extends Node

# SessionManager - Proactive session refresh and expiry handling
# Monitors session health and refreshes tokens before expiry

signal session_refreshed()
signal session_expired()

# =============================================================================
# Configuration
# =============================================================================

const CHECK_INTERVAL: float = 60.0          # Check every 60s
const REFRESH_BEFORE_EXPIRY: float = 300.0  # Refresh when <5min to expiry
const MAX_RETRY_ATTEMPTS: int = 3
const BASE_RETRY_DELAY: float = 1.0         # 1s, 2s, 4s exponential backoff

# =============================================================================
# State
# =============================================================================

var _refresh_timer: float = 0.0
var _is_refreshing: bool = false

# =============================================================================
# Lifecycle
# =============================================================================

func _ready():
	set_process(false)
	# Start monitoring when session is available
	if NakamaManager:
		if NakamaManager.session and not NakamaManager.session.is_expired():
			_start_monitoring()

func _process(delta: float) -> void:
	_refresh_timer -= delta
	if _refresh_timer <= 0.0:
		_refresh_timer = CHECK_INTERVAL
		_check_session_health()

# =============================================================================
# Public API
# =============================================================================

func start_monitoring() -> void:
	"""Start monitoring session health. Call after successful login."""
	_start_monitoring()

func stop_monitoring() -> void:
	"""Stop monitoring session health."""
	set_process(false)

# =============================================================================
# Internal
# =============================================================================

func _start_monitoring() -> void:
	_refresh_timer = CHECK_INTERVAL
	set_process(true)
	print("[SessionManager] Monitoring started")

func _check_session_health() -> void:
	if not NakamaManager or not NakamaManager.session:
		return
	
	if NakamaManager.session.is_expired():
		print("[SessionManager] Session expired!")
		session_expired.emit()
		if EventBus:
			EventBus.emit(EventBus.EVENT_SESSION_EXPIRED)
		return
	
	# Check if within refresh window
	var time_to_expiry = NakamaManager.session.expires_at - Time.get_unix_time_from_system()
	if time_to_expiry < REFRESH_BEFORE_EXPIRY:
		print("[SessionManager] Session expiring soon (%.0fs), refreshing..." % time_to_expiry)
		_refresh_session()

func _refresh_session() -> void:
	if _is_refreshing:
		return
	
	_is_refreshing = true
	var success = await _attempt_refresh_with_retry()
	_is_refreshing = false
	
	if success:
		print("[SessionManager] Session refreshed successfully")
		session_refreshed.emit()
		if EventBus:
			EventBus.emit(EventBus.EVENT_SESSION_REFRESHED)
	else:
		print("[SessionManager] Session refresh failed after all retries")
		session_expired.emit()
		if EventBus:
			EventBus.emit(EventBus.EVENT_SESSION_EXPIRED)

func _attempt_refresh_with_retry() -> bool:
	for attempt in range(MAX_RETRY_ATTEMPTS):
		var delay = BASE_RETRY_DELAY * pow(2, attempt)
		
		if attempt > 0:
			print("[SessionManager] Retry attempt %d/%d after %.1fs" % [attempt + 1, MAX_RETRY_ATTEMPTS, delay])
			await get_tree().create_timer(delay).timeout
		
		var result = await _do_refresh()
		if result:
			return true
	
	return false

func _do_refresh() -> bool:
	if not NakamaManager or not NakamaManager.client or not NakamaManager.session:
		return false
	
	var refresh_result = await NakamaManager.client.session_refresh_async(NakamaManager.session)
	
	if refresh_result.is_exception():
		print("[SessionManager] Refresh error: ", refresh_result.get_exception().message)
		return false
	
	# Update the session in NakamaManager
	NakamaManager.session = refresh_result
	return true