## Sprint 2 Proof: Fog of Perception (#357)
## Verifies the original acceptance criteria through the full server pipeline.
##
## REVIVED (T-1068): disabled in sprint-36, re-enabled against the current
## protocol (handshake + StartupMessage exchange per #555/#175, streamed
## snapshots). The proof room layout below is still what main.rs
## setup_proof_room() spawns for non-test-mode servers.
##
## Server proof room layout (setup_proof_room in server/src/main.rs):
##   (16,13) = NPC1   (16,14) = WALL    (16,16) = Player start
##   (14,18) = NPC2   (18,14) = NPC3
##   Player facing North → NPC1 blocked by wall.
##   Move East+North around the wall → NPC1 becomes visible.
class_name TestSprint2Proof
extends GdUnitTestSuite

const CONNECT_TIMEOUT: float = 3.0
const RESPONSE_TIMEOUT: float = 5.0
# Server move cooldown: the Gauntlet player is Walk stance (ticks_per_move = 2,
# server stance.rs). A move input arriving within that window is silently
# throttled away (movement.rs::apply_move -> PlayerMoveCooldown::try_move).
# Space consecutive sends past it (2 ticks + 1 margin for apply/snapshot lag)
# so back-to-back moves can never race the cooldown.
const COOLDOWN_TICKS: int = 3
const MAX_PORT_ATTEMPTS: int = 5

var _server_pid: int = -1
var _bridge: LocalBridge = null
var _test_port: int = 0


func _server_binary_path() -> String:
	var project_dir := ProjectSettings.globalize_path("res://")
	return project_dir.path_join("../server/target/debug/settled-reach-server")


static func _random_test_port() -> int:
	return 49152 + (randi() % (65535 - 49152 + 1))


func _spawn_server(server_path: String) -> bool:
	for attempt in range(MAX_PORT_ATTEMPTS):
		_test_port = _random_test_port()
		var addr := "127.0.0.1:%d" % _test_port
		_server_pid = OS.create_process(server_path, [addr])
		if _server_pid <= 0:
			continue
		await get_tree().create_timer(0.15).timeout
		if OS.is_process_running(_server_pid):
			return true
		_server_pid = -1
	return false


func after_test() -> void:
	if _bridge != null:
		_bridge.disconnect_from_server()
		_bridge = null
	if _server_pid > 0 and OS.is_process_running(_server_pid):
		OS.kill(_server_pid)
		_server_pid = -1


## Find the player entity in a snapshot by kind.
static func _find_player(snapshot: Dictionary) -> Dictionary:
	for entity in snapshot.entities:
		if entity.kind.variant == "Player":
			return entity
	return {}


## Send a batch input and receive a snapshot that reflects it.
## The server free-runs at ~20 ticks/sec and STREAMS a snapshot every tick —
## it is not request/response. Drain stale queued snapshots first, then:
## - expect_position != null (Vector2, render coords): wait until the player
##   reaches that position and assert it. Deterministic under load — tick
##   margins race the free-running server when the test process is descheduled
##   between drain and send.
## - expect_position == null: wait for a snapshot at least 2 ticks past the
##   drain point (enough for no-op actions).
func _send_and_receive(
	action_name: String,
	tick: int = 0,
	expect_position: Variant = null,
	action_data: Variant = null,
) -> Variant:
	# Drain queued stale snapshots, remembering the newest tick seen.
	var last_tick: int = -1
	_bridge.poll()
	var pending := _bridge.poll_message()
	while pending.size() > 0:
		var stale: Variant = Protocol.decode_snapshot(pending)
		if stale != null:
			last_tick = stale.tick
		_bridge.poll()
		pending = _bridge.poll_message()

	var inputs: Array = [{"tick": tick, "action_name": action_name}]
	if action_data != null:
		inputs[0]["action_data"] = action_data
	var encoded := Protocol.encode_player_inputs(inputs)
	assert_that(encoded.size()).is_greater(0)
	var send_err := _bridge.send_message(encoded)
	assert_that(send_err).is_equal(OK)

	# Wait for a snapshot that reflects the processed input.
	var min_tick: int = last_tick + 2
	var snapshot: Variant = null
	var elapsed := 0.0
	while elapsed < RESPONSE_TIMEOUT:
		_bridge.poll()
		var msg := _bridge.poll_message()
		if msg.size() > 0:
			var decoded: Variant = Protocol.decode_snapshot(msg)
			if decoded == null:
				continue  # undecodable frame — keep draining
			if expect_position != null:
				snapshot = decoded  # keep latest so a timeout reports actual state
				var player := _find_player(decoded)
				if (
					not player.is_empty()
					and is_equal_approx(player.x, expect_position.x)
					and is_equal_approx(player.y, expect_position.y)
				):
					break
			elif decoded.tick >= min_tick:
				snapshot = decoded
				break
			continue
		await get_tree().create_timer(0.05).timeout
		elapsed += 0.05

	assert_that(snapshot).override_failure_message(
		"no snapshot received within %.1fs after '%s'" % [RESPONSE_TIMEOUT, action_name]
	).is_not_null()
	if expect_position != null and snapshot != null:
		var player := _find_player(snapshot)
		var actual := Vector2(player.x, player.y) if not player.is_empty() else Vector2.INF
		assert_that(actual.is_equal_approx(expect_position)).override_failure_message(
			"player must reach %s after '%s' — last seen %s" % [expect_position, action_name, actual]
		).is_true()
		# Space the next move past the per-stance cooldown. The server silently
		# drops a move that arrives within ticks_per_move ticks of the previous
		# one; without this wait, back-to-back sends race the cooldown and an
		# occasional move is throttled, leaving the player one tile short (flaky).
		# Wait for the server clock to advance COOLDOWN_TICKS past the landing
		# tick so the next send can never be throttled. The player is stationary
		# meanwhile, so the fresher snapshot is still valid for the caller.
		var landed_tick: int = int(snapshot.tick)
		var spacing_elapsed := 0.0
		while spacing_elapsed < RESPONSE_TIMEOUT:
			_bridge.poll()
			var m := _bridge.poll_message()
			if m.size() > 0:
				var d: Variant = Protocol.decode_snapshot(m)
				if d != null:
					snapshot = d
					if int(d.tick) >= landed_tick + COOLDOWN_TICKS:
						break
				continue
			await get_tree().create_timer(0.05).timeout
			spacing_elapsed += 0.05
	return snapshot


## Protocol handshake (#555, #175): the server sends a HandshakeMessage as the
## first framed message; the client validates it and replies with a
## StartupMessage carrying world_seed before any input is accepted.
## Mirrors sim_bridge.gd's HANDSHAKING state.
func _do_handshake(world_seed: int = 42) -> bool:
	var msg := PackedByteArray()
	var elapsed := 0.0
	while elapsed < CONNECT_TIMEOUT:
		_bridge.poll()
		msg = _bridge.poll_message()
		if msg.size() > 0:
			break
		await get_tree().create_timer(0.05).timeout
		elapsed += 0.05
	if msg.is_empty():
		push_warning("No HandshakeMessage received within %.1fs" % CONNECT_TIMEOUT)
		return false
	var MP = load("res://addons/messagepack/messagepack.gd")
	var decoded: Variant = MP.decode(msg)
	if decoded.status != null or not (decoded.value is Dictionary):
		push_warning("Malformed HandshakeMessage")
		return false
	var startup_bytes := Protocol.encode_startup_message(world_seed)
	if startup_bytes.is_empty():
		return false
	return _bridge.send_message(startup_bytes) == OK


## Spawn the server, connect, and complete the protocol handshake.
## Binary absence is handled by per-test `_do_skip` — by the time this runs the
## binary exists, so any failure here is a real failure (asserted loudly).
func _connect_to_server() -> bool:
	var server_path := _server_binary_path()

	var spawned := await _spawn_server(server_path)
	assert_bool(spawned).override_failure_message(
		"server spawn failed after %d port attempts" % MAX_PORT_ATTEMPTS
	).is_true()
	if not spawned:
		return false

	_bridge = LocalBridge.new()
	var connected := false
	var elapsed := 0.0
	while elapsed < CONNECT_TIMEOUT:
		if _server_pid > 0 and not OS.is_process_running(_server_pid):
			push_warning("Server process died during connection")
			break
		if _bridge.get_status() == StreamPeerTCP.STATUS_NONE:
			_bridge.connect_to_server("127.0.0.1", _test_port)
		_bridge.poll()
		if _bridge.get_status() == StreamPeerTCP.STATUS_CONNECTED:
			connected = true
			break
		if _bridge.get_status() == StreamPeerTCP.STATUS_ERROR:
			_bridge.disconnect_from_server()
			_bridge.reset()
		await get_tree().create_timer(0.1).timeout
		elapsed += 0.1

	assert_bool(connected).override_failure_message(
		"TCP connect to spawned server failed within %.1fs" % CONNECT_TIMEOUT
	).is_true()
	if not connected:
		return false

	# Handshake + startup exchange (#555, #175) — required before input is accepted
	var handshake_ok := await _do_handshake()
	assert_bool(handshake_ok).override_failure_message(
		"protocol handshake + StartupMessage exchange must complete (#555, #175)"
	).is_true()
	return handshake_ok


# -- AC#1, AC#2, AC#3, AC#5: Movement, camera, tiles, fog -------------------------

func test_proof_player_moves_and_v2_snapshot(
	_do_skip := not FileAccess.file_exists(_server_binary_path()),
	_skip_reason := "server binary not built — run `cargo build` in server/"
) -> void:
	var ok := await _connect_to_server()
	if not ok:
		return

	var snapshot: Dictionary = await _send_and_receive("MoveNorth", 0, Vector2(16.5, 15.5))

	# AC#1: Player moved from (16,16) to (16,15)
	var player := _find_player(snapshot)
	assert_that(player.size()).is_greater(0)
	assert_float(player.x).is_equal_approx(16.5, 0.001)
	assert_float(player.y).is_equal_approx(15.5, 0.001)

	# v4 protocol fields present
	assert_that(snapshot.player_facing).is_equal("North")
	assert_that(snapshot.game_time).is_not_null()

	# AC#3: Tiles flowing through bridge (visible_tiles non-empty)
	assert_that(snapshot.visible_tiles.size()).is_greater(0)

	# AC#5: Not all 1024 tiles visible — blind spot behind player
	assert_that(snapshot.visible_tiles.size()).is_less(1024)


# -- AC#6: Wall hides entity -------------------------------------------------------

func test_proof_wall_hides_entity(
	_do_skip := not FileAccess.file_exists(_server_binary_path()),
	_skip_reason := "server binary not built — run `cargo build` in server/"
) -> void:
	var ok := await _connect_to_server()
	if not ok:
		return

	# After MoveNorth: player at (16,15) facing North.
	# Wall at (16,14) blocks LOS to NPC1 at (16,13).
	var snapshot: Dictionary = await _send_and_receive("MoveNorth", 0, Vector2(16.5, 15.5))

	# NPC1 at (16,13) should be hidden — wall at (16,14) blocks LOS.
	# Other NPCs (NPC2 at (14,18), NPC3 at (18,14)) may be visible.
	var hidden_npc_visible := false
	for entity in snapshot.entities:
		if entity.kind.variant == "Npc":
			if is_equal_approx(entity.x, 16.5) and is_equal_approx(entity.y, 13.5):
				hidden_npc_visible = true
				break
	assert_that(hidden_npc_visible).is_false()


# -- AC#4, AC#7: Entity appears via LOS / corner reveal ----------------------------

func test_proof_corner_reveal(
	_do_skip := not FileAccess.file_exists(_server_binary_path()),
	_skip_reason := "server binary not built — run `cargo build` in server/"
) -> void:
	var ok := await _connect_to_server()
	if not ok:
		return

	# Step 1: Move East three times — column x=18 is blocked at (18,14) by
	# NPC3 (entities are unwalkable), so route around via x=19.
	# (16,16) → (17,16) → (18,16) → (19,16)
	await _send_and_receive("MoveEast", 0, Vector2(17.5, 16.5))
	await _send_and_receive("MoveEast", 1, Vector2(18.5, 16.5))
	await _send_and_receive("MoveEast", 2, Vector2(19.5, 16.5))

	# Step 2: Move North past the wall line (y=14)
	# (19,16) → (19,15) → (19,14) → (19,13)
	await _send_and_receive("MoveNorth", 3, Vector2(19.5, 15.5))
	await _send_and_receive("MoveNorth", 4, Vector2(19.5, 14.5))
	await _send_and_receive("MoveNorth", 5, Vector2(19.5, 13.5))

	# Step 3: Move West onto (18,13), then LOOK West explicitly — D-252: moves
	# no longer write Facing, the view changes only via SetFacing. NPC1 at
	# (16,13) is two tiles dead ahead with no wall between ((17,13) is open).
	await _send_and_receive("MoveWest", 6, Vector2(18.5, 13.5))
	var snapshot: Dictionary = await _send_and_receive(
		"SetFacing", 7, null, {"facing": "West"}
	)
	# The +2-tick wait can catch the snapshot where the facing field flipped but
	# the entity-visibility recompute hasn't landed — keep draining (bounded)
	# until the westward cone content arrives.
	var settle := 0.0
	while settle < RESPONSE_TIMEOUT and not _has_npc_at(snapshot, 16.5, 13.5):
		_bridge.poll()
		var msg := _bridge.poll_message()
		if msg.size() > 0:
			var decoded: Variant = Protocol.decode_snapshot(msg)
			if decoded != null:
				snapshot = decoded
			continue
		await get_tree().create_timer(0.05).timeout
		settle += 0.05

	# Player at (18,13) facing West. NPC1 at (16,13) is 2 tiles dead ahead —
	# inside the vision cone, no wall between. NPC1 should be visible.
	assert_that(_has_npc_at(snapshot, 16.5, 13.5)).is_true()


## True when the snapshot's visible entities include an Npc at (x, y).
func _has_npc_at(snapshot: Dictionary, x: float, y: float) -> bool:
	for entity in snapshot.entities:
		if entity.kind.variant == "Npc":
			if is_equal_approx(entity.x, x) and is_equal_approx(entity.y, y):
				return true
	return false