extends Node
class_name Selection
## Pawn selection + click-to-move input handler.
##
## A click on a pawn selects it; a click on a walkable tile while a pawn is
## selected pathfinds + commands the walk. Drags belong to the camera (pan)
## — we discriminate clicks from drags by motion + duration thresholds.
##
## Lives as a child of World; `_unhandled_input` runs after the camera rig
## and after any CanvasLayer UI swallows its own clicks.

const CLICK_MAX_DRIFT_PX: float = 8.0
const CLICK_MAX_DURATION_MS: int = 300

var _pathfinder: Pathfinder = null
var _selected_pawn: Pawn = null

var _press_screen_pos: Vector2 = Vector2.ZERO
var _press_time_ms: int = 0
var _pressing: bool = false


func bind(pathfinder: Pathfinder) -> void:
	assert(pathfinder != null, "Selection.bind: pathfinder is null")
	_pathfinder = pathfinder


func selected() -> Pawn:
	return _selected_pawn


func _unhandled_input(event: InputEvent) -> void:
	if not (event is InputEventMouseButton):
		return
	if event.button_index != MOUSE_BUTTON_LEFT:
		return
	if event.pressed:
		_press_screen_pos = event.position
		_press_time_ms = Time.get_ticks_msec()
		_pressing = true
		return
	if not _pressing:
		return
	_pressing = false
	var drift: float = event.position.distance_to(_press_screen_pos)
	var dt_ms: int = Time.get_ticks_msec() - _press_time_ms
	# Anything that drifted more than a few pixels or sat for more than 300 ms
	# is the camera's drag-pan; ignore it as a select/move action.
	if drift > CLICK_MAX_DRIFT_PX or dt_ms > CLICK_MAX_DURATION_MS:
		return
	_handle_click(event.position)


func _handle_click(screen_pos: Vector2) -> void:
	if _pathfinder == null:
		Audit.log("selection", "click before bind() — ignored")
		return

	var world_pos: Vector2 = get_viewport().get_canvas_transform().affine_inverse() * screen_pos
	var tile: Vector2i = Vector2i(
		floori(world_pos.x / float(Pawn.TILE_SIZE_PX)),
		floori(world_pos.y / float(Pawn.TILE_SIZE_PX)),
	)

	# Click on a pawn → select.
	var hit_pawn: Pawn = World.pawn_at_tile(tile)
	if hit_pawn != null:
		_select(hit_pawn)
		return

	# Empty tile with no current selection → no-op.
	if _selected_pawn == null:
		return

	# Empty walkable tile with a selection → pathfind + command move.
	if not _pathfinder.is_walkable(tile):
		Audit.log("selection", "destination %s not walkable" % tile)
		return
	var path: Array[Vector2i] = _pathfinder.find_path(_selected_pawn.tile, tile)
	if path.is_empty():
		Audit.log("selection", "no path %s → %s" % [_selected_pawn.tile, tile])
		return
	_selected_pawn.walk_along_path(path)


func _select(pawn: Pawn) -> void:
	if _selected_pawn == pawn:
		return
	if _selected_pawn != null:
		_selected_pawn.set_selected(false)
	_selected_pawn = pawn
	pawn.set_selected(true)
	Audit.log("selection", "selected %s at %s" % [pawn.pawn_name, pawn.tile])