class_name ImplantApp
extends Control
## Base class for all implant apps. Absorbs HudGroups boilerplate; subclasses
## override lifecycle hooks only (#844, D-191).
##
## === Lifecycle ordering ===
##
## on_install() — called once from _ready(), after nav is created but BEFORE any
##   HudGroups open event fires. The nav stack is EMPTY at this point. Use this
##   hook to: construct screens and call register_screen(id, screen), set
##   nav.set_default("..."), wire intra-screen signals. Do NOT rely on
##   current_screen_id() here — no screen has been pushed yet.
##
## on_open(mode) — called every time HudGroups activates this app (FULLSCREEN or
##   INSERT). By the time on_open fires, the base has ensured the nav stack is
##   non-empty: if preserves_state=false, nav.reset_to_default() was called; if
##   preserves_state=true and the stack was empty, nav.push_default() was called.
##   nav.current() returns the visible screen id. Safe to read navigation state
##   and trigger data refreshes here.
##
## on_close() — called every time HudGroups deactivates this app (GAMEPLAY mode
##   or another app taking focus). Nav stack state is preserved here — do not
##   push or pop screens in on_close. Use this hook for: pausing timers, stopping
##   animations, unsubscribing from high-frequency feeds. The stack survives
##   intact for the next on_open (if preserves_state=true).
##
## on_insert_deactivated() — called by SnapshotConsumers when the server drops
##   insert state. The base implementation closes the app only if it is currently
##   active in INSERT mode. FULLSCREEN apps inherit a no-op; override to add
##   custom handling (e.g. save draft, emit warning). Do not call close_app()
##   manually — call super() or replicate the guard condition.
##
## === Subclass _ready() pattern ===
##   func _ready() -> void:
##       manifest = load("res://ui/implant/apps/my_app/app.tres")
##       super._ready()
##       # additional init here if needed

signal app_opened(mode: int)
signal app_closed

var manifest: ImplantAppManifest = null
var nav: ImplantNavStack = null

var _screens: Dictionary = {}  # screen_id → Control
var _current_screen_id: String = ""


func _ready() -> void:
	set_anchors_preset(Control.PRESET_FULL_RECT)
	mouse_filter = Control.MOUSE_FILTER_STOP
	visible = false

	if manifest:
		HudGroups.register(self, manifest.app_path)
	HudGroups.app_changed.connect(_internal_app_changed)

	nav = ImplantNavStack.new()
	nav.screen_changed.connect(_on_screen_changed)
	add_child(nav)

	on_install()


func _internal_app_changed(app_path: String, mode: int) -> void:
	if manifest == null:
		return
	if app_path != manifest.app_path:
		if visible:
			visible = false
			on_close()
			app_closed.emit()
		return

	match mode:
		HudGroups.Mode.FULLSCREEN, HudGroups.Mode.INSERT:
			if not visible:
				visible = true
				if not manifest.preserves_state:
					nav.reset_to_default()
				elif nav.is_empty():
					nav.push_default()
				on_open(mode)
				app_opened.emit(mode)
		HudGroups.Mode.GAMEPLAY:
			if visible:
				visible = false
				on_close()
				app_closed.emit()


# --- Lifecycle hooks — subclasses override ---


func on_install() -> void:
	pass


func on_open(_mode: int) -> void:
	pass


func on_close() -> void:
	pass


func on_insert_deactivated() -> void:
	# Default: close only if active in INSERT mode. FULLSCREEN apps override to customize.
	if manifest and HudGroups.is_app_active(manifest.app_path):
		if HudGroups.get_active_mode() == HudGroups.Mode.INSERT:
			HudGroups.close_app()


# --- Screen management ---


## Register a screen under an id. Base adds it as a child and starts it hidden.
## Call from on_install(). Wire signals before calling register_screen.
func register_screen(id: String, screen: Control) -> void:
	if _screens.has(id):
		push_warning("ImplantApp: screen id '%s' already registered" % id)
		return
	_screens[id] = screen
	screen.visible = false
	if screen.get_parent() == null:
		add_child(screen)


func current_screen_id() -> String:
	return _current_screen_id


## T-971 (AtlasAgentInterface, D-226 item 4): a generic, read-only screen
## lookup by id — the same `_screens` dict register_screen() already
## maintains, exposed so an agent-control channel can reach a specific
## screen instance (StepCanvasViewer via RegionalScreen.get_viewer(), etc.)
## without every ImplantApp subclass growing its own bespoke getters. Returns
## null for an unregistered id, matching Dictionary.get()'s own default.
func get_screen(screen_id: String) -> Variant:
	return _screens.get(screen_id, null)


func _on_screen_changed(new_id: String) -> void:
	if _current_screen_id != new_id:
		var old: Control = _screens.get(_current_screen_id, null)
		if old:
			if old.has_method("leave"):
				old.leave()
			old.visible = false
	_current_screen_id = new_id
	var s: Control = _screens.get(new_id, null)
	if s:
		s.visible = true
		if s.has_method("enter"):
			s.enter(nav.current_payload())


func handle_intent(_action: String, _params: Dictionary) -> void:
	pass