WIP

lib/live_beats/media_library.ex

@@ -163,6 +163,7 @@ defmodule LiveBeats.MediaLibrary do
 
     multi =
       Ecto.Multi.new()
+      |> lock_playlist(user.id)
       |> Ecto.Multi.run(:starting_position, fn repo, _changes ->
         count = repo.one(from s in Song, where: s.user_id == ^user.id, select: count(s.id))
         {:ok, count - 1}
@@ -358,27 +359,28 @@ defmodule LiveBeats.MediaLibrary do
 
     multi =
       Ecto.Multi.new()
-      |> Ecto.Multi.run(:valid_index, fn repo, _changes ->
+      |> lock_playlist(song.user_id)
+      |> Ecto.Multi.run(:index, fn repo, _changes ->
         case repo.one(from s in Song, where: s.user_id == ^song.user_id, select: count(s.id)) do
-          count when new_index < count -> {:ok, count}
-          _count -> {:error, :index_out_of_range}
+          count when new_index < count -> {:ok, new_index}
+          count -> {:ok, count - 1}
         end
       end)
-      |> multi_update_all(:dec_positions, fn _ ->
+      |> multi_update_all(:dec_positions, fn %{index: new_index} ->
         from(s in Song,
           where: s.user_id == ^song.user_id and s.id != ^song.id,
           where: s.position > ^old_index and s.position <= ^new_index,
           update: [inc: [position: -1]]
         )
       end)
-      |> multi_update_all(:inc_positions, fn _ ->
+      |> multi_update_all(:inc_positions, fn %{index: new_index} ->
         from(s in Song,
           where: s.user_id == ^song.user_id and s.id != ^song.id,
           where: s.position < ^old_index and s.position >= ^new_index,
           update: [inc: [position: 1]]
         )
       end)
-      |> multi_update_all(:position, fn _ ->
+      |> multi_update_all(:position, fn %{index: new_index} ->
         from(s in Song,
           where: s.id == ^song.id,
           update: [set: [position: ^new_index]]
@@ -406,6 +408,7 @@ defmodule LiveBeats.MediaLibrary do
     old_index = song.position
 
     Ecto.Multi.new()
+    |> lock_playlist(song.user_id)
     |> Ecto.Multi.delete(:delete, song)
     |> multi_update_all(:dec_positions, fn _ ->
       from(s in Song,
@@ -533,4 +536,8 @@ defmodule LiveBeats.MediaLibrary do
   defp multi_update_all(multi, name, func, opts \\ []) do
     Ecto.Multi.update_all(multi, name, func, opts)
   end
+
+  defp lock_playlist(%Ecto.Multi{} = multi, user_id) do
+    Repo.multi_transaction_lock(multi, :playlist, user_id)
+  end
 end

lib/live_beats/media_library/song.ex

@@ -13,7 +13,7 @@ defmodule LiveBeats.MediaLibrary.Song do
     field :date_recorded, :naive_datetime
     field :date_released, :naive_datetime
     field :duration, :integer
-    field :status, Ecto.Enum, values: [stopped: 1, playing: 2, paused: 3]
+    field :status, Ecto.Enum, values: [stopped: 1, playing: 2, paused: 3], default: :stopped
     field :title, :string
     field :attribution, :string
     field :mp3_url, :string

lib/live_beats/repo.ex

@@ -4,6 +4,16 @@ defmodule LiveBeats.Repo do
     adapter: Ecto.Adapters.Postgres
 
   def replica, do: LiveBeats.config([:replica])
+
+  @locks %{playlist: 1}
+
+  def multi_transaction_lock(multi, scope, id) when is_atom(scope) and is_integer(id) do
+    scope_int = Map.fetch!(@locks, scope)
+
+    Ecto.Multi.run(multi, scope, fn repo, _changes ->
+      repo.query("SELECT pg_advisory_xact_lock(#{scope_int}, #{id})")
+    end)
+  end
 end
 
 defmodule LiveBeats.ReplicaRepo do

lib/live_beats_web/components/core_components.ex

@@ -582,7 +582,7 @@ defmodule LiveBeatsWeb.CoreComponents do
           <tbody
             id={"#{@id}-body"}
             class="bg-white divide-y divide-gray-100"
-            phx-stream={@streamable}
+            phx-update={@streamable && "stream"}
             phx-hook={@sortable_drop && "Sortable"}
             data-drop={@sortable_drop}
           >

lib/live_beats_web/live/profile_live.ex

@@ -16,6 +16,7 @@ defmodule LiveBeatsWeb.ProfileLive do
           <%= if @owns_profile? do %>
             (you)
           <% end %>
+          <%= @songs_count %>
         </div>
         <.link href={@profile.external_homepage_url} target="_blank" class="text-sm text-gray-600">
           <.icon name={:code} /> <span class=""><%= url_text(@profile.external_homepage_url) %></span>
@@ -59,8 +60,8 @@ defmodule LiveBeatsWeb.ProfileLive do
       total_count={@presences_count}
     />
 
-    <div id="dialogs" phx-update="append">
-      <%= for {_id, song} <- if(@owns_profile?, do: @songs, else: []), id = "delete-modal-#{song.id}" do %>
+    <div id="dialogs" phx-update="stream">
+      <%= for {_id, song} <- if(@owns_profile?, do: @streams.songs, else: []), id = "delete-modal-#{song.id}" do %>
         <.modal
           id={id}
           on_confirm={
@@ -80,14 +81,18 @@ defmodule LiveBeatsWeb.ProfileLive do
 
     <.table
       id="songs"
-      rows={@songs}
+      rows={@streams.songs}
       row_id={fn {id, _song} -> id end}
       row_click={fn {_id, song} -> JS.push("play_or_pause", value: %{id: song.id}) end}
       row_remove={fn {id, _song} -> hide("##{id}") end}
       streamable
       sortable_drop="row_dropped"
     >
-      <:col :let={{_id, song}} label="Title" class!="px-6 py-3 text-sm font-medium text-gray-900 min-w-[20rem] cursor-pointer">
+      <:col
+        :let={{_id, song}}
+        label="Title"
+        class!="px-6 py-3 text-sm font-medium text-gray-900 md:min-w-[20rem] cursor-pointer"
+      >
         <span :if={song.status == :playing} class="flex pt-1 relative mr-2 w-4">
           <span class="w-3 h-3 animate-ping bg-purple-400 rounded-full absolute"></span>
           <.icon name={:volume_up} class="h-5 w-5 -mt-1 -ml-1" aria-label="Playing" role="button" />
@@ -117,7 +122,7 @@ defmodule LiveBeatsWeb.ProfileLive do
         label="Attribution"
         class="max-w-5xl break-words text-gray-600 font-light"
       >
-        <%= song.attribution %>
+        <%= song.position %>
       </:col>
       <:col :let={{_id, song}} label="Duration"><%= MP3Stat.to_mmss(song.duration) %></:col>
       <:col :let={{_id, song}} :if={@owns_profile?} label="">
@@ -151,15 +156,18 @@ defmodule LiveBeatsWeb.ProfileLive do
         song.id
       end
 
+    songs = MediaLibrary.list_profile_songs(profile, 50)
+
     socket =
       socket
       |> assign(
         active_song_id: active_song_id,
         active_profile_id: current_user.active_profile_user_id,
         profile: profile,
-        owns_profile?: MediaLibrary.owns_profile?(current_user, profile)
+        owns_profile?: MediaLibrary.owns_profile?(current_user, profile),
+        songs_count: Enum.count(songs)
       )
-      |> stream_songs()
+      |> stream(:songs, songs)
       |> assign_presences()
 
     {:ok, socket, temporary_assigns: [presences: %{}]}
@@ -201,6 +209,7 @@ defmodule LiveBeatsWeb.ProfileLive do
   def handle_event("row_dropped", %{"id" => dom_id, "old" => old_idx, "new" => new_idx}, socket) do
     "songs-" <> id = dom_id
     song = MediaLibrary.get_song!(id)
+
     if song.user_id == socket.assigns.current_user.id and song.position == old_idx do
       :ok = MediaLibrary.update_song_position(song, new_idx)
       {:noreply, socket}
@@ -247,11 +256,19 @@ defmodule LiveBeatsWeb.ProfileLive do
   end
 
   def handle_info({MediaLibrary, %MediaLibrary.Events.SongsImported{songs: songs}}, socket) do
-    {:noreply, Enum.reduce(songs, socket, fn song, acc -> stream_insert(acc, :songs, song) end)}
+    {:noreply,
+     Enum.reduce(songs, socket, fn song, acc ->
+       acc
+       |> update(:songs_count, &(&1 + 1))
+       |> stream_insert(:songs, song)
+     end)}
   end
 
   def handle_info({MediaLibrary, %MediaLibrary.Events.SongDeleted{song: song}}, socket) do
-    {:noreply, stream_delete(socket, :songs, song)}
+    {:noreply,
+     socket
+     |> update(:songs_count, &(&1 - 1))
+     |> stream_delete(:songs, song)}
   end
 
   def handle_info({MediaLibrary, {:ping, ping}}, socket) do
@@ -338,10 +355,6 @@ defmodule LiveBeatsWeb.ProfileLive do
     socket
   end
 
-  defp stream_songs(socket) do
-    stream(socket, :songs, MediaLibrary.list_profile_songs(socket.assigns.profile, 50))
-  end
-
   defp assign_presences(socket) do
     socket = assign(socket, presences_count: 0, presences: %{}, presence_ids: %{})