Render embedded content

PostResponse::Paragraph's that are of type IFRAME have extra data in the
iframe attribute to specify what's in the iframe. Not all data is the
same, however. I've identified three types and am using the new
EmbeddedConverter class to convert them:

* EmbeddedContent, the full iframe experience
* GithubGist, because medium or github treat embeds differently for
  whatever reason
* EmbeddedLink, the old style, just a link to the content. Effectively
  a fallback

The size of the original iframe is also specified as an attribute. This
code resizes it. The resizing is determined by figuring out the
width/height ratio and setting the width to 800.

EmbeddedContent can be displayed if we have an embed.ly url, which most
iframe response data has. GitHub gists are a notable exception. Gists
instead can be embedded simply by taking the gist URL and attaching .js
to the end. That becomes the iframe's src attribute.

The PostResponse::Paragraph's iframe attribute is nillable. Previous
code used lots of if-statements with variable bindings to work with the
possible nil values:

```crystal
if foo = obj.nillable_value
  # obj.nillable_value was not nil and foo contains the value
else
  # obj.nillable_value was nil so do something else
end
```

See https://crystal-lang.org/reference/syntax_and_semantics/if_var.html
for more info

In the EmbeddedConverter the monads library has been introduced to get
rid of at least one level of nillability. This wraps values in Maybe
which allows for a cleaner interface:

```crystal
Monads::Try(Value).new(->{ obj.nillable_value })
  .to_maybe
  .fmap(->(value: Value) { # do something with value })
  .value_or(# value was nil, do something else)
```

This worked to get the iframe attribute from a Paragraph:

```crystal
Monads::Try(PostResponse::IFrame).new(->{ paragraph.iframe })
  .to_maybe
  .fmap(->(iframe : PostResponse::IFrame) { # iframe is not nil! })
  .fmap(#and so on)
  .value_or(Empty.new)
```

iframe only has one attribute: mediaResource which contains the iframe
data. That was used to determine one of the three types above.

Finally, Tufte.css has options for iframes. They mostly look good except
for tweets which are too small and weirdly in the center of the page
which actually looks off-center. That's for another day though.

shard.lock

@@ -60,6 +60,10 @@ shards:
     git: https://github.com/luckyframework/lucky_task.git
     version: 0.1.0
 
+  monads:
+    git: https://github.com/alex-lairan/monads.git
+    version: 1.0.0
+
   pg:
     git: https://github.com/will/crystal-pg.git
     version: 0.23.2

shard.yml

@@ -26,6 +26,8 @@ dependencies:
   lucky_task:
     github: luckyframework/lucky_task
     version: ~> 0.1.0
+  monads:
+    github: alex-lairan/monads
 development_dependencies:
   lucky_flow:
     github: luckyframework/lucky_flow

spec/classes/embedded_converter_spec.cr

@@ -0,0 +1,99 @@
+require "../spec_helper"
+
+include Nodes
+
+describe EmbeddedConverter do
+  context "when the mediaResource has an iframeSrc value" do
+    it "returns an EmbeddedContent node" do
+      paragraph = PostResponse::Paragraph.from_json <<-JSON
+        {
+          "text": "",
+          "type": "IFRAME",
+          "href": null,
+          "layout": "INSET_CENTER",
+          "markups": [],
+          "iframe": {
+            "mediaResource": {
+              "id": "abc123",
+              "href": "https://twitter.com/user/status/1",
+              "iframeSrc": "https://cdn.embedly.com/widgets/...",
+              "iframeWidth": 500,
+              "iframeHeight": 281
+            }
+          },
+          "metadata": null
+        }
+      JSON
+
+      result = EmbeddedConverter.convert(paragraph)
+
+      result.should eq(
+        EmbeddedContent.new(
+          src: "https://cdn.embedly.com/widgets/...",
+          originalWidth: 500,
+          originalHeight: 281,
+        )
+      )
+    end
+  end
+
+  context "when the mediaResource has a blank iframeSrc value" do
+    context "and the href is unknown" do
+      it "returns an EmbeddedLink node" do
+        paragraph = PostResponse::Paragraph.from_json <<-JSON
+          {
+            "text": "",
+            "type": "IFRAME",
+            "href": null,
+            "layout": "INSET_CENTER",
+            "markups": [],
+            "iframe": {
+              "mediaResource": {
+                "id": "abc123",
+                "href": "https://example.com",
+                "iframeSrc": "",
+                "iframeWidth": 0,
+                "iframeHeight": 0
+              }
+            },
+            "metadata": null
+          }
+        JSON
+
+        result = EmbeddedConverter.convert(paragraph)
+
+        result.should eq(EmbeddedLink.new(href: "https://example.com"))
+      end
+    end
+
+    context "and the href is gist.github.com" do
+      it "returns an GithubGist node" do
+        paragraph = PostResponse::Paragraph.from_json <<-JSON
+          {
+            "text": "",
+            "type": "IFRAME",
+            "href": null,
+            "layout": "INSET_CENTER",
+            "markups": [],
+            "iframe": {
+              "mediaResource": {
+                "id": "abc123",
+                "href": "https://gist.github.com/user/someid",
+                "iframeSrc": "",
+                "iframeWidth": 0,
+                "iframeHeight": 0
+              }
+            },
+            "metadata": null
+          }
+        JSON
+
+        result = EmbeddedConverter.convert(paragraph)
+
+        result.should eq(
+          GithubGist.new(href: "https://gist.github.com/user/someid")
+        )
+      end
+    end
+  end
+end

spec/classes/paragraph_converter_spec.cr

@@ -272,7 +272,10 @@ describe ParagraphConverter do
           "markups": [],
           "iframe": {
             "mediaResource": {
-              "href": "https://example.com"
+              "href": "https://example.com",
+              "iframeSrc": "",
+              "iframeWidth": 0,
+              "iframeHeight": 0
             }
           },
           "layout": null,
@@ -312,7 +315,7 @@ describe ParagraphConverter do
         Image.new(src: "1*miroimage.png", originalWidth: 618, originalHeight: 682),
         FigureCaption.new(children: [Text.new("text")] of Child),
       ] of Child),
-      IFrame.new(href: "https://example.com"),
+      EmbeddedLink.new(href: "https://example.com"),
       MixtapeEmbed.new(children: [
         Anchor.new(
           children: [Text.new("Mixtape")] of Child,

spec/components/page_content_spec.cr

@@ -152,6 +152,24 @@ describe PageContent do
     HTML
   end
 
+  it "renders a GitHub Gist" do
+    page = Page.new(
+      title: "Title",
+      subtitle: nil,
+      author: "Author",
+      created_at: Time.local,
+      nodes: [
+        GithubGist.new(href: "https://gist.github.com/user/some_id"),
+      ] of Child
+    )
+
+    html = PageContent.new(page: page).render_to_string
+
+    html.should eq stripped_html <<-HTML
+      <script src="https://gist.github.com/user/some_id.js"></script>
+    HTML
+  end
+
   it "renders an H3" do
     page = Page.new(
       title: "Title",
@@ -210,7 +228,32 @@ describe PageContent do
     HTML
   end
 
-  it "renders an iframe container" do
+  it "renders embedded content" do
+    page = Page.new(
+      title: "Title",
+      subtitle: nil,
+      author: "Author",
+      created_at: Time.local,
+      nodes: [
+        EmbeddedContent.new(
+          src: "https://example.com",
+          originalWidth: 1000,
+          originalHeight: 600,
+        ),
+      ] of Child
+    )
+
+    html = PageContent.new(page: page).render_to_string
+
+    html.should eq stripped_html <<-HTML
+      <div class="iframe-wrapper">
+        <iframe src="https://example.com" width="800" height="480" frameborder="0" allowfullscreen="true">
+        </iframe>
+      </div>
+    HTML
+  end
+
+  it "renders an embedded link container" do
     page = Page.new(
       title: "Title",
       subtitle: nil,
@@ -218,7 +261,7 @@ describe PageContent do
       created_at: Time.local,
       nodes: [
         Paragraph.new(children: [
-          IFrame.new(href: "https://example.com"),
+          EmbeddedLink.new(href: "https://example.com"),
         ] of Child),
       ] of Child
     )

spec/models/nodes_spec.cr

@@ -1,9 +1,9 @@
 require "../spec_helper"
 
 module Nodes
-  describe IFrame do
+  describe EmbeddedLink do
     it "returns embedded url with subdomains" do
-      iframe = IFrame.new(href: "https://dev.example.com/page")
+      iframe = EmbeddedLink.new(href: "https://dev.example.com/page")
 
       iframe.domain.should eq("dev.example.com")
     end
@@ -23,4 +23,17 @@ module Nodes
       image.src.should eq("https://cdn-images-1.medium.com/fit/c/800/482/image.png")
     end
   end
+
+  describe EmbeddedContent do
+    it "adjusts the width and height proportionally" do
+      content = EmbeddedContent.new(
+        src: "https://example.com",
+        originalWidth: 1000,
+        originalHeight: 600,
+      )
+
+      content.width.should eq("800")
+      content.height.should eq("480")
+    end
+  end
 end

src/classes/embedded_converter.cr

@@ -0,0 +1,42 @@
+class EmbeddedConverter
+  include Nodes
+
+  GIST_HOST = "https://gist.github.com"
+
+  getter paragraph : PostResponse::Paragraph
+
+  def self.convert(paragraph : PostResponse::Paragraph) : Embedded | Empty
+    new(paragraph).convert
+  end
+
+  def initialize(@paragraph : PostResponse::Paragraph)
+  end
+
+  def convert : Embedded | Empty
+    Monads::Try(PostResponse::IFrame).new(->{ paragraph.iframe })
+      .to_maybe
+      .fmap(->(iframe : PostResponse::IFrame) { iframe.mediaResource })
+      .fmap(->media_to_embedded(PostResponse::MediaResource))
+      .value_or(Empty.new)
+  end
+
+  private def media_to_embedded(media : PostResponse::MediaResource) : Embedded
+    if media.iframeSrc.blank?
+      custom_embed(media)
+    else
+      EmbeddedContent.new(
+        src: media.iframeSrc,
+        originalWidth: media.iframeWidth,
+        originalHeight: media.iframeHeight
+      )
+    end
+  end
+
+  private def custom_embed(media : PostResponse::MediaResource) : Embedded
+    if media.href.starts_with?(GIST_HOST)
+      GithubGist.new(href: media.href)
+    else
+      EmbeddedLink.new(href: media.href)
+    end
+  end
+end

src/classes/paragraph_converter.cr

@@ -20,11 +20,7 @@ class ParagraphConverter
         node = Heading3.new(children: children)
       when PostResponse::ParagraphType::IFRAME
         paragraph = paragraphs.shift
-        if iframe = paragraph.iframe
+        node = EmbeddedConverter.convert(paragraph)
-          node = IFrame.new(href: iframe.mediaResource.href)
-        else
-          node = Empty.new
-        end
       when PostResponse::ParagraphType::IMG
         paragraph = paragraphs.shift
         node = convert_img(paragraph)

src/clients/medium_client.cr

@@ -43,6 +43,9 @@ class MediumClient
                 iframe {
                   mediaResource {
                     href
+                    iframeSrc
+                    iframeWidth
+                    iframeHeight
                   }
                 }
                 metadata {

src/components/page_content.cr

@@ -29,6 +29,26 @@ class PageContent < BaseComponent
     raw "<!-- a Container was rendered -->"
   end
 
+  def render_child(child : EmbeddedContent)
+    div class: "iframe-wrapper" do
+      iframe(
+        src: child.src,
+        width: child.width,
+        height: child.height,
+        frameborder: "0",
+        allowfullscreen: true,
+      )
+    end
+  end
+
+  def render_child(child : EmbeddedLink)
+    div class: "embedded" do
+      a href: child.href do
+        text "Embedded content at #{child.domain}"
+      end
+    end
+  end
+
   def render_child(node : Emphasis)
     em { render_children(node.children) }
   end
@@ -55,6 +75,10 @@ class PageContent < BaseComponent
     end
   end
 
+  def render_child(child : GithubGist)
+    script src: child.src
+  end
+
   def render_child(node : Heading2)
     h2 { render_children(node.children) }
   end
@@ -63,14 +87,6 @@ class PageContent < BaseComponent
     h3 { render_children(node.children) }
   end
 
-  def render_child(child : IFrame)
-    div class: "embedded" do
-      a href: child.href do
-        text "Embedded content at #{child.domain}"
-      end
-    end
-  end
-
   def render_child(child : Image)
     img src: child.src, width: child.width
   end

src/models/nodes.cr

@@ -1,5 +1,6 @@
 module Nodes
-  alias Leaf = Text | Image | IFrame
+  alias Embedded = EmbeddedLink | EmbeddedContent | GithubGist
+  alias Leaf = Text | Image | Embedded
   alias Child = Container | Leaf | Empty
   alias Children = Array(Child)
 
@@ -120,7 +121,40 @@ module Nodes
     end
   end
 
-  class IFrame
+  class EmbeddedContent
+    MAX_WIDTH = 800
+
+    getter src : String
+
+    def initialize(@src : String, @originalWidth : Int32, @originalHeight : Int32)
+    end
+
+    def width
+      [@originalWidth, MAX_WIDTH].min.to_s
+    end
+
+    def height
+      if @originalWidth > MAX_WIDTH
+        (@originalHeight * ratio).round.to_i.to_s
+      else
+        @originalHeight.to_s
+      end
+    end
+
+    private def ratio
+      MAX_WIDTH / @originalWidth
+    end
+
+    def ==(other : EmbeddedContent)
+      other.src == src && other.width == width && other.height == height
+    end
+
+    def empty?
+      false
+    end
+  end
+
+  class EmbeddedLink
     getter href : String
 
     def initialize(@href : String)
@@ -130,7 +164,7 @@ module Nodes
       URI.parse(href).host
     end
 
-    def ==(other : IFrame)
+    def ==(other : EmbeddedLink)
       other.href == href
     end
 
@@ -171,4 +205,21 @@ module Nodes
       false
     end
   end
+
+  class GithubGist
+    def initialize(@href : String)
+    end
+
+    def src
+      "#{@href}.js"
+    end
+
+    def ==(other : GithubGist)
+      other.src == src
+    end
+
+    def empty?
+      false
+    end
+  end
 end

src/models/post_response.cr

@@ -82,6 +82,9 @@ class PostResponse
 
   class MediaResource < Base
     property href : String
+    property iframeSrc : String
+    property iframeWidth : Int32
+    property iframeHeight : Int32
   end
 
   class Metadata < Base

src/shards.cr

@@ -7,3 +7,4 @@ require "avram"
 require "lucky"
 require "carbon"
 require "authentic"
+require "monads"