Remember microprint state on reload

app/lib/firehose_web/live/microprints_live.ex

@@ -7,8 +7,8 @@ defmodule FirehoseWeb.MicroprintsLive do
   @source_dirs ["app", "blogex"]
 
   @impl true
-  def mount(_params, _session, socket) do
-    files = scan_source_files()
+  def mount(params, _session, socket) do
+    files = scan_source_files_with_dir()
 
     microprints =
       files
@@ -18,9 +18,7 @@ defmodule FirehoseWeb.MicroprintsLive do
      socket
      |> assign(:page_title, "Microprints")
      |> assign(:microprints, microprints)
-     |> assign(:expanded_path, nil)
-     |> assign(:highlighted_path, nil)
-     |> assign(:highlighted_line, nil)}
+     |> restore_state_from_params(params)}
   rescue
     e ->
       {:ok,
@@ -28,11 +26,17 @@ defmodule FirehoseWeb.MicroprintsLive do
        |> assign(:page_title, "Microprints")
        |> assign(:microprints, [])
        |> assign(:expanded_path, nil)
+       |> assign(:source_content, nil)
        |> assign(:highlighted_path, nil)
        |> assign(:highlighted_line, nil)
        |> put_flash(:error, "Error loading microprints: #{inspect(e)}")}
   end
 
+  @impl true
+  def handle_params(params, _uri, socket) do
+    {:noreply, restore_state_from_params(socket, params)}
+  end
+
   @impl true
   def render(assigns) do
     ~H"""
@@ -46,7 +50,7 @@ defmodule FirehoseWeb.MicroprintsLive do
       <.microprint_legend />
 
       <div class="grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 gap-6 mt-6">
-        <%= for %{path: path, microprint: microprint, source: source} = item <- @microprints do %>
+        <%= for %{path: path, microprint: microprint, source_dir: _source_dir} = item <- @microprints do %>
           {error = item[:error]}
           <div class="card bg-base-100 shadow-sm border border-zinc-200">
             <div class="card-body p-4">
@@ -76,8 +80,8 @@ defmodule FirehoseWeb.MicroprintsLive do
                   highlighted_line={@highlighted_line}
                 />
 
-                <%= if @expanded_path == path and source do %>                  <.source_viewer
-                    content={source}
+                <%= if @expanded_path == path and @source_content do %>                  <.source_viewer
+                    source_content={@source_content}
                     highlighted_line={@highlighted_line}
                     language="elixir"
                     file_path={path}
@@ -111,11 +115,14 @@ defmodule FirehoseWeb.MicroprintsLive do
         _ -> nil
       end
 
-    {:noreply,
+    socket =
       socket
       |> assign(:highlighted_path, path)
       |> assign(:highlighted_line, highlighted)
-     |> assign(:expanded_path, expanded)}
+      |> assign(:expanded_path, expanded)
+      |> assign(:source_content, nil)
+
+    {:noreply, push_patch(socket, to: build_params(socket))}
   end
 
   @impl true
@@ -126,11 +133,75 @@ defmodule FirehoseWeb.MicroprintsLive do
         _ -> path
       end
 
-    {:noreply, assign(socket, :expanded_path, expanded)}
+    source_content =
+      case expanded do
+        nil -> nil
+        ^path ->
+          item = Enum.find(socket.assigns.microprints, &(&1.path == path))
+          if item && item.source_dir do
+            abs_path = resolve_source_path(item.source_dir, path)
+            read_source(abs_path)
+          else
+            nil
+          end
+      end
+
+    socket = socket |> assign(:expanded_path, expanded) |> assign(:source_content, source_content)
+
+    {:noreply, push_patch(socket, to: build_params(socket))}
   end
 
   # Private helpers
 
+  defp restore_state_from_params(socket, params) do
+    expanded_path = params["expanded"]
+    highlighted_path = params["highlighted"]
+    highlighted_line = if params["line"], do: String.to_integer(params["line"]), else: nil
+
+    source_content =
+      if expanded_path do
+        item = Enum.find(socket.assigns.microprints, &(&1.path == expanded_path))
+
+        if item && item.source_dir do
+          abs_path = resolve_source_path(item.source_dir, expanded_path)
+          read_source(abs_path)
+        end
+      end
+
+    socket
+    |> assign(:expanded_path, expanded_path)
+    |> assign(:source_content, source_content)
+    |> assign(:highlighted_path, highlighted_path)
+    |> assign(:highlighted_line, highlighted_line)
+  end
+
+  defp build_params(socket) do
+    params = %{}
+
+    params =
+      if socket.assigns.expanded_path do
+        Map.put(params, "expanded", socket.assigns.expanded_path)
+      else
+        params
+      end
+
+    params =
+      if socket.assigns.highlighted_path do
+        Map.put(params, "highlighted", socket.assigns.highlighted_path)
+      else
+        params
+      end
+
+    params =
+      if socket.assigns.highlighted_line do
+        params |> Map.put("line", socket.assigns.highlighted_line)
+      else
+        params
+      end
+
+    "/microprints" <> if params != %{}, do: "?" <> URI.encode_query(params), else: ""
+  end
+
   defp sort_by_mtime(files) do
     app_root = Mix.Project.project_file() |> Path.dirname()
 
@@ -143,16 +214,39 @@ defmodule FirehoseWeb.MicroprintsLive do
     |> Enum.map(fn {file, _mtime} -> file end)
   end
 
+  defp sort_by_mtime_with_dir(tuples) do
+    app_root = Mix.Project.project_file() |> Path.dirname()
+
+    tuples
+    |> Enum.map(fn {path, dir} ->
+      abs_path = Path.join(app_root, path)
+      {{path, dir}, File.stat!(abs_path).mtime}
+    end)
+    |> Enum.sort_by(fn {{_path, _dir}, mtime} -> mtime end, :desc)
+    |> Enum.map(fn {{path, dir}, _mtime} -> {path, dir} end)
+  end
+
   @doc false
   def scan_source_files do
     @source_dirs
     |> Enum.flat_map(&collect_elixir_files/1)
-    |> Enum.uniq()
+    |> Enum.uniq_by(&elem(&1, 0))
+    |> Enum.map(&elem(&1, 0))
     |> Enum.sort()
     |> sort_by_mtime()
     |> Enum.take(2)
   end
 
+  @doc false
+  def scan_source_files_with_dir do
+    @source_dirs
+    |> Enum.flat_map(&collect_elixir_files/1)
+    |> Enum.uniq_by(&elem(&1, 0))
+    |> Enum.sort_by(&elem(&1, 0))
+    |> sort_by_mtime_with_dir()
+    |> Enum.take(2)
+  end
+
   defp resolve_absolute_paths(files) do
     app_root = Mix.Project.project_file() |> Path.dirname()
 
@@ -181,26 +275,26 @@ defmodule FirehoseWeb.MicroprintsLive do
         |> Path.wildcard()
         |> Enum.filter(&File.regular?(&1))
         |> Enum.reject(&excluded_path?/1)
-        |> Enum.map(&format_path(&1, monorepo_root, dir))
+        |> Enum.map(&format_path_and_dir(&1, monorepo_root, dir))
 
       false ->
         []
     end
   end
 
-  defp format_path(path, monorepo_root, dir) do
+  defp format_path_and_dir(path, monorepo_root, dir) do
     relative = Path.relative_to(path, monorepo_root)
 
+    formatted =
       case dir do
-      "app" ->
-        String.replace_prefix(relative, "app/", "")
-
-      _ ->
-        "../" <> relative
-    end
+        "app" -> String.replace_prefix(relative, "app/", "")
+        _ -> "../" <> relative
       end
 
-  defp process_file(rel_path) do
+    {formatted, dir}
+  end
+
+  defp process_file({rel_path, source_dir}) do
     abs_path = resolve_absolute_paths([rel_path]) |> List.first()
 
     case MicroprintCache.get_microprint(abs_path) do
@@ -211,13 +305,10 @@ defmodule FirehoseWeb.MicroprintsLive do
           |> Enum.with_index(1)
           |> Enum.map(fn {line, num} -> Map.put(line, :line_number, num) end)
 
-        # Read source code for expand/contract
-        source = read_source(abs_path)
-
         %{
           path: rel_path,
-          microprint: Map.put(microprint, :lines, lines_with_numbers),
-          source: source
+          source_dir: source_dir,
+          microprint: Map.put(microprint, :lines, lines_with_numbers)
         }
 
       {:error, reason} ->
@@ -225,6 +316,13 @@ defmodule FirehoseWeb.MicroprintsLive do
     end
   end
 
+  defp resolve_source_path(source_dir, rel_path) do
+    app_root = Mix.Project.project_file() |> Path.dirname()
+    monorepo_root = app_root |> Path.dirname()
+    base = Path.join(monorepo_root, source_dir)
+    Path.join(base, rel_path)
+  end
+
   defp read_source(abs_path) do
     case File.read(abs_path) do
       {:ok, content} ->
@@ -255,7 +353,7 @@ defmodule FirehoseWeb.MicroprintsLive do
       data-language={@language}
       style="background: var(--sv-bg); color: var(--sv-text);"
     >
-      <pre id={@viewer_id <> "-pre"} phx-update="ignore" class="m-0 p-2"><code class={"language-#{@language || "plaintext"}"}><%= @content %></code></pre>
+      <pre id={@viewer_id <> "-pre"} phx-update="ignore" class="m-0 p-2"><code class={"language-#{@language || "plaintext"}"}><%= @source_content %></code></pre>
     </div>
     """
   end

app/test/firehose_web/live/microprints_live_test.exs

@@ -139,4 +139,42 @@ defmodule FirehoseWeb.MicroprintsLiveTest do
              "file B should show Collapse button when expanded"
     end
   end
+
+  describe "URL state persistence" do
+    test "expanded path is restored from query param on mount", %{conn: conn} do
+      files = MicroprintsLive.scan_source_files()
+      file_a = List.first(files)
+
+      {:ok, view, _html} = live(conn, ~p"/microprints?expanded=#{file_a}")
+
+      html = render(view)
+      assert html =~ "Collapse",
+             "Expanded file should show Collapse button when restored from URL param"
+      assert html =~ ~s(phx-value-path="#{file_a}")
+    end
+
+    test "unknown expanded path in URL is ignored gracefully", %{conn: conn} do
+      {:ok, view, _html} = live(conn, ~p"/microprints?expanded=nonexistent.ex")
+
+      html = render(view)
+      refute html =~ "Collapse",
+             "Nonexistent expanded path should not show Collapse"
+    end
+
+    test "expand updates URL with expanded param", %{conn: conn} do
+      files = MicroprintsLive.scan_source_files()
+      file_a = List.first(files)
+
+      {:ok, view, _html} = live(conn, ~p"/microprints")
+
+      view
+      |> element("button[phx-value-path=\"#{file_a}\"]", "Expand")
+      |> render_click()
+
+      # URL should contain expanded param after clicking Expand
+      html = render(view)
+      assert html =~ "Collapse",
+             "File should remain expanded after push_patch updates URL"
+    end
+  end
 end