"""
PostgreSQL database backend for Django.

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

import threading
import warnings

from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
from django.db import DEFAULT_DB_ALIAS
from django.db.backends.base.base import BaseDatabaseWrapper
from django.db.utils import DatabaseError as WrappedDatabaseError
from django.utils.functional import cached_property
from django.utils.safestring import SafeText
from django.utils.version import get_version_tuple

try:
    import psycopg2 as Database
    import psycopg2.extensions
    import psycopg2.extras
except ImportError as e:
    raise ImproperlyConfigured("Error loading psycopg2 module: %s" % e)


def psycopg2_version():
    version = psycopg2.__version__.split(' ', 1)[0]
    return get_version_tuple(version)


PSYCOPG2_VERSION = psycopg2_version()

if PSYCOPG2_VERSION < (2, 5, 4):
    raise ImproperlyConfigured("psycopg2_version 2.5.4 or newer is required; you have %s" % psycopg2.__version__)


# Some of these import psycopg2, so import them after checking if it's installed.
from .client import DatabaseClient                          # NOQA isort:skip
from .creation import DatabaseCreation                      # NOQA isort:skip
from .features import DatabaseFeatures                      # NOQA isort:skip
from .introspection import DatabaseIntrospection            # NOQA isort:skip
from .operations import DatabaseOperations                  # NOQA isort:skip
from .schema import DatabaseSchemaEditor                    # NOQA isort:skip
from .utils import utc_tzinfo_factory                       # NOQA isort:skip

psycopg2.extensions.register_adapter(SafeText, psycopg2.extensions.QuotedString)
psycopg2.extras.register_uuid()

# Register support for inet[] manually so we don't have to handle the Inet()
# object on load all the time.
INETARRAY_OID = 1041
INETARRAY = psycopg2.extensions.new_array_type(
    (INETARRAY_OID,),
    'INETARRAY',
    psycopg2.extensions.UNICODE,
)
psycopg2.extensions.register_type(INETARRAY)


class DatabaseWrapper(BaseDatabaseWrapper):
    vendor = 'postgresql'
    display_name = 'PostgreSQL'
    # This dictionary maps Field objects to their associated PostgreSQL column
    # types, as strings. Column-type strings can contain format strings; they'll
    # be interpolated against the values of Field.__dict__ before being output.
    # If a column type is set to None, it won't be included in the output.
    data_types = {
        'AutoField': 'serial',
        'BigAutoField': 'bigserial',
        'BinaryField': 'bytea',
        'BooleanField': 'boolean',
        'CharField': 'varchar(%(max_length)s)',
        'DateField': 'date',
        'DateTimeField': 'timestamp with time zone',
        'DecimalField': 'numeric(%(max_digits)s, %(decimal_places)s)',
        'DurationField': 'interval',
        'FileField': 'varchar(%(max_length)s)',
        'FilePathField': 'varchar(%(max_length)s)',
        'FloatField': 'double precision',
        'IntegerField': 'integer',
        'BigIntegerField': 'bigint',
        'IPAddressField': 'inet',
        'GenericIPAddressField': 'inet',
        'NullBooleanField': 'boolean',
        'OneToOneField': 'integer',
        'PositiveIntegerField': 'integer',
        'PositiveSmallIntegerField': 'smallint',
        'SlugField': 'varchar(%(max_length)s)',
        'SmallIntegerField': 'smallint',
        'TextField': 'text',
        'TimeField': 'time',
        'UUIDField': 'uuid',
    }
    data_type_check_constraints = {
        'PositiveIntegerField': '"%(column)s" >= 0',
        'PositiveSmallIntegerField': '"%(column)s" >= 0',
    }
    operators = {
        'exact': '= %s',
        'iexact': '= UPPER(%s)',
        'contains': 'LIKE %s',
        'icontains': 'LIKE UPPER(%s)',
        'regex': '~ %s',
        'iregex': '~* %s',
        'gt': '> %s',
        'gte': '>= %s',
        'lt': '< %s',
        'lte': '<= %s',
        'startswith': 'LIKE %s',
        'endswith': 'LIKE %s',
        'istartswith': 'LIKE UPPER(%s)',
        'iendswith': 'LIKE UPPER(%s)',
    }

    # The patterns below are used to generate SQL pattern lookup clauses when
    # the right-hand side of the lookup isn't a raw string (it might be an expression
    # or the result of a bilateral transformation).
    # In those cases, special characters for LIKE operators (e.g. \, *, _) should be
    # escaped on database side.
    #
    # Note: we use str.format() here for readability as '%' is used as a wildcard for
    # the LIKE operator.
    pattern_esc = r"REPLACE(REPLACE(REPLACE({}, '\', '\\'), '%%', '\%%'), '_', '\_')"
    pattern_ops = {
        'contains': "LIKE '%%' || {} || '%%'",
        'icontains': "LIKE '%%' || UPPER({}) || '%%'",
        'startswith': "LIKE {} || '%%'",
        'istartswith': "LIKE UPPER({}) || '%%'",
        'endswith': "LIKE '%%' || {}",
        'iendswith': "LIKE '%%' || UPPER({})",
    }

    Database = Database
    SchemaEditorClass = DatabaseSchemaEditor
    # Classes instantiated in __init__().
    client_class = DatabaseClient
    creation_class = DatabaseCreation
    features_class = DatabaseFeatures
    introspection_class = DatabaseIntrospection
    ops_class = DatabaseOperations
    # PostgreSQL backend-specific attributes.
    _named_cursor_idx = 0

    def get_connection_params(self):
        settings_dict = self.settings_dict
        # None may be used to connect to the default 'postgres' db
        if settings_dict['NAME'] == '':
            raise ImproperlyConfigured(
                "settings.DATABASES is improperly configured. "
                "Please supply the NAME value.")
        conn_params = {
            'database': settings_dict['NAME'] or 'postgres',
            **settings_dict['OPTIONS'],
        }
        conn_params.pop('isolation_level', None)
        if settings_dict['USER']:
            conn_params['user'] = settings_dict['USER']
        if settings_dict['PASSWORD']:
            conn_params['password'] = settings_dict['PASSWORD']
        if settings_dict['HOST']:
            conn_params['host'] = settings_dict['HOST']
        if settings_dict['PORT']:
            conn_params['port'] = settings_dict['PORT']
        return conn_params

    def get_new_connection(self, conn_params):
        connection = Database.connect(**conn_params)

        # self.isolation_level must be set:
        # - after connecting to the database in order to obtain the database's
        #   default when no value is explicitly specified in options.
        # - before calling _set_autocommit() because if autocommit is on, that
        #   will set connection.isolation_level to ISOLATION_LEVEL_AUTOCOMMIT.
        options = self.settings_dict['OPTIONS']
        try:
            self.isolation_level = options['isolation_level']
        except KeyError:
            self.isolation_level = connection.isolation_level
        else:
            # Set the isolation level to the value from OPTIONS.
            if self.isolation_level != connection.isolation_level:
                connection.set_session(isolation_level=self.isolation_level)

        return connection

    def ensure_timezone(self):
        self.ensure_connection()
        conn_timezone_name = self.connection.get_parameter_status('TimeZone')
        timezone_name = self.timezone_name
        if timezone_name and conn_timezone_name != timezone_name:
            with self.connection.cursor() as cursor:
                cursor.execute(self.ops.set_time_zone_sql(), [timezone_name])
            return True
        return False

    def init_connection_state(self):
        self.connection.set_client_encoding('UTF8')

        timezone_changed = self.ensure_timezone()
        if timezone_changed:
            # Commit after setting the time zone (see #17062)
            if not self.get_autocommit():
                self.connection.commit()

    def create_cursor(self, name=None):
        if name:
            # In autocommit mode, the cursor will be used outside of a
            # transaction, hence use a holdable cursor.
            cursor = self.connection.cursor(name, scrollable=False, withhold=self.connection.autocommit)
        else:
            cursor = self.connection.cursor()
        cursor.tzinfo_factory = utc_tzinfo_factory if settings.USE_TZ else None
        return cursor

    def chunked_cursor(self):
        self._named_cursor_idx += 1
        return self._cursor(
            name='_django_curs_%d_%d' % (
                # Avoid reusing name in other threads
                threading.current_thread().ident,
                self._named_cursor_idx,
            )
        )

    def _set_autocommit(self, autocommit):
        with self.wrap_database_errors:
            self.connection.autocommit = autocommit

    def check_constraints(self, table_names=None):
        """
        Check constraints by setting them to immediate. Return them to deferred
        afterward.
        """
        self.cursor().execute('SET CONSTRAINTS ALL IMMEDIATE')
        self.cursor().execute('SET CONSTRAINTS ALL DEFERRED')

    def is_usable(self):
        try:
            # Use a psycopg cursor directly, bypassing Django's utilities.
            self.connection.cursor().execute("SELECT 1")
        except Database.Error:
            return False
        else:
            return True

    @property
    def _nodb_connection(self):
        nodb_connection = super()._nodb_connection
        try:
            nodb_connection.ensure_connection()
        except (Database.DatabaseError, WrappedDatabaseError):
            warnings.warn(
                "Normally Django will use a connection to the 'postgres' database "
                "to avoid running initialization queries against the production "
                "database when it's not needed (for example, when running tests). "
                "Django was unable to create a connection to the 'postgres' database "
                "and will use the default database instead.",
                RuntimeWarning
            )
            settings_dict = self.settings_dict.copy()
            settings_dict['NAME'] = settings.DATABASES[DEFAULT_DB_ALIAS]['NAME']
            nodb_connection = self.__class__(
                self.settings_dict.copy(),
                alias=self.alias,
                allow_thread_sharing=False)
        return nodb_connection

    @cached_property
    def pg_version(self):
        with self.temporary_connection():
            return self.connection.server_version
