Serve an ATOM feed (#9)

Dockerfile

@@ -25,14 +25,16 @@ RUN crystal build src/crankypants_cli.cr -o ./crankypants --release --no-debug
 RUN strip crankypants
 
 # We use this to identify dependencies used later:
-# RUN crystal run ./support/list-deps.cr -- ./crankypants
+RUN crystal run ./support/list-deps.cr -- ./crankypants
 
 # Finally, let's build the actual Docker image... from scratch.
 FROM scratch
 
 # We'll copy over our dependencies from the previously used crystal container.
 # If we ever need to refresh this list, uncomment the `crystal run` line found
 # above.
+COPY --from=crystal /usr/lib/x86_64-linux-gnu/libxml2.so.2 /usr/lib/x86_64-linux-gnu/libxml2.so.2
+COPY --from=crystal /usr/lib/x86_64-linux-gnu/libxml2.so.2.9.3 /usr/lib/x86_64-linux-gnu/libxml2.so.2.9.3
 COPY --from=crystal /lib/x86_64-linux-gnu/libz.so.1 /lib/x86_64-linux-gnu/libz.so.1
 COPY --from=crystal /lib/x86_64-linux-gnu/libz.so.1.2.8 /lib/x86_64-linux-gnu/libz.so.1.2.8
 COPY --from=crystal /lib/x86_64-linux-gnu/libssl.so.1.0.0 /lib/x86_64-linux-gnu/libssl.so.1.0.0
@@ -56,6 +58,15 @@ COPY --from=crystal /lib/x86_64-linux-gnu/libc.so.6 /lib/x86_64-linux-gnu/libc.s
 COPY --from=crystal /lib/x86_64-linux-gnu/libc-2.23.so /lib/x86_64-linux-gnu/libc-2.23.so
 COPY --from=crystal /lib64/ld-linux-x86-64.so.2 /lib64/ld-linux-x86-64.so.2
 COPY --from=crystal /lib/x86_64-linux-gnu/ld-2.23.so /lib/x86_64-linux-gnu/ld-2.23.so
+COPY --from=crystal /usr/lib/x86_64-linux-gnu/libicuuc.so.55 /usr/lib/x86_64-linux-gnu/libicuuc.so.55
+COPY --from=crystal /usr/lib/x86_64-linux-gnu/libicuuc.so.55.1 /usr/lib/x86_64-linux-gnu/libicuuc.so.55.1
+COPY --from=crystal /lib/x86_64-linux-gnu/liblzma.so.5 /lib/x86_64-linux-gnu/liblzma.so.5
+COPY --from=crystal /lib/x86_64-linux-gnu/liblzma.so.5.0.0 /lib/x86_64-linux-gnu/liblzma.so.5.0.0
+COPY --from=crystal /usr/lib/x86_64-linux-gnu/libicudata.so.55 /usr/lib/x86_64-linux-gnu/libicudata.so.55
+COPY --from=crystal /usr/lib/x86_64-linux-gnu/libicudata.so.55.1 /usr/lib/x86_64-linux-gnu/libicudata.so.55.1
+COPY --from=crystal /usr/lib/x86_64-linux-gnu/libstdc++.so.6 /usr/lib/x86_64-linux-gnu/libstdc++.so.6
+COPY --from=crystal /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.21 /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.21
+
 COPY --from=crystal /work/crankypants /crankypants
 
 EXPOSE 3000

crappy/src/crappy.cr

@@ -1,6 +1,7 @@
 require "http/server"
 require "http/request"
 require "json"
+require "xml"
 
 module Crappy
   class Handler(T)
@@ -30,7 +31,7 @@ module Crappy
 
     abstract def call
 
-    private def render(object = nil, text = nil, html = nil, json = nil, content_type = nil, status = 200)
+    private def render(object = nil, text = nil, html = nil, json = nil, xml = nil, content_type = nil, status = 200)
       response.status_code  = status if status
       response.content_type = content_type if content_type
 
@@ -45,6 +46,9 @@ module Crappy
       elsif json
         response.content_type = content_type || "application/json"
         response << json.to_json
+      elsif xml
+        response.content_type = content_type || "application/xml"
+        response << xml
       elsif object
         response << object
       end

spec/ext/uri_spec.cr

@@ -0,0 +1,14 @@
+require "spec"
+require "../../src/ext/uri"
+
+describe "URI Extensions" do
+  describe "URI.join" do
+    it "replaces the path part if only a path is given" do
+      URI.join("http://foo.com/foo", "/bar").to_s.should eq("http://foo.com/bar")
+    end
+
+    it "replaces the full URI if the second URI is fully qualified" do
+      URI.join("http://foo.com/foo", "http://bar.com/bar").to_s.should eq("http://bar.com/bar")
+    end
+  end
+end

src/crankypants.cr

@@ -1,4 +1,5 @@
 require "habitat"
+require "./ext/*"
 require "./crankypants/migrator"
 
 module Crankypants

src/crankypants/data.cr

@@ -12,8 +12,12 @@ module Crankypants
       Repo.aggregate(Post, :count, :id).as(Int64)
     end
 
-    def self.load_posts
-      Repo.all(Post, Query.order_by("created_at DESC"))
+    def self.load_posts(limit : Int32? = nil)
+      query = Query
+        .order_by("created_at DESC")
+        .limit(limit)
+
+      Repo.all(Post, query)
     end
 
     def self.load_post(id : Int32)

src/crankypants/web/routers/blog.cr

@@ -1,4 +1,6 @@
 require "crappy"
+require "../../../tools/atom_feed"
+require "../helpers"
 
 module Crankypants::Web::Routers
   class Blog < Crappy::Router
@@ -9,6 +11,35 @@ module Crankypants::Web::Routers
         render html: PostView.index(Data.load_posts)
       end
 
+      get "posts.atom" do
+        uri = URI.parse("http://#{request.host_with_port}/")
+        posts = Data.load_posts(limit: 15)
+
+        feed = ATOM.build do |feed|
+          feed.title   Crankypants.settings.site_title
+          feed.link    URI.join(uri, "/").to_s
+          feed.id      URI.join(uri, "/").to_s
+          feed.updated posts.map { |p| p.updated_at.not_nil! }.max
+
+          feed.author do |author|
+            author.name Crankypants.settings.site_title
+            author.uri  URI.join(uri, "/").to_s
+          end
+
+          posts.each do |post|
+            feed.entry do |entry|
+              entry.id      URI.join(uri, post.url).to_s
+              entry.title   post.title.presence || "Post from #{post.created_at}"
+              entry.link    URI.join(uri, post.url).to_s
+              entry.updated post.updated_at || Time.now
+              entry.content post.body_html || ""
+            end
+          end
+        end
+
+        render xml: feed
+      end
+
       within "posts" do
         get :id do |params|
           post_id = params["id"].not_nil!.to_i

src/crankypants/web/views/layouts/blog.slang

@@ -5,6 +5,7 @@ html
     meta charset="utf-8"
     title = page_title
     link rel="stylesheet" type="text/css" href="#{asset_url("blog.css")}"
+    link rel="alternate" type="application/atom+xml" title="ATOM Feed" href="/posts.atom" />
     script type="application/javascript" src="#{asset_url("blog-bundle.js")}" defer=true
   body
     header role="main"

src/ext/presence.cr

@@ -0,0 +1,11 @@
+struct Nil
+  def presence
+    nil
+  end
+end
+
+class String
+  def presence
+    blank? ? nil : self
+  end
+end

src/ext/time.cr

@@ -0,0 +1,5 @@
+struct Time
+  def to_iso8601
+    to_s("%FT%X%:z")
+  end
+end

src/ext/uri.cr

@@ -0,0 +1,18 @@
+require "uri"
+
+class URI
+  def self.join(origin : URI | String, other : URI | String)
+    origin = URI.parse(origin) unless origin.is_a?(URI)
+    other  = URI.parse(other)  unless other.is_a?(URI)
+
+    origin.dup.tap do |result|
+      result.path = other.path
+
+      if other.host
+        result.scheme = other.scheme
+        result.host = other.host
+        result.port = other.port
+      end
+    end
+  end
+end

src/tools/README.md

@@ -0,0 +1,2 @@
+This directory contains various bits and pieces that are prime candidates
+for extraction into actual shards later on.

src/tools/atom_feed.cr

@@ -0,0 +1,105 @@
+# Here's a little ATOM module that we could eventually extract
+# into a shard. Woohoo!
+module ATOM
+  def self.build
+    output = String::Builder.new
+    xml = XML::Builder.new(output)
+    xml.indent = 2
+
+    ATOM::FeedBuilder.new(xml).build do |feed|
+      yield feed
+    end
+
+    output.to_s
+  end
+
+
+  module Shortcuts
+    def field(name : String, value : String? = nil, **opts)
+      @xml.element(name, **opts) do
+        if value
+          @xml.text value
+        end
+      end
+    end
+
+    def text_field(name : String, value : String, **opts)
+      field name, value, **opts
+    end
+  end
+
+  module CommonBuilderMethods
+    include Shortcuts
+
+    def id(id : String)
+      text_field "id", id
+    end
+
+    def title(title : String)
+      text_field "title", title
+    end
+
+    def link(url : String)
+      return if url.nil? || url.blank?
+      field "link", href: url, rel: "self"
+    end
+
+    def updated(t : Time)
+      return if t.nil?
+      text_field "updated", t.to_iso8601
+    end
+
+    def author
+      @xml.element "author" do
+        yield PersonBuilder.new(@xml)
+      end
+    end
+  end
+
+  class FeedBuilder
+    include CommonBuilderMethods
+
+    def initialize(@xml : XML::Builder)
+    end
+
+    def build
+      @xml.document do
+        @xml.element "feed", xmlns: "http://www.w3.org/2005/Atom" do
+          yield self
+        end
+      end
+    end
+
+    def entry
+      @xml.element "entry" do
+        yield EntryBuilder.new(@xml)
+      end
+    end
+  end
+
+  class EntryBuilder
+    include CommonBuilderMethods
+
+    def initialize(@xml : XML::Builder)
+    end
+
+    def content(html : String)
+      field "content", html, type: "html"
+    end
+  end
+
+  class PersonBuilder
+    include Shortcuts
+
+    def initialize(@xml : XML::Builder)
+    end
+
+    def name(name : String)
+      text_field "name", name
+    end
+
+    def uri(uri : String)
+      text_field "uri", uri
+    end
+  end
+end

support/list-deps.cr

@@ -28,8 +28,8 @@ puts
 puts "=" * 30
 puts "FROM scratch"
 deps.each do |dep|
-  puts "COPY --from=0 #{dep} #{dep}"
+  puts "COPY --from=crystal #{dep} #{dep}"
 end
-puts "COPY --from=0 #{executable} /#{File.basename(executable)}"
+puts "COPY --from=crystal #{executable} /#{File.basename(executable)}"
 puts "ENTRYPOINT [\"/#{File.basename(executable)}\"]"
 puts "=" * 30