defmodule ToweropsWeb.AgentChannel.Subscriptions do
  @moduledoc """
  PubSub subscription management for agent channels.

  Handles all PubSub topic subscriptions and event broadcasting for agent
  lifecycle events (connection, disconnection, heartbeat).
  """

  @doc """
  Subscribes the current process to all PubSub topics relevant to the given
  agent token.

  Topics subscribed:
  - `agent:{id}:assignments` — device assignment changes
  - `agent:{id}:discovery` — discovery requests
  - `agent:{id}:backup` — backup requests
  - `agent:{id}:credential_test` — credential test requests
  - `agent:{id}:live_poll` — live poll requests
  - `checks:agent:{id}` — check changes
  - `agent:{id}:lifecycle` — token lifecycle events
  - `agent:{id}:latency_probe` — latency probes (cloud pollers only)
  """
  @spec subscribe_all(map()) :: :ok
  def subscribe_all(agent_token) do
    id = agent_token.id

    _ = Phoenix.PubSub.subscribe(Towerops.PubSub, "agent:#{id}:assignments")
    _ = Phoenix.PubSub.subscribe(Towerops.PubSub, "agent:#{id}:discovery")
    _ = Phoenix.PubSub.subscribe(Towerops.PubSub, "agent:#{id}:backup")
    _ = Phoenix.PubSub.subscribe(Towerops.PubSub, "agent:#{id}:credential_test")
    _ = Phoenix.PubSub.subscribe(Towerops.PubSub, "agent:#{id}:live_poll")
    _ = Phoenix.PubSub.subscribe(Towerops.PubSub, "checks:agent:#{id}")
    _ = Phoenix.PubSub.subscribe(Towerops.PubSub, "agent:#{id}:lifecycle")

    subscribe_latency_if_cloud_poller(agent_token)

    :ok
  end

  # Cloud pollers additionally subscribe to latency probe requests
  defp subscribe_latency_if_cloud_poller(%{is_cloud_poller: true} = agent_token) do
    _ = Phoenix.PubSub.subscribe(Towerops.PubSub, "agent:#{agent_token.id}:latency_probe")
    :ok
  end

  defp subscribe_latency_if_cloud_poller(_agent_token), do: :ok

  @doc """
  Broadcasts an agent connection event to the `agents:health` topic.
  """
  @spec broadcast_connection(Ecto.UUID.t(), Ecto.UUID.t()) :: :ok
  def broadcast_connection(agent_token_id, organization_id) do
    _ =
      Phoenix.PubSub.broadcast(
        Towerops.PubSub,
        "agents:health",
        {:agent_connected, agent_token_id, organization_id}
      )

    :ok
  end

  @doc """
  Broadcasts an agent disconnection event to the `agents:health` topic.
  """
  @spec broadcast_disconnection(Ecto.UUID.t(), Ecto.UUID.t()) :: :ok
  def broadcast_disconnection(agent_token_id, organization_id) do
    _ =
      Phoenix.PubSub.broadcast(
        Towerops.PubSub,
        "agents:health",
        {:agent_disconnected, agent_token_id, organization_id}
      )

    :ok
  end

  @doc """
  Broadcasts an agent heartbeat event to the `agents:health` topic.
  """
  @spec broadcast_heartbeat(Ecto.UUID.t(), Ecto.UUID.t()) :: :ok
  def broadcast_heartbeat(agent_token_id, organization_id) do
    _ =
      Phoenix.PubSub.broadcast(
        Towerops.PubSub,
        "agents:health",
        {:agent_heartbeat, agent_token_id, organization_id}
      )

    :ok
  end
end