from django.db.backends import BaseDatabaseIntrospection

class DatabaseIntrospection(BaseDatabaseIntrospection):

    # Maps type codes to Django Field types.

    data_types_reverse = {

        16: 'BooleanField',

        21: 'SmallIntegerField',

        23: 'IntegerField',

        25: 'TextField',

        700: 'FloatField',

        701: 'FloatField',

        869: 'IPAddressField',

        1043: 'CharField',

        1082: 'DateField',

        1083: 'TimeField',

        1114: 'DateTimeField',

        1184: 'DateTimeField',

        1266: 'TimeField',

        1700: 'DecimalField',

    }

    def get_table_list(self, cursor):

        "Returns a list of table names in the current database."

        cursor.execute("""

            SELECT c.relname

            FROM pg_catalog.pg_class c

            LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace

            WHERE c.relkind IN ('r', 'v', '')

                AND n.nspname NOT IN ('pg_catalog', 'pg_toast')

                AND pg_catalog.pg_table_is_visible(c.oid)""")

        return [row[0] for row in cursor.fetchall()]

    def get_table_description(self, cursor, table_name):

        "Returns a description of the table, with the DB-API cursor.description interface."

        cursor.execute("SELECT * FROM %s LIMIT 1" % self.connection.ops.quote_name(table_name))

        return cursor.description

    def get_relations(self, cursor, table_name):

        """

        Returns a dictionary of {field_index: (field_index_other_table, other_table)}

        representing all relationships to the given table. Indexes are 0-based.

        """

        cursor.execute("""

            SELECT con.conkey, con.confkey, c2.relname

            FROM pg_constraint con, pg_class c1, pg_class c2

            WHERE c1.oid = con.conrelid

                AND c2.oid = con.confrelid

                AND c1.relname = %s

                AND con.contype = 'f'""", [table_name])

        relations = {}

        for row in cursor.fetchall():

            try:

                # row[0] and row[1] are like "{2}", so strip the curly braces.

                relations[int(row[0][1:-1]) - 1] = (int(row[1][1:-1]) - 1, row[2])

            except ValueError:

                continue

        return relations

    def get_indexes(self, cursor, table_name):

        """

        Returns a dictionary of fieldname -> infodict for the given table,

        where each infodict is in the format:

            {'primary_key': boolean representing whether it's the primary key,

             'unique': boolean representing whether it's a unique index}

        """

        # This query retrieves each index on the given table, including the

        # first associated field name

        cursor.execute("""

            SELECT attr.attname, idx.indkey, idx.indisunique, idx.indisprimary

            FROM pg_catalog.pg_class c, pg_catalog.pg_class c2,

                pg_catalog.pg_index idx, pg_catalog.pg_attribute attr

            WHERE c.oid = idx.indrelid

                AND idx.indexrelid = c2.oid

                AND attr.attrelid = c.oid

                AND attr.attnum = idx.indkey[0]

                AND c.relname = %s""", [table_name])

        indexes = {}

        for row in cursor.fetchall():

            # row[1] (idx.indkey) is stored in the DB as an array. It comes out as

            # a string of space-separated integers. This designates the field

            # indexes (1-based) of the fields that have indexes on the table.

            # Here, we skip any indexes across multiple fields.

            if ' ' in row[1]:

                continue

            indexes[row[0]] = {'primary_key': row[3], 'unique': row[2]}

        return indexes