module Scrivito
  module Migrations
    # CMS Migrations can alter the structure and content of the CMS and allow
    # other developers to simultaneously apply changes. Migrations provide a set
    # of methods to create, update or delete CMS objects, attributes and object
    # classes.
    #
    # @example Simple Migration
    #
    #   class CreateTestAttribute < Scrivito::Migrations::Migration
    #     def up
    #       ObjClass.find('Homepage').attributes.add(Attribute.new(name: 'test', type: :string))
    #     end
    #   end
    class Migration
      class << self
        def copy(destination, sources)
          unless File.exist?(destination)
            FileUtils.mkdir_p(destination)
          end

          destination_migrations = Scrivito::Migrations::Migrator.determine_migrations(destination)
          last = destination_migrations.last

          sources.each do |scope, path|
            source_migrations = Scrivito::Migrations::Migrator.determine_migrations(path)

            source_migrations.each do |migration|
              next if duplicate_migration?(destination_migrations, migration.name, scope)

              name = migration.name
              version = next_migration_number(last ? last.version : 0)
              filename = File.join(destination, "#{version}_#{name.underscore}.#{scope}.rb")

              new_migration = self.new(name, version, filename, scope)

              FileUtils.cp(migration.filename, new_migration.filename)

              last = new_migration
              destination_migrations << new_migration
            end
          end
        end

        def duplicate_migration?(migrations, name, scope)
          migrations.detect do |migration|
            migration.name == name && migration.scope == scope.to_s
          end
        end

        def next_migration_number(max)
          timestamp = Time.now.utc.strftime("%Y%m%d%H%M%S").to_i

          if max >= timestamp
            timestamp = max + 1
          end

          timestamp
        end
      end

      attr_accessor :name
      attr_accessor :version
      attr_accessor :filename
      attr_accessor :scope

      def initialize(name, version, filename, scope)
        @name = name
        @version = version.to_i
        @filename = filename
        @scope = scope.to_s
      end

      def migrate
        announce 'migrating'

        time = Benchmark.measure { up }

        announce 'migrated (%.4fs)' % time.real; puts
      end

      private

      def announce(message)
        text = "#{version} #{name}: #{message}"
        length = [0, 75 - text.length].max
        puts('== %s %s' % [text, '=' * length])
      end
    end
  end
end