try:

    # Only exists in Python 2.4+

    from threading import local

except ImportError:

    # Import copy of _thread_local.py from Python 2.4

    from django.utils._threading_local import local

try:

    set

except NameError:

    # Python 2.3 compat

    from sets import Set as set

from django.db.backends import util

from django.utils import datetime_safe

class BaseDatabaseWrapper(local):

    """

    Represents a database connection.

    """

    ops = None

    def __init__(self, **kwargs):

        self.connection = None

        self.queries = []

        self.options = kwargs

    def _commit(self):

        if self.connection is not None:

            return self.connection.commit()

    def _rollback(self):

        if self.connection is not None:

            return self.connection.rollback()

    def _savepoint(self, sid):

        if not self.features.uses_savepoints:

            return

        self.connection.cursor().execute(self.ops.savepoint_create_sql(sid))

    def _savepoint_rollback(self, sid):

        if not self.features.uses_savepoints:

            return

        self.connection.cursor().execute(self.ops.savepoint_rollback_sql(sid))

    def _savepoint_commit(self, sid):

        if not self.features.uses_savepoints:

            return

        self.connection.cursor().execute(self.ops.savepoint_commit_sql(sid))

    def close(self):

        if self.connection is not None:

            self.connection.close()

            self.connection = None

    def cursor(self):

        from django.conf import settings

        cursor = self._cursor(settings)

        if settings.DEBUG:

            return self.make_debug_cursor(cursor)

        return cursor

    def make_debug_cursor(self, cursor):

        return util.CursorDebugWrapper(cursor, self)

class BaseDatabaseFeatures(object):

    # True if django.db.backend.utils.typecast_timestamp is used on values

    # returned from dates() calls.

    needs_datetime_string_cast = True

    uses_custom_query_class = False

    empty_fetchmany_value = []

    update_can_self_select = True

    interprets_empty_strings_as_nulls = False

    can_use_chunked_reads = True

    uses_savepoints = False

    # If True, don't use integer foreign keys referring to, e.g., positive

    # integer primary keys.

    related_fields_match_type = False

class BaseDatabaseOperations(object):

    """

    This class encapsulates all backend-specific differences, such as the way

    a backend performs ordering or calculates the ID of a recently-inserted

    row.

    """

    def autoinc_sql(self, table, column):

        """

        Returns any SQL needed to support auto-incrementing primary keys, or

        None if no SQL is necessary.

        This SQL is executed when a table is created.

        """

        return None

    def date_extract_sql(self, lookup_type, field_name):

        """

        Given a lookup_type of 'year', 'month' or 'day', returns the SQL that

        extracts a value from the given date field field_name.

        """

        raise NotImplementedError()

    def date_trunc_sql(self, lookup_type, field_name):

        """

        Given a lookup_type of 'year', 'month' or 'day', returns the SQL that

        truncates the given date field field_name to a DATE object with only

        the given specificity.

        """

        raise NotImplementedError()

    def datetime_cast_sql(self):

        """

        Returns the SQL necessary to cast a datetime value so that it will be

        retrieved as a Python datetime object instead of a string.

        This SQL should include a '%s' in place of the field's name.

        """

        return "%s"

    def deferrable_sql(self):

        """

        Returns the SQL necessary to make a constraint "initially deferred"

        during a CREATE TABLE statement.

        """

        return ''

    def drop_foreignkey_sql(self):

        """

        Returns the SQL command that drops a foreign key.

        """

        return "DROP CONSTRAINT"

    def drop_sequence_sql(self, table):

        """

        Returns any SQL necessary to drop the sequence for the given table.

        Returns None if no SQL is necessary.

        """

        return None

    def field_cast_sql(self, db_type):

        """

        Given a column type (e.g. 'BLOB', 'VARCHAR'), returns the SQL necessary

        to cast it before using it in a WHERE statement. Note that the

        resulting string should contain a '%s' placeholder for the column being

        searched against.

        """

        return '%s'

    def fulltext_search_sql(self, field_name):

        """

        Returns the SQL WHERE clause to use in order to perform a full-text

        search of the given field_name. Note that the resulting string should

        contain a '%s' placeholder for the value being searched against.

        """

        raise NotImplementedError('Full-text search is not implemented for this database backend')

    def last_executed_query(self, cursor, sql, params):

        """

        Returns a string of the query last executed by the given cursor, with

        placeholders replaced with actual values.

        `sql` is the raw query containing placeholders, and `params` is the

        sequence of parameters. These are used by default, but this method

        exists for database backends to provide a better implementation

        according to their own quoting schemes.

        """

        from django.utils.encoding import smart_unicode, force_unicode

        # Convert params to contain Unicode values.

        to_unicode = lambda s: force_unicode(s, strings_only=True)

        if isinstance(params, (list, tuple)):

            u_params = tuple([to_unicode(val) for val in params])

        else:

            u_params = dict([(to_unicode(k), to_unicode(v)) for k, v in params.items()])

        return smart_unicode(sql) % u_params

    def last_insert_id(self, cursor, table_name, pk_name):

        """

        Given a cursor object that has just performed an INSERT statement into

        a table that has an auto-incrementing ID, returns the newly created ID.

        This method also receives the table name and the name of the primary-key

        column.

        """

        return cursor.lastrowid

    def lookup_cast(self, lookup_type):

        """

        Returns the string to use in a query when performing lookups

        ("contains", "like", etc). The resulting string should contain a '%s'

        placeholder for the column being searched against.

        """

        return "%s"

    def max_name_length(self):

        """

        Returns the maximum length of table and column names, or None if there

        is no limit.

        """

        return None

    def no_limit_value(self):

        """

        Returns the value to use for the LIMIT when we are wanting "LIMIT

        infinity". Returns None if the limit clause can be omitted in this case.

        """

        # FIXME: API may need to change once Oracle backend is repaired.

        raise NotImplementedError()

    def pk_default_value(self):

        """

        Returns the value to use during an INSERT statement to specify that

        the field should use its default value.

        """

        return 'DEFAULT'

    def query_class(self, DefaultQueryClass):

        """

        Given the default Query class, returns a custom Query class

        to use for this backend. Returns None if a custom Query isn't used.

        See also BaseDatabaseFeatures.uses_custom_query_class, which regulates

        whether this method is called at all.

        """

        return None

    def quote_name(self, name):

        """

        Returns a quoted version of the given table, index or column name. Does

        not quote the given name if it's already been quoted.

        """

        raise NotImplementedError()

    def random_function_sql(self):

        """

        Returns a SQL expression that returns a random value.

        """

        return 'RANDOM()'

    def regex_lookup(self, lookup_type):

        """

        Returns the string to use in a query when performing regular expression

        lookups (using "regex" or "iregex"). The resulting string should

        contain a '%s' placeholder for the column being searched against.

        If the feature is not supported (or part of it is not supported), a

        NotImplementedError exception can be raised.

        """

        raise NotImplementedError

    def savepoint_create_sql(self, sid):

        """

        Returns the SQL for starting a new savepoint. Only required if the

        "uses_savepoints" feature is True. The "sid" parameter is a string

        for the savepoint id.

        """

        raise NotImplementedError

    def savepoint_commit_sql(self, sid):

        """

        Returns the SQL for committing the given savepoint.

        """

        raise NotImplementedError

    def savepoint_rollback_sql(self, sid):

        """

        Returns the SQL for rolling back the given savepoint.

        """

        raise NotImplementedError

    def sql_flush(self, style, tables, sequences):

        """

        Returns a list of SQL statements required to remove all data from

        the given database tables (without actually removing the tables

        themselves).

        The `style` argument is a Style object as returned by either

        color_style() or no_style() in django.core.management.color.

        """

        raise NotImplementedError()

    def sequence_reset_sql(self, style, model_list):

        """

        Returns a list of the SQL statements required to reset sequences for

        the given models.

        The `style` argument is a Style object as returned by either

        color_style() or no_style() in django.core.management.color.

        """

        return [] # No sequence reset required by default.

    def start_transaction_sql(self):

        """

        Returns the SQL statement required to start a transaction.

        """

        return "BEGIN;"

    def tablespace_sql(self, tablespace, inline=False):

        """

        Returns the SQL that will be appended to tables or rows to define

        a tablespace. Returns '' if the backend doesn't use tablespaces.

        """

        return ''

    def prep_for_like_query(self, x):

        """Prepares a value for use in a LIKE query."""

        from django.utils.encoding import smart_unicode

        return smart_unicode(x).replace("\\", "\\\\").replace("%", "\%").replace("_", "\_")

    # Same as prep_for_like_query(), but called for "iexact" matches, which

    # need not necessarily be implemented using "LIKE" in the backend.

    prep_for_iexact_query = prep_for_like_query

    def value_to_db_date(self, value):

        """

        Transform a date value to an object compatible with what is expected

        by the backend driver for date columns.

        """

        if value is None:

            return None

        return datetime_safe.new_date(value).strftime('%Y-%m-%d')

    def value_to_db_datetime(self, value):

        """

        Transform a datetime value to an object compatible with what is expected

        by the backend driver for datetime columns.

        """

        if value is None:

            return None

        return unicode(value)

    def value_to_db_time(self, value):

        """

        Transform a datetime value to an object compatible with what is expected

        by the backend driver for time columns.

        """

        if value is None:

            return None

        return unicode(value)

    def value_to_db_decimal(self, value, max_digits, decimal_places):

        """

        Transform a decimal.Decimal value to an object compatible with what is

        expected by the backend driver for decimal (numeric) columns.

        """

        if value is None:

            return None

        return util.format_number(value, max_digits, decimal_places)

    def year_lookup_bounds(self, value):

        """

        Returns a two-elements list with the lower and upper bound to be used

        with a BETWEEN operator to query a field value using a year lookup

        `value` is an int, containing the looked-up year.

        """

        first = '%s-01-01 00:00:00'

        second = '%s-12-31 23:59:59.999999'

        return [first % value, second % value]

    def year_lookup_bounds_for_date_field(self, value):

        """

        Returns a two-elements list with the lower and upper bound to be used

        with a BETWEEN operator to query a DateField value using a year lookup

        `value` is an int, containing the looked-up year.

        By default, it just calls `self.year_lookup_bounds`. Some backends need

        this hook because on their DB date fields can't be compared to values

        which include a time part.

        """

        return self.year_lookup_bounds(value)

class BaseDatabaseIntrospection(object):

    """

    This class encapsulates all backend-specific introspection utilities

    """

    data_types_reverse = {}

    def __init__(self, connection):

        self.connection = connection

    def table_name_converter(self, name):

        """Apply a conversion to the name for the purposes of comparison.

        The default table name converter is for case sensitive comparison.

        """

        return name

    def table_names(self):

        "Returns a list of names of all tables that exist in the database."

        cursor = self.connection.cursor()

        return self.get_table_list(cursor)

    def django_table_names(self, only_existing=False):

        """

        Returns a list of all table names that have associated Django models and

        are in INSTALLED_APPS.

        If only_existing is True, the resulting list will only include the tables

        that actually exist in the database.

        """

        from django.db import models

        tables = set()

        for app in models.get_apps():

            for model in models.get_models(app):

                tables.add(model._meta.db_table)

                tables.update([f.m2m_db_table() for f in model._meta.local_many_to_many])

        if only_existing:

            tables = [t for t in tables if t in self.table_names()]

        return tables

    def installed_models(self, tables):

        "Returns a set of all models represented by the provided list of table names."

        from django.db import models

        all_models = []

        for app in models.get_apps():

            for model in models.get_models(app):

                all_models.append(model)

        return set([m for m in all_models

            if self.table_name_converter(m._meta.db_table) in map(self.table_name_converter, tables)

        ])

    def sequence_list(self):

        "Returns a list of information about all DB sequences for all models in all apps."

        from django.db import models

        apps = models.get_apps()

        sequence_list = []

        for app in apps:

            for model in models.get_models(app):

                for f in model._meta.local_fields:

                    if isinstance(f, models.AutoField):

                        sequence_list.append({'table': model._meta.db_table, 'column': f.column})

                        break # Only one AutoField is allowed per model, so don't bother continuing.

                for f in model._meta.local_many_to_many:

                    sequence_list.append({'table': f.m2m_db_table(), 'column': None})

        return sequence_list

class BaseDatabaseClient(object):

    """

    This class encapsulates all backend-specific methods for opening a

    client shell.

    """

    # This should be a string representing the name of the executable

    # (e.g., "psql"). Subclasses must override this.

    executable_name = None

    def runshell(self):

        raise NotImplementedError()

class BaseDatabaseValidation(object):

    """

    This class encapsualtes all backend-specific model validation.

    """

    def validate_field(self, errors, opts, f):

        "By default, there is no backend-specific validation"

        pass