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

from MySQLdb import ProgrammingError, OperationalError

from MySQLdb.constants import FIELD_TYPE

import re

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("SHOW TABLES")

    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 _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.

    """

    my_field_dict = _name_to_index(cursor, table_name)

    constraints = []

    relations = {}

    try:

        # This should work for MySQL 5.0.

        cursor.execute("""

            SELECT column_name, referenced_table_name, referenced_column_name

            FROM information_schema.key_column_usage

            WHERE table_name = %s

                AND table_schema = DATABASE()

                AND referenced_table_name IS NOT NULL

                AND referenced_column_name IS NOT NULL""", [table_name])

        constraints.extend(cursor.fetchall())

    except (ProgrammingError, OperationalError):

        # Fall back to "SHOW CREATE TABLE", for previous MySQL versions.

        # Go through all constraints and save the equal matches.

        cursor.execute("SHOW CREATE TABLE %s" % quote_name(table_name))

        for row in cursor.fetchall():

            pos = 0

            while True:

                match = foreign_key_re.search(row[1], pos)

                if match == None:

                    break

                pos = match.end()

                constraints.append(match.groups())

    for my_fieldname, other_table, other_field in constraints:

        other_field_index = _name_to_index(cursor, other_table)[other_field]

        my_field_index = my_field_dict[my_fieldname]

        relations[my_field_index] = (other_field_index, other_table)

    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}

    """

    cursor.execute("SHOW INDEX FROM %s" % quote_name(table_name))

    indexes = {}

    for row in cursor.fetchall():

        indexes[row[4]] = {'primary_key': (row[2] == 'PRIMARY'), 'unique': not bool(row[1])}

    return indexes

DATA_TYPES_REVERSE = {

    FIELD_TYPE.BLOB: 'TextField',

    FIELD_TYPE.CHAR: 'CharField',

    FIELD_TYPE.DECIMAL: 'DecimalField',

    FIELD_TYPE.DATE: 'DateField',

    FIELD_TYPE.DATETIME: 'DateTimeField',

    FIELD_TYPE.DOUBLE: 'FloatField',

    FIELD_TYPE.FLOAT: 'FloatField',

    FIELD_TYPE.INT24: 'IntegerField',

    FIELD_TYPE.LONG: 'IntegerField',

    FIELD_TYPE.LONGLONG: 'IntegerField',

    FIELD_TYPE.SHORT: 'IntegerField',

    FIELD_TYPE.STRING: 'CharField',

    FIELD_TYPE.TIMESTAMP: 'DateTimeField',

    FIELD_TYPE.TINY: 'IntegerField',

    FIELD_TYPE.TINY_BLOB: 'TextField',

    FIELD_TYPE.MEDIUM_BLOB: 'TextField',

    FIELD_TYPE.LONG_BLOB: 'TextField',

    FIELD_TYPE.VAR_STRING: 'CharField',

}