from django.db import DatabaseError, InterfaceError
from django.db.backends.base.features import BaseDatabaseFeatures
from django.utils.functional import cached_property


class DatabaseFeatures(BaseDatabaseFeatures):
    minimum_database_version = (19,)
    # Oracle crashes with "ORA-00932: inconsistent datatypes: expected - got
    # BLOB" when grouping by LOBs (#24096).
    allows_group_by_lob = False
    interprets_empty_strings_as_nulls = True
    has_select_for_update = True
    has_select_for_update_nowait = True
    has_select_for_update_skip_locked = True
    has_select_for_update_of = True
    select_for_update_of_column = True
    can_return_columns_from_insert = True
    supports_subqueries_in_group_by = False
    ignores_unnecessary_order_by_in_subqueries = False
    supports_transactions = True
    supports_timezones = False
    has_native_duration_field = True
    can_defer_constraint_checks = True
    supports_partially_nullable_unique_constraints = False
    supports_deferrable_unique_constraints = True
    truncates_names = True
    supports_tablespaces = True
    supports_sequence_reset = False
    can_introspect_materialized_views = True
    atomic_transactions = False
    nulls_order_largest = True
    requires_literal_defaults = True
    closed_cursor_error_class = InterfaceError
    bare_select_suffix = " FROM DUAL"
    # Select for update with limit can be achieved on Oracle, but not with the
    # current backend.
    supports_select_for_update_with_limit = False
    supports_temporal_subtraction = True
    # Oracle doesn't ignore quoted identifiers case but the current backend
    # does by uppercasing all identifiers.
    ignores_table_name_case = True
    supports_index_on_text_field = False
    create_test_procedure_without_params_sql = """
        CREATE PROCEDURE "TEST_PROCEDURE" AS
            V_I INTEGER;
        BEGIN
            V_I := 1;
        END;
    """
    create_test_procedure_with_int_param_sql = """
        CREATE PROCEDURE "TEST_PROCEDURE" (P_I INTEGER) AS
            V_I INTEGER;
        BEGIN
            V_I := P_I;
        END;
    """
    supports_callproc_kwargs = True
    supports_over_clause = True
    supports_frame_range_fixed_distance = True
    supports_ignore_conflicts = False
    max_query_params = 2**16 - 1
    supports_partial_indexes = False
    can_rename_index = True
    supports_slicing_ordering_in_compound = True
    allows_multiple_constraints_on_same_fields = False
    supports_boolean_expr_in_select_clause = False
    supports_primitives_in_json_field = False
    supports_json_field_contains = False
    supports_collation_on_textfield = False
    test_collations = {
        "ci": "BINARY_CI",
        "cs": "BINARY",
        "non_default": "SWEDISH_CI",
        "swedish_ci": "SWEDISH_CI",
    }
    test_now_utc_template = "CURRENT_TIMESTAMP AT TIME ZONE 'UTC'"

    django_test_skips = {
        "Oracle doesn't support SHA224.": {
            "db_functions.text.test_sha224.SHA224Tests.test_basic",
            "db_functions.text.test_sha224.SHA224Tests.test_transform",
        },
        "Oracle doesn't correctly calculate ISO 8601 week numbering before "
        "1583 (the Gregorian calendar was introduced in 1582).": {
            "db_functions.datetime.test_extract_trunc.DateFunctionTests."
            "test_trunc_week_before_1000",
            "db_functions.datetime.test_extract_trunc.DateFunctionWithTimeZoneTests."
            "test_trunc_week_before_1000",
        },
        "Oracle extracts seconds including fractional seconds (#33517).": {
            "db_functions.datetime.test_extract_trunc.DateFunctionTests."
            "test_extract_second_func_no_fractional",
            "db_functions.datetime.test_extract_trunc.DateFunctionWithTimeZoneTests."
            "test_extract_second_func_no_fractional",
        },
        "Oracle doesn't support bitwise XOR.": {
            "expressions.tests.ExpressionOperatorTests.test_lefthand_bitwise_xor",
            "expressions.tests.ExpressionOperatorTests.test_lefthand_bitwise_xor_null",
            "expressions.tests.ExpressionOperatorTests."
            "test_lefthand_bitwise_xor_right_null",
        },
        "Oracle requires ORDER BY in row_number, ANSI:SQL doesn't.": {
            "expressions_window.tests.WindowFunctionTests.test_row_number_no_ordering",
        },
        "Raises ORA-00600: internal error code.": {
            "model_fields.test_jsonfield.TestQuerying.test_usage_in_subquery",
        },
        "Oracle doesn't support changing collations on indexed columns (#33671).": {
            "migrations.test_operations.OperationTests."
            "test_alter_field_pk_fk_db_collation",
        },
        "Oracle raises an error when a subquery contains unnecessary ORDER BY "
        "clause (#32786).": {
            "queries.test_qs_combinators.QuerySetSetOperationTests."
            "test_union_in_with_ordering",
        },
    }
    django_test_expected_failures = {
        # A bug in Django/cx_Oracle with respect to string handling (#23843).
        "annotations.tests.NonAggregateAnnotationTestCase.test_custom_functions",
        "annotations.tests.NonAggregateAnnotationTestCase."
        "test_custom_functions_can_ref_other_functions",
    }

    @cached_property
    def introspected_field_types(self):
        return {
            **super().introspected_field_types,
            "GenericIPAddressField": "CharField",
            "PositiveBigIntegerField": "BigIntegerField",
            "PositiveIntegerField": "IntegerField",
            "PositiveSmallIntegerField": "IntegerField",
            "SmallIntegerField": "IntegerField",
            "TimeField": "DateTimeField",
        }

    @cached_property
    def supports_collation_on_charfield(self):
        with self.connection.cursor() as cursor:
            try:
                cursor.execute("SELECT CAST('a' AS VARCHAR2(4001)) FROM dual")
            except DatabaseError as e:
                if e.args[0].code == 910:
                    return False
                raise
            return True
