"""
Oracle database backend for Django.

Requires cx_Oracle: http://cx-oracle.sourceforge.net/
"""
from __future__ import unicode_literals

import datetime
import decimal
import os
import platform
import sys
import warnings

from django.conf import settings
from django.db import utils
from django.db.backends.base.base import BaseDatabaseWrapper
from django.db.backends.base.validation import BaseDatabaseValidation
from django.utils import six, timezone
from django.utils.deprecation import RemovedInDjango20Warning
from django.utils.duration import duration_string
from django.utils.encoding import force_bytes, force_text
from django.utils.functional import cached_property


def _setup_environment(environ):
    # Cygwin requires some special voodoo to set the environment variables
    # properly so that Oracle will see them.
    if platform.system().upper().startswith('CYGWIN'):
        try:
            import ctypes
        except ImportError as e:
            from django.core.exceptions import ImproperlyConfigured
            raise ImproperlyConfigured("Error loading ctypes: %s; "
                                       "the Oracle backend requires ctypes to "
                                       "operate correctly under Cygwin." % e)
        kernel32 = ctypes.CDLL('kernel32')
        for name, value in environ:
            kernel32.SetEnvironmentVariableA(name, value)
    else:
        os.environ.update(environ)

_setup_environment([
    # Oracle takes client-side character set encoding from the environment.
    ('NLS_LANG', '.UTF8'),
    # This prevents unicode from getting mangled by getting encoded into the
    # potentially non-unicode database character set.
    ('ORA_NCHAR_LITERAL_REPLACE', 'TRUE'),
])


try:
    import cx_Oracle as Database
except ImportError as e:
    from django.core.exceptions import ImproperlyConfigured
    raise ImproperlyConfigured("Error loading cx_Oracle module: %s" % e)

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

DatabaseError = Database.DatabaseError
IntegrityError = Database.IntegrityError


class _UninitializedOperatorsDescriptor(object):

    def __get__(self, instance, owner):
        # If connection.operators is looked up before a connection has been
        # created, transparently initialize connection.operators to avert an
        # AttributeError.
        if instance is None:
            raise AttributeError("operators not available as class attribute")
        # Creating a cursor will initialize the operators.
        instance.cursor().close()
        return instance.__dict__['operators']


class DatabaseWrapper(BaseDatabaseWrapper):
    vendor = 'oracle'
    # This dictionary maps Field objects to their associated Oracle 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.
    #
    # Any format strings starting with "qn_" are quoted before being used in the
    # output (the "qn_" prefix is stripped before the lookup is performed.
    data_types = {
        'AutoField': 'NUMBER(11)',
        'BinaryField': 'BLOB',
        'BooleanField': 'NUMBER(1)',
        'CharField': 'NVARCHAR2(%(max_length)s)',
        'CommaSeparatedIntegerField': 'VARCHAR2(%(max_length)s)',
        'DateField': 'DATE',
        'DateTimeField': 'TIMESTAMP',
        'DecimalField': 'NUMBER(%(max_digits)s, %(decimal_places)s)',
        'DurationField': 'INTERVAL DAY(9) TO SECOND(6)',
        'FileField': 'NVARCHAR2(%(max_length)s)',
        'FilePathField': 'NVARCHAR2(%(max_length)s)',
        'FloatField': 'DOUBLE PRECISION',
        'IntegerField': 'NUMBER(11)',
        'BigIntegerField': 'NUMBER(19)',
        'IPAddressField': 'VARCHAR2(15)',
        'GenericIPAddressField': 'VARCHAR2(39)',
        'NullBooleanField': 'NUMBER(1)',
        'OneToOneField': 'NUMBER(11)',
        'PositiveIntegerField': 'NUMBER(11)',
        'PositiveSmallIntegerField': 'NUMBER(11)',
        'SlugField': 'NVARCHAR2(%(max_length)s)',
        'SmallIntegerField': 'NUMBER(11)',
        'TextField': 'NCLOB',
        'TimeField': 'TIMESTAMP',
        'URLField': 'VARCHAR2(%(max_length)s)',
        'UUIDField': 'VARCHAR2(32)',
    }
    data_type_check_constraints = {
        'BooleanField': '%(qn_column)s IN (0,1)',
        'NullBooleanField': '(%(qn_column)s IN (0,1)) OR (%(qn_column)s IS NULL)',
        'PositiveIntegerField': '%(qn_column)s >= 0',
        'PositiveSmallIntegerField': '%(qn_column)s >= 0',
    }

    operators = _UninitializedOperatorsDescriptor()

    _standard_operators = {
        'exact': '= %s',
        'iexact': '= UPPER(%s)',
        'contains': "LIKE TRANSLATE(%s USING NCHAR_CS) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
        'icontains': "LIKE UPPER(TRANSLATE(%s USING NCHAR_CS)) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
        'gt': '> %s',
        'gte': '>= %s',
        'lt': '< %s',
        'lte': '<= %s',
        'startswith': "LIKE TRANSLATE(%s USING NCHAR_CS) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
        'endswith': "LIKE TRANSLATE(%s USING NCHAR_CS) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
        'istartswith': "LIKE UPPER(TRANSLATE(%s USING NCHAR_CS)) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
        'iendswith': "LIKE UPPER(TRANSLATE(%s USING NCHAR_CS)) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
    }

    _likec_operators = _standard_operators.copy()
    _likec_operators.update({
        'contains': "LIKEC %s ESCAPE '\\'",
        'icontains': "LIKEC UPPER(%s) ESCAPE '\\'",
        'startswith': "LIKEC %s ESCAPE '\\'",
        'endswith': "LIKEC %s ESCAPE '\\'",
        'istartswith': "LIKEC UPPER(%s) ESCAPE '\\'",
        'iendswith': "LIKEC UPPER(%s) ESCAPE '\\'",
    })

    # 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': "'%%' || {} || '%%'",
        'icontains': "'%%' || UPPER({}) || '%%'",
        'startswith': "{} || '%%'",
        'istartswith': "UPPER({}) || '%%'",
        'endswith': "'%%' || {}",
        'iendswith': "'%%' || UPPER({})",
    }

    _standard_pattern_ops = {k: "LIKE TRANSLATE( " + v + " USING NCHAR_CS)"
                                " ESCAPE TRANSLATE('\\' USING NCHAR_CS)"
                             for k, v in _pattern_ops.items()}
    _likec_pattern_ops = {k: "LIKEC " + v + " ESCAPE '\\'"
                          for k, v in _pattern_ops.items()}

    Database = Database
    SchemaEditorClass = DatabaseSchemaEditor

    def __init__(self, *args, **kwargs):
        super(DatabaseWrapper, self).__init__(*args, **kwargs)

        self.features = DatabaseFeatures(self)
        use_returning_into = self.settings_dict["OPTIONS"].get('use_returning_into', True)
        self.features.can_return_id_from_insert = use_returning_into
        self.ops = DatabaseOperations(self)
        self.client = DatabaseClient(self)
        self.creation = DatabaseCreation(self)
        self.introspection = DatabaseIntrospection(self)
        self.validation = BaseDatabaseValidation(self)

    def _connect_string(self):
        settings_dict = self.settings_dict
        if not settings_dict['HOST'].strip():
            settings_dict['HOST'] = 'localhost'
        if settings_dict['PORT'].strip():
            dsn = Database.makedsn(settings_dict['HOST'],
                                   int(settings_dict['PORT']),
                                   settings_dict['NAME'])
        else:
            dsn = settings_dict['NAME']
        return "%s/%s@%s" % (settings_dict['USER'],
                             settings_dict['PASSWORD'], dsn)

    def get_connection_params(self):
        conn_params = self.settings_dict['OPTIONS'].copy()
        if 'use_returning_into' in conn_params:
            del conn_params['use_returning_into']
        return conn_params

    def get_new_connection(self, conn_params):
        conn_string = convert_unicode(self._connect_string())
        return Database.connect(conn_string, **conn_params)

    def init_connection_state(self):
        cursor = self.create_cursor()
        # Set the territory first. The territory overrides NLS_DATE_FORMAT
        # and NLS_TIMESTAMP_FORMAT to the territory default. When all of
        # these are set in single statement it isn't clear what is supposed
        # to happen.
        cursor.execute("ALTER SESSION SET NLS_TERRITORY = 'AMERICA'")
        # Set Oracle date to ANSI date format.  This only needs to execute
        # once when we create a new connection. We also set the Territory
        # to 'AMERICA' which forces Sunday to evaluate to a '1' in
        # TO_CHAR().
        cursor.execute(
            "ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS'"
            " NLS_TIMESTAMP_FORMAT = 'YYYY-MM-DD HH24:MI:SS.FF'"
            + (" TIME_ZONE = 'UTC'" if settings.USE_TZ else ''))
        cursor.close()
        if 'operators' not in self.__dict__:
            # Ticket #14149: Check whether our LIKE implementation will
            # work for this connection or we need to fall back on LIKEC.
            # This check is performed only once per DatabaseWrapper
            # instance per thread, since subsequent connections will use
            # the same settings.
            cursor = self.create_cursor()
            try:
                cursor.execute("SELECT 1 FROM DUAL WHERE DUMMY %s"
                               % self._standard_operators['contains'],
                               ['X'])
            except DatabaseError:
                self.operators = self._likec_operators
                self.pattern_ops = self._likec_pattern_ops
            else:
                self.operators = self._standard_operators
                self.pattern_ops = self._standard_pattern_ops
            cursor.close()

        try:
            self.connection.stmtcachesize = 20
        except AttributeError:
            # Django docs specify cx_Oracle version 4.3.1 or higher, but
            # stmtcachesize is available only in 4.3.2 and up.
            pass
        # Ensure all changes are preserved even when AUTOCOMMIT is False.
        if not self.get_autocommit():
            self.commit()

    def create_cursor(self):
        return FormatStylePlaceholderCursor(self.connection)

    def _commit(self):
        if self.connection is not None:
            try:
                return self.connection.commit()
            except Database.DatabaseError as e:
                # cx_Oracle 5.0.4 raises a cx_Oracle.DatabaseError exception
                # with the following attributes and values:
                #  code = 2091
                #  message = 'ORA-02091: transaction rolled back
                #            'ORA-02291: integrity constraint (TEST_DJANGOTEST.SYS
                #               _C00102056) violated - parent key not found'
                # We convert that particular case to our IntegrityError exception
                x = e.args[0]
                if hasattr(x, 'code') and hasattr(x, 'message') \
                   and x.code == 2091 and 'ORA-02291' in x.message:
                    six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
                raise

    # Oracle doesn't support releasing savepoints. But we fake them when query
    # logging is enabled to keep query counts consistent with other backends.
    def _savepoint_commit(self, sid):
        if self.queries_logged:
            self.queries_log.append({
                'sql': '-- RELEASE SAVEPOINT %s (faked)' % self.ops.quote_name(sid),
                'time': '0.000',
            })

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

    def check_constraints(self, table_names=None):
        """
        To check constraints, we set constraints to immediate. Then, when, we're done we must ensure they
        are returned to deferred.
        """
        self.cursor().execute('SET CONSTRAINTS ALL IMMEDIATE')
        self.cursor().execute('SET CONSTRAINTS ALL DEFERRED')

    def is_usable(self):
        try:
            self.connection.ping()
        except Database.Error:
            return False
        else:
            return True

    @cached_property
    def oracle_full_version(self):
        with self.temporary_connection():
            return self.connection.version

    @cached_property
    def oracle_version(self):
        try:
            return int(self.oracle_full_version.split('.')[0])
        except ValueError:
            return None


class OracleParam(object):
    """
    Wrapper object for formatting parameters for Oracle. If the string
    representation of the value is large enough (greater than 4000 characters)
    the input size needs to be set as CLOB. Alternatively, if the parameter
    has an `input_size` attribute, then the value of the `input_size` attribute
    will be used instead. Otherwise, no input size will be set for the
    parameter when executing the query.
    """

    def __init__(self, param, cursor, strings_only=False):
        # With raw SQL queries, datetimes can reach this function
        # without being converted by DateTimeField.get_db_prep_value.
        if settings.USE_TZ and (isinstance(param, datetime.datetime) and
                                not isinstance(param, Oracle_datetime)):
            if timezone.is_aware(param):
                warnings.warn(
                    "The Oracle database adapter received an aware datetime (%s), "
                    "probably from cursor.execute(). Update your code to pass a "
                    "naive datetime in the database connection's time zone (UTC by "
                    "default).", RemovedInDjango20Warning)