## #411: Integration test — full input roundtrip through live server.
## Validates the complete path: encode inputs → TCP wire → server deserialize →
## simulation systems → ObserverSnapshot → client decode.
## Catches integration seams that unit tests miss by exercising both movement
## and interaction actions against the real server binary.
## Requires: server binary built (cargo build in server/)
class_name TestInputRoundtrip
extends GdUnitTestSuite

const CONNECT_TIMEOUT: float = 3.0
const RESPONSE_TIMEOUT: float = 5.0
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


## 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


## 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


## 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 like Interact).
func _send_and_receive(
	action_name: String, tick: int = 0, action_data: Variant = null,
	expect_position: 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 input_entry := {"tick": tick, "action_name": action_name}
	if action_data != null:
		input_entry["action_data"] = action_data
	var inputs: Array = [input_entry]
	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()
	return snapshot


## 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 {}


# -- Movement roundtrip: send movement, verify position changes ----------------

func test_movement_roundtrip(
	_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

	# Use Interact (server no-op) to get a baseline snapshot without moving.
	var baseline: Dictionary = await _send_and_receive("Interact", 0)
	var player := _find_player(baseline)
	assert_that(player.size()).is_greater(0)

	# Player starts at (16,16) → render coords (16.5, 16.5)
	var start_x: float = player.x
	var start_y: float = player.y
	assert_float(start_x).is_equal_approx(16.5, 0.001)
	assert_float(start_y).is_equal_approx(16.5, 0.001)

	# Send MoveNorth — player should move to (16, 15) → (16.5, 15.5)
	var snap1: Dictionary = await _send_and_receive("MoveNorth", 1, null, Vector2(16.5, 15.5))
	var p1 := _find_player(snap1)
	assert_that(p1.size()).is_greater(0)
	assert_float(p1.x).is_equal_approx(16.5, 0.001)
	assert_float(p1.y).is_equal_approx(15.5, 0.001)

	# Send MoveEast — player should move to (17, 15) → (17.5, 15.5)
	var snap2: Dictionary = await _send_and_receive("MoveEast", 2, null, Vector2(17.5, 15.5))
	var p2 := _find_player(snap2)
	assert_that(p2.size()).is_greater(0)
	assert_float(p2.x).is_equal_approx(17.5, 0.001)
	assert_float(p2.y).is_equal_approx(15.5, 0.001)

	# Verify position actually changed from baseline
	assert_that(p2.x != start_x or p2.y != start_y).is_true()


# -- Interact roundtrip: server accepts without crashing -----------------------

func test_interact_roundtrip(
	_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

	# Send Interact action — unit variant, no target data.
	# Server accepts it (currently a no-op) and responds with a valid snapshot.
	var snapshot: Dictionary = await _send_and_receive("Interact", 0)

	assert_that(snapshot.entities.size()).is_greater(0)

	# Player should be at start position (Interact doesn't move)
	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(16.5, 0.001)

	# Send Interact again at next tick — server should still accept it
	var snap2: Dictionary = await _send_and_receive("Interact", 1)
	assert_that(snap2).is_not_null()


# -- Mixed sequence: movement then interact in one session ---------------------

func test_move_then_interact(
	_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

	# Move player first — (16,16) → (16,15) → render (16.5, 15.5)
	var snap1: Dictionary = await _send_and_receive("MoveNorth", 0, null, Vector2(16.5, 15.5))
	var p1 := _find_player(snap1)
	assert_that(p1.size()).is_greater(0)
	var moved_x: float = p1.x
	var moved_y: float = p1.y

	# Now send Interact — player should stay where they moved to
	var snap2: Dictionary = await _send_and_receive("Interact", 1)
	var p2 := _find_player(snap2)
	assert_that(p2.size()).is_greater(0)
	assert_float(p2.x).is_equal_approx(moved_x, 0.001)
	assert_float(p2.y).is_equal_approx(moved_y, 0.001)