Added module with functions for managing SASS/CSS themes of website

lib/sukaato_web/theme.ex

@@ -0,0 +1,136 @@
+defmodule SukaatoWeb.Theme do
+  @moduledoc """
+  Manage website themes.
+  """
+
+  @rel_proj_root "../.."
+  @central_sass "export.sass"
+  @site_config Toml.decode_file(Path.expand(@rel_proj_root <> "/site.toml", __DIR__))
+  @theme_filepath Path.expand(@rel_proj_root <> "/assets/sass/themes/" <> elem(@site_config, 1)["site"]["theme"] <> "/" <> @central_sass, __DIR__)
+  @theme_glob Path.expand(@rel_proj_root <> "/assets/sass/themes/*/" <> @central_sass, __DIR__)
+  @theme_linkpath Path.expand(@rel_proj_root <> "/assets/sass/app.sass", __DIR__)
+
+  defp get_installed() do
+    path_list = Path.wildcard(@theme_glob)
+    extract_theme = fn theme_path -> Enum.at(Path.split(theme_path), length(Path.split(theme_path)) - 2) end
+    installed = Enum.map(path_list, fn p -> extract_theme.(p) end)
+
+    installed
+  end
+
+  @doc """
+  List installed website themes.
+  """
+  def list() do
+    get_installed()
+  end
+
+  defp get_current() do
+    if File.exists?(@theme_linkpath) do
+      link_path = File.read_link(@theme_linkpath)
+
+      if elem(link_path, 0) == :ok do
+        split_path = Path.split(elem(link_path, 1))
+        current_theme = Enum.at(split_path, length(split_path) - 2)
+        {:ok, current_theme}
+      else
+        {:error, "link not traceable--sure its a link?"}
+      end
+    else
+      {:error, "symbolic link does not exist"}
+    end
+  end
+
+  @doc """
+  List website themes under project root's 'assets/sass/themes' path.
+  """
+  def list(status) do
+    case status do
+      :installed ->
+        get_installed()
+      :current ->
+        elem(get_current(), 1)
+    end
+  end
+
+  defp change_theme_path(theme_name) do
+    Path.expand(@rel_proj_root <> "/assets/sass/themes/" <> theme_name <> "/" <> @central_sass, __DIR__)
+  end
+
+  @doc """
+  Update website theme based on stored website settings, refreshes current theme otherwise.
+  """
+  def update() do
+    if File.exists?(@theme_filepath) do
+      result = File.ln_s(@theme_filepath, @theme_linkpath)
+
+      if result == :ok do
+        {:ok, @theme_linkpath}
+      else
+        {:error, {@theme_filepath, @theme_linkpath}}
+      end
+    else
+      link_path = File.read_link(@theme_linkpath)
+
+      if Enum.at(link_path, 0) == :ok do
+        split_path = Path.split(Enum.at(link_path, 1))
+        current_theme = Enum.at(split_path, length(split_path) - 2)
+
+        # @TODO find some way to notify theme could not be found
+        current_path = change_theme_path(current_theme)
+        result = File.ln_s(current_path, @theme_linkpath)
+
+        if result == :ok do
+          {:ok, "current theme '" <> current_theme <> "' reinstated as no declared theme"}
+        else
+          result = File.ln_s(change_theme_path("default"), @theme_linkpath)
+
+          if result == :ok do
+            {:ok, "current theme '" <> current_theme <> "' unavailable, successful fallback to default theme"}
+          else
+            {:error, "current theme '" <> current_theme <> "' unavailable, failed fallback to default theme"}
+          end
+        end
+      else
+        {:error, @theme_linkpath}
+      end
+    end
+  end
+
+  @doc """
+  Update website theme in-memory, independent of stored website settings.
+  """
+  def update(theme_name) do
+    theme_path = change_theme_path(theme_name)
+
+    if File.exists?(theme_path) do
+      # @TODO find some way to notify theme could not be found
+      result = File.ln_s(theme_path, @theme_linkpath)
+
+      if result == :ok do
+        {:ok, @theme_linkpath}
+      else
+        update()
+      end
+    else
+      update()
+    end
+  end
+
+  def grab(), do: nil
+
+  def unpack(), do: nil
+
+  def install(), do: nil
+
+  def remove(theme_name) do
+    theme_path = change_theme_path(theme_name)
+
+    if theme_name != "default" do
+      result = File.rm_rf(theme_path)
+      result
+    else
+      {:error, theme_name <> " cannot be uninstalled"}
+    end
+  end
+end