defmodule Symbiont.Application do
  @moduledoc """
  OTP Application for Symbiont — the self-sustaining AI orchestrator.

  Supervision tree (dev/prod):
    Symbiont.Supervisor
    ├── Task.Supervisor (Symbiont.TaskSupervisor)
    ├── Symbiont.Ledger        — append-only cost log
    ├── Symbiont.Queue         — persistent task queue
    ├── Symbiont.Engram        — cross-session memory (SQLite)
    ├── Symbiont.Heartbeat     — periodic health checks + queue processing
    ├── Symbiont.Telepathy.Supervisor — email communication layer (if enabled)
    │   ├── Symbiont.Telepathy.MessageStore — JSONL-backed message persistence
    │   ├── Symbiont.Telepathy.JMAP         — Fastmail JMAP client + polling
    │   └── Symbiont.Telepathy.SMTP         — gen_smtp listener on port 25
    └── Bandit (Symbiont.API)  — HTTP API

  In test mode, the supervisor starts empty — tests manage their own processes.

  ## Graceful shutdown

  Bandit is configured with a long ThousandIsland `shutdown_timeout` so that
  in-flight `/task` requests (which can take up to 600s while Claude runs)
  are not killed when systemd restarts the service. The Bandit child spec
  also carries a matching `:shutdown` value so the OTP supervisor itself
  waits long enough before forcing a kill.

  The matching systemd unit must set `TimeoutStopSec=620` for this to take
  effect end to end.
  """
  use Application

  # 615s for Bandit to drain its sockets, 620s for the OTP child shutdown
  # window. Keep these slightly larger than the Claude CLI timeout (600s)
  # used by Muse's SMTP dispatcher.
  @bandit_drain_ms 615_000
  @bandit_child_shutdown_ms 620_000

  @impl true
  def start(_type, _args) do
    if Application.get_env(:symbiont, :port) == 0 do
      # Test mode: start an empty supervisor, tests manage their own processes
      Supervisor.start_link([], strategy: :one_for_one, name: Symbiont.Supervisor)
    else
      start_full()
    end
  end

  defp start_full do
    data_dir = Application.get_env(:symbiont, :data_dir, "data")
    File.mkdir_p!(data_dir)

    port = Application.get_env(:symbiont, :port, 8111)
    engram_db = Application.get_env(:symbiont, :engram_db, "/data/symbiont/engram.db")

    bandit_spec =
      Supervisor.child_spec(
        {Bandit,
         plug: Symbiont.API,
         port: port,
         scheme: :http,
         thousand_island_options: [shutdown_timeout: @bandit_drain_ms]},
        shutdown: @bandit_child_shutdown_ms
      )

    telepathy_cfg = Application.get_env(:symbiont, :telepathy, [])
    telepathy_enabled = Keyword.get(telepathy_cfg, :enabled, true)
    poll_ms = Keyword.get(telepathy_cfg, :poll_interval_ms, 60_000)
    smtp_port = Keyword.get(telepathy_cfg, :smtp_port, 25)

    telepathy_children =
      if telepathy_enabled do
        [{Symbiont.Telepathy.Supervisor, poll_interval_ms: poll_ms, smtp_port: smtp_port}]
      else
        []
      end

    children =
      [
        {Task.Supervisor, name: Symbiont.TaskSupervisor},
        {Symbiont.Ledger, data_dir: data_dir},
        {Symbiont.Queue, data_dir: data_dir},
        {Symbiont.Engram, db_path: engram_db},
        {Symbiont.Heartbeat, []}
      ] ++ telepathy_children ++ [bandit_spec]

    opts = [strategy: :rest_for_one, name: Symbiont.Supervisor]
    Supervisor.start_link(children, opts)
  end
end