request().
        """
        try:
            request, client_address = self.get_request()
        except socket.error:
            return
        if self.verify_request(request, client_address):
            try:
                self.process_request(request, client_address)
            except Exception:
                self.handle_error(request, client_address)
                self.close_request(request)


class _MediaFilesHandler(StaticFilesHandler):
    """
    Handler for serving the media files. This is a private class that is
    meant to be used solely as a convenience by LiveServerThread.
    """

    def get_base_dir(self):
        return settings.MEDIA_ROOT

    def get_base_url(self):
        return settings.MEDIA_URL

    def serve(self, request):
        return serve(request, self.file_path(request.path),
            document_root=self.get_base_dir())


class LiveServerThread(threading.Thread):
    """
    Thread for running a live http server while the tests are running.
    """

    def __init__(self, host, possible_ports, connections_override=None):
        self.host = host
        self.port = None
        self.possible_ports = possible_ports
        self.is_ready = threading.Event()
        self.error = None
        self.connections_override = connections_override
        super(LiveServerThread, self).__init__()

    def run(self):
        """
        Sets up the live server and databases, and then loops over handling
        http requests.
        """
        if self.connections_override:
            from django.db import connections
            # Override this thread's database connections with the ones
            # provided by the main thread.
            for alias, conn in self.connections_override.items():
                conn.allow_thread_sharing = True
                connections._connections[alias] = conn

        try:
            # Create the handler for serving static and media files
            handler = StaticFilesHandler(_MediaFilesHandler(WSGIHandler()))

            # Go through the list of possible ports, hoping that we can find
            # one that is free to use for the WSGI server.
            for index, port in enumerate(self.possible_ports):
                try:
                    self.httpd = StoppableWSGIServer(
                        (self.host, port), QuietWSGIRequestHandler)
                except WSGIServerException, e:
                    if sys.version_info < (2, 6):
                        error_code = e.args[0].args[0]
                    else:
                        error_code = e.args[0].errno
                    if (index + 1 < len(self.possible_ports) and
                        error_code == errno.EADDRINUSE):
                        # This port is already in use, so we go on and try with
                        # the next one in the list.
                        continue
                    else:
                        # Either none of the given ports are free or the error
                        # is something else than "Address already in use". So
                        # we let that error bubble up to the main thread.
                        raise
                else:
                    # A free port was found.
                    self.port = port
                    break

            self.httpd.set_app(handler)
            self.is_ready.set()
            self.httpd.serve_forever()
        except Exception, e:
            self.error = e
            self.is_ready.set()

    def join(self, timeout=None):
        if hasattr(self, 'httpd'):
            # Stop the WSGI server
            self.httpd.shutdown()
            self.httpd.server_close()
        super(LiveServerThread, self).join(timeout)


class LiveServerTestCase(TransactionTestCase):
    """
    Does basically the same as TransactionTestCase but also launches a live
    http server in a separate thread so that the tests may use another testing
    framework, such as Selenium for example, instead of the built-in dummy
    client.
    Note that it inherits from TransactionTestCase instead of TestCase because
    the threads do not share the same transactions (unless if using in-memory
    sqlite) and each thread needs to commit all their transactions so that the
    other thread can see the changes.
    """

    @property
    def live_server_url(self):
        return 'http://%s:%s' % (
            self.server_thread.host, self.server_thread.port)

    @classmethod
    def setUpClass(cls):
        connections_override = {}
        for conn in connections.all():
            # If using in-memory sqlite databases, pass the connections to
            # the server thread.
            if (conn.settings_dict['ENGINE'] == 'django.db.backends.sqlite3'
                and conn.settings_dict['NAME'] == ':memory:'):
                # Explicitly enable thread-shareability for this connection
                conn.allow_thread_sharing = True
                connections_override[conn.alias] = conn

        # Launch the live server's thread
        specified_address = os.environ.get(
            'DJANGO_LIVE_TEST_SERVER_ADDRESS', 'localhost:8081')

        # The specified ports may be of the form '8000-8010,8080,9200-9300'
        # i.e. a comma-separated list of ports or ranges of ports, so we break
        # it down into a detailed list of all possible ports.
        possible_ports = []
        try:
            host, port_ranges = specified_address.split(':')
            for port_range in port_ranges.split(','):
                # A port range can be of either form: '8000' or '8000-8010'.
                extremes = map(int, port_range.split('-'))
                assert len(extremes) in [1, 2]
                if len(extremes) == 1:
                    # Port range of the form '8000'
                    possible_ports.append(extremes[0])
                else:
                    # Port range of the form '8000-8010'
                    for port in range(extremes[0], extremes[1] + 1):
                        possible_ports.append(port)
        except Exception:
            raise ImproperlyConfigured('Invalid address ("%s") for live '
                'server.' % specified_address)
        cls.server_thread = LiveServerThread(
            host, possible_ports, connections_override)
        cls.server_thread.daemon = True
        cls.server_thread.start()

        # Wait for the live server to be ready
        cls.server_thread.is_ready.wait()
        if cls.server_thread.error:
            raise cls.server_thread.error

        super(LiveServerTestCase, cls).setUpClass()

    @classmethod
    def tearDownClass(cls):
        # There may not be a 'server_thread' attribute if setUpClass() for some
        # reasons has raised an exception.
        if hasattr(cls, 'server_thread'):
            # Terminate the live server's thread
            cls.server_thread.join()
        super(LiveServerTestCase, cls).tearDownClass()
