From 7708779b9fd4eeef6b04279260e88af8fac0a5b7 Mon Sep 17 00:00:00 2001
From: Chris McCord <chris@chrismccord.com>
Date: Wed, 10 Nov 2021 14:29:53 -0500
Subject: [PATCH] Auto advance to next song via client

---
 assets/js/app.js                       |  5 +++++
 lib/live_beats/media_library.ex        | 30 ++++++++++++++++++++++++++
 lib/live_beats_web/live/player_live.ex |  7 ++++++
 3 files changed, 42 insertions(+)

diff --git a/assets/js/app.js b/assets/js/app.js
index a6c6a9a..849a104 100644
--- a/assets/js/app.js
+++ b/assets/js/app.js
@@ -78,6 +78,11 @@ Hooks.AudioPlayer = {
 
   updateProgress(){
     if(isNaN(this.player.duration)){ return false }
+    if(this.player.currentTime >= this.player.duration){
+      this.pushEvent("next-song-auto")
+      clearInterval(this.progressTimer)
+      return
+    }
 		this.progress.style.width = `${(this.player.currentTime / (this.player.duration) * 100)}%`
     this.duration.innerText = this.formatTime(this.player.duration)
     this.currentTime.innerText = this.formatTime(this.player.currentTime)
diff --git a/lib/live_beats/media_library.ex b/lib/live_beats/media_library.ex
index 7ae0912..01980a7 100644
--- a/lib/live_beats/media_library.ex
+++ b/lib/live_beats/media_library.ex
@@ -10,6 +10,7 @@ defmodule LiveBeats.MediaLibrary do
   alias Ecto.{Multi, Changeset}
 
   @pubsub LiveBeats.PubSub
+  @auto_next_threshold_seconds 5
 
   defdelegate stopped?(song), to: Song
   defdelegate playing?(song), to: Song
@@ -81,6 +82,16 @@ defmodule LiveBeats.MediaLibrary do
     Phoenix.PubSub.broadcast!(@pubsub, topic(song.user_id), {:pause, song})
   end
 
+  def play_next_song_auto(user_id) do
+    song = get_current_active_song(user_id) || get_first_song(user_id)
+
+    if song && elapsed_playback(song) >= song.duration - @auto_next_threshold_seconds do
+      song
+      |> get_next_song()
+      |> play_song()
+    end
+  end
+
   defp topic(user_id), do: "room:#{user_id}"
 
   def store_mp3(%Song{} = song, tmp_path) do
@@ -90,6 +101,7 @@ defmodule LiveBeats.MediaLibrary do
 
   def put_stats(%Ecto.Changeset{} = changeset, %MP3Stat{} = stat) do
     chset = Song.put_duration(changeset, stat.duration)
+
     if error = chset.errors[:duration] do
       {:error, %{duration: error}}
     else
@@ -166,6 +178,24 @@ defmodule LiveBeats.MediaLibrary do
 
   def get_song!(id), do: Repo.get!(Song, id)
 
+  def get_first_song(user_id) do
+    Repo.one(
+      from s in Song,
+        where: s.user_id == ^user_id,
+        order_by: [asc: s.inserted_at, asc: s.id],
+        limit: 1
+    )
+  end
+
+  def get_next_song(%Song{} = song) do
+    Repo.one(
+      from s in Song,
+        where: s.user_id == ^song.user_id and s.id > ^song.id,
+        order_by: [asc: s.inserted_at, asc: s.id],
+        limit: 1
+    ) || get_first_song(song.user_id)
+  end
+
   def create_song(attrs \\ %{}) do
     %Song{}
     |> Song.changeset(attrs)
diff --git a/lib/live_beats_web/live/player_live.ex b/lib/live_beats_web/live/player_live.ex
index 308b073..c0bfe96 100644
--- a/lib/live_beats_web/live/player_live.ex
+++ b/lib/live_beats_web/live/player_live.ex
@@ -135,6 +135,13 @@ defmodule LiveBeatsWeb.PlayerLive do
     end
   end
 
+  def handle_event("next-song-auto", _, socket) do
+    if socket.assigns.song do
+      MediaLibrary.play_next_song_auto(socket.assigns.song.user_id)
+    end
+    {:noreply, socket}
+  end
+
   def handle_info(:play_current, socket) do
     # we raced a pubsub, noop
     if socket.assigns.song do