extends GutTest
## The security tests. Each one describes something a modified client would try
## and asserts that the authoritative world does not let it happen.
##
## The design intent is that these are boring to write, because the client has
## no message that expresses the cheat in the first place -- it can only send
## intent. These tests pin that property down so a future "just let the client
## send its position, it is simpler" change fails loudly.

var world: SimWorld
const PEER := 7


func before_each() -> void:
	world = SimWorld.new(1)
	world.add_player(PEER, "tester")


func _send(frame_tick: int, move := Vector2.ZERO, buttons := 0, aim := 0.0) -> void:
	var frames: Array[InputFrame] = [InputFrame.make(frame_tick, move, aim, buttons)]
	world.queue_input(PEER, frames)


## Drive the player for [param ticks] ticks with one fresh input per tick.
func _drive(ticks: int, move := Vector2.ZERO, buttons := 0, aim := 0.0) -> void:
	for _i in ticks:
		_send(world.tick + 1, move, buttons, aim)
		world.step()


func test_player_cannot_outrun_the_configured_speed() -> void:
	var start: Vector2 = world.players[PEER].pos
	_drive(60, Vector2(1.0, 0.0))
	var travelled: float = world.players[PEER].pos.distance_to(start)
	assert_almost_eq(travelled, SimConfig.PLAYER_SPEED, 1.0,
		"one second of held input must cover exactly one second of movement")


func test_replayed_input_is_dropped() -> void:
	_drive(5, Vector2.RIGHT)
	var pos_after: Vector2 = world.players[PEER].pos
	var acked: int = world.players[PEER].last_input_tick
	# Re-send an already-consumed tick, the classic replay attack.
	_send(acked, Vector2.RIGHT)
	assert_eq(world.players[PEER].input_queue.size(), 0)
	world.step()
	# The held input coasts one more tick, which is expected; what matters is
	# that the stale frame did not stack a second move on top of it.
	assert_almost_eq(world.players[PEER].pos.distance_to(pos_after),
		SimConfig.PLAYER_SPEED * SimConfig.TICK_DELTA, 0.001)


func test_input_from_the_far_future_is_dropped() -> void:
	_send(world.tick + SimConfig.INPUT_MAX_LEAD + 50, Vector2.RIGHT)
	assert_eq(world.players[PEER].input_queue.size(), 0,
		"a client cannot buy a head start by claiming a future tick")


func test_ancient_input_is_dropped() -> void:
	world.tick = 10000
	_send(1, Vector2.RIGHT)
	assert_eq(world.players[PEER].input_queue.size(), 0)


func test_input_flood_cannot_grow_the_queue_without_bound() -> void:
	for i in 500:
		_send(world.tick + 1 + i, Vector2.RIGHT)
	assert_lte(world.players[PEER].input_queue.size(), SimConfig.INPUT_MAX_AGE,
		"a flood of inputs must not become unbounded server memory")


func test_fire_rate_is_enforced_by_the_server() -> void:
	# Hold fire every single tick; the server still applies its own cooldown.
	_drive(60, Vector2.ZERO, InputFrame.BTN_FIRE)
	var expected := 60 / SimConfig.PLAYER_FIRE_COOLDOWN
	assert_almost_eq(float(world.pool.live_count), float(expected), 2.0,
		"holding fire must not fire faster than the cooldown allows")


func test_a_starved_player_eventually_stops_moving() -> void:
	_drive(3, Vector2.RIGHT)
	var pos_at_starve: Vector2 = world.players[PEER].pos
	# Send nothing at all for a long time, as a disconnecting client would.
	for _i in SimConfig.INPUT_MAX_AGE + 120:
		world.step()
	var coasted: float = world.players[PEER].pos.distance_to(pos_at_starve)
	assert_lt(coasted, SimConfig.PLAYER_SPEED * 1.0,
		"a silent client must coast briefly, then stop, not drift forever")


func test_enemy_bullets_damage_the_player_and_are_consumed() -> void:
	var p: SimPlayer = world.players[PEER]
	p.pos = Vector2.ZERO
	p.iframes = 0
	world.pool.spawn(Vector2(-1.0, 0.0), Vector2.ZERO, 6.0, 60, 25,
		SimConfig.TEAM_ENEMY, SimConfig.KIND_ORB)
	world.step()
	assert_eq(p.hp, SimConfig.PLAYER_MAX_HP - 25)
	assert_eq(world.pool.live_count, 0, "a bullet that hits must be consumed")


func test_invulnerability_frames_stop_a_second_hit() -> void:
	var p: SimPlayer = world.players[PEER]
	p.pos = Vector2.ZERO
	p.iframes = 0
	for _i in 2:
		world.pool.spawn(Vector2.ZERO, Vector2.ZERO, 6.0, 60, 25,
			SimConfig.TEAM_ENEMY, SimConfig.KIND_ORB)
	world.step()
	assert_eq(p.hp, SimConfig.PLAYER_MAX_HP - 25, "two bullets in one tick is still one hit")


func test_a_replica_world_never_resolves_a_hit() -> void:
	world.authoritative = false
	var p: SimPlayer = world.players[PEER]
	p.pos = Vector2.ZERO
	p.iframes = 0
	world.pool.spawn(Vector2.ZERO, Vector2.ZERO, 6.0, 60, 25,
		SimConfig.TEAM_ENEMY, SimConfig.KIND_ORB)
	world.step()
	assert_eq(p.hp, SimConfig.PLAYER_MAX_HP,
		"only the server decides damage; a client replica must never apply it")


func test_player_death_and_respawn() -> void:
	var p: SimPlayer = world.players[PEER]
	p.pos = Vector2.ZERO
	p.hp = 5
	p.iframes = 0
	world.pool.spawn(Vector2.ZERO, Vector2.ZERO, 6.0, 60, 25,
		SimConfig.TEAM_ENEMY, SimConfig.KIND_ORB)
	world.step()
	assert_false(p.alive)
	for _i in SimConfig.PLAYER_RESPAWN_DELAY + 1:
		world.step()
	assert_true(p.alive)
	assert_eq(p.hp, SimConfig.PLAYER_MAX_HP)
	assert_eq(p.pos, world.spawn_point)