feat: unified watch server under org-garden

org-garden/lib/org_garden/index.ex

@@ -0,0 +1,83 @@
+defmodule OrgGarden.Index do
+  @moduledoc """
+  Generates a fallback `index.md` in the content directory if none was
+  exported from an `.org` file.
+
+  The generated index lists all markdown pages alphabetically with links.
+  """
+
+  @doc """
+  Generate `content_dir/index.md` if it does not already exist.
+
+  If an `index.md` was already created by ox-hugo (from an `index.org`),
+  it is left untouched.
+  """
+  @spec generate(String.t()) :: :ok
+  def generate(content_dir) do
+    index_path = Path.join(content_dir, "index.md")
+
+    unless File.exists?(index_path) do
+      IO.puts("  generating default index.md")
+
+      pages =
+        Path.join(content_dir, "**/*.md")
+        |> Path.wildcard()
+        |> Enum.map(fn path ->
+          slug = Path.relative_to(path, content_dir) |> Path.rootname()
+
+          title =
+            path
+            |> File.read!()
+            |> then(fn content ->
+              case Regex.run(~r/^title\s*=\s*"(.+)"/m, content) do
+                [_, t] -> t
+                _ -> slug
+              end
+            end)
+
+          {slug, title}
+        end)
+        |> Enum.sort_by(fn {_, title} -> title end)
+        |> Enum.map(fn {slug, title} -> "- [#{title}](#{slug})" end)
+        |> Enum.join("\n")
+
+      File.write!(index_path, """
+      ---
+      title: Index
+      ---
+
+      #{pages}
+      """)
+    end
+
+    :ok
+  end
+
+  @doc """
+  Regenerate the index by removing any previously generated one first.
+
+  Only removes the index if it was generated by us (contains `title: Index`).
+  User-exported index files (from `index.org`) are left untouched.
+  """
+  @spec regenerate(String.t()) :: :ok
+  def regenerate(content_dir) do
+    index_path = Path.join(content_dir, "index.md")
+
+    if File.exists?(index_path) do
+      content = File.read!(index_path)
+
+      if generated_index?(content) do
+        File.rm!(index_path)
+      end
+    end
+
+    generate(content_dir)
+  end
+
+  defp generated_index?(content) do
+    # Our generated index uses "title: Index" in YAML frontmatter.
+    # ox-hugo uses TOML frontmatter (title = "..."), so this won't
+    # match user-exported files.
+    String.contains?(content, "title: Index")
+  end
+end