extends Node3D
## Der Zugverband: Lok + Waggons auf der Strecke, Fahrphysik,
## und die Abbildung "Laengsposition im Zug" -> Weltkoordinate.

const CarScene = preload("res://scripts/car.gd")
const Defs = preload("res://scripts/car_defs.gd")
const Cargo = preload("res://scripts/cargo.gd")

signal consist_changed()

const GAP := 0.75              ## Abstand zwischen zwei Waggons
const DRAG := 0.6
const DOCK_RANGE := 3.0

var loco_id := "steam"
var consist: Array[String] = []   ## nur die Waggons, ohne Lok
var cars: Array = []              ## Car-Knoten, Index 0 = Lok
var followers: Array[PathFollow3D] = []

var progress := 0.0               ## Position der Zugspitze auf der Kurve
var speed := 0.0
var throttle := 0.0
var braking := false
var cargo: Dictionary = {}        ## Cargo.Type -> int
var stations: Array = []
var docked_at: Node = null

var _track
var _stand_time := 0.0

func setup(track, station_list: Array) -> void:
	_track = track
	stations = station_list

func max_speed() -> float:
	return float(Defs.LOCOS[loco_id]["max_speed"])

func accel() -> float:
	return float(Defs.LOCOS[loco_id]["accel"])

func brake_power() -> float:
	return float(Defs.LOCOS[loco_id]["brake"])

func speed_kmh() -> float:
	return speed * 3.6

func cargo_capacity() -> int:
	var n := 0
	for c in cars:
		n += c.capacity
	return n

func total_cargo() -> int:
	var n := 0
	for v in cargo.values():
		n += int(v)
	return n

func has_dining() -> bool:
	for c in cars:
		if c.kind == Defs.Kind.DINING:
			return true
	return false

func seat_count() -> int:
	var n := 0
	for c in cars:
		n += c.seats.size()
	return n

# --- Verband aufbauen -----------------------------------------------------

func rebuild() -> void:
	for f in followers:
		f.queue_free()
	followers.clear()
	cars.clear()

	var ids: Array[String] = [loco_id]
	ids.append_array(consist)
	var s := 0.0
	for i in ids.size():
		var car = CarScene.new()
		car.build(ids[i])
		car.index = i
		car.center_s = s - car.length * 0.5
		s = car.center_s - car.length * 0.5 - GAP
		var f := PathFollow3D.new()
		f.loop = true
		f.rotation_mode = PathFollow3D.ROTATION_Y
		f.use_model_front = true
		f.cubic_interp = true
		f.add_child(car)
		_track.path.add_child(f)
		followers.append(f)
		cars.append(car)
	_sync_followers()
	refresh_cargo_visuals()
	consist_changed.emit()

func total_length() -> float:
	if cars.is_empty():
		return 0.0
	var last = cars[cars.size() - 1]
	return abs(last.center_s - last.length * 0.5)

## Begehbarer Bereich als [hinten, vorne] in Zug-Laengskoordinaten.
func walk_range() -> Vector2:
	if cars.is_empty():
		return Vector2.ZERO
	var front = cars[0]
	var back = cars[cars.size() - 1]
	return Vector2(back.center_s + back.inner_z0 + 0.35, front.center_s + front.inner_z1 - 0.35)

## Findet den Waggon zu einer Laengsposition.
func locate(s: float) -> Dictionary:
	var best := 0
	var best_d := INF
	for i in cars.size():
		var c = cars[i]
		var lo: float = c.center_s + c.inner_z0
		var hi: float = c.center_s + c.inner_z1
		if s >= lo and s <= hi:
			return {"index": i, "local_z": s - c.center_s, "gangway": false}
		var d: float = min(absf(s - lo), absf(s - hi))
		if d < best_d:
			best_d = d
			best = i
	var c2 = cars[best]
	return {"index": best, "local_z": s - c2.center_s, "gangway": true}

func car_transform(i: int) -> Transform3D:
	return followers[i].global_transform

## Weltposition eines Punktes im Zug (x quer, y hoch, s laengs).
func world_point(s: float, x: float, y: float) -> Transform3D:
	var loc := locate(s)
	var xf: Transform3D = car_transform(int(loc["index"]))
	return xf.translated_local(Vector3(x, y, float(loc["local_z"])))

func _sync_followers() -> void:
	var l: float = _track.length()
	for i in cars.size():
		followers[i].progress = fposmod(progress + cars[i].center_s, l)

# --- Ladung ---------------------------------------------------------------

func refresh_cargo_visuals() -> void:
	var units: Array[int] = []
	for t in cargo.keys():
		for i in int(cargo[t]):
			units.append(int(t))
	var idx := 0
	for c in cars:
		if c.capacity <= 0:
			continue
		var take: int = mini(c.capacity, units.size() - idx)
		if take <= 0:
			c.show_cargo(0, Color.WHITE)
			continue
		c.show_cargo(take, Cargo.COLORS[units[idx]])
		idx += take

func add_cargo(t: int, amount: int) -> int:
	var free: int = cargo_capacity() - total_cargo()
	var take: int = mini(free, amount)
	if take > 0:
		cargo[t] = int(cargo.get(t, 0)) + take
		refresh_cargo_visuals()
	return take

func remove_cargo(t: int, amount: int) -> int:
	var have: int = int(cargo.get(t, 0))
	var take: int = mini(have, amount)
	if take > 0:
		cargo[t] = have - take
		if cargo[t] <= 0:
			cargo.erase(t)
		refresh_cargo_visuals()
	return take

# --- Fahrt ----------------------------------------------------------------

func drive(delta: float) -> void:
	if braking:
		speed = maxf(speed - brake_power() * delta, 0.0)
	elif throttle > 0.0:
		speed = minf(speed + accel() * throttle * delta, max_speed())
	else:
		speed = maxf(speed - DRAG * delta, 0.0)
	progress = fposmod(progress + speed * delta, _track.length())
	_sync_followers()
	_update_dock(delta)

## Nur Anzeige aktualisieren (Clients im Netzspiel).
func apply_snapshot(p: float, v: float) -> void:
	progress = p
	speed = v
	_sync_followers()
	_update_dock(0.0)

func _update_dock(delta: float) -> void:
	var near := nearest_station()
	var st: Node = near[0]
	var dist: float = near[1]
	if st == null:
		return
	if speed > 0.15 or dist > DOCK_RANGE:
		_stand_time = 0.0
		docked_at = null
		return
	_stand_time += delta
	docked_at = st

## Abstand eines Bahnhofs zum Zug. 0, solange der Bahnsteig neben dem
## Zug liegt - sonst waere ein langer Zug nie richtig am Bahnsteig.
func station_gap(st) -> float:
	var l: float = _track.length()
	var behind: float = fposmod(progress - st.progress, l)
	var len_train: float = total_length()
	if behind <= len_train:
		return 0.0
	return minf(behind - len_train, l - behind)

func nearest_station() -> Array:
	var best: Node = null
	var best_d := INF
	for s in stations:
		var d: float = station_gap(s)
		if d < best_d:
			best_d = d
			best = s
	return [best, best_d]

func next_station() -> Array:
	var best: Node = null
	var best_d := INF
	var l: float = _track.length()
	for s in stations:
		var d: float = fposmod(s.progress - progress, l)
		if d < best_d:
			best_d = d
			best = s
	return [best, best_d]