Render [[Example]] links as links to the collection search

lib/music_library_web/components/notes_component.ex

@@ -3,6 +3,7 @@ defmodule MusicLibraryWeb.NotesComponent do
 
   alias MusicLibrary.Notes
   alias MusicLibrary.Notes.Note
+  alias MusicLibraryWeb.Markdown
 
   def open(id), do: Fluxon.open_dialog(id)
 
@@ -148,7 +149,7 @@ defmodule MusicLibraryWeb.NotesComponent do
 
   defp render_notes(notes) do
     (notes || "")
-    |> Earmark.as_html!(%Earmark.Options{gfm: true})
+    |> Markdown.to_html()
     |> raw()
   end
 end

lib/music_library_web/markdown.ex

@@ -0,0 +1,42 @@
+defmodule MusicLibraryWeb.Markdown do
+  @moduledoc """
+  Custom markdown processor that handles double square bracket links.
+
+  Text wrapped in double square brackets like `[[Foo]]` will be rendered as 
+  search links to the collection page.
+  """
+
+  @doc """
+  Converts markdown with custom `[[link]]` syntax to HTML.
+
+  Double square brackets are converted to search links before the markdown is processed.
+  """
+  def to_html(markdown_text) when is_binary(markdown_text) do
+    markdown_text
+    |> process_double_bracket_links()
+    |> Earmark.as_html!(%Earmark.Options{gfm: true})
+  end
+
+  def to_html(nil), do: ""
+
+  @doc """
+  Processes text to convert [[text]] patterns into markdown links.
+
+  ## Examples
+
+      iex> MusicLibraryWeb.Markdown.process_double_bracket_links("Check out [[Porcupine Tree]]")
+      "Check out [Porcupine Tree](/collection?query=Porcupine+Tree)"
+      
+      iex> MusicLibraryWeb.Markdown.process_double_bracket_links("Albums like [[Steven Wilson - The Raven That Refused to Sing (and Other Stories) (2013)]] are great")
+      "Albums like [Steven Wilson - The Raven That Refused to Sing (and Other Stories) (2013)](/collection?query=Steven+Wilson+-+The+Raven+That+Refused+to+Sing+%28and+Other+Stories%29+%282013%29) are great"
+  """
+  def process_double_bracket_links(text) do
+    # Regex to match [[text]] patterns
+    ~r/\[\[([^\]]+)\]\]/
+    |> Regex.replace(text, fn _match, content ->
+      # URL encode the content for the search query
+      encoded_content = URI.encode_www_form(content)
+      "[#{content}](/collection?query=#{encoded_content})"
+    end)
+  end
+end