add dead link monitoring for outgoing content links

Scans page blocks and nav items for broken URLs (internal via DB
lookup, external via HTTP HEAD). Daily Oban cron at 03:30, plus
on-demand checks when pages are saved. Admin UI tab on redirects
page with re-check, ignore, and clickable source links.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/berrypod_web/live/admin/redirects.ex

@@ -2,8 +2,9 @@ defmodule BerrypodWeb.Admin.Redirects do
   use BerrypodWeb, :live_view
 
   alias Berrypod.Redirects
+  alias Berrypod.Redirects.LinkScanner
 
-  @valid_tabs ~w(redirects broken create)
+  @valid_tabs ~w(redirects broken dead_links create)
 
   @impl true
   def mount(_params, _session, socket) do
@@ -11,14 +12,18 @@ defmodule BerrypodWeb.Admin.Redirects do
 
     redirect_page = Redirects.list_redirects_paginated(page: 1)
     broken_page = Redirects.list_broken_urls_paginated(page: 1)
+    dead_link_page = Redirects.list_dead_links_paginated(page: 1)
 
     socket =
       socket
       |> assign(:page_title, "Redirects")
       |> assign(:redirect_pagination, redirect_page)
       |> assign(:broken_url_pagination, broken_page)
+      |> assign(:dead_link_pagination, dead_link_page)
+      |> assign(:dead_link_count, Redirects.count_dead_links())
       |> stream(:redirects, redirect_page.items)
       |> stream(:broken_urls, broken_page.items)
+      |> stream(:dead_links, dead_link_page.items)
       |> assign(
         :form,
         to_form(%{"from_path" => "", "to_path" => "", "status_code" => "301"}, as: :redirect)
@@ -50,6 +55,13 @@ defmodule BerrypodWeb.Admin.Redirects do
           |> assign(:broken_url_pagination, page)
           |> stream(:broken_urls, page.items, reset: true)
 
+        "dead_links" ->
+          page = Redirects.list_dead_links_paginated(page: page_num)
+
+          socket
+          |> assign(:dead_link_pagination, page)
+          |> stream(:dead_links, page.items, reset: true)
+
         _ ->
           socket
       end
@@ -76,6 +88,16 @@ defmodule BerrypodWeb.Admin.Redirects do
      |> stream(:broken_urls, page.items, reset: true)}
   end
 
+  def handle_info(:dead_links_changed, socket) do
+    page = Redirects.list_dead_links_paginated(page: socket.assigns.dead_link_pagination.page)
+
+    {:noreply,
+     socket
+     |> assign(:dead_link_pagination, page)
+     |> assign(:dead_link_count, Redirects.count_dead_links())
+     |> stream(:dead_links, page.items, reset: true)}
+  end
+
   @impl true
   def handle_event("switch_tab", %{"tab" => tab}, socket) do
     {:noreply, push_patch(socket, to: ~p"/admin/redirects?#{%{tab: tab}}")}
@@ -132,6 +154,32 @@ defmodule BerrypodWeb.Admin.Redirects do
      |> stream(:broken_urls, page.items, reset: true)}
   end
 
+  def handle_event("ignore_dead_link", %{"id" => id}, socket) do
+    dead_link = Redirects.get_dead_link!(id)
+    {:ok, _} = Redirects.ignore_dead_link(dead_link)
+
+    page = Redirects.list_dead_links_paginated(page: socket.assigns.dead_link_pagination.page)
+
+    {:noreply,
+     socket
+     |> assign(:dead_link_pagination, page)
+     |> assign(:dead_link_count, Redirects.count_dead_links())
+     |> stream(:dead_links, page.items, reset: true)}
+  end
+
+  def handle_event("recheck_dead_link", %{"id" => id}, socket) do
+    dead_link = Redirects.get_dead_link!(id)
+
+    Oban.insert(Berrypod.Workers.DeadLinkCheckerWorker.new(%{"check_url" => dead_link.url}))
+
+    {:noreply, put_flash(socket, :info, "Re-checking #{dead_link.url}...")}
+  end
+
+  def handle_event("check_all_links", _params, socket) do
+    Oban.insert(Berrypod.Workers.DeadLinkCheckerWorker.new(%{}))
+    {:noreply, put_flash(socket, :info, "Full link check started...")}
+  end
+
   def handle_event("redirect_broken_url", %{"path" => path}, socket) do
     socket =
       socket
@@ -164,6 +212,12 @@ defmodule BerrypodWeb.Admin.Redirects do
         count={@broken_url_pagination.total_count}
         active={@tab}
       />
+      <.tab_button
+        tab="dead_links"
+        label="Dead links"
+        count={@dead_link_count}
+        active={@tab}
+      />
       <.tab_button tab="create" label="Create" active={@tab} />
     </div>
 
@@ -175,6 +229,10 @@ defmodule BerrypodWeb.Admin.Redirects do
       <.broken_urls_table streams={@streams} pagination={@broken_url_pagination} />
     <% end %>
 
+    <%= if @tab == "dead_links" do %>
+      <.dead_links_table streams={@streams} pagination={@dead_link_pagination} />
+    <% end %>
+
     <%= if @tab == "create" do %>
       <.create_form form={@form} />
     <% end %>
@@ -287,6 +345,71 @@ defmodule BerrypodWeb.Admin.Redirects do
     """
   end
 
+  defp dead_links_table(assigns) do
+    ~H"""
+    <div class="flex justify-end mb-4">
+      <button phx-click="check_all_links" class="admin-btn admin-btn-sm admin-btn-ghost">
+        Check all
+      </button>
+    </div>
+
+    <%= if @pagination.total_count == 0 do %>
+      <p>No dead links detected.</p>
+    <% else %>
+      <div class="admin-table-wrap">
+        <table class="admin-table">
+          <thead>
+            <tr>
+              <th>URL</th>
+              <th>Type</th>
+              <th>Error</th>
+              <th>Used in</th>
+              <th>Last checked</th>
+              <th></th>
+            </tr>
+          </thead>
+          <tbody id="dead-links-table" phx-update="stream">
+            <tr :for={{dom_id, dead_link} <- @streams.dead_links} id={dom_id}>
+              <td class="max-w-xs truncate"><code>{dead_link.url}</code></td>
+              <td>
+                <span class={"badge badge-#{dead_link_type_colour(dead_link.url_type)}"}>
+                  {dead_link.url_type}
+                </span>
+              </td>
+              <td>{format_dead_link_error(dead_link)}</td>
+              <td><.dead_link_sources url={dead_link.url} /></td>
+              <td>{Calendar.strftime(dead_link.last_checked_at, "%d %b %Y %H:%M")}</td>
+              <td class="flex gap-2">
+                <button
+                  phx-click="recheck_dead_link"
+                  phx-value-id={dead_link.id}
+                  class="admin-btn admin-btn-sm admin-btn-ghost"
+                >
+                  Re-check
+                </button>
+                <button
+                  phx-click="ignore_dead_link"
+                  phx-value-id={dead_link.id}
+                  data-confirm="Ignore this dead link?"
+                  class="admin-btn admin-btn-sm admin-btn-ghost"
+                >
+                  Ignore
+                </button>
+              </td>
+            </tr>
+          </tbody>
+        </table>
+      </div>
+
+      <.admin_pagination
+        page={@pagination}
+        patch={~p"/admin/redirects"}
+        params={%{"tab" => "dead_links"}}
+      />
+    <% end %>
+    """
+  end
+
   defp create_form(assigns) do
     ~H"""
     <.form for={@form} phx-submit="create_redirect" style="max-width: 32rem;">
@@ -335,6 +458,36 @@ defmodule BerrypodWeb.Admin.Redirects do
     """
   end
 
+  defp dead_link_type_colour("internal"), do: "warning"
+  defp dead_link_type_colour("external"), do: "info"
+  defp dead_link_type_colour(_), do: "neutral"
+
+  defp format_dead_link_error(%{http_status: status, error: error}) when not is_nil(status) do
+    "#{status} #{error}"
+  end
+
+  defp format_dead_link_error(%{error: error}) when not is_nil(error), do: error
+  defp format_dead_link_error(_), do: "—"
+
+  defp dead_link_sources(assigns) do
+    assigns = assign(assigns, :sources, LinkScanner.find_sources(assigns.url))
+
+    ~H"""
+    <%= case @sources do %>
+      <% [] -> %>
+        <span>—</span>
+      <% [source] -> %>
+        <.link navigate={source.edit_path} class="underline">{source.label}</.link>
+      <% sources -> %>
+        <ul class="list-none p-0 m-0 space-y-1">
+          <li :for={source <- sources}>
+            <.link navigate={source.edit_path} class="underline">{source.label}</.link>
+          </li>
+        </ul>
+    <% end %>
+    """
+  end
+
   defp resolve_matching_broken_url(from_path) do
     case Redirects.get_broken_url_by_path(from_path) do
       nil -> :ok