extends SceneTree

## Regression for the original "slide, then walk, then run" locomotion bug.
##
##   godot --headless --path . -s res://debug/transition_check.gd -- [skin_glb]
##
## Ground acceleration is the same exponential response as state_ground.gd.
## The test proves that the authored BlendSpace receives that physical speed on
## the same frame, including the first high-acceleration frame and the stop
## frame. It also proves that the removed procedural lean/brake layer stays off.

const RESPONSE := 60.0
const TOP := 11.0
const DT := 1.0 / 60.0
const RUN_FRAMES := 24

var _frames := 0
var _model: SkinnedPlayerModel = null
var _speed := 0.0
var _first_speed := -1.0
var _first_stride := -1.0
var _worst_error := 0.0
var _stop_stride := -1.0
var _manual_tick := false
var _foot_bone := -1
var _foot_rotation_start := Quaternion.IDENTITY
var _foot_rotation_delta := 0.0


func _initialize() -> void:
	var args := OS.get_cmdline_user_args()
	var path: String = args[0] if args.size() > 0 \
		else "res://assets/characters/skins/miku.glb"
	var scene := Node3D.new()
	root.add_child(scene)
	current_scene = scene
	_model = SkinnedPlayerModel.new()
	_model.model_path = path
	scene.add_child(_model)


func _process(_delta: float) -> bool:
	_frames += 1
	if _frames < 8 or not _model.loaded:
		return false
	if not _manual_tick:
		_model.set_process(false)
		_manual_tick = true
		_foot_bone = _model._role_bone("foot.L",
			["foot.L", "LeftFoot", "Left ankle"])

	var sample := _frames - 8
	if sample < RUN_FRAMES:
		var response := 1.0 - exp(-RESPONSE * DT)
		_speed = lerpf(_speed, TOP, response)
	else:
		_speed = 0.0

	# Same order as the live controller: direction first, then physical speed.
	_model.set_locomotion(0.0, 1.0 if _speed > 0.01 else 0.0, 0.0)
	_model.update_state("ground", _speed, false)
	_model._process(DT)

	var stride := _model.locomotion_effective_speed_debug()
	_worst_error = maxf(_worst_error, absf(stride - _speed))
	if _foot_bone >= 0:
		var foot_rotation := _model.skeleton.get_bone_pose_rotation(_foot_bone)
		if sample == 1:
			_foot_rotation_start = foot_rotation
		elif sample > 1 and sample < RUN_FRAMES:
			_foot_rotation_delta = maxf(_foot_rotation_delta,
				_foot_rotation_start.angle_to(foot_rotation))
	if sample == 0:
		_first_speed = _speed
		_first_stride = stride
	if sample == RUN_FRAMES:
		_stop_stride = stride

	if sample > RUN_FRAMES + 2:
		print("\n=== velocity-driven locomotion ===")
		print("  first frame: body %.3f m/s, authored stride %.3f m/s" \
			% [_first_speed, _first_stride])
		print("  worst stride/speed error: %.5f m/s" % _worst_error)
		print("  stop-frame stride: %.5f m/s" % _stop_stride)
		print("  animated foot rotation delta: %.5f rad" % _foot_rotation_delta)
		print("  procedural lean %.5f, brake %.5f" \
			% [_model.get_lean_debug(), _model.get_brake_debug()])

		var failures: Array[String] = []
		if _first_speed < 6.0:
			failures.append("test did not reproduce high first-frame acceleration")
		if absf(_first_stride - _first_speed) > 0.02:
			failures.append("legs did not receive first-frame physical speed")
		if _worst_error > 0.02:
			failures.append("authored stride diverged from physical speed")
		if _stop_stride > 0.02:
			failures.append("legs did not reach Idle on the stop frame")
		if _foot_bone < 0:
			failures.append("could not resolve a foot bone")
		elif _foot_rotation_delta < 0.03:
			failures.append("runtime foot pose stayed static")
		if absf(_model.get_lean_debug()) > 0.02:
			failures.append("procedural locomotion lean is still active")
		if absf(_model.get_brake_debug()) > 0.02:
			failures.append("procedural stop pose is still active")

		if failures.is_empty():
			print("TRANSITION_CHECK PASS: same-frame, authored locomotion\n")
			quit(0)
		else:
			for failure in failures:
				push_error("TRANSITION_CHECK FAIL: " + failure)
			quit(1)
		return true
	return false