from django.db.backends import BaseDatabaseIntrospection

import cx_Oracle

import re

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

class DatabaseIntrospection(BaseDatabaseIntrospection):

    # Maps type objects to Django Field types.

    data_types_reverse = {

        cx_Oracle.CLOB: 'TextField',

        cx_Oracle.DATETIME: 'DateField',

        cx_Oracle.FIXED_CHAR: 'CharField',

        cx_Oracle.NCLOB: 'TextField',

        cx_Oracle.NUMBER: 'DecimalField',

        cx_Oracle.STRING: 'CharField',

        cx_Oracle.TIMESTAMP: 'DateTimeField',

    }

    try:

        data_types_reverse[cx_Oracle.NATIVE_FLOAT] = 'FloatField'

    except AttributeError:

        pass

    try:

        data_types_reverse[cx_Oracle.UNICODE] = 'CharField'

    except AttributeError:

        pass

    def get_field_type(self, data_type, description):

        # If it's a NUMBER with scale == 0, consider it an IntegerField

        if data_type == cx_Oracle.NUMBER and description[5] == 0:

            return 'IntegerField'

        else:

            return super(DatabaseIntrospection, self).get_field_type(

                data_type, description)

    def get_table_list(self, cursor):

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

        cursor.execute("SELECT TABLE_NAME FROM USER_TABLES")

        return [row[0].lower() 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 WHERE ROWNUM < 2" % self.connection.ops.quote_name(table_name))

        description = []

        for desc in cursor.description:

            description.append((desc[0].lower(),) + desc[1:])

        return description

    def table_name_converter(self, name):

        "Table name comparison is case insensitive under Oracle"

        return name.lower()

    def _name_to_index(self, 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(self.get_table_description(cursor, table_name))])

    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 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(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

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

        sql = """\

SELECT LOWER(all_tab_cols.column_name) AS column_name,

       CASE user_constraints.constraint_type

           WHEN 'P' THEN 1 ELSE 0

       END AS is_primary_key,

       CASE user_indexes.uniqueness

           WHEN 'UNIQUE' THEN 1 ELSE 0

       END AS is_unique

FROM   all_tab_cols, user_cons_columns, user_constraints, user_ind_columns, user_indexes

WHERE  all_tab_cols.column_name = user_cons_columns.column_name (+)

  AND  all_tab_cols.table_name = user_cons_columns.table_name (+)

  AND  user_cons_columns.constraint_name = user_constraints.constraint_name (+)

  AND  user_constraints.constraint_type (+) = 'P'

  AND  user_ind_columns.column_name (+) = all_tab_cols.column_name

  AND  user_ind_columns.table_name (+) = all_tab_cols.table_name

  AND  user_indexes.uniqueness (+) = 'UNIQUE'

  AND  user_indexes.index_name (+) = user_ind_columns.index_name

  AND  all_tab_cols.table_name = UPPER(%s)

"""

        cursor.execute(sql, [table_name])

        indexes = {}

        for row in cursor.fetchall():

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

        return indexes