Add support for JSON LD in Onebox (#17007)

* FIX: Fix a bug that is accessing the values in a hash wrongly and write tests

I decided to write tests in order to be confident in my refactor that's in the next commit.
Meanwhile I have discovered a potential bug. The `title_attr` key was accessed as a string,
but all the keys are actually symbols so it was never evaluated to be true.

irb(main):025:0> d = {key: 'value'}
=> {:key=>"value"}
irb(main):026:0> d['key']
=> nil
irb(main):027:0> d[:key]
=> "value"

* DEV: Extract methods for readability

I will be adding a new method following the conventions in place for adding a new normalizer. And this will make the readability of the `raw` block even more difficult; so I am extracting self contained private methods beforehand.

* FEATURE: Parse JSON-LD and introduce Movie object

JSON LD data is very easily transferable to Ruby objects because they contain types. If these types are mapped to Ruby objects, it is also better to make all the parsed data very explicit and easily extendable.

JSON-LD has many more standardized item types, with a full list here: https://schema.org/docs/full.html
However in order to decrease the scope, I only adapted the movie type.

* DEV: Change inheritance between normalizers

Normalizers are not supposed to have an inheritance relationships amongst each other. They are all normalizers, but all normalizing separate protocols. This is why I chose to extract a parent class and relieve Open Graph off that responsibility. Removing the parent class altogether could also a possibility, but I am keeping the scope limited to having a more accurate representation of the normalizers while making it easier to add a new one.

* Lint changes

* Bring back the Oembed OpenGraph inheritance

There is one test that caught that this inheritance was necessary. I still think modelling wise this inheritance shouldn't exist, but this can be tackled separately.

* Return empty hash if the json received is invalid

Before this change if there was a parsing error with JSON it would throw an exception. The goal of this commit is to rescue that exception and then log a warning. I chose to use Discourse's logger wrapper `warn_exception` to have the backtrace and not just used Rails logger. I considered raising an `InvalidParameters` error however if the JSON here is invalid it should not block showing of the Onebox, so logging is enough.

* Prep to support more JSONLD schema types with case

* Extract mustache template object created from JSONLD

lib/onebox/engine/standard_embed.rb

@@ -1,8 +1,10 @@
 # frozen_string_literal: true
 
-require "cgi"
-require "onebox/open_graph"
+require 'cgi'
+require 'onebox/normalizer'
+require 'onebox/open_graph'
 require 'onebox/oembed'
+require 'onebox/json_ld'
 
 module Onebox
   module Engine
@@ -38,32 +40,14 @@ module Onebox
       def raw
         return @raw if defined?(@raw)
 
-        og = get_opengraph
-        twitter = get_twitter
-        oembed = get_oembed
-
         @raw = {}
 
-        og.data.each do |k, v|
-          next if k == "title_attr"
-          v = og.send(k)
-          @raw[k] ||= v unless v.nil?
-        end
-
-        twitter.each { |k, v| @raw[k] ||= v unless Onebox::Helpers::blank?(v) }
-
-        oembed.data.each do |k, v|
-          v = oembed.send(k)
-          @raw[k] ||= v unless v.nil?
-        end
-
-        favicon = get_favicon
-        @raw[:favicon] = favicon unless Onebox::Helpers::blank?(favicon)
-
-        unless @raw[:description]
-          description = get_description
-          @raw[:description] = description unless Onebox::Helpers::blank?(description)
-        end
+        set_opengraph_data_on_raw
+        set_twitter_data_on_raw
+        set_oembed_data_on_raw
+        set_json_ld_data_on_raw
+        set_favicon_data_on_raw
+        set_description_on_raw
 
         @raw
       end
@@ -154,6 +138,50 @@ module Onebox
 
         oembed_url
       end
+
+      def get_json_ld
+        @json_ld ||= Onebox::JsonLd.new(html_doc)
+      end
+
+      def set_from_normalizer_data(normalizer)
+        normalizer.data.each do |k, v|
+          v = normalizer.send(k)
+          @raw[k] ||= v unless v.nil?
+        end
+      end
+
+      def set_opengraph_data_on_raw
+        og = get_opengraph
+        set_from_normalizer_data(og)
+        @raw.except!(:title_attr)
+      end
+
+      def set_twitter_data_on_raw
+        twitter = get_twitter
+        twitter.each { |k, v| @raw[k] ||= v unless Onebox::Helpers::blank?(v) }
+      end
+
+      def set_oembed_data_on_raw
+        oembed = get_oembed
+        set_from_normalizer_data(oembed)
+      end
+
+      def set_json_ld_data_on_raw
+        json_ld = get_json_ld
+        set_from_normalizer_data(json_ld)
+      end
+
+      def set_favicon_data_on_raw
+        favicon = get_favicon
+        @raw[:favicon] = favicon unless Onebox::Helpers::blank?(favicon)
+      end
+
+      def set_description_on_raw
+        unless @raw[:description]
+          description = get_description
+          @raw[:description] = description unless Onebox::Helpers::blank?(description)
+        end
+      end
     end
   end
 end

lib/onebox/json_ld.rb

@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+module Onebox
+  class JsonLd < Normalizer
+    # Full schema.org hierarchy can be found here: https://schema.org/docs/full.html
+    MOVIE_JSON_LD_TYPE = "Movie"
+
+    def initialize(doc)
+      @data = extract(doc)
+    end
+
+    private
+
+    def extract(doc)
+      extracted_json = extract_json_from(doc)
+      parsed_json = parse_json(extracted_json)
+
+      extracted =
+        case parsed_json["@type"]
+        when MOVIE_JSON_LD_TYPE
+          Onebox::Movie.new(parsed_json)
+        else
+          {}
+        end
+
+      extracted.to_h
+    end
+
+    def extract_json_from(doc)
+      return {} if Onebox::Helpers::blank?(doc)
+      json_ld = doc.search('script[type="application/ld+json"]').text
+      return {} if Onebox::Helpers::blank?(json_ld)
+      json_ld
+    end
+
+    def parse_json(json)
+      begin
+        JSON[json]
+      rescue JSON::ParserError => e
+        Discourse.warn_exception(e, message: "Error parsing JSON-LD json: #{json}")
+        {}
+      end
+    end
+  end
+end

lib/onebox/movie.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+module Onebox
+  class Movie
+    def initialize(json_ld_data)
+      @json_ld_data = json_ld_data
+    end
+
+    def name
+      @json_ld_data['name']
+    end
+
+    def image
+      @json_ld_data['image']
+    end
+
+    def description
+      @json_ld_data['description']
+    end
+
+    def rating
+      @json_ld_data.dig('aggregateRating', 'ratingValue')
+    end
+
+    def genres
+      @json_ld_data['genre']
+    end
+
+    def duration
+      return nil unless @json_ld_data['duration']
+
+      Time.parse(@json_ld_data['duration']).strftime '%H:%M'
+    end
+
+    def to_h
+      {
+        name: name,
+        image: image,
+        description: description,
+        rating: rating,
+        genres: genres,
+        duration: duration
+      }
+    end
+  end
+end

lib/onebox/normalizer.rb

@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+module Onebox
+  class Normalizer
+    attr_reader :data
+
+    def get(attr, length = nil, sanitize = true)
+      return nil if Onebox::Helpers::blank?(data)
+
+      value = data[attr]
+
+      return nil if Onebox::Helpers::blank?(value)
+
+      value = html_entities.decode(value)
+      value = Sanitize.fragment(value) if sanitize
+      value.strip!
+      value = Onebox::Helpers.truncate(value, length) unless length.nil?
+
+      value
+    end
+
+    def method_missing(attr, *args, &block)
+      value = get(attr, *args)
+
+      return nil if Onebox::Helpers::blank?(value)
+
+      method_name = attr.to_s
+      if method_name.end_with?(*integer_suffixes)
+        value.to_i
+      elsif method_name.end_with?(*url_suffixes)
+        result = Onebox::Helpers.normalize_url_for_output(value)
+        result unless Onebox::Helpers::blank?(result)
+      else
+        value
+      end
+    end
+
+    private
+
+    def integer_suffixes
+      ['width', 'height']
+    end
+
+    def url_suffixes
+      ['url', 'image', 'video']
+    end
+
+    def html_entities
+      @html_entities ||= HTMLEntities.new
+    end
+  end
+end

lib/onebox/oembed.rb

@@ -2,12 +2,11 @@
 
 module Onebox
   class Oembed < OpenGraph
-
     def initialize(response)
       @data = Onebox::Helpers.symbolize_keys(::MultiJson.load(response))
 
       # never use oembed from WordPress 4.4 (it's broken)
-      data.delete(:html) if data[:html] && data[:html]["wp-embedded-content"]
+      @data.delete(:html) if @data[:html] && @data[:html]["wp-embedded-content"]
     end
 
     def html

lib/onebox/open_graph.rb

@@ -1,9 +1,7 @@
 # frozen_string_literal: true
 
 module Onebox
-  class OpenGraph
-
-    attr_reader :data
+  class OpenGraph < Normalizer
 
     def initialize(doc)
       @data = extract(doc)
@@ -23,51 +21,8 @@ module Onebox
       secure_url.to_s
     end
 
-    def method_missing(attr, *args, &block)
-      value = get(attr, *args)
-
-      return nil if Onebox::Helpers::blank?(value)
-
-      method_name = attr.to_s
-      if method_name.end_with?(*integer_suffixes)
-        value.to_i
-      elsif method_name.end_with?(*url_suffixes)
-        result = Onebox::Helpers.normalize_url_for_output(value)
-        result unless Onebox::Helpers::blank?(result)
-      else
-        value
-      end
-    end
-
-    def get(attr, length = nil, sanitize = true)
-      return nil if Onebox::Helpers::blank?(data)
-
-      value = data[attr]
-
-      return nil if Onebox::Helpers::blank?(value)
-
-      value = html_entities.decode(value)
-      value = Sanitize.fragment(value) if sanitize
-      value.strip!
-      value = Onebox::Helpers.truncate(value, length) unless length.nil?
-
-      value
-    end
-
     private
 
-    def integer_suffixes
-      ['width', 'height']
-    end
-
-    def url_suffixes
-      ['url', 'image', 'video']
-    end
-
-    def html_entities
-      @html_entities ||= HTMLEntities.new
-    end
-
     def extract(doc)
       return {} if Onebox::Helpers::blank?(doc)
 
@@ -88,6 +43,5 @@ module Onebox
 
       data
     end
-
   end
 end

lib/onebox/templates/allowlistedgeneric.mustache

@@ -4,6 +4,7 @@
 
 {{#description}}
   <p>{{description}}</p>
+  {{> json_ld_partials/movie}}
 {{/description}}
 
 {{#data_1}}

lib/onebox/templates/json_ld_partials/movie.mustache

@@ -0,0 +1,6 @@
+{{#rating}}
+    <p>Average Rating: {{rating}}</p>
+{{/rating}}
+{{#duration}}
+    <p>Duration: {{duration}}</p>
+{{/duration}}