## D-030 Layer 1: Cross-language MessagePack tests
## Validates that Protocol.gd correctly decodes fixtures generated by Rust (rmp_serde).
## Fixtures generated by: cargo test --test gen_fixtures -- --ignored
class_name TestProtocol
extends GdUnitTestSuite

const FIXTURE_DIR = "res://tests/fixtures/msgpack/"


func _load_fixture(name: String) -> PackedByteArray:
	var path = FIXTURE_DIR + name + ".msgpack"
	var file = FileAccess.open(path, FileAccess.READ)
	assert_that(file).is_not_null()
	return file.get_buffer(file.get_length())


# -- Snapshot decoding ----------------------------------------------------------

func test_decode_snapshot_one_npc() -> void:
	var bytes = _load_fixture("snapshot_one_npc")
	var snapshot = Protocol.decode_snapshot(bytes)

	assert_that(snapshot).is_not_null()
	assert_that(snapshot.tick).is_equal(42)
	assert_that(snapshot.entities.size()).is_equal(1)

	var entity = snapshot.entities[0]
	assert_that(entity.entity_id).is_equal(1)
	assert_float(entity.x).is_equal_approx(10.0, 0.001)
	assert_float(entity.y).is_equal_approx(20.0, 0.001)
	assert_that(entity.z).is_equal(0)
	assert_that(entity.kind.variant).is_equal("Npc")
	assert_that(entity.kind.data).is_null()


func test_decode_snapshot_empty() -> void:
	var bytes = _load_fixture("snapshot_empty")
	var snapshot = Protocol.decode_snapshot(bytes)

	assert_that(snapshot).is_not_null()
	assert_that(snapshot.tick).is_equal(0)
	assert_that(snapshot.entities.size()).is_equal(0)


func test_decode_snapshot_multi_entity() -> void:
	var bytes = _load_fixture("snapshot_multi_entity")
	var snapshot = Protocol.decode_snapshot(bytes)

	assert_that(snapshot).is_not_null()
	assert_that(snapshot.tick).is_equal(999)
	assert_that(snapshot.entities.size()).is_equal(3)

	# NPC at (5, 10, 0)
	var npc = snapshot.entities[0]
	assert_that(npc.entity_id).is_equal(1)
	assert_float(npc.x).is_equal_approx(5.0, 0.001)
	assert_float(npc.y).is_equal_approx(10.0, 0.001)
	assert_that(npc.z).is_equal(0)
	assert_that(npc.kind.variant).is_equal("Npc")

	# Object at (15.5, 3, 1)
	var obj = snapshot.entities[1]
	assert_that(obj.entity_id).is_equal(2)
	assert_float(obj.x).is_equal_approx(15.5, 0.001)
	assert_float(obj.y).is_equal_approx(3.0, 0.001)
	assert_that(obj.z).is_equal(1)
	assert_that(obj.kind.variant).is_equal("Object")

	# Terrain at (0, 0, -1)
	var terrain = snapshot.entities[2]
	assert_that(terrain.entity_id).is_equal(3)
	assert_float(terrain.x).is_equal_approx(0.0, 0.001)
	assert_float(terrain.y).is_equal_approx(0.0, 0.001)
	assert_that(terrain.z).is_equal(-1)
	assert_that(terrain.kind.variant).is_equal("Terrain")


# -- PlayerInput decoding -------------------------------------------------------

func test_decode_input_move_north() -> void:
	var bytes = _load_fixture("input_move_north")
	var input = Protocol.decode_player_input(bytes)

	assert_that(input).is_not_null()
	assert_that(input.tick).is_equal(100)
	assert_that(input.action.variant).is_equal("MoveNorth")
	assert_that(input.action.data).is_null()


func test_decode_input_perception_mode() -> void:
	var bytes = _load_fixture("input_perception_mode")
	var input = Protocol.decode_player_input(bytes)

	assert_that(input).is_not_null()
	assert_that(input.tick).is_equal(200)
	assert_that(input.action.variant).is_equal("UsePerceptionMode")
	assert_that(input.action.data).is_equal("thermal")


# -- PlayerInput encoding -------------------------------------------------------

func test_encode_decode_roundtrip_unit_variant() -> void:
	var bytes = Protocol.encode_player_input(50, "MoveEast")
	assert_that(bytes.size()).is_greater(0)

	var decoded = Protocol.decode_player_input(bytes)
	assert_that(decoded).is_not_null()
	assert_that(decoded.tick).is_equal(50)
	assert_that(decoded.action.variant).is_equal("MoveEast")
	assert_that(decoded.action.data).is_null()


func test_encode_decode_roundtrip_data_variant() -> void:
	var bytes = Protocol.encode_player_input(75, "UsePerceptionMode", "infrared")
	assert_that(bytes.size()).is_greater(0)

	var decoded = Protocol.decode_player_input(bytes)
	assert_that(decoded).is_not_null()
	assert_that(decoded.tick).is_equal(75)
	assert_that(decoded.action.variant).is_equal("UsePerceptionMode")
	assert_that(decoded.action.data).is_equal("infrared")


# -- Cross-language roundtrip: GDScript encode matches Rust decode ---------------

func test_gdscript_encode_matches_rust_fixture() -> void:
	# Encode the same MoveNorth input as the Rust fixture
	var bytes = Protocol.encode_player_input(100, "MoveNorth")

	# Decode and verify the content matches the Rust fixture
	var rust_bytes = _load_fixture("input_move_north")
	var from_gd = Protocol.decode_player_input(bytes)
	var from_rust = Protocol.decode_player_input(rust_bytes)

	assert_that(from_gd.tick).is_equal(from_rust.tick)
	assert_that(from_gd.action.variant).is_equal(from_rust.action.variant)
	assert_that(from_gd.action.data).is_equal(from_rust.action.data)


# -- Negative tests: malformed/truncated input -----------------------------------

func test_decode_snapshot_truncated_bytes() -> void:
	var truncated := PackedByteArray([0x82, 0xa4])  # Incomplete msgpack map
	var result = Protocol.decode_snapshot(truncated)
	assert_that(result).is_null()


func test_decode_snapshot_wrong_type() -> void:
	# Encode an array instead of a map — should fail validation
	var encoded = Messagepack.encode([1, 2, 3])
	var result = Protocol.decode_snapshot(encoded.value)
	assert_that(result).is_null()


func test_decode_snapshot_missing_fields() -> void:
	# Map with wrong keys
	var encoded = Messagepack.encode({"foo": "bar"})
	var result = Protocol.decode_snapshot(encoded.value)
	assert_that(result).is_null()


func test_decode_player_input_empty_bytes() -> void:
	var result = Protocol.decode_player_input(PackedByteArray())
	assert_that(result).is_null()


func test_encode_produces_nonempty_bytes() -> void:
	var bytes = Protocol.encode_player_input(1, "MoveNorth")
	assert_that(bytes.size()).is_greater(0)


# -- Diagonal movement fixtures (D-030 Layer 1 cross-language) -----------------

func test_decode_diagonal_fixtures() -> void:
	# All 4 diagonal fixtures: clockwise NE, SE, SW, NW
	var diagonals: Array = [
		["input_move_northeast", "MoveNortheast"],
		["input_move_southeast", "MoveSoutheast"],
		["input_move_southwest", "MoveSouthwest"],
		["input_move_northwest", "MoveNorthwest"],
	]

	for pair in diagonals:
		var bytes = _load_fixture(pair[0])
		var input: Variant = Protocol.decode_player_input(bytes)
		assert_that(input).is_not_null()
		assert_that(input.tick).is_equal(100)
		assert_that(input.action.variant).is_equal(pair[1])
		assert_that(input.action.data).is_null()