module Foreigner
  module ConnectionAdapters
    module Sql2003
      def supports_foreign_keys?
        true
      end

      def drop_table(*args)
        options = args.extract_options!
        if options[:force]
          disable_referential_integrity { super }
        else
          super
        end
      end

      def foreign_key_exists?(from_table, options)
        foreign_key_name = decipher_foreign_key_name(from_table, options)

        foreign_keys(from_table).any? { |fk| fk.name == foreign_key_name }
      end

      def add_foreign_key(from_table, to_table, options = {})
        sql = "ALTER TABLE #{quote_table_name(from_table)} #{add_foreign_key_sql(from_table, to_table, options)}"
        execute(sql)
      end

      def add_foreign_key_sql(from_table, to_table, options = {})
        column  = options[:column] || "#{to_table.to_s.singularize}_id"
        foreign_key_name = options.key?(:name) ? options[:name].to_s : foreign_key_name(from_table, column)
        primary_key = options[:primary_key] || "id"
        dependency = dependency_sql(options[:dependent])

        proper_name = proper_table_name(to_table)

        sql =
          "ADD CONSTRAINT #{quote_column_name(foreign_key_name)} " +
          "FOREIGN KEY (#{quote_column_name(column)}) " +
          "REFERENCES #{quote_table_name(proper_name)}(#{primary_key})"
        sql << " #{dependency}" if dependency.present?
        sql << " #{options[:options]}" if options[:options]

        sql
      end

      def proper_table_name(to_table)
        if ActiveRecord::Migration.instance_methods(false).include? :proper_table_name
          ActiveRecord::Migration.new.proper_table_name(to_table)
        else
          ActiveRecord::Migrator.proper_table_name(to_table)
        end
      end

      def remove_foreign_key(table, options)
        execute "ALTER TABLE #{quote_table_name(table)} #{remove_foreign_key_sql(table, options)}"
      end

      def remove_foreign_key_sql(table, options)
        foreign_key_name = decipher_foreign_key_name(table, options)
        "DROP CONSTRAINT #{quote_column_name(foreign_key_name)}"
      end

      private
        def foreign_key_name(from_table, column)
          "#{from_table}_#{column}_fk"
        end

        def foreign_key_column(to_table)
          "#{to_table.to_s.singularize}_id"
        end

        def decipher_foreign_key_name(from_table, options)
          if Hash === options
            options.key?(:name) ? options[:name].to_s : foreign_key_name(from_table, options[:column])
          else
            foreign_key_name(from_table, foreign_key_column(options))
          end
        end

        def dependency_sql(dependency)
          case dependency
            when :nullify then "ON DELETE SET NULL"
            when :delete  then "ON DELETE CASCADE"
            when :restrict then "ON DELETE RESTRICT"
            else ""
          end
        end
    end
  end
end