LiveView hooks for automatic presence tracking.

Use this module with Phoenix LiveView's on_mount callback to automatically track and update presence when users join and interact with documents.

Usage

In your LiveView:

defmodule MyAppWeb.DocumentLive do
  use MyAppWeb, :live_view

  # Auto-track presence when connected
  on_mount {Grove.LiveView.Presence, :track_presence}

  def mount(%{"id" => doc_id}, session, socket) do
    # Mount the tree first (sets grove_doc_id and grove_replica_id)
    socket = Grove.LiveView.mount_tree(socket, doc_id,
      replica_id: session["user_id"] || socket.id
    )

    # Initialize presence list
    {:ok, assign(socket, :presences, Grove.Presence.list_replicas(doc_id))}
  end

  # Handle presence updates
  def handle_info(%Phoenix.Socket.Broadcast{event: "presence_diff", payload: diff}, socket) do
    presences = Grove.Presence.sync_diff(socket.assigns.presences, diff)
    {:noreply, assign(socket, :presences, presences)}
  end
end

Requirements

The on_mount hook expects the following assigns to be set before it runs:

• :grove_doc_id - Document identifier (set by Grove.LiveView.mount_tree/3)
• :grove_replica_id - Replica identifier (set by Grove.LiveView.mount_tree/3)

If these are not set, the hook will skip tracking and continue normally.

Session Data

The hook reads the following from the session (if available):

• "user_id" - User identifier (stored in meta)
• "user_name" - User display name (stored in meta)

Initial Metadata

When tracking begins, the following metadata is set:

%{
  user_id: session["user_id"],
  user_name: session["user_name"],
  color: Grove.Presence.assign_color(replica_id),
  cursor: nil,
  selection: nil,
  focus: nil,
  joined_at: System.system_time(:second)
}