extends CharacterBody3D

const JUMP_SPEED: float = 5
const MOUSE_SENSITIVITY: float = 0.002
const CROUCH_MOVE_SPEED: float = 3
const BASE_MOVE_SPEED: float = 5
const SPRINT_MOVE_SPEED: float = 8
const BASE_HEIGHT: float = 2.0
const CROUCH_HEIGHT: float = 1.0
const FRICTION: float = 0.2
const AIR_FRICTION: float = 0.025
const CROUCH_TRANSITION_SPEED: float = 0.1

enum MovementMode {
	Crouching,
	Sprinting,
	Walking,
}

var current_movement := MovementMode.Walking
var gravity: float = ProjectSettings.get_setting("physics/3d/default_gravity")
var move_speed: float = BASE_MOVE_SPEED
var target_height: float = BASE_HEIGHT
var flying := false

@onready var body_collision_shape: CollisionShape3D = $BodyCollisionShape
@onready var fps_camera: Camera3D = $FPSCamera
@onready var head_collision_shape: CollisionShape3D \
	= $HeadCollider/HeadCollisionShape
@onready var head_collider: Area3D = $HeadCollider

func _ready() -> void:
	Input.mouse_mode = Input.MOUSE_MODE_CAPTURED
	head_collision_shape.set_deferred("disabled", true)

func _process(_delta: float) -> void:
	if Input.is_action_just_pressed("pause"):
		if Input.mouse_mode == Input.MOUSE_MODE_CAPTURED:
			Input.mouse_mode = Input.MOUSE_MODE_VISIBLE
		else:
			Input.mouse_mode = Input.MOUSE_MODE_CAPTURED

func _physics_process(delta: float) -> void:
	handle_state_transition()
	handle_movement(delta)
	
	body_collision_shape.shape.height = lerpf(body_collision_shape.shape.height, 
		target_height, CROUCH_TRANSITION_SPEED)
		
	move_and_slide()
	if (is_on_floor() or flying) and Input.is_action_just_pressed("jump"):
		velocity.y = JUMP_SPEED
		
func _input(event: InputEvent) -> void:
	if event is InputEventMouseMotion \
		and Input.mouse_mode == Input.MOUSE_MODE_CAPTURED:
		rotate_y(-event.relative.x * MOUSE_SENSITIVITY)
		fps_camera.rotate_x(-event.relative.y * MOUSE_SENSITIVITY)
		fps_camera.rotation.x = clampf(fps_camera.rotation.x, 
			-deg_to_rad(70), deg_to_rad(70))

func handle_movement(delta: float) -> void:
	velocity.y += 0.0 if flying else -gravity * delta
	
	if Input.is_action_just_pressed("_cheat_fly"):
		flying = not flying
	
	var input = Input.get_vector("strafe_left", "strafe_right",
		"move_forward", "move_backward")
	
	var movement_dir := transform.basis * Vector3(input.x, 0, input.y)
	if movement_dir.x == 0:
		velocity.x = lerpf(velocity.x, 0.0, 
			FRICTION if is_on_floor() else AIR_FRICTION)
	else:
		velocity.x = movement_dir.x * move_speed
		
	if movement_dir.z == 0:
		velocity.z = lerpf(velocity.z, 0.0, 
			FRICTION if is_on_floor() else AIR_FRICTION)
	else:
		velocity.z = movement_dir.z * move_speed

func handle_state_transition() -> void:
	match current_movement:
		MovementMode.Crouching:
			if not Input.is_action_pressed("crouch") \
				and not head_collider.has_overlapping_bodies():
				change_state(MovementMode.Walking)
		MovementMode.Walking:
			if Input.is_action_pressed("crouch"):
				change_state(MovementMode.Crouching)
			elif Input.is_action_pressed("sprint"):
				change_state(MovementMode.Sprinting)
		MovementMode.Sprinting:
			if Input.is_action_pressed("crouch"):
				change_state(MovementMode.Crouching)
			elif not Input.is_action_pressed("sprint"):
				change_state(MovementMode.Walking)

func change_state(new_state: MovementMode) -> void:
	if new_state == current_movement:
		return
	
	exit_state()
	current_movement = new_state
	enter_state()

func exit_state() -> void:
	match current_movement:
		MovementMode.Crouching:
			head_collision_shape.set_deferred("disabled", true)

func enter_state() -> void:
	match current_movement:
		MovementMode.Walking:
			move_speed = BASE_MOVE_SPEED
			target_height = BASE_HEIGHT
		MovementMode.Crouching:
			head_collision_shape.set_deferred("disabled", false)
			move_speed = CROUCH_MOVE_SPEED
			target_height = CROUCH_HEIGHT
		MovementMode.Sprinting:
			move_speed = SPRINT_MOVE_SPEED
			target_height = BASE_HEIGHT