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

import re

import cx_Oracle

quote_name = DatabaseOperations().quote_name

foreign_key_re = re.compile(r"\sCONSTRAINT `[^`]*` FOREIGN KEY \(`([^`]*)`\) REFERENCES `([^`]*)` \(`([^`]*)`\)")

def get_table_list(cursor):

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

    cursor.execute("SELECT TABLE_NAME FROM USER_TABLES")

    return [row[0].upper() 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 WHERE ROWNUM < 2" % quote_name(table_name))

    return cursor.description

def _name_to_index(cursor, table_name):

    """

    Returns a dictionary of {field_name: field_index} for the given table.

    Indexes are 0-based.

    """

    return dict([(d[0], i) for i, d in enumerate(get_table_description(cursor, table_name))])

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 ta.column_id - 1, tb.table_name, tb.column_id - 1

FROM   user_constraints, USER_CONS_COLUMNS ca, USER_CONS_COLUMNS cb,

       user_tab_cols ta, user_tab_cols tb

WHERE  user_constraints.table_name = %s AND

       ta.table_name = %s AND

       ta.column_name = ca.column_name AND

       ca.table_name = %s AND

       user_constraints.constraint_name = ca.constraint_name AND

       user_constraints.r_constraint_name = cb.constraint_name AND

       cb.table_name = tb.table_name AND

       cb.column_name = tb.column_name AND

       ca.position = cb.position""", [table_name, table_name, table_name])

    relations = {}

    for row in cursor.fetchall():

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

    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

    # "We were in the nick of time; you were in great peril!"

    sql = """

WITH primarycols AS (

 SELECT user_cons_columns.table_name, user_cons_columns.column_name, 1 AS PRIMARYCOL

 FROM   user_cons_columns, user_constraints

 WHERE  user_cons_columns.constraint_name = user_constraints.constraint_name AND

        user_constraints.constraint_type = 'P' AND

        user_cons_columns.table_name = %s),

 uniquecols AS (

 SELECT user_ind_columns.table_name, user_ind_columns.column_name, 1 AS UNIQUECOL

 FROM   user_indexes, user_ind_columns

 WHERE  uniqueness = 'UNIQUE' AND

        user_indexes.index_name = user_ind_columns.index_name AND

        user_ind_columns.table_name = %s)

SELECT allcols.column_name, primarycols.primarycol, uniquecols.UNIQUECOL

FROM   (SELECT column_name FROM primarycols UNION SELECT column_name FROM

uniquecols) allcols,

      primarycols, uniquecols

WHERE  allcols.column_name = primarycols.column_name (+) AND

      allcols.column_name = uniquecols.column_name (+)

    """

    cursor.execute(sql, [table_name, 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.

        indexes[row[0]] = {'primary_key': row[1], 'unique': row[2]}

    return indexes

# Maps type objects to Django Field types.

DATA_TYPES_REVERSE = {

    cx_Oracle.CLOB: 'TextField',

    cx_Oracle.DATETIME: 'DateTimeField',

    cx_Oracle.FIXED_CHAR: 'CharField',

    cx_Oracle.NCLOB: 'TextField',

    cx_Oracle.NUMBER: 'DecimalField',

    cx_Oracle.STRING: 'CharField',

    cx_Oracle.TIMESTAMP: 'DateTimeField',

}