Build FileTree header to be used when decompressing

lib/bakeware/file_tree.ex

@@ -0,0 +1,63 @@
+defmodule Bakeware.FileTree do
+  alias Bakeware.Assembler
+
+  @moduledoc """
+  Builds a FileTree header for recreating decompressed files
+
+  Header structure:
+
+  `<<bw_ft_magic, bw_ft_version, header_length, file_tree_items>>`
+
+  where `file_tree_items` is a repeating structure of:
+
+  `<<file_type, size, path_len, relative_path::size(path_len)-unit(8)>>`
+  """
+
+  # ?F + ?T
+  @bw_ft_magic 154
+  @bw_ft_version 1
+
+  def build(%Assembler{} = assembler) do
+    find_files(assembler.rel_path, assembler.rel_path)
+    |> finalize_header()
+
+    # TODO: Do something with this
+
+    assembler
+  end
+
+  def find_files(path, absolute, acc \\ <<>>) do
+    for fp <- File.ls!(path), file_or_dir = Path.join(path, fp), into: acc do
+      if File.dir?(file_or_dir) do
+        acc = acc <> build_stat(file_or_dir, absolute)
+        find_files(file_or_dir, absolute, acc)
+      else
+        build_stat(file_or_dir, absolute)
+      end
+    end
+  end
+
+  def finalize_header(header) do
+    len = byte_size(header)
+    <<@bw_ft_magic, @bw_ft_version, len, header::binary>>
+  end
+
+  defp build_stat(path, absolute) do
+    relative = Path.relative_to(path, absolute)
+    stat = File.lstat!(path)
+    path_len = byte_size(path)
+    <<type_val(stat.type), stat.size, path_len, relative::binary>>
+  end
+
+  defp type_val(type) do
+    case type do
+      :device -> 1
+      :directory -> 2
+      :regular -> 3
+      :symlink -> 4
+      :other -> 5
+      # unknown
+      _ -> 0
+    end
+  end
+end