# engine/interfaces.py
# Copyright (C) 2005-2018 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php

"""Define core interfaces used by the engine system."""

from .. import util

# backwards compat
from ..sql.compiler import Compiled, TypeCompiler


class Dialect(object):
    """Define the behavior of a specific database and DB-API combination.

    Any aspect of metadata definition, SQL query generation,
    execution, result-set handling, or anything else which varies
    between databases is defined under the general category of the
    Dialect.  The Dialect acts as a factory for other
    database-specific object implementations including
    ExecutionContext, Compiled, DefaultGenerator, and TypeEngine.

    All Dialects implement the following attributes:

    name
      identifying name for the dialect from a DBAPI-neutral point of view
      (i.e. 'sqlite')

    driver
      identifying name for the dialect's DBAPI

    positional
      True if the paramstyle for this Dialect is positional.

    paramstyle
      the paramstyle to be used (some DB-APIs support multiple
      paramstyles).

    convert_unicode
      True if Unicode conversion should be applied to all ``str``
      types.

    encoding
      type of encoding to use for unicode, usually defaults to
      'utf-8'.

    statement_compiler
      a :class:`.Compiled` class used to compile SQL statements

    ddl_compiler
      a :class:`.Compiled` class used to compile DDL statements

    server_version_info
      a tuple containing a version number for the DB backend in use.
      This value is only available for supporting dialects, and is
      typically populated during the initial connection to the database.

    default_schema_name
     the name of the default schema.  This value is only available for
     supporting dialects, and is typically populated during the
     initial connection to the database.

    execution_ctx_cls
      a :class:`.ExecutionContext` class used to handle statement execution

    execute_sequence_format
      either the 'tuple' or 'list' type, depending on what cursor.execute()
      accepts for the second argument (they vary).

    preparer
      a :class:`~sqlalchemy.sql.compiler.IdentifierPreparer` class used to
      quote identifiers.

    supports_alter
      ``True`` if the database supports ``ALTER TABLE``.

    max_identifier_length
      The maximum length of identifier names.

    supports_unicode_statements
      Indicate whether the DB-API can receive SQL statements as Python
      unicode strings

    supports_unicode_binds
      Indicate whether the DB-API can receive string bind parameters
      as Python unicode strings

    supports_sane_rowcount
      Indicate whether the dialect properly implements rowcount for
      ``UPDATE`` and ``DELETE`` statements.

    supports_sane_multi_rowcount
      Indicate whether the dialect properly implements rowcount for
      ``UPDATE`` and ``DELETE`` statements when executed via
      executemany.

    preexecute_autoincrement_sequences
      True if 'implicit' primary key functions must be executed separately
      in order to get their value.   This is currently oriented towards
      PostgreSQL.

    implicit_returning
      use RETURNING or equivalent during INSERT execution in order to load
      newly generated primary keys and other column defaults in one execution,
      which are then available via inserted_primary_key.
      If an insert statement has returning() specified explicitly,
      the "implicit" functionality is not used and inserted_primary_key
      will not be available.

    colspecs
      A dictionary of TypeEngine classes from sqlalchemy.types mapped
      to subclasses that are specific to the dialect class.  This
      dictionary is class-level only and is not accessed from the
      dialect instance itself.

    supports_default_values
      Indicates if the construct ``INSERT INTO tablename DEFAULT
      VALUES`` is supported

    supports_sequences
      Indicates if the dialect supports CREATE SEQUENCE or similar.

    sequences_optional
      If True, indicates if the "optional" flag on the Sequence() construct
      should signal to not generate a CREATE SEQUENCE. Applies only to
      dialects that support sequences. Currently used only to allow PostgreSQL
      SERIAL to be used on a column that specifies Sequence() for usage on
      other backends.

    supports_native_enum
      Indicates if the dialect supports a native ENUM construct.
      This will prevent types.Enum from generating a CHECK
      constraint when that type is used.

    supports_native_boolean
      Indicates if the dialect supports a native boolean construct.
      This will prevent types.Boolean from generating a CHECK
      constraint when that type is used.

    dbapi_exception_translation_map
       A dictionary of names that will contain as values the names of
       pep-249 exceptions ("IntegrityError", "OperationalError", etc)
       keyed to alternate class names, to support the case where a
       DBAPI has exception classes that aren't named as they are
       referred to (e.g. IntegrityError = MyException).   In the vast
       majority of cases this dictionary is empty.

       .. versionadded:: 1.0.5

    """

    _has_events = False

    def create_connect_args(self, url):
        """Build DB-API compatible connection arguments.

        Given a :class:`~sqlalchemy.engine.url.URL` object, returns a tuple
        consisting of a `*args`/`**kwargs` suitable to send directly
        to the dbapi's connect function.

        """

        raise NotImplementedError()

    @classmethod
    def type_descriptor(cls, typeobj):
        """Transform a generic type to a dialect-specific type.

        Dialect classes will usually use the
        :func:`.types.adapt_type` function in the types module to
        accomplish this.

        The returned result is cached *per dialect class* so can
        contain no dialect-instance state.

        """

        raise NotImplementedError()

    def initialize(self, connection):
        """Called during strategized creation of the dialect with a
        connection.

        Allows dialects to configure options based on server version info or
        other properties.

        The connection passed here is a SQLAlchemy Connection object,
        with full capabilities.

        The initialize() method of the base dialect should be called via
        super().

        """

        pass

    def reflecttable(
            self, connection, table, include_columns, exclude_columns):
        """Load table description from the database.

        Given a :class:`.Connection` and a
        :class:`~sqlalchemy.schema.Table` object, reflect its columns and
        properties from the database.

        The implementation of this method is provided by
        :meth:`.DefaultDialect.reflecttable`, which makes use of
        :class:`.Inspector` to retrieve column information.

        Dialects should **not** seek to implement this method, and should
        instead implement individual schema inspection operations such as
        :meth:`.Dialect.get_columns`, :meth:`.Dialect.get_pk_constraint`,
        etc.

        """

        raise NotImplementedError()

    def get_columns(self, connection, table_name, schema=None, **kw):
        """Return information about columns in `table_name`.

        Given a :class:`.Connection`, a string
        `table_name`, and an optional string `schema`, return column
        information as a list of dictionaries with these keys:

        name
          the column's name

        type
          [sqlalchemy.types#TypeEngine]

        nullable
          boolean

        default
          the column's default value

        autoincrement
          boolean

        sequence
          a dictionary of the form
              {'name' : str, 'start' :int, 'increment': int, 'minvalue': int,
               'maxvalue': int, 'nominvalue': bool, 'nomaxvalue': bool,
               'cycle': bool, 'cache': int, 'order': bool}

        Additional column attributes may be present.
        """

        raise NotImplementedError()

    def get_primary_keys(self, connection, table_name, schema=None, **kw):
        """Return information about primary keys in `table_name`.


        Deprecated.  This method is only called by the default
        implementation of :meth:`.Dialect.get_pk_constraint`.  Dialects should
        instead implement the :meth:`.Dialect.get_pk_constraint` method
        directly.

        """

        raise NotImplementedError()

    def get_pk_constraint(self, connection, table_name, schema=None, **kw):
        """Return information about the primary key constraint on
        table_name`.

        Given a :class:`.Connection`, a string
        `table_name`, and an optional string `schema`, return primary
        key information as a dictionary with these keys:

        constrained_columns
          a list of column names that make up the primary key

        name
          optional name of the primary key constraint.

        """
        raise NotImplementedError()

    def get_foreign_keys(self, connection, table_name, schema=None, **kw):
        """Return information about foreign_keys in `table_name`.

        Given a :class:`.Connection`, a string
        `table_name`, and an optional string `schema`, return foreign
        key information as a list of dicts with these keys:

        name
          the constraint's name

        constrained_columns
          a list of column names that make up the foreign key

        referred_schema
          the name of the referred schema

        referred_table
          the name of the referred table

        referred_columns
          a list of column names in the referred table that correspond to
          constrained_columns
        """

        raise NotImplementedError()

    def get_table_names(self, connection, schema=None, **kw):
        """Return a list of table names for `schema`."""

        raise NotImplementedError()

    def get_temp_table_names(self, connection, schema=None, **kw):
        """Return a list of temporary table names on the given connection,
        if supported by the underlying backend.

        """

        raise NotImplementedError()

    def get_view_names(self, connection, schema=None, **kw):
        """Return a list of all view names available in the database.

        schema:
          Optional, retrieve names from a non-default schema.
        """

        raise NotImplementedError()

    def get_temp_view_names(self, connection, schema=None, **kw):
        """Return a list of temporary view names on the given connection,
        if supported by the underlying backend.

        """

        raise NotImplementedError()

    def get_view_definition(self, connection, view_name, schema=None, **kw):
        """Return view definition.

        Given a :class:`.Connection`, a string
        `view_name`, and an optional string `schema`, return the view
        definition.