extends Node3D

signal province_selected(index : int)
signal map_view_camera_changed(near_left : Vector2, far_left : Vector2, far_right : Vector2, near_right : Vector2)

const _action_north : StringName = &"map_north"
const _action_east : StringName = &"map_east"
const _action_south : StringName = &"map_south"
const _action_west : StringName = &"map_west"
const _action_zoom_in : StringName = &"map_zoom_in"
const _action_zoom_out : StringName = &"map_zoom_out"
const _action_drag : StringName = &"map_drag"
const _action_click : StringName = &"map_click"

@export var _camera : Camera3D

@export var _cardinal_move_speed : float = 1.0
@export var _edge_move_threshold: float = 0.01
@export var _edge_move_speed: float = 2.5
var _drag_anchor : Vector2
var _drag_active : bool = false

var _mouse_over_viewport : bool = true

@export var _zoom_target_min : float = 0.05
@export var _zoom_target_max : float = 5.0
@export var _zoom_target_step : float = 0.1
@export var _zoom_epsilon : float = _zoom_target_step * 0.1
@export var _zoom_speed : float = 5.0
@export var _zoom_target : float = 1.0:
	get: return _zoom_target
	set(v): _zoom_target = clamp(v, _zoom_target_min, _zoom_target_max)

@export var _map_mesh_instance : MeshInstance3D
var _map_mesh : MapMesh
var _map_shader_material : ShaderMaterial
var _map_mesh_corner : Vector2
var _map_mesh_dims : Vector2

var _mouse_pos_viewport : Vector2 = Vector2(0.5, 0.5)
var _mouse_pos_map : Vector2 = Vector2(0.5, 0.5)
var _viewport_dims : Vector2 = Vector2(1, 1)

# ??? Strange Godot/GDExtension Bug ???
# Upon first opening a clone of this repo with the Godot Editor,
# if GameSingleton.get_province_index_image is called before MapMesh
# is referenced in the script below, then the editor will crash due
# to a failed HashMap lookup. I'm not sure if this is a bug in the
# editor, GDExtension, my own extension, or a combination of them.
# This was an absolute pain to track down. --- hop311
func _ready():
	if _camera == null:
		push_error("MapView's _camera variable hasn't been set!")
		return
	_zoom_target = _camera.position.y
	if _map_mesh_instance == null:
		push_error("MapView's _map_mesh variable hasn't been set!")
		return

	# Shader Material
	var map_material := _map_mesh_instance.get_active_material(0)
	if Events.ShaderManager.set_up_shader(map_material, true) != OK:
		push_error("Failed to set up map shader")
		return
	_map_shader_material = map_material

	if not _map_mesh_instance.mesh is MapMesh:
		push_error("Invalid map mesh class: ", _map_mesh_instance.mesh.get_class(), "(expected MapMesh)")
		return
	_map_mesh = _map_mesh_instance.mesh

	# Set map mesh size and get bounds
	_map_mesh.aspect_ratio = GameSingleton.get_aspect_ratio()
	_map_shader_material.set_shader_parameter(Events.ShaderManager.param_terrain_tile_factor, float(GameSingleton.get_height()) / 64.0)
	var map_mesh_aabb := _map_mesh.get_core_aabb() * _map_mesh_instance.transform
	_map_mesh_corner = Vector2(
		min(map_mesh_aabb.position.x, map_mesh_aabb.end.x),
		min(map_mesh_aabb.position.z, map_mesh_aabb.end.z)
	)
	_map_mesh_dims = abs(Vector2(
		map_mesh_aabb.position.x - map_mesh_aabb.end.x,
		map_mesh_aabb.position.z - map_mesh_aabb.end.z
	))

func _notification(what : int):
	match what:
		NOTIFICATION_WM_MOUSE_ENTER: # Mouse inside window
			_on_mouse_entered_viewport()
		NOTIFICATION_WM_MOUSE_EXIT: # Mouse out of window
			_on_mouse_exited_viewport()

func _world_to_map_coords(pos : Vector3) -> Vector2:
	return (Vector2(pos.x, pos.z) - _map_mesh_corner) / _map_mesh_dims

func _viewport_to_map_coords(pos_viewport : Vector2) -> Vector2:
	var ray_origin := _camera.project_ray_origin(pos_viewport)
	var ray_normal := _camera.project_ray_normal(pos_viewport)
	# Plane with normal (0,1,0) facing upwards, at a distance 0 from the origin
	var intersection = Plane(0, 1, 0, 0).intersects_ray(ray_origin, ray_normal)
	if typeof(intersection) == TYPE_VECTOR3:
		return _world_to_map_coords(intersection as Vector3)
	else:
		# Normals parallel to the xz-plane could cause null intersections,
		# but the camera's orientation should prevent such normals
		push_error("Invalid intersection: ", intersection)
		return Vector2(0.5, 0.5)

func zoom_in() -> void:
	_zoom_target -= _zoom_target_step

func zoom_out() -> void:
	_zoom_target += _zoom_target_step

# REQUIREMENTS
# * SS-31
func _unhandled_input(event : InputEvent):
	if _mouse_over_viewport and event.is_action_pressed(_action_click):
		# Check if the mouse is outside of bounds
		if _map_mesh.is_valid_uv_coord(_mouse_pos_map):
			var selected_index := GameSingleton.get_province_index_from_uv_coords(_mouse_pos_map)
			_map_shader_material.set_shader_parameter(Events.ShaderManager.param_selected_index, selected_index)
			province_selected.emit(selected_index)
		else:
			print("Clicked outside the map!")
	elif event.is_action_pressed(_action_drag):
		if _drag_active:
			push_warning("Drag being activated while already active!")
		_drag_active = true
		_drag_anchor = _mouse_pos_map
	elif event.is_action_released(_action_drag):
		if not _drag_active:
			push_warning("Drag being deactivated while already not active!")
		_drag_active = false
	elif event.is_action_pressed(_action_zoom_in, true):
		zoom_in()
	elif event.is_action_pressed(_action_zoom_out, true):
		zoom_out()

func _physics_process(delta : float):
	_mouse_pos_viewport = get_viewport().get_mouse_position()
	_viewport_dims = Vector2(Resolution.get_current_resolution())
	# Process movement
	_movement_process(delta)
	# Keep within map bounds
	_clamp_over_map()
	# Process zooming
	_zoom_process(delta)
	# Orient based on height
	_update_orientation()
	# Update viewport on minimap
	_update_minimap_viewport()
	# Calculate where the mouse lies on the map
	_update_mouse_map_position()

# REQUIREMENTS
# * UIFUN-124
func _movement_process(delta : float) -> void:
	var direction : Vector2
	if _drag_active:
		direction = (_drag_anchor - _mouse_pos_map) * _map_mesh_dims
	else:
		direction = _edge_scrolling_vector() + _cardinal_movement_vector()
		# Scale movement speed with height
		direction *= _camera.position.y * delta
	_camera.position += Vector3(direction.x, 0, direction.y)

# REQUIREMENTS
# * UIFUN-125
func _edge_scrolling_vector() -> Vector2:
	if not _mouse_over_viewport:
		return Vector2()
	var mouse_vector := _mouse_pos_viewport / _viewport_dims - Vector2(0.5, 0.5)
	if abs(mouse_vector.x) < 0.5 - _edge_move_threshold and abs(mouse_vector.y) < 0.5 - _edge_move_threshold:
		mouse_vector *= 0
	return mouse_vector * _edge_move_speed

# REQUIREMENTS
# * SS-75
func _cardinal_movement_vector() -> Vector2:
	var move := Vector2(
		float(Input.is_action_pressed(_action_east)) - float(Input.is_action_pressed(_action_west)),
		float(Input.is_action_pressed(_action_south)) - float(Input.is_action_pressed(_action_north))
	)
	return move * _cardinal_move_speed

func _clamp_over_map() -> void:
	_camera.position.x = _map_mesh_corner.x + fposmod(_camera.position.x - _map_mesh_corner.x, _map_mesh_dims.x)
	_camera.position.z = clamp(_camera.position.z, _map_mesh_corner.y, _map_mesh_corner.y + _map_mesh_dims.y)

# REQUIREMENTS
# * SS-74
# * UIFUN-123
func _zoom_process(delta : float) -> void:
	var height := _camera.position.y
	var zoom := _zoom_target - height
	height += zoom * _zoom_speed * delta
	var new_zoom := _zoom_target - height
	# Set to target if height is within _zoom_epsilon of it or has overshot past it
	if abs(new_zoom) < _zoom_epsilon or sign(zoom) != sign(new_zoom):
		height = _zoom_target
	_camera.position.y = height

func _update_orientation() -> void:
	var dir := Vector3(0, -1, -exp(-_camera.position.y - 1))
	_camera.look_at(_camera.position + dir)

func _update_minimap_viewport() -> void:
	var near_left := _viewport_to_map_coords(Vector2(0, _viewport_dims.y))
	var far_left := _viewport_to_map_coords(Vector2(0, 0))
	var far_right := _viewport_to_map_coords(Vector2(_viewport_dims.x, 0))
	var near_right := _viewport_to_map_coords(_viewport_dims)
	map_view_camera_changed.emit(near_left, far_left, far_right, near_right)

func _update_mouse_map_position() -> void:
	_mouse_pos_map = _viewport_to_map_coords(_mouse_pos_viewport)
	var hover_index := GameSingleton.get_province_index_from_uv_coords(_mouse_pos_map)
	if _mouse_over_viewport:
		_map_shader_material.set_shader_parameter(Events.ShaderManager.param_hover_index, hover_index)

func _on_mouse_entered_viewport():
	_mouse_over_viewport = true

func _on_mouse_exited_viewport():
	_mouse_over_viewport = false

func _on_minimap_clicked(pos_clicked : Vector2):
	pos_clicked *= _map_mesh_dims
	_camera.position.x = pos_clicked.x
	_camera.position.z = pos_clicked.y
	_clamp_over_map()

func enable_processing() -> void:
	set_process_unhandled_input(true)
	set_physics_process(true)

func disable_processing() -> void:
	set_process_unhandled_input(false)
	set_physics_process(false)