A nanoc blogging helper (without AtomFeedBuilder inheritance) for producing a JSON feed. See https://jsonfeed.org/

blogging_json.rb

# frozen_string_literal: true

module Nanoc::Helpers
  # @see http://nanoc.ws/doc/reference/helpers/#blogging
  module Blogging_JSON
    # @return [Array]
    def articles
      blk = -> { @items.select { |item| item[:kind] == 'article' } }
      if @items.frozen?
        @article_items ||= blk.call
      else
        blk.call
      end
    end

    # @return [Array]
    def sorted_articles
      blk = -> { articles.sort_by { |a| attribute_to_time(a[:created_at]) }.reverse }

      if @items.frozen?
        @sorted_article_items ||= blk.call
      else
        blk.call
      end
    end

    class JSONFeedBuilder
      include Nanoc::Helpers::Blogging

      attr_accessor :config

      attr_accessor :limit
      attr_accessor :relevant_articles
      attr_accessor :preserve_order
      attr_accessor :content_proc
      attr_accessor :excerpt_proc
      attr_accessor :title
      attr_accessor :author_name
      attr_accessor :author_uri
      attr_accessor :icon
      attr_accessor :logo

      def initialize(config, item)
        @config = config
        @item = item
      end

      def validate
        validate_config
        validate_feed_item
        validate_articles
      end

      def build
        require 'json'
        JSON[build_for_feed()]
      end

      protected

      def sorted_relevant_articles
        all = relevant_articles

        unless @preserve_order
          all = all.sort_by { |a| attribute_to_time(a[:created_at]) }
        end

        all.reverse.first(limit)
      end

      def last_article
        sorted_relevant_articles.first
      end

      def updated
        relevant_articles.map { |a| attribute_to_time(a[:updated_at] || a[:created_at]) }.max
      end

      def validate_config
        if @config[:base_url].nil?
          raise Nanoc::Int::Errors::GenericTrivial.new('Cannot build JSON feed: site configuration has no base_url')
        end
      end

      def validate_feed_item
        if title.nil?
          raise Nanoc::Int::Errors::GenericTrivial.new('Cannot build JSON feed: no title in params, item or site config')
        end
        if author_name.nil?
          raise Nanoc::Int::Errors::GenericTrivial.new('Cannot build JSON feed: no author_name in params, item or site config')
        end
        if author_uri.nil?
          raise Nanoc::Int::Errors::GenericTrivial.new('Cannot build JSON feed: no author_uri in params, item or site config')
        end
      end

      def validate_articles
        if relevant_articles.empty?
          raise Nanoc::Int::Errors::GenericTrivial.new('Cannot build JSON feed: no articles')
        end
        if relevant_articles.any? { |a| a[:created_at].nil? }
          raise Nanoc::Int::Errors::GenericTrivial.new('Cannot build JSON feed: one or more articles lack created_at')
        end
      end

      def build_for_feed()
        root_url = @config[:base_url] + '/'
        json = {}
        json['version'] = 'https://jsonfeed.org/version/1'
        
        # Add primary attributes
        json['home_page_url'] = root_url
        json['title'] = title

        ## Add date
        #xml.updated(updated.__nanoc_to_iso8601_time)

        # Add links
        json['feed_url'] = feed_url

        # Add author information
        json['author'] = {}
        json['author']['name'] = author_name
        json['author']['url'] = author_uri

        # Add icon and logo
        json['icon'] = icon if icon
        json['favicon'] = logo if logo

        # Add articles
        json['items'] = []
        sorted_relevant_articles.each do |a|
          json['items'] << build_for_article(a)
        end
        json
      end

      def build_for_article(a)
        # Get URL
        url = url_for(a)
        return if url.nil?

        json = {}

        # Add primary attributes
        json['id'] = json_tag_for(a)
        json['title'] = a[:title]

        # Add dates
        json['date_published'] = attribute_to_time(a[:created_at]).__nanoc_to_iso8601_time
        json['date_modified'] = attribute_to_time(a[:updated_at] || a[:created_at]).__nanoc_to_iso8601_time

        # Add specific author information
        if a[:author_name] || a[:author_uri]
          json['author']['name'] = a[:author_name] || author_name
          json['url'] = a[:author_uri] || author_uri
        end

        # Add link
        json['url'] = url

        # Add content
        summary = excerpt_proc.call(a)
        json['content_html'] = content_proc.call(a)
        json
      end
    end

    # @option params [Number] :limit
    # @option params [Array] :articles
    # @option params [Boolean] :preserve_order
    # @option params [Proc] :content_proc
    # @option params [Proc] :excerpt_proc
    # @option params [String] :title
    # @option params [String] :author_name
    # @option params [String] :author_uri
    # @option params [String] :icon
    # @option params [String] :logo
    #
    # @return [String]
    def json_feed(params = {})
      require 'builder'

      # Create builder
      builder = JSONFeedBuilder.new(@config, @item)

      # Fill builder
      builder.limit             = params[:limit] || 5
      builder.relevant_articles = params[:articles] || articles || []
      builder.preserve_order    = params.fetch(:preserve_order, false)
      builder.content_proc      = params[:content_proc] || ->(a) { a.compiled_content(snapshot: :pre) }
      builder.excerpt_proc      = params[:excerpt_proc] || ->(a) { a[:excerpt] }
      builder.title             = params[:title] || @item[:title] || @config[:title]
      builder.author_name       = params[:author_name] || @item[:author_name] || @config[:author_name]
      builder.author_uri        = params[:author_uri] || @item[:author_uri] || @config[:author_uri]
      builder.icon              = params[:icon]
      builder.logo              = params[:logo]

      # Run
      builder.validate
      builder.build
    end

    # @return [String]
    def url_for(item)
      # Check attributes
      if @config[:base_url].nil?
        raise Nanoc::Int::Errors::GenericTrivial.new('Cannot build JSON feed: site configuration has no base_url')
      end

      # Build URL
      if item[:custom_url_in_feed]
        item[:custom_url_in_feed]
      elsif item[:custom_path_in_feed]
        @config[:base_url] + item[:custom_path_in_feed]
      elsif item.path
        @config[:base_url] + item.path
      end
    end

    # @return [String]
    def feed_url
      # Check attributes
      if @config[:base_url].nil?
        raise Nanoc::Int::Errors::GenericTrivial.new('Cannot build JSON feed: site configuration has no base_url')
      end

      @item[:feed_url] || @config[:base_url] + @item.path
    end

    # @return [String]
    def json_tag_for(item)
      hostname, base_dir = %r{^.+?://([^/]+)(.*)$}.match(@config[:base_url])[1..2]

      formatted_date = attribute_to_time(item[:created_at]).__nanoc_to_iso8601_date

      'tag:' + hostname + ',' + formatted_date + ':' + base_dir + (item.path || item.identifier.to_s)
    end

    # @param [String, Time, Date, DateTime] arg
    #
    # @return [Time]
    def attribute_to_time(arg)
      case arg
      when DateTime
        arg.to_time
      when Date
        Time.utc(arg.year, arg.month, arg.day)
      when String
        Time.parse(arg)
      else
        arg
      end
    end
  end
end