from optparse import make_option

from django.core.management.base import LabelCommand

from django.db import connections, transaction, models, DEFAULT_DB_ALIAS

class Command(LabelCommand):

    help = "Creates the table needed to use the SQL cache backend."

    args = "<tablename>"

    label = 'tablename'

    option_list = LabelCommand.option_list + (

        make_option('--database', action='store', dest='database',

            default=DEFAULT_DB_ALIAS, help='Nominates a database onto '

                'which the cache table will be installed. '

                'Defaults to the "default" database.'),

    )

    requires_model_validation = False

    def handle_label(self, tablename, **options):

        alias = options.get('database', DEFAULT_DB_ALIAS)

        connection = connections[alias]

        fields = (

            # "key" is a reserved word in MySQL, so use "cache_key" instead.

            models.CharField(name='cache_key', max_length=255, unique=True, primary_key=True),

            models.TextField(name='value'),

            models.DateTimeField(name='expires', db_index=True),

        )

        table_output = []

        index_output = []

        qn = connection.ops.quote_name

        for f in fields:

            field_output = [qn(f.name), f.db_type(connection=connection)]

            field_output.append("%sNULL" % (not f.null and "NOT " or ""))

            if f.primary_key:

                field_output.append("PRIMARY KEY")

            elif f.unique:

                field_output.append("UNIQUE")

            if f.db_index:

                unique = f.unique and "UNIQUE " or ""

                index_output.append("CREATE %sINDEX %s ON %s (%s);" % \

                    (unique, qn('%s_%s' % (tablename, f.name)), qn(tablename),

                    qn(f.name)))

            table_output.append(" ".join(field_output))

        full_statement = ["CREATE TABLE %s (" % qn(tablename)]

        for i, line in enumerate(table_output):

            full_statement.append('    %s%s' % (line, i < len(table_output)-1 and ',' or ''))

        full_statement.append(');')

        curs = connection.cursor()

        curs.execute("\n".join(full_statement))

        for statement in index_output:

            curs.execute(statement)

        transaction.commit_unless_managed(using=alias)