import sys, time

from django.conf import settings

from django.db import connection, transaction, backend

from django.core import management

from django.dispatch import dispatcher

from django.test import signals

from django.template import Template

# The prefix to put on the default database name when creating

# the test database.

TEST_DATABASE_PREFIX = 'test_'

def instrumented_test_render(self, context):

    """An instrumented Template render method, providing a signal 

    that can be intercepted by the test system Client

    """

    dispatcher.send(signal=signals.template_rendered, sender=self, template=self, context=context)

    return self.nodelist.render(context)

def setup_test_environment():

    """Perform any global pre-test setup. This involves:

        - Installing the instrumented test renderer

    """

    Template.original_render = Template.render

    Template.render = instrumented_test_render

def teardown_test_environment():

    """Perform any global post-test teardown. This involves:

        - Restoring the original test renderer

    """

    Template.render = Template.original_render

    del Template.original_render

def _set_autocommit(connection):

    "Make sure a connection is in autocommit mode."

    if hasattr(connection.connection, "autocommit"):

        connection.connection.autocommit(True)

    elif hasattr(connection.connection, "set_isolation_level"):

        connection.connection.set_isolation_level(0)

def create_test_db(verbosity=1, autoclobber=False):

    if verbosity >= 1:

        print "Creating test database..."

    # If we're using SQLite, it's more convenient to test against an

    # in-memory database.

    if settings.DATABASE_ENGINE == "sqlite3":

        TEST_DATABASE_NAME = ":memory:"

    else:

        if settings.TEST_DATABASE_NAME:

            TEST_DATABASE_NAME = settings.TEST_DATABASE_NAME

        else:

            TEST_DATABASE_NAME = TEST_DATABASE_PREFIX + settings.DATABASE_NAME

        # Create the test database and connect to it. We need to autocommit

        # if the database supports it because PostgreSQL doesn't allow 

        # CREATE/DROP DATABASE statements within transactions.

        cursor = connection.cursor()

        _set_autocommit(connection)

        try:

            cursor.execute("CREATE DATABASE %s" % backend.quote_name(TEST_DATABASE_NAME))

        except Exception, e:            

            sys.stderr.write("Got an error creating the test database: %s\n" % e)

            if not autoclobber:

                confirm = raw_input("It appears the test database, %s, already exists. Type 'yes' to delete it, or 'no' to cancel: " % TEST_DATABASE_NAME)

            if autoclobber or confirm == 'yes':

                try:

                    if verbosity >= 1:

                        print "Destroying old test database..."                

                    cursor.execute("DROP DATABASE %s" % backend.quote_name(TEST_DATABASE_NAME))

                    if verbosity >= 1:

                        print "Creating test database..."

                    cursor.execute("CREATE DATABASE %s" % backend.quote_name(TEST_DATABASE_NAME))

                except Exception, e:

                    sys.stderr.write("Got an error recreating the test database: %s\n" % e)

                    sys.exit(2)

            else:

                print "Tests cancelled."

                sys.exit(1)

    connection.close()

    settings.DATABASE_NAME = TEST_DATABASE_NAME

    management.syncdb(verbosity, interactive=False)

    # Get a cursor (even though we don't need one yet). This has

    # the side effect of initializing the test database.

    cursor = connection.cursor()

def destroy_test_db(old_database_name, verbosity=1):

    # Unless we're using SQLite, remove the test database to clean up after

    # ourselves. Connect to the previous database (not the test database)

    # to do so, because it's not allowed to delete a database while being

    # connected to it.

    if verbosity >= 1:

        print "Destroying test database..."

    connection.close()

    TEST_DATABASE_NAME = settings.DATABASE_NAME

    settings.DATABASE_NAME = old_database_name

    if settings.DATABASE_ENGINE != "sqlite3":

        cursor = connection.cursor()

        _set_autocommit(connection)

        time.sleep(1) # To avoid "database is being accessed by other users" errors.

        cursor.execute("DROP DATABASE %s" % backend.quote_name(TEST_DATABASE_NAME))

        connection.close()