improvement: wrap up initial ash_blog behavior

lib/ash_blog.ex

@@ -2,4 +2,67 @@ defmodule AshBlog do
   @moduledoc """
   Documentation for `AshBlog`.
   """
+
+  import XmlBuilder
+
+  def rss_feed(blog_posts, opts \\ []) do
+    blog_posts = Enum.filter(blog_posts, &(&1.state == :published))
+
+    element(
+      :feed,
+      %{xmlns: "http://www.w3.org/2005/Atom"},
+      [
+        element(:title, "Ash Framework Blog"),
+        element(:link, "https://ash-hq.org/blog"),
+        element(
+          :description,
+          "News and information about Ash Framework, a declarative, resource oriented Elixir application development framework."
+        )
+      ] ++
+        Enum.map(blog_posts, fn %resource{} = blog_post ->
+          data = [
+            title: Map.get(blog_post, AshBlog.DataLayer.Info.title_attribute(resource))
+          ]
+
+          data =
+            if opts[:linker] do
+              Keyword.put(data, :link, opts[:linker].(blog_post))
+            else
+              data
+            end
+
+          inners =
+            if opts[:html_body] do
+              [element(:content, %{type: "html"}, {:cdata, opts[:html_body].(blog_post)})]
+            else
+              []
+            end
+
+          inners =
+            if opts[:summary] do
+              [element(:summary, %{type: "html"}, {:cdata, opts[:summary].(blog_post)}) | inners]
+            else
+              inners
+            end
+
+          inners =
+            if opts[:author] do
+              [element(:author, name: opts[:author].(blog_post)) | inners]
+            else
+              inners
+            end
+
+          data =
+            Keyword.put(
+              data,
+              :id,
+              Ash.Resource.Info.primary_key(resource)
+              |> Enum.map_join("-", &to_string(Map.get(blog_post, &1)))
+            )
+
+          element(:item, data, inners)
+        end)
+    )
+    |> XmlBuilder.generate()
+  end
 end

lib/data_layer/changes/set_and_track_slug.ex

@@ -0,0 +1,45 @@
+defmodule AshBlog.DataLayer.Changes.SetAndTrackSlug do
+  use Ash.Resource.Change
+
+  def change(changeset, _, _) do
+    slug_attribute = AshBlog.DataLayer.Info.slug_attribute(changeset.resource)
+
+    if changeset.action_type == :create do
+      if Ash.Changeset.get_attribute(changeset, :slug) do
+        changeset
+      else
+        set_default_slug(changeset, slug_attribute)
+      end
+    else
+      if Ash.Changeset.changing_attribute?(changeset, slug_attribute) && changeset.data.slug do
+        past_slugs = Ash.Changeset.get_attribute(changeset, :past_slugs) || []
+
+        Ash.Changeset.force_change_attribute(changeset, :past_slugs, [
+          changeset.data.slug | past_slugs
+        ])
+      else
+        changeset
+      end
+    end
+  end
+
+  defp set_default_slug(changeset, slug_attribute) do
+    title_attribute = AshBlog.DataLayer.Info.title_attribute(changeset.resource)
+
+    Ash.Changeset.force_change_attribute(
+      changeset,
+      slug_attribute,
+      to_slug(Ash.Changeset.get_attribute(changeset, title_attribute))
+    )
+  end
+
+  defp to_slug(nil), do: nil
+
+  defp to_slug(title) do
+    title
+    |> String.replace(~r/\s+/, " ")
+    |> String.replace(" ", "-")
+    |> String.replace(~r/[^A-Za-z0-9-]/, "")
+    |> String.downcase()
+  end
+end

lib/data_layer/data_layer.ex

@@ -41,6 +41,12 @@ defmodule AshBlog.DataLayer do
         doc:
           "The attribute name to use for the body of the post. Wil be created if it doesn't exist."
       ],
+      slug_attribute: [
+        type: :atom,
+        default: :slug,
+        doc:
+          "The attribute name to use for the slug. All past slugs will be stored and used when looking up by slug."
+      ],
       folder: [
         type: :string,
         default: "blog/published",
@@ -468,7 +474,9 @@ defmodule AshBlog.DataLayer do
     |> Ash.Resource.Info.attributes()
     |> Enum.reject(&(&1.name == body_attribute))
     |> Enum.reduce_while({:ok, []}, fn attr, {:ok, acc} ->
-      if Ash.Type.storage_type(attr.type) in [
+      storage_type = Ash.Type.storage_type(unwrap_array(attr.type))
+
+      if storage_type in [
            :string,
            :integer,
            :uuid,
@@ -483,7 +491,9 @@ defmodule AshBlog.DataLayer do
             {:halt, {:error, error}}
         end
       else
-        {:halt, {:error, "#{inspect(attr.type)} is not yet supported by `AshBlog.DataLayer`"}}
+        {:halt,
+         {:error,
+          "#{inspect(attr.type)} with storage type #{inspect(storage_type)} is not yet supported by `AshBlog.DataLayer`"}}
       end
     end)
     |> case do
@@ -492,16 +502,7 @@ defmodule AshBlog.DataLayer do
          attrs
          |> Enum.reverse()
          |> Enum.map_join("\n", fn {name, value} ->
-           case value do
-             value when is_binary(value) ->
-               "#{name}: '#{escape_string(value)}'"
-
-             %DateTime{} = value ->
-               "#{name}: '#{escape_string(value)}'"
-
-             other ->
-               "#{name}: #{other}"
-           end
+           "#{name}: #{encode(value)}"
          end)}
 
       {:error, error} ->
@@ -509,6 +510,34 @@ defmodule AshBlog.DataLayer do
     end
   end
 
+  def encode(value, indentation \\ 2) do
+    case value do
+      value when is_binary(value) ->
+        "'#{escape_string(value)}'"
+
+      %DateTime{} = value ->
+        "'#{escape_string(value)}'"
+
+      [] ->
+        "[]"
+
+      list when is_list(value) ->
+        "\n#{listify(list, indentation)}"
+
+      other ->
+        to_string(other)
+    end
+  end
+
+  def listify(value, indentation \\ 2) do
+    Enum.map_join(value, "\n", fn value ->
+      "#{String.duplicate(" ", indentation)}- #{encode(value, indentation + 2)}"
+    end)
+  end
+
+  defp unwrap_array({:array, value}), do: unwrap_array(value)
+  defp unwrap_array(value), do: value
+
   defp escape_string(value) do
     value
     |> to_string()
@@ -647,7 +676,7 @@ defmodule AshBlog.DataLayer do
 
     all_in_transaction(tx_identifiers, fn ->
       try do
-        fun.()
+        {:ok, fun.()}
       catch
         {{:blog_rollback, rolled_back_tx_identifiers}, value} = thrown ->
           if Enum.any?(tx_identifiers, &(&1 in rolled_back_tx_identifiers)) do
@@ -660,7 +689,7 @@ defmodule AshBlog.DataLayer do
   end
 
   defp all_in_transaction([], fun) do
-    {:ok, fun.()}
+    fun.()
   end
 
   defp all_in_transaction([tx_identifier | rest], fun) do

lib/data_layer/info.ex

@@ -29,6 +29,10 @@ defmodule AshBlog.DataLayer.Info do
     Extension.get_opt(resource, [:blog], :body_attribute, :body)
   end
 
+  def slug_attribute(resource) do
+    Extension.get_opt(resource, [:blog], :slug_attribute, :slug)
+  end
+
   def title_attribute(resource) do
     Extension.get_opt(resource, [:blog], :title_attribute, :title)
   end

lib/data_layer/transformers/add_structure.ex

@@ -9,21 +9,39 @@ defmodule AshBlog.DataLayer.Transformers.AddStructure do
     |> Ash.Resource.Builder.add_new_attribute(Info.title_attribute(dsl_state), :string,
       allow_nil?: false
     )
+    |> Ash.Resource.Builder.add_new_attribute(Info.slug_attribute(dsl_state), :string,
+      allow_nil?: false
+    )
+    |> Ash.Resource.Builder.add_new_attribute(:past_slugs, {:array, :string},
+      allow_nil?: false,
+      default: [],
+      writable?: false
+    )
     |> Ash.Resource.Builder.add_new_attribute(Info.body_attribute(dsl_state), :string,
       allow_nil?: false
     )
     |> Ash.Resource.Builder.add_new_attribute(:state, :atom,
       constraints: [one_of: [:staged, :published, :archived]],
-      default: :staged
+      default: :staged,
+      writable?: false
+    )
+    |> Ash.Resource.Builder.add_new_attribute(:published_at, :utc_datetime_usec, writable?: false)
+    |> Ash.Resource.Builder.add_change(AshBlog.DataLayer.Changes.SetAndTrackSlug,
+      on: [:create, :update]
     )
     |> Ash.Resource.Builder.add_new_action(:update, :publish,
+      accept: [],
       changes: [
         Ash.Resource.Builder.build_action_change(
           Ash.Resource.Change.Builtins.set_attribute(:state, :published)
+        ),
+        Ash.Resource.Builder.build_action_change(
+          Ash.Resource.Change.Builtins.set_attribute(:published_at, &DateTime.utc_now/0)
         )
       ]
     )
     |> Ash.Resource.Builder.add_new_action(:update, :stage,
+      accept: [],
       changes: [
         Ash.Resource.Builder.build_action_change(
           Ash.Resource.Change.Builtins.set_attribute(:state, :staged)
@@ -31,6 +49,7 @@ defmodule AshBlog.DataLayer.Transformers.AddStructure do
       ]
     )
     |> Ash.Resource.Builder.add_new_action(:update, :archive,
+      accept: [],
       changes: [
         Ash.Resource.Builder.build_action_change(
           Ash.Resource.Change.Builtins.set_attribute(:state, :archived)

mix.exs

@@ -109,9 +109,10 @@ defmodule AshBlog.MixProject do
   # Run "mix help deps" to learn about dependencies.
   defp deps do
     [
-      {:ash, github: "ash-project/ash"},
-      # {:ash, path: "../ash"},
+      # {:ash, github: "ash-project/ash"},
+      {:ash, path: "../ash"},
       {:yaml_elixir, "~> 2.9"},
+      {:xml_builder, "~> 2.2"},
 
       # dev/test dependencies
       {:elixir_sense,

mix.lock

@@ -33,14 +33,16 @@
   "parse_trans": {:hex, :parse_trans, "3.3.1", "16328ab840cc09919bd10dab29e431da3af9e9e7e7e6f0089dd5a2d2820011d8", [:rebar3], [], "hexpm", "07cd9577885f56362d414e8c4c4e6bdf10d43a8767abb92d24cbe8b24c54888b"},
   "picosat_elixir": {:hex, :picosat_elixir, "0.2.2", "1cacfdb4fb0c3ead5e5e9b1e98ac822a777f07eab35e29c3f8fc7086de2bfb36", [:make, :mix], [{:elixir_make, "~> 0.6", [hex: :elixir_make, repo: "hexpm", optional: false]}], "hexpm", "9d0cc569552cca417abea8270a54b71153a63be4b951ff249e94642f1c0f35d1"},
   "providers": {:hex, :providers, "1.8.1", "70b4197869514344a8a60e2b2a4ef41ca03def43cfb1712ecf076a0f3c62f083", [:rebar3], [{:getopt, "1.0.1", [hex: :getopt, repo: "hexpm", optional: false]}], "hexpm", "e45745ade9c476a9a469ea0840e418ab19360dc44f01a233304e118a44486ba0"},
+  "rss": {:hex, :rss, "0.2.1", "034f2fe5250a490862e692eb34a31bb5c142913c2fe0fb093e1fd982f010e15d", [:mix], [], "hexpm", "1af49c787fc789740a0fa7e0e197a7cb779a63c4eb703f013fea400126eac1f2"},
   "sobelow": {:hex, :sobelow, "0.11.1", "23438964486f8112b41e743bbfd402da3e5b296fdc9eacab29914b79c48916dd", [:mix], [{:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "9897363a7eff96f4809304a90aad819e2ad5e5d24db547af502885146746a53c"},
   "sourceror": {:hex, :sourceror, "0.11.2", "549ce48be666421ac60cfb7f59c8752e0d393baa0b14d06271d3f6a8c1b027ab", [:mix], [], "hexpm", "9ab659118896a36be6eec68ff7b0674cba372fc8e210b1e9dc8cf2b55bb70dfb"},
-  "spark": {:hex, :spark, "0.2.3", "3678177ca1f1f4c7919da90b49f5e378c39e1bdf2f59ad8909c0c3591fe8dbb6", [:mix], [{:nimble_options, "~> 0.4.0", [hex: :nimble_options, repo: "hexpm", optional: false]}, {:sourceror, "~> 0.1", [hex: :sourceror, repo: "hexpm", optional: false]}], "hexpm", "933dadc7fcce93198104e7d88243772bbde9e54b001929a4c04bc733812e8e3b"},
+  "spark": {:hex, :spark, "0.2.6", "84dbfe7153dc51f988a2b43f28031be87dee724d2ac535069d05807cfacde7c4", [:mix], [{:nimble_options, "~> 0.4.0", [hex: :nimble_options, repo: "hexpm", optional: false]}, {:sourceror, "~> 0.1", [hex: :sourceror, repo: "hexpm", optional: false]}], "hexpm", "f0fba891abc70d4e7431b3ed6283ee46ccd6e8045e0bfdce13bc06e8904bbd25"},
   "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.6", "cf344f5692c82d2cd7554f5ec8fd961548d4fd09e7d22f5b62482e5aeaebd4b0", [:make, :mix, :rebar3], [], "hexpm", "bdb0d2471f453c88ff3908e7686f86f9be327d065cc1ec16fa4540197ea04680"},
   "stream_data": {:hex, :stream_data, "0.5.0", "b27641e58941685c75b353577dc602c9d2c12292dd84babf506c2033cd97893e", [:mix], [], "hexpm", "012bd2eec069ada4db3411f9115ccafa38540a3c78c4c0349f151fc761b9e271"},
   "telemetry": {:hex, :telemetry, "1.1.0", "a589817034a27eab11144ad24d5c0f9fab1f58173274b1e9bae7074af9cbee51", [:rebar3], [], "hexpm", "b727b2a1f75614774cff2d7565b64d0dfa5bd52ba517f16543e6fc7efcc0df48"},
   "typable": {:hex, :typable, "0.3.0", "0431e121d124cd26f312123e313d2689b9a5322b15add65d424c07779eaa3ca1", [:mix], [], "hexpm", "880a0797752da1a4c508ac48f94711e04c86156f498065a83d160eef945858f8"},
   "unicode_util_compat": {:hex, :unicode_util_compat, "0.7.0", "bc84380c9ab48177092f43ac89e4dfa2c6d62b40b8bd132b1059ecc7232f9a78", [:rebar3], [], "hexpm", "25eee6d67df61960cf6a794239566599b09e17e668d3700247bc498638152521"},
+  "xml_builder": {:hex, :xml_builder, "2.2.0", "cc5f1eeefcfcde6e90a9b77fb6c490a20bc1b856a7010ce6396f6da9719cbbab", [:mix], [], "hexpm", "9d66d52fb917565d358166a4314078d39ef04d552904de96f8e73f68f64a62c9"},
   "yamerl": {:hex, :yamerl, "0.10.0", "4ff81fee2f1f6a46f1700c0d880b24d193ddb74bd14ef42cb0bcf46e81ef2f8e", [:rebar3], [], "hexpm", "346adb2963f1051dc837a2364e4acf6eb7d80097c0f53cbdc3046ec8ec4b4e6e"},
   "yaml_elixir": {:hex, :yaml_elixir, "2.9.0", "9a256da867b37b8d2c1ffd5d9de373a4fda77a32a45b452f1708508ba7bbcb53", [:mix], [{:yamerl, "~> 0.10", [hex: :yamerl, repo: "hexpm", optional: false]}], "hexpm", "0cb0e7d4c56f5e99a6253ed1a670ed0e39c13fc45a6da054033928607ac08dfc"},
 }

test/ash_blog_test.exs

@@ -24,6 +24,13 @@ defmodule AshBlogTest do
     end
   end
 
+  describe "slug" do
+    test "a slug is auto generated" do
+      Post.create!("first", "the body") |> IO.inspect()
+      Post.read!()
+    end
+  end
+
   describe "updating blog posts" do
     test "blog posts can be published" do
       post = Post.create!("first\"", "the body")

test/support/blog/post.ex

@@ -5,7 +5,7 @@ defmodule AshBlog.Test.Post do
     data_layer: AshBlog.DataLayer
 
   actions do
-    defaults [:create, :read]
+    defaults [:create, :read, :update]
   end
 
   attributes do