from django.db.models import Index

__all__ = ['BrinIndex', 'GinIndex']


class BrinIndex(Index):
    suffix = 'brin'
    # Allow an index name longer than 30 characters since the suffix is 4
    # characters (usual limit is 3). Since this index can only be used on
    # PostgreSQL, the 30 character limit for cross-database compatibility isn't
    # applicable.
    max_name_length = 31

    def __init__(self, fields=[], name=None, pages_per_range=None):
        if pages_per_range is not None and pages_per_range <= 0:
            raise ValueError('pages_per_range must be None or a positive integer')
        self.pages_per_range = pages_per_range
        super().__init__(fields, name)

    def deconstruct(self):
        path, args, kwargs = super().deconstruct()
        kwargs['pages_per_range'] = self.pages_per_range
        return path, args, kwargs

    def get_sql_create_template_values(self, model, schema_editor, using):
        parameters = super().get_sql_create_template_values(model, schema_editor, using=' USING brin')
        if self.pages_per_range is not None:
            parameters['extra'] = ' WITH (pages_per_range={})'.format(
                schema_editor.quote_value(self.pages_per_range)) + parameters['extra']
        return parameters


class GinIndex(Index):
    suffix = 'gin'

    def create_sql(self, model, schema_editor):
        return super().create_sql(model, schema_editor, using=' USING gin')