extends GutTest
## What upgrades actually do in the simulation: shot geometry, splitting,
## poison and the eraser.
##
## Driven through the real firing and hit-resolution paths rather than by
## calling the effects directly, because the claim being tested is that
## SimWorld needs no per-upgrade branches -- only that PlayerStats reaches it.

const ME := 1

var world: SimWorld
var me: SimPlayer


func before_each() -> void:
	world = SimWorld.new(11)
	me = world.add_player(ME, "me")
	me.pos = Vector2.ZERO
	me.spawn_grace = 0


func _give(ids: Array) -> void:
	var typed: Array[StringName] = []
	for id in ids:
		typed.append(id)
	me.stats = PlayerStats.build(typed)
	me.recompute_max_hp()


## One trigger pull, aimed along +x.
func _fire_once() -> int:
	me.aim = 0.0
	me.fire_cooldown = 0
	world.pool.clear()
	var frames: Array[InputFrame] = [
		InputFrame.make(world.tick + 1, Vector2.ZERO, 0.0, InputFrame.BTN_FIRE)]
	world.queue_input(ME, frames)
	world.step()
	return world.pool.live_count


func _player_bullets() -> Array[int]:
	var out: Array[int] = []
	for i in world.pool.high_water:
		if world.pool.alive[i] == 1 and world.pool.team[i] == SimConfig.TEAM_PLAYER:
			out.append(i)
	return out


# --- Shot geometry ----------------------------------------------------------

func test_a_plain_shot_is_one_bullet() -> void:
	assert_eq(_fire_once(), 1)


func test_spread_adds_two_and_fans_them() -> void:
	_give([Upgrades.SPREAD])
	assert_eq(_fire_once(), 3)
	var angles: Array[float] = []
	for i in _player_bullets():
		angles.append(world.pool.vel[i].angle())
	angles.sort()
	assert_almost_eq(angles[1], 0.0, 0.01, "the aimed shot is still dead ahead")
	assert_almost_eq(angles[0], -deg_to_rad(SimConfig.SPREAD_STEP_DEG), 0.01)
	assert_almost_eq(angles[2], deg_to_rad(SimConfig.SPREAD_STEP_DEG), 0.01)


func test_two_spreads_widen_the_cone_rather_than_doubling_the_middle() -> void:
	_give([Upgrades.SPREAD, Upgrades.SPREAD])
	assert_eq(_fire_once(), 5)
	var widest := 0.0
	for i in _player_bullets():
		widest = maxf(widest, absf(world.pool.vel[i].angle()))
	assert_almost_eq(widest, deg_to_rad(SimConfig.SPREAD_STEP_DEG * 2.0), 0.01)


## Parallel, not fanned: same heading, offset sideways. That is the difference
## between Doubleshot and Spread, and it is entirely in the geometry.
func test_doubleshot_adds_a_parallel_projectile() -> void:
	_give([Upgrades.DOUBLESHOT])
	assert_eq(_fire_once(), 2)
	var offsets: Array[float] = []
	for i in _player_bullets():
		assert_almost_eq(world.pool.vel[i].angle(), 0.0, 0.01,
			"parallel means the same heading")
		offsets.append(world.pool.pos[i].y)
	assert_gt(absf(offsets[0] - offsets[1]), 1.0, "and a different lane")


func test_spread_and_doubleshot_stack_into_one_volley() -> void:
	_give([Upgrades.SPREAD, Upgrades.DOUBLESHOT])
	assert_eq(_fire_once(), 4, "one aimed, two fanned, one parallel")


func test_sniper_slows_the_trigger_and_speeds_the_bullet() -> void:
	_give([Upgrades.SNIPER])
	_fire_once()
	assert_eq(me.fire_cooldown, SimConfig.PLAYER_FIRE_COOLDOWN * 2)
	for i in _player_bullets():
		assert_almost_eq(world.pool.vel[i].length(),
			SimConfig.PLAYER_BULLET_SPEED * 2.0, 1.0)


func test_a_shot_carries_the_shooters_upgrades_onto_the_bullet() -> void:
	_give([Upgrades.SPLIT_SHOT, Upgrades.POISON, Upgrades.ERASER])
	_fire_once()
	for i in _player_bullets():
		assert_eq(world.pool.split[i], 1)
		assert_gt(world.pool.poison[i], 0.0)
		assert_gt(world.pool.erase[i], 0.0)


## A bullet keeps what it was fired with. Taking Poison while a shot is in
## flight must not reach back and poison it.
func test_a_bullet_in_flight_is_not_changed_by_a_later_upgrade() -> void:
	_fire_once()
	var before := _player_bullets()
	_give([Upgrades.POISON])
	for i in before:
		assert_eq(world.pool.poison[i], 0.0)


# --- Split shot -------------------------------------------------------------

func _shoot_at(target: Vector2, split: int, poison: float = 0.0,
		erase: float = 0.0) -> int:
	# Placed just short of the target with a crawl, so exactly one tick of
	# integration puts it inside and hit resolution runs on it.
	var slot := world.pool.spawn(target - Vector2(1.0, 0.0), Vector2(60.0, 0.0),
		SimConfig.PLAYER_BULLET_RADIUS, 90, SimConfig.PLAYER_BULLET_DAMAGE,
		SimConfig.TEAM_PLAYER, SimConfig.KIND_PLAYER_SHOT)
	world.pool.set_mods(slot, split, poison, erase)
	return slot


func test_a_hit_with_a_split_charge_produces_two_children() -> void:
	var e := world.spawn_enemy(Content.turret(), Vector2(150.0, 0.0))
	e.hp = 100000
	_shoot_at(e.pos, 1)
	world.step()
	assert_eq(_player_bullets().size(), 2, "the parent is consumed, two children remain")


func test_the_children_leave_at_forty_five_degrees_to_either_side() -> void:
	var e := world.spawn_enemy(Content.turret(), Vector2(150.0, 0.0))
	e.hp = 100000
	_shoot_at(e.pos, 1)
	world.step()
	var angles: Array[float] = []
	for i in _player_bullets():
		angles.append(rad_to_deg(world.pool.vel[i].angle()))
	angles.sort()
	assert_almost_eq(angles[0], -SimConfig.SPLIT_ANGLE_DEG, 0.5)
	assert_almost_eq(angles[1], SimConfig.SPLIT_ANGLE_DEG, 0.5)


## Children are born past the target. Spawned on top of it they would be
## resolved against it again on the same tick -- a free second hit, and with
## several charges a free chain of them.
func test_children_do_not_immediately_hit_the_enemy_they_were_born_on() -> void:
	var e := world.spawn_enemy(Content.turret(), Vector2(150.0, 0.0))
	e.hp = 100000
	var before := e.hp
	_shoot_at(e.pos, 1)
	# Several ticks, not one: children spawned during hit resolution are not
	# visited again until the NEXT tick, so a single step cannot tell a child
	# born clear of the enemy from one born inside it.
	for _i in 8:
		world.step()
	assert_eq(before - e.hp, SimConfig.PLAYER_BULLET_DAMAGE,
		"exactly one hit's worth of damage, not three")


func test_a_child_of_a_single_charge_cannot_split_again() -> void:
	var e := world.spawn_enemy(Content.turret(), Vector2(150.0, 0.0))
	e.hp = 100000
	_shoot_at(e.pos, 1)
	world.step()
	for i in _player_bullets():
		assert_eq(world.pool.split[i], 0, "the charge was spent by the parent")


func test_two_charges_let_a_child_split_once_more() -> void:
	var e := world.spawn_enemy(Content.turret(), Vector2(150.0, 0.0))
	e.hp = 100000
	_shoot_at(e.pos, 2)
	world.step()
	for i in _player_bullets():
		assert_eq(world.pool.split[i], 1)


func test_a_shot_with_no_charges_does_not_split() -> void:
	var e := world.spawn_enemy(Content.turret(), Vector2(150.0, 0.0))
	e.hp = 100000
	_shoot_at(e.pos, 0)
	world.step()
	assert_eq(_player_bullets().size(), 0)


func test_splitting_works_on_the_boss_too() -> void:
	var boss := world.spawn_boss(Content.warden())
	boss.pos = Vector2(150.0, 0.0)
	_shoot_at(boss.pos, 1)
	world.step()
	assert_eq(_player_bullets().size(), 2)


# --- Poison -----------------------------------------------------------------

func test_a_poisoned_hit_keeps_damaging_after_the_bullet_is_gone() -> void:
	var e := world.spawn_enemy(Content.turret(), Vector2(150.0, 0.0))
	e.hp = 100000
	_shoot_at(e.pos, 0, 0.5)
	world.step()
	var after_hit := e.hp
	for _i in SimConfig.POISON_DURATION_TICKS:
		world.step()
	assert_lt(e.hp, after_hit, "poison should have kept working")


## The user's decision: stacks are independent, so a second dose adds to the
## first rather than replacing it.
func test_doses_stack_rather_than_refreshing() -> void:
	var one := PoisonTrack.new()
	one.add(600.0, 0)
	var two := PoisonTrack.new()
	two.add(600.0, 0)
	two.add(600.0, 0)
	var single := 0
	var double := 0
	# From tick 0, the way the world drives it: a dose applied on tick T ticks
	# on T and the DURATION-1 ticks after it.
	for t in SimConfig.POISON_DURATION_TICKS:
		single += one.step(t)
		double += two.step(t)
	assert_almost_eq(float(single), 600.0, 2.0)
	assert_almost_eq(float(double), 1200.0, 2.0,
		"two doses must deliver two doses' worth")


func test_a_dose_delivers_its_whole_value_over_the_window() -> void:
	var track := PoisonTrack.new()
	track.add(300.0, 0)
	var total := 0
	for t in SimConfig.POISON_DURATION_TICKS:
		total += track.step(t)
	assert_eq(total, 300, "the whole dose, to the hit point")
	track.step(SimConfig.POISON_DURATION_TICKS)
	assert_false(track.active(), "and then stops")


## Doses all last the same number of ticks, so they expire in the order they
## were added. That is the property that lets the queue be a plain FIFO whose
## front is the only entry ever examined -- and therefore the property that
## makes dozens of concurrent stacks cost nothing.
func test_poison_expires_in_the_order_it_was_applied() -> void:
	var track := PoisonTrack.new()
	track.add(600.0, 0)
	track.add(600.0, 300)
	assert_eq(track.dose_count(), 2)
	for t in range(0, SimConfig.POISON_DURATION_TICKS + 1):
		track.step(t)
	assert_true(track.active(), "the later dose is still running")
	assert_eq(track.dose_count(), 1, "the earlier one retired first")
	for t in range(SimConfig.POISON_DURATION_TICKS + 1, 300 + SimConfig.POISON_DURATION_TICKS + 1):
		track.step(t)
	assert_false(track.active())
	assert_eq(track.dose_count(), 0)


func test_fractions_below_one_hit_point_are_not_lost() -> void:
	var track := PoisonTrack.new()
	# 3 damage over 600 ticks is 0.005/tick -- it would round to nothing on
	# every single tick without the carry.
	track.add(3.0, 0)
	var total := 0
	for t in SimConfig.POISON_DURATION_TICKS:
		total += track.step(t)
	assert_eq(total, 3)


## Poison must be able to finish something off, or a kill it caused would never
## be scored and the experience would vanish.
func test_a_kill_by_poison_is_still_announced() -> void:
	var e := world.spawn_enemy(Content.turret(), Vector2(150.0, 0.0))
	e.hp = 3
	e.poison_track().add(600.0, world.tick)
	var died := false
	for _i in 120:
		world.step()
		for ev in world.events:
			if int(ev["t"]) == SimEvent.Type.ENEMY_DIED:
				died = true
		world.drain_events()
	assert_true(died, "experience is keyed on this event")


## Poison lands many times a second. Putting each tick on the reliable event
## channel would be a flood, and the client learns hp from the snapshot anyway.
func test_poison_ticks_are_not_announced_as_hits() -> void:
	var e := world.spawn_enemy(Content.turret(), Vector2(150.0, 0.0))
	e.hp = 100000
	e.poison_track().add(6000.0, world.tick)
	world.drain_events()
	for _i in 120:
		world.step()
	var hits := 0
	for ev in world.events:
		if int(ev["t"]) == SimEvent.Type.ENEMY_HIT:
			hits += 1
	assert_eq(hits, 0)
	assert_lt(e.hp, 100000, "but the damage still happened")


## The boss takes extra damage in later phases. Poison is derived from the
## damage actually applied, so it inherits that -- and must not be scaled a
## second time when it ticks.
func test_boss_poison_is_scaled_once_not_twice() -> void:
	var boss := world.spawn_boss(Content.warden())
	boss.pos = Vector2(150.0, 0.0)
	# Hurt into a phase that actually has an armour multiplier -- at full health
	# the multiplier is 1.0 and scaling twice is indistinguishable from scaling
	# once, which is exactly how this test used to pass while proving nothing.
	# Two things have to be true for this test to be able to fail. The boss has
	# to be in a phase with an armour multiplier at all -- at full health it is
	# 1.0, and scaling twice is then indistinguishable from scaling once. And
	# the per-tick poison has to be big enough that the multiplier survives
	# rounding: at 1 damage a tick, roundi(1 x 1.15) is still 1, so the bug
	# hides completely. A large pool gives both.
	boss.def.max_hp = 100000
	boss.hp = 20000                      # 20% -> a phase that takes extra
	world.step()
	var armour := boss.current_phase().damage_taken_mult
	assert_gt(armour, 1.0, "setup: this phase has to have armour")
	var track := boss.poison_track()
	track.add(6000.0, world.tick)        # 10 damage per tick
	var before := boss.hp
	for _i in SimConfig.POISON_DURATION_TICKS + 5:
		world.step()
	var dealt := float(before - boss.hp)
	assert_almost_eq(dealt, 6000.0, 60.0,
		"scaled a second time this would be about %.0f" % (6000.0 * armour))


func test_a_replica_never_applies_poison() -> void:
	var replica := SimWorld.new(1)
	replica.authoritative = false
	var e := replica.spawn_enemy(Content.turret(), Vector2(150.0, 0.0))
	e.hp = 500
	e.poison_track().add(600.0, 0)
	for _i in 200:
		replica.step()
	assert_eq(e.hp, 500, "a client must never decide it dealt damage")


# --- Eraser -----------------------------------------------------------------

func _enemy_bullet(at: Vector2) -> int:
	return world.pool.spawn(at, Vector2.ZERO, 8.0, 600, 5,
		SimConfig.TEAM_ENEMY, SimConfig.KIND_ORB)


## Certainty rather than 1%, so the test measures the mechanism instead of the
## random number generator.
func test_an_erasing_shot_deletes_an_enemy_projectile_it_overlaps() -> void:
	var target := Vector2(100.0, 0.0)
	var incoming := _enemy_bullet(target)
	_shoot_at(target, 0, 0.0, 1.0)
	world.step()
	assert_eq(world.pool.alive[incoming], 0)


func test_the_deletion_is_announced_so_no_client_keeps_a_phantom() -> void:
	var target := Vector2(100.0, 0.0)
	var incoming := _enemy_bullet(target)
	var incoming_uid: int = world.pool.uid[incoming]
	world.drain_events()
	_shoot_at(target, 0, 0.0, 1.0)
	world.step()
	var announced := false
	for ev in world.events:
		if int(ev["t"]) == SimEvent.Type.BULLET_DESPAWN and int(ev["uid"]) == incoming_uid:
			announced = true
	assert_true(announced)


func test_a_shot_without_the_upgrade_passes_straight_through() -> void:
	var target := Vector2(100.0, 0.0)
	var incoming := _enemy_bullet(target)
	_shoot_at(target, 0, 0.0, 0.0)
	world.step()
	assert_eq(world.pool.alive[incoming], 1,
		"enemy bullets are not obstacles for ordinary shots")


func test_an_erasing_shot_is_not_consumed_by_erasing() -> void:
	var target := Vector2(100.0, 0.0)
	_enemy_bullet(target)
	var mine := _shoot_at(target, 0, 0.0, 1.0)
	world.step()
	assert_eq(world.pool.alive[mine], 1, "the shot keeps going")


## One roll per shot per tick, not one per overlapping pair. A boss ring puts
## dozens of bullets in the same place, and rolling against each would multiply
## the 1% the player was promised.
func test_only_one_projectile_is_erased_per_tick() -> void:
	var target := Vector2(100.0, 0.0)
	for _i in 5:
		_enemy_bullet(target)
	_shoot_at(target, 0, 0.0, 1.0)
	world.step()
	var left := 0
	for i in world.pool.high_water:
		if world.pool.alive[i] == 1 and world.pool.team[i] == SimConfig.TEAM_ENEMY:
			left += 1
	assert_eq(left, 4, "four of the five survive the tick")