# frozen_string_literal: true

require 'lt/lcms/lesson/downloader/gdoc'

module Lcms
  module Engine
    class DocumentBuildService
      EVENT_BUILT = 'document:built'

      def initialize(credentials, opts = {})
        @credentials = credentials
        @options = opts
      end

      #
      # @return Document ActiveRecord::Model
      #
      def build_for(url, expand: false)
        @content = download url
        @expand_document = expand
        @template = DocTemplate::Template.parse @content

        create_document
        clear_preview_link

        content_key = foundational? ? :foundational_content : :original_content
        @document.update! content_key => content

        build
        @document.create_parts_for(template)

        ActiveSupport::Notifications.instrument EVENT_BUILT, id: document.id

        document.activate!
        document
      end

      private

      attr_reader :credentials, :content, :document, :downloader, :expand_document, :options, :template

      #
      # Building the document. Handles workflow:
      # Core-first FS-second and FS-first Core-second.
      #
      def build
        if expand_document
          combine_layout
          combine_activity_metadata
          document.update! build_params
        else
          document.document_parts.delete_all
          document.update! document_params.merge(toc: template.toc, material_ids: template.toc.collect_material_ids)
        end
      end

      def build_params
        params =
          if foundational?
            {
              foundational_metadata: template.foundational_metadata,
              fs_name: downloader.file.name
            }
          else
            document_params.merge(
              foundational_metadata: document.foundational_metadata,
              fs_name: document.name,
              name: downloader.file.name
            )
          end

        params[:toc] = combine_toc
        params[:material_ids] = params[:toc].collect_material_ids
        params
      end

      def clear_preview_link
        links = document.links
        links['pdf']&.delete('preview')
        document.links = links
      end

      def combine_activity_metadata
        old_data = document.activity_metadata
        new_data =
          if foundational?
            old_data.concat template.activity_metadata
            old_data
          else
            template.activity_metadata.concat old_data
            template.activity_metadata
          end
        document.activity_metadata = new_data
      end

      def combine_layout
        DocumentPart.context_types.each_key do |context_type|
          existing_layout = document.layout(context_type)
          new_layout = template.remove_part :layout, context_type
          new_layout_content =
            if foundational?
              "#{existing_layout.content}#{new_layout[:content]}"
            else
              "#{new_layout[:content]}#{existing_layout.content}"
            end
          existing_layout.update content: new_layout_content
        end
      end

      def combine_toc
        modifier = foundational? ? :append : :prepend
        toc = document.toc
        toc.send modifier, template.toc
        toc
      end

      # Initiate or update existing document:
      # - fills in original or fs contents
      # - stores specific file_id for each type of a lesson
      def create_document
        if template.metadata['subject'].presence &&
           template.metadata['subject'].casecmp('ela').zero? || template.prereq?
          @document = Document.actives.find_or_initialize_by(file_id: downloader.file_id)
        else
          @document = foundational? ? find_core_document : find_fs_document
          id_field = foundational? ? :foundational_file_id : :file_id

          @expand_document ||= @document.present?

          @document[id_field] = downloader.file_id if @document.present?
          @document ||= Document.actives.find_or_initialize_by(id_field => downloader.file_id)
        end
      end

      def document_params
        {
          activity_metadata: template.metadata_service.try(:activity_metadata),
          agenda_metadata: template.metadata_service.try(:agenda),
          css_styles: template.css_styles,
          foundational_metadata: template.metadata_service.try(:foundational_metadata),
          name: downloader.file.name,
          last_modified_at: downloader.file.modified_time,
          last_author_email: downloader.file.last_modifying_user.try(:email_address),
          last_author_name: downloader.file.last_modifying_user.try(:display_name),
          metadata: template.metadata,
          sections_metadata: template.metadata_service.try(:section_metadata),
          version: downloader.file.version
        }
      end

      def download(url)
        @downloader = ::Lt::Lcms::Lesson::Downloader::Gdoc.new(credentials, url, options).download
        @downloader.content
      end

      #
      # If there is existing lesson with Core-type - return it. Nil otherwise.
      #
      def find_core_document
        return unless (core_doc = find_resource)
        return if core_doc.foundational?

        core_doc
      end

      #
      # If there is existing lesson with FS-type - return it. Nil otherwise.
      #
      def find_fs_document
        return unless (fs_doc = find_resource)
        return unless fs_doc.foundational?

        fs_doc
      end

      def find_resource
        context = DocTemplate.config.dig('metadata', 'context').constantize
        dir = context.new(template.metadata.with_indifferent_access).directory
        Resource.find_by_directory(dir)&.document
      end

      def foundational?
        !!template.metadata_service.try(:foundational?)
      end
    end
  end
end