Consolidate duration formatting

lib/music_library_web/duration.ex

@@ -0,0 +1,39 @@
+defmodule MusicLibraryWeb.Duration do
+  def format_duration(milliseconds) do
+    milliseconds
+    |> System.convert_time_unit(:millisecond, :second)
+    |> format_seconds()
+  end
+
+  defp format_seconds(seconds) when seconds <= 59 do
+    "0:#{zero_pad(seconds)}"
+  end
+
+  defp format_seconds(seconds) do
+    minutes = div(seconds, 60)
+    remaining_seconds = rem(seconds, 60)
+
+    format_minutes(minutes, remaining_seconds)
+  end
+
+  defp format_minutes(minutes, seconds) when minutes <= 59 do
+    "#{minutes}:#{zero_pad(seconds)}"
+  end
+
+  defp format_minutes(minutes, seconds) do
+    hours = div(minutes, 60)
+    remaining_minutes = rem(minutes, 60)
+
+    format_hours(hours, remaining_minutes, seconds)
+  end
+
+  defp format_hours(hours, minutes, seconds) do
+    "#{hours}:#{zero_pad(minutes)}:#{zero_pad(seconds)}"
+  end
+
+  defp zero_pad(integer) do
+    integer
+    |> to_string()
+    |> String.pad_leading(2, "0")
+  end
+end