module Scrivito
  module Migrations
    class Migrator
      class << self
        def migrations_path
          Rails.root + Scrivito::Configuration.migration_path
        end

        def determine_migrations(paths)
          paths = Array(paths)
          files = Dir[*paths.map { |path| "#{path}/**/[0-9]*_*.rb" }]
          splitter = /([0-9]+)_([_a-z0-9]*)\.?([_a-z0-9]*)?\.rb\z/

          migrations = files.map do |filename|
            version, name, scope = filename.scan(splitter).first

            unless version
              raise ScrivitoError.new("Illegal name for migration file: #{filename}\n\t
                (only lower case letters, numbers, and '_' allowed)")
            end

            version = version
            name = name.camelize

            require(File.expand_path(filename))
            name.constantize.new(name, version, filename, scope)
          end

          migrations.sort_by(&:version)
        end
      end

      attr_reader :migrations
      attr_reader :workspace_lock

      def initialize(migration_store=nil, workspace_lock=nil)
        @migrations = determine_migrations
        @migration_store = migration_store || MigrationStore.instance
        @workspace_lock = workspace_lock || WorkspaceLock.instance

        validate
      end

      def migrate
        workspace.as_current do
          runnable.each do |migration|
            migration.migrate
            @migration_store.add_version(migration.version)
          end
        end
      end

      def needs_migration?
        runnable.present?
      end

      def publish
        remove_workspace_with do
          CmsRestApi.put("workspaces/#{workspace.id}/publish", {})
        end
      end

      def abort
        remove_workspace_with do
          CmsRestApi.delete("workspaces/#{workspace.id}")
        end
      end

      private

      def workspace
        workspace = migration_workspace

        if workspace
          if workspace_lock.exists?
            workspace_lock.validate(workspace)
          end
        else
          workspace = Workspace.create(title: 'Migration Working Copy', id: 'rtc')
          workspace_lock.write(workspace)
        end

        workspace
      end

      def migration_workspace
        Workspace.find('rtc')
      rescue ResourceNotFound
      end

      def remove_workspace_with(&block)
        workspace = migration_workspace

        if workspace
          workspace_lock.validate(workspace)

          yield

          workspace_lock.remove
        else
          raise ScrivitoError.new('Migration workspace does not exist')
        end
      end

      def determine_migrations
        self.class.determine_migrations(self.class.migrations_path)
      end

      def runnable
        migrations.reject do |migration|
          migrated_versions.include?(migration.version)
        end
      end

      def migrated_versions
        @migration_store.versions
      end

      def validate
        name, _ = migrations.group_by(&:name).find { |_, value| value.length > 1 }

        if name
          raise ScrivitoError.new("Multiple migrations have the name #{name}")
        end

        version, _ = migrations.group_by(&:version).find { |_, value| value.length > 1 }

        if version
          raise ScrivitoError.new("Multiple migrations have the version number #{version}")
        end
      end
    end
  end
end