from django.db.backends.postgresql_psycopg2.base import DatabaseOperations

quote_name = DatabaseOperations().quote_name

def get_table_list(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(cursor, table_name):

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

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

    return cursor.description

def get_relations(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():

        # row[0] and row[1] are single-item lists, so grab the single item.

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

    return relations

def get_indexes(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

# Maps type codes to Django Field types.

DATA_TYPES_REVERSE = {

    16: 'BooleanField',

    21: 'SmallIntegerField',

    23: 'IntegerField',

    25: 'TextField',

    701: 'FloatField',

    869: 'IPAddressField',

    1043: 'CharField',

    1082: 'DateField',

    1083: 'TimeField',

    1114: 'DateTimeField',

    1184: 'DateTimeField',

    1266: 'TimeField',

    1700: 'DecimalField',

}