Add support for missing posts

Posts, like 8661f4724aa9, can go missing if the account or post was
removed. In this case, the API returns data like this:

```json
{
  "data": {
    "post": null
  }
}
```

When this happens, we can detect it because the parsed response now has
a nil value: `response.data.post == nil` and construct an `EmptyPage`
instead of a `Page`. The `Articles::Show` action can then render
conditionally based on if the response from `PageConverter` is a `Page`
or an `EmptyPage`.

CHANGELOG

@@ -1,5 +1,9 @@
 2022-05-21
 
+* Show error page for missing posts
+
+2022-05-21
+
 * Remove the need for a fake DATABASE_URL
 
 2022-04-04

spec/actions/articles/show_spec.cr

@@ -0,0 +1,15 @@
+require "../../spec_helper"
+
+include ActionHelpers
+
+describe Articles::Show do
+  context "if the article is missing" do
+    it "should raise a MissingPageError" do
+      context = action_context(path: "/abc123")
+
+      expect_raises(MissingPageError) do
+        Articles::Show.new(context, params).call
+      end
+    end
+  end
+end

spec/classes/page_converter_spec.cr

@@ -17,8 +17,8 @@ describe PageConverter do
         }
       ]
     JSON
-    data_json = default_data_json(title, paragraph_json)
+    data_json = default_post_json(title, paragraph_json)
-    data = PostResponse::Data.from_json(data_json)
+    data = PostResponse::Post.from_json(data_json)
 
     page = PageConverter.new.convert(data)
 
@@ -26,9 +26,8 @@ describe PageConverter do
   end
 
   it "sets the author" do
-    data_json = <<-JSON
+    post_json = <<-JSON
       {
-        "post": {
         "title": "This is a story",
         "createdAt": 0,
         "creator": {
@@ -41,20 +40,18 @@ describe PageConverter do
           }
         }
       }
-      }
     JSON
-    data = PostResponse::Data.from_json(data_json)
+    post = PostResponse::Post.from_json(post_json)
 
-    page = PageConverter.new.convert(data)
+    page = PageConverter.new.convert(post)
 
     page.author.name.should eq "Author"
     page.author.id.should eq "abc123"
   end
 
   it "sets the publish date/time" do
-    data_json = <<-JSON
+    post_json = <<-JSON
       {
-        "post": {
         "title": "This is a story",
         "createdAt": 1000,
         "creator": {
@@ -67,11 +64,10 @@ describe PageConverter do
           }
         }
       }
-      }
     JSON
-    data = PostResponse::Data.from_json(data_json)
+    post = PostResponse::Post.from_json(post_json)
 
-    page = PageConverter.new.convert(data)
+    page = PageConverter.new.convert(post)
 
     page.created_at.should eq Time.utc(1970, 1, 1, 0, 0, 1)
   end
@@ -98,8 +94,8 @@ describe PageConverter do
         }
       ]
     JSON
-    data_json = default_data_json(title, paragraph_json)
+    post_json = default_post_json(title, paragraph_json)
-    data = PostResponse::Data.from_json(data_json)
+    data = PostResponse::Post.from_json(post_json)
 
     page = PageConverter.new.convert(data)
 
@@ -115,13 +111,12 @@ def default_paragraph_json
   "[]"
 end
 
-def default_data_json(
+def default_post_json(
   title : String = "This is a story",
   paragraph_json : String = default_paragraph_json
 )
   <<-JSON
     {
-      "post": {
       "title": "#{title}",
       "createdAt": 1628974309758,
       "creator": {
@@ -134,6 +129,5 @@ def default_data_json(
         }
       }
     }
-    }
   JSON
 end

spec/setup/clean_database.cr

@@ -1,3 +0,0 @@
-Spec.before_each do
-  AppDatabase.truncate
-end

spec/support/action_helpers.cr

@@ -0,0 +1,12 @@
+module ActionHelpers
+  private def action_context(path = "/")
+    io = IO::Memory.new
+    request = HTTP::Request.new("GET", path)
+    response = HTTP::Server::Response.new(io)
+    HTTP::Server::Context.new(request, response)
+  end
+
+  private def params
+    {} of String => String
+  end
+end

src/actions/articles/show.cr

@@ -6,8 +6,8 @@ class Articles::Show < BrowserAction
     case post_id
     in Monads::Just
       response = client_class.post_data(post_id.value!)
-      page = PageConverter.new.convert(response.data)
+      page = PageConverter.new.convert(response.data.post)
-      html ShowPage, page: page
+      render_page(page)
     in Monads::Nothing, Monads::Maybe
       html(
         Errors::ParseErrorPage,
@@ -18,6 +18,14 @@ class Articles::Show < BrowserAction
     end
   end
 
+  def render_page(page : Page)
+    html ShowPage, page: page
+  end
+
+  def render_page(page : MissingPage)
+    raise MissingPageError.new
+  end
+
   def client_class
     if use_local?
       LocalClient

src/actions/errors/show.cr

@@ -4,6 +4,10 @@ class Errors::Show < Lucky::ErrorAction
   default_format :html
   dont_report [Lucky::RouteNotFoundError, Avram::RecordNotFoundError]
 
+  def render(error : MissingPageError)
+    error_html message: "This article is missing.", status: 404
+  end
+
   def render(error : Lucky::RouteNotFoundError | Avram::RecordNotFoundError)
     if html?
       error_html "Sorry, we couldn't find that page.", status: 404

src/classes/page_converter.cr

@@ -1,20 +1,24 @@
 class PageConverter
-  def convert(data : PostResponse::Data) : Page
+  def convert(post : PostResponse::Post) : Page
-    title, content = title_and_content(data)
+    title, content = title_and_content(post)
-    author = data.post.creator
+    author = post.creator
-    created_at = Time.unix_ms(data.post.createdAt)
+    created_at = Time.unix_ms(post.createdAt)
     gist_store = gist_store(content)
     Page.new(
       title: title,
       author: author,
-      created_at: Time.unix_ms(data.post.createdAt),
+      created_at: Time.unix_ms(post.createdAt),
       nodes: ParagraphConverter.new.convert(content, gist_store)
     )
   end
 
-  def title_and_content(data : PostResponse::Data) : {String, Array(PostResponse::Paragraph)}
+  def convert(post : Nil) : MissingPage
-    title = data.post.title
+    MissingPage.new
-    paragraphs = data.post.content.bodyModel.paragraphs
+  end
+
+  def title_and_content(post : PostResponse::Post) : {String, Array(PostResponse::Paragraph)}
+    title = post.title
+    paragraphs = post.content.bodyModel.paragraphs
     non_content_paragraphs = paragraphs.reject { |para| para.text == title }
     {title, non_content_paragraphs}
   end

src/models/missing_page.cr

@@ -0,0 +1,5 @@
+class MissingPage
+end
+
+class MissingPageError < Exception
+end

src/models/post_response.cr

@@ -8,7 +8,7 @@ class PostResponse
   end
 
   class Data < Base
-    property post : Post
+    property post : Post?
   end
 
   class Post < Base

src/version.cr

@@ -1,3 +1,3 @@
 module Scribe
-  VERSION = "2022-05-21"
+  VERSION = "2022-06-17"
 end