extends SceneTree

## Asset-free semantic, dependency and timing regression for chunk queue planning.

const PLANNER_SCRIPT := preload(
	"res://src/render/terrain/terrain_chunk_geometry_queue_planner.gd"
)
const POSITION_SCRIPT := preload("res://src/domain/coordinates/godot_world_position.gd")
const LOADER_PATH := "res://src/scenes/streaming/streaming_world_loader.gd"


func _initialize() -> void:
	var failures: Array[String] = []
	_verify_create_remove_and_order(failures)
	_verify_tile_lod_removes_all(failures)
	_verify_fallback_origin_and_vertical_invariance(failures)
	_verify_invalid_focus(failures)
	_verify_loader_boundary(failures)
	var elapsed_milliseconds := _verify_bounded_timing(failures)
	if not failures.is_empty():
		for failure in failures:
			push_error("TERRAIN_CHUNK_GEOMETRY_QUEUE_PLANNER: %s" % failure)
		quit(1)
		return
	print(
		"TERRAIN_CHUNK_GEOMETRY_QUEUE_PLANNER PASS cases=8 iterations=100 elapsed_ms=%.3f"
		% elapsed_milliseconds
	)
	quit(0)


func _verify_create_remove_and_order(failures: Array[String]) -> void:
	var planner: RefCounted = PLANNER_SCRIPT.new()
	var tile_states := {
		"A": _create_tile_state(
			{0: {"lod": 0}, 1: {"lod": 1}, 3: {"lod": 0}},
			{0: 0, 1: 2, 2: 1},
			[
				{"origin": Vector3(100.0, 0.0, 0.0)},
				{"origin": Vector3(30.0, 8000.0, 0.0)},
				{"origin": Vector3(10.0, -8000.0, 0.0)},
			]
		),
		"B": _create_tile_state({5: {"lod": 0}}, {}, []),
	}
	var plan: Dictionary = planner.call("plan", tile_states, POSITION_SCRIPT.new(0.0, 50.0, 0.0))
	var creates: Array = plan["create_requests"]
	var removes: Array = plan["remove_requests"]
	_expect_equal(creates.size(), 2, "missing and mismatched chunks create", failures)
	_expect_equal(int(creates[0]["chunk"]), 2, "nearest missing chunk first", failures)
	_expect_equal(int(creates[1]["chunk"]), 1, "farther LOD mismatch second", failures)
	_expect_equal(int(creates[1]["lod"]), 2, "mismatch uses desired LOD", failures)
	_expect_equal(removes.size(), 2, "undesired current chunks remove", failures)
	_expect_string_equal(String(removes[0]["tile"]), "A", "stable tile removal order", failures)
	_expect_equal(int(removes[0]["chunk"]), 3, "first undesired chunk", failures)
	_expect_equal(int(removes[1]["chunk"]), 5, "second tile undesired chunk", failures)


func _verify_tile_lod_removes_all(failures: Array[String]) -> void:
	var tile_state := _create_tile_state({7: {"lod": 0}, 8: {"lod": 1}}, {7: 0}, [])
	tile_state["desired_tile_lod"] = 3
	var plan: Dictionary = PLANNER_SCRIPT.new().call(
		"plan",
		{"tile": tile_state},
		POSITION_SCRIPT.new(0.0, 0.0, 0.0)
	)
	_expect_true((plan["create_requests"] as Array).is_empty(), "tile LOD suppresses chunk creates", failures)
	_expect_equal((plan["remove_requests"] as Array).size(), 2, "tile LOD removes every chunk", failures)


func _verify_fallback_origin_and_vertical_invariance(failures: Array[String]) -> void:
	var tile_state := _create_tile_state({}, {9: 1}, [])
	tile_state["origin"] = Vector3(4.0, 99999.0, 3.0)
	var plan: Dictionary = PLANNER_SCRIPT.new().call(
		"plan",
		{"fallback": tile_state},
		POSITION_SCRIPT.new(0.0, -99999.0, 0.0)
	)
	var request: Dictionary = (plan["create_requests"] as Array)[0]
	_expect_near(float(request["dist_sq"]), 25.0, "fallback origin uses horizontal distance", failures)


func _verify_invalid_focus(failures: Array[String]) -> void:
	var plan: Dictionary = PLANNER_SCRIPT.new().call("plan", {}, null)
	_expect_true((plan["create_requests"] as Array).is_empty(), "invalid focus create empty", failures)
	_expect_true((plan["remove_requests"] as Array).is_empty(), "invalid focus remove empty", failures)


func _verify_loader_boundary(failures: Array[String]) -> void:
	var source := _read_text(LOADER_PATH, failures)
	_expect_true(source.contains("TERRAIN_CHUNK_GEOMETRY_QUEUE_PLANNER_SCRIPT.new()"), "loader composes planner", failures)
	_expect_true(source.contains("_terrain_chunk_geometry_operation_planner.plan("), "loader delegates plan", failures)
	_expect_true(not source.contains("func _chunk_origin_for("), "loader omits chunk-origin planning", failures)
	_expect_true(source.contains("_remove_chunk(_chunk_remove_queue.pop_back())"), "loader retains removal-first drain", failures)
	_expect_true(source.contains("_create_chunk(_chunk_create_queue.pop_front())"), "loader retains nearest-first drain", failures)


func _verify_bounded_timing(failures: Array[String]) -> float:
	var tile_states: Dictionary = {}
	for tile_index in range(64):
		var current_chunks: Dictionary = {}
		var desired_lods: Dictionary = {}
		var parsed_chunks: Array = []
		for chunk_index in range(16):
			current_chunks[chunk_index] = {"lod": chunk_index % 3}
			desired_lods[chunk_index] = (chunk_index + 1) % 3
			parsed_chunks.append({
				"origin": Vector3(float(tile_index * 16 + chunk_index), 0.0, float(tile_index))
			})
		tile_states["tile-%d" % tile_index] = _create_tile_state(
			current_chunks,
			desired_lods,
			parsed_chunks
		)
	var planner: RefCounted = PLANNER_SCRIPT.new()
	var focus: RefCounted = POSITION_SCRIPT.new(0.0, 0.0, 0.0)
	var started_microseconds := Time.get_ticks_usec()
	for _iteration in range(100):
		planner.call("plan", tile_states, focus)
	var elapsed_milliseconds := float(Time.get_ticks_usec() - started_microseconds) / 1000.0
	_expect_true(elapsed_milliseconds < 1000.0, "100 multi-tile plans remain bounded", failures)
	return elapsed_milliseconds


func _create_tile_state(
		current_chunks: Dictionary,
		desired_lods: Dictionary,
		parsed_chunks: Array
) -> Dictionary:
	return {
		"chunks": current_chunks,
		"desired_lods": desired_lods,
		"desired_tile_lod": -1,
		"data": {"chunks": parsed_chunks},
		"origin": Vector3.ZERO,
	}


func _read_text(path: String, failures: Array[String]) -> String:
	var file := FileAccess.open(path, FileAccess.READ)
	if file == null:
		failures.append("cannot open %s" % path)
		return ""
	return file.get_as_text()


func _expect_equal(actual_value: int, expected_value: int, label: String, failures: Array[String]) -> void:
	if actual_value != expected_value:
		failures.append("%s expected %d, got %d" % [label, expected_value, actual_value])


func _expect_near(actual_value: float, expected_value: float, label: String, failures: Array[String]) -> void:
	if not is_equal_approx(actual_value, expected_value):
		failures.append("%s expected %.3f, got %.3f" % [label, expected_value, actual_value])


func _expect_string_equal(
		actual_value: String,
		expected_value: String,
		label: String,
		failures: Array[String]
) -> void:
	if actual_value != expected_value:
		failures.append("%s expected %s, got %s" % [label, expected_value, actual_value])


func _expect_true(actual_value: bool, label: String, failures: Array[String]) -> void:
	if not actual_value:
		failures.append("%s expected true" % label)