"""
PostgreSQL database backend for Django.

Requires psycopg 2: http://initd.org/projects/psycopg2
"""

from django.db.backends import BaseDatabaseWrapper, BaseDatabaseFeatures
from django.db.backends.postgresql.operations import DatabaseOperations as PostgresqlDatabaseOperations
from django.utils.safestring import SafeUnicode
try:
    import psycopg2 as Database
    import psycopg2.extensions
except ImportError, e:
    from django.core.exceptions import ImproperlyConfigured
    raise ImproperlyConfigured("Error loading psycopg2 module: %s" % e)

DatabaseError = Database.DatabaseError
IntegrityError = Database.IntegrityError

psycopg2.extensions.register_type(psycopg2.extensions.UNICODE)
psycopg2.extensions.register_adapter(SafeUnicode, psycopg2.extensions.QuotedString)

class DatabaseFeatures(BaseDatabaseFeatures):
    needs_datetime_string_cast = False

class DatabaseOperations(PostgresqlDatabaseOperations):
    def last_executed_query(self, cursor, sql, params):
        # With psycopg2, cursor objects have a "query" attribute that is the
        # exact query sent to the database. See docs here:
        # http://www.initd.org/tracker/psycopg/wiki/psycopg2_documentation#postgresql-status-message-and-executed-query
        return cursor.query

class DatabaseWrapper(BaseDatabaseWrapper):
    features = DatabaseFeatures()
    ops = DatabaseOperations()
    operators = {
        'exact': '= %s',
        'iexact': 'ILIKE %s',
        'contains': 'LIKE %s',
        'icontains': 'ILIKE %s',
        'regex': '~ %s',
        'iregex': '~* %s',
        'gt': '> %s',
        'gte': '>= %s',
        'lt': '< %s',
        'lte': '<= %s',
        'startswith': 'LIKE %s',
        'endswith': 'LIKE %s',
        'istartswith': 'ILIKE %s',
        'iendswith': 'ILIKE %s',
    }

    def _cursor(self, settings):
        set_tz = False
        if self.connection is None:
            set_tz = True
            if settings.DATABASE_NAME == '':
                from django.core.exceptions import ImproperlyConfigured
                raise ImproperlyConfigured("You need to specify DATABASE_NAME in your Django settings file.")
            conn_string = "dbname=%s" % settings.DATABASE_NAME
            if settings.DATABASE_USER:
                conn_string = "user=%s %s" % (settings.DATABASE_USER, conn_string)
            if settings.DATABASE_PASSWORD:
                conn_string += " password='%s'" % settings.DATABASE_PASSWORD
            if settings.DATABASE_HOST:
                conn_string += " host=%s" % settings.DATABASE_HOST
            if settings.DATABASE_PORT:
                conn_string += " port=%s" % settings.DATABASE_PORT
            self.connection = Database.connect(conn_string, **self.options)
            self.connection.set_isolation_level(1) # make transactions transparent to all cursors
            self.connection.set_client_encoding('UTF8')
        cursor = self.connection.cursor()
        cursor.tzinfo_factory = None
        if set_tz:
            cursor.execute("SET TIME ZONE %s", [settings.TIME_ZONE])
        return cursor