"""
PostgreSQL database backend for Django.

Requires psycopg 2: https://www.psycopg.org/
"""

import asyncio
import threading
import warnings
from contextlib import contextmanager

from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
from django.db import DatabaseError as WrappedDatabaseError, connections
from django.db.backends.base.base import BaseDatabaseWrapper
from django.db.backends.utils import (
    CursorDebugWrapper as BaseCursorDebugWrapper,
)
from django.utils.asyncio import async_unsafe
from django.utils.functional import cached_property
from django.utils.safestring import SafeString
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
from .creation import DatabaseCreation  # NOQA
from .features import DatabaseFeatures  # NOQA
from .introspection import DatabaseIntrospection  # NOQA
from .operations import DatabaseOperations  # NOQA
from .schema import DatabaseSchemaEditor  # NOQA

psycopg2.extensions.register_adapter(SafeString, 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',
        'JSONField': 'jsonb',
        'NullBooleanField': 'boolean',
        'OneToOneField': 'integer',
        'PositiveBigIntegerField': 'bigint',
        'PositiveIntegerField': 'integer',
        'PositiveSmallIntegerField': 'smallint',
        'SlugField': 'varchar(%(max_length)s)',
        'SmallAutoField': 'smallserial',
        'SmallIntegerField': 'smallint',
        'TextField': 'text',
        'TimeField': 'time',
        'UUIDField': 'uuid',
    }
    data_type_check_constraints = {
        'PositiveBigIntegerField': '"%(column)s" >= 0',
        '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({}, E'\\', E'\\\\'), E'%%', E'\\%%'), E'_', E'\\_')"
    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.")
        if len(settings_dict['NAME'] or '') > self.ops.max_name_length():
            raise ImproperlyConfigured(
                "The database name '%s' (%d characters) is longer than "
                "PostgreSQL's limit of %d characters. Supply a shorter NAME "
                "in settings.DATABASES." % (
                    settings_dict['NAME'],
                    len(settings_dict['NAME']),
                    self.ops.max_name_length(),
                )
            )
        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

    @async_unsafe
    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)
        # Register dummy loads() to avoid a round trip from psycopg2's decode
        # to json.dumps() to json.loads(), when using a custom decoder in
        # JSONField.
        psycopg2.extras.register_default_jsonb(conn_or_curs=connection, loads=lambda x: x)
        return connection

    def ensure_timezone(self):
        if self.connection is None:
            return False
        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()

    @async_unsafe
    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 = self.tzinfo_factory if settings.USE_TZ else None
        return cursor

    def tzinfo_factory(self, offset):
        return self.timezone

    @async_unsafe
    def chunked_cursor(self):
        self._named_cursor_idx += 1
        # Get the current async task
        # Note that right now this is behind @async_unsafe, so this is
        # unreachable, but in future we'll start loosening this restriction.
        # For now, it's here so that every use of "threading" is
        # also async-compatible.
        try:
            if hasattr(asyncio, 'current_task'):
                # Python 3.7 and up
                current_task = asyncio.current_task()
            else:
                # Python 3.6
                current_task = asyncio.Task.current_task()
        except RuntimeError:
            current_task = None
        # Current task can be none even if the current_task call didn't error
        if current_task:
            task_ident = str(id(current_task))
        else:
            task_ident = 'sync'
        # Use that and the thread ident to get a unique name
        return self._cursor(
            name='_django_curs_%d_%s_%d' % (
                # Avoid reusing name in other threads / tasks
                threading.current_thread().ident,
                task_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.
        """
        with self.cursor() as cursor:
            cursor.execute('SET CONSTRAINTS ALL IMMEDIATE')
            cursor.execute('SET CONSTRAINTS ALL DEFERRED')

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

    @contextmanager
    def _nodb_cursor(self):
        try:
            with super()._nodb_cursor() as cursor:
                yield cursor
        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 first PostgreSQL database instead.",
                RuntimeWarning
            )
            for connection in connections.all():
                if connection.vendor == 'postgresql' and connection.settings_dict['NAME'] != 'postgres':
                    conn = self.__class__(
                        {**self.settings_dict, 'NAME': connection.settings_dict['NAME']},
                        alias=self.alias,
                    )
                    try:
                        with conn.cursor() as cursor:
                            yield cursor
                    finally:
                        conn.close()
                    break
            else:
                raise

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

    def make_debug_cursor(self, cursor):
        return CursorDebugWrapper(cursor, self)


class CursorDebugWrapper(BaseCursorDebugWrapper):
    def copy_expert(self, sql, file, *args):
        with self.debug_sql(sql):
            return self.cursor.copy_expert(sql, file, *args)

    def copy_to(self, file, table, *args, **kwargs):
        with self.debug_sql(sql='COPY %s TO STDOUT' % table):
            return self.cursor.copy_to(file, table, *args, **kwargs)