module CassandraObject
  module Schema
    class Migration

      @@verbose = true
      cattr_accessor :verbose

      class << self
        def connection
          CassandraObject::Base.connection
        end

        def migrate(direction)
          return unless respond_to?(direction)

          case direction
          when :up   then announce "migrating"
          when :down then announce "reverting"
          end

          result = nil
          time = Benchmark.measure { result = send("#{direction}") }

          case direction
          when :up   then announce "migrated (%.4fs)" % time.real; write
          when :down then announce "reverted (%.4fs)" % time.real; write
          end

          result
        end

        # Creates a new column family with the given name.  Column family configurations can be set within
        # a block like this:
        #
        #  create_column_family(:users) do |cf|
        #    cf.comment = 'Users column family'
        #    cf.comparator_type = 'TimeUUIDType'
        #  end
        #
        # A complete list of available configuration settings is here:
        #
        # http://github.com/fauna/cassandra/blob/master/vendor/0.7/gen-rb/cassandra_types.rb
        #
        # Scroll down to the CfDef definition.
        def create_column_family(name, &block)
          say_with_time("create_column_family #{name}") do
            column_family_tasks.create(name, &block)
          end
        end

        # Drops the given column family
        def drop_column_family(name)
          say_with_time("drop_column_family #{name}") do
            column_family_tasks.drop(name)
          end
        end

        # Renames the column family from the old name to the new name
        def rename_column_family(old_name, new_name)
          say_with_time("rename_column_family #{name}") do
            column_family_tasks.rename(old_name, new_name)
          end
        end

        def write(text="")
          puts(text) if verbose
        end

        def announce(message)
          version = defined?(@version) ? @version : nil

          text = "#{version} #{name}: #{message}"
          length = [0, 75 - text.length].max
          write "== %s %s" % [text, "=" * length]
        end

        def say(message, subitem=false)
          write "#{subitem ? "   ->" : "--"} #{message}"
        end

        def say_with_time(message)
          say(message)
          result = nil
          time = Benchmark.measure { result = yield }
          say "%.4fs" % time.real, :subitem
          say("#{result} rows", :subitem) if result.is_a?(Integer)
          result
        end

        def suppress_messages
          save, self.verbose = verbose, false
          yield
        ensure
          self.verbose = save
        end

        private
          def column_family_tasks
            Tasks::ColumnFamily.new(CassandraObject::Base.connection.keyspace)
          end
      end
    end
  end
end