extends Node3D

@export var camera    : Camera
@export var skeleton  : Skeleton3D
@export var root_bone : BoneAttachment3D

@onready var player      := find_parent("Player") as Player
@onready var anim_tree   := $AnimationTree as AnimationTree
@onready var anim_player := anim_tree.get_node(anim_tree.anim_player) as AnimationPlayer

@onready var camera_default_transform := camera.transform

@onready var walk_forward_anim  := anim_player.get_animation("walk_forward")
@onready var walk_backward_anim := anim_player.get_animation("walk_backward")

# TODO: @onready var walk_loop_length := walk_forward_anim.length

# Contains all the bones in the skeleton, keyed by name (e.g. "LowerArm_L").
var bones := {  }

# Whether the player's body is currently turning to match up with the camera rotation.
var is_turning := false

# Current amount the body is turned due to walking sideways.
var body_yaw := 0.0 # radians


func _ready() -> void:
	var add_bone := func(bone: BoneAttachment3D) -> void:
		bone.override_pose = true
		bones[bone.name] = bone

	add_bone.call(root_bone)
	for child in root_bone.find_children("*", "BoneAttachment3D"):
		add_bone.call(child as BoneAttachment3D)


func _process(delta: float) -> void:
	reset_transforms()
	handle_turning(delta)
	handle_looking_animation(delta)
	handle_walking_animation(delta)


func reset_transforms() -> void:
	for bone_name in bones:
		var bone := bones[bone_name] as BoneAttachment3D
		bone.transform = skeleton.get_bone_pose(bone.bone_idx)
	camera.transform = camera_default_transform


func handle_turning(delta: float) -> void:
	const TURN_BEGIN := 60.0 # Start turning when camera is rotated this much.
	const TURN_END   :=  5.0 # Stop turning when body is this close to camera rotation.
	const TURN_SPEED :=  6.0

	var yaw := camera.current_yaw # Camera yaw relative to player yaw.
	if player.is_moving || abs(yaw) > deg_to_rad(TURN_BEGIN):
		is_turning = true
	if is_turning:
		var yaw_delta = sign(yaw) * min(abs(yaw), (abs(yaw) * TURN_SPEED) * delta)
		player.rotate_y(yaw_delta)
		camera.current_yaw -= yaw_delta
		if abs(camera.current_yaw) < deg_to_rad(TURN_END):
			is_turning = false


func handle_looking_animation(_delta: float) -> void:
	const PITCH_FACTOR_NECK := 0.25
	const PITCH_FACTOR_HEAD := 0.35

	var pitch := camera.current_pitch
	bones["Neck"].rotate_x(-pitch * PITCH_FACTOR_NECK)
	bones["Head"].rotate_x(-pitch * PITCH_FACTOR_HEAD)
	camera.rotate_x(pitch * (1 - PITCH_FACTOR_NECK - PITCH_FACTOR_HEAD))

	const YAW_FACTOR_LOWER_BODY := 0.06
	const YAW_FACTOR_UPPER_BODY := 0.18
	const YAW_FACTOR_NECK := 0.2
	const YAW_FACTOR_HEAD := 0.3

	var yaw := camera.current_yaw
	bones["LowerBody"].global_rotate(Vector3.UP, yaw * YAW_FACTOR_LOWER_BODY)
	bones["UpperBody"].global_rotate(Vector3.UP, yaw * YAW_FACTOR_UPPER_BODY)
	bones["Neck"].global_rotate(Vector3.UP, yaw * YAW_FACTOR_NECK)
	bones["Head"].global_rotate(Vector3.UP, yaw * YAW_FACTOR_HEAD)
	camera.global_rotate(Vector3.UP, yaw * (1 - YAW_FACTOR_LOWER_BODY - YAW_FACTOR_UPPER_BODY - YAW_FACTOR_NECK - YAW_FACTOR_HEAD))

	# How much of the "ideal" camera rotation (rather than animation rotation) should be applied.
	const CAMERA_FACTOR_IDEAL_PITCH := 1.0 # 0.7
	const CAMERA_FACTOR_IDEAL_YAW   := 1.0 # 0.8
	const CAMERA_FACTOR_IDEAL_ROLL  := 1.0 # 0.9

	var global_yaw := player.rotation.y + yaw
	camera.global_rotation.x = lerp_angle(camera.global_rotation.x, pitch, CAMERA_FACTOR_IDEAL_PITCH)
	camera.global_rotation.y = lerp_angle(camera.global_rotation.y, global_yaw, CAMERA_FACTOR_IDEAL_YAW)
	camera.global_rotation.z = lerp_angle(camera.global_rotation.z, 0, CAMERA_FACTOR_IDEAL_ROLL)


func handle_walking_animation(delta: float) -> void:
	var input := Input.get_vector("move_strafe_left", "move_strafe_right", "move_forward", "move_backward")
	var is_on_floor := player.time_since_on_floor < 0.25
	var is_moving_forward := input.y <= 0

	var walk_state : String
	var walk_direction : String
	var target_body_yaw : float

	if is_on_floor && player.is_moving:
		walk_state = "move"
	else:
		walk_state = "idle"

	if is_moving_forward:
		walk_direction = "forward"
		target_body_yaw = -Vector2.UP.angle_to(input)
	else:
		walk_direction = "backward"
		target_body_yaw = -Vector2.DOWN.angle_to(input)

	anim_tree["parameters/walk_state/transition_request"] = walk_state
	anim_tree["parameters/walk_direction/transition_request"] = walk_direction

	const YAW_FACTOR_LOWER_BODY := 0.25
	const YAW_FACTOR_UPPER_BODY := 0.25
	const YAW_FACTOR_NECK       := 0.50

	body_yaw += (target_body_yaw - body_yaw) * delta * 6

	bones["Root"].global_rotate(Vector3.UP, body_yaw)
	bones["LowerBody"].global_rotate(Vector3.UP, -body_yaw * YAW_FACTOR_LOWER_BODY)
	bones["UpperBody"].global_rotate(Vector3.UP, -body_yaw * YAW_FACTOR_UPPER_BODY)
	bones["Neck"].global_rotate(Vector3.UP, -body_yaw * YAW_FACTOR_NECK)


static func angle_difference(from: float, to: float) -> float:
	return fposmod(to - from + PI, TAU) - PI