## D-030 Layer 1: Fixture-based tests for snapshot parsing
## Validates that GameState correctly parses Protocol-format ObserverSnapshot data
class_name TestSnapshotParsing
extends GdUnitTestSuite

# Valid snapshot in Protocol format (matches Protocol.decode_snapshot output)
var _valid_snapshot: Dictionary = {
	"tick": 1,
	"entities": [
		{"entity_id": 1, "x": 10.0, "y": 15.0, "z": 0, "kind": {"variant": "Npc", "data": null}},
		{"entity_id": 2, "x": 5.0, "y": 20.0, "z": 0, "kind": {"variant": "Npc", "data": null}},
	],
}

func test_apply_valid_snapshot() -> void:
	GameState.player_entity_id = 1
	GameState.apply_snapshot(_valid_snapshot)

	assert_that(GameState.current_tick).is_equal(1)
	assert_that(GameState.player_position).is_equal(Vector2(10, 15))
	assert_that(GameState.visible_entities.size()).is_equal(2)

func test_empty_snapshot_no_crash() -> void:
	# Reset state
	GameState.player_position = Vector2.ZERO
	GameState.visible_entities = []

	GameState.apply_snapshot({})

	# State should remain at defaults
	assert_that(GameState.player_position).is_equal(Vector2.ZERO)
	assert_that(GameState.visible_entities.size()).is_equal(0)

func test_no_player_entity_position_unchanged() -> void:
	GameState.player_entity_id = 999  # No entity with this ID
	GameState.player_position = Vector2(5, 5)

	GameState.apply_snapshot(_valid_snapshot)

	# Position stays at previous value since no matching entity
	assert_that(GameState.player_position).is_equal(Vector2(5, 5))

func test_missing_fields_partial_update() -> void:
	# First apply valid snapshot
	GameState.player_entity_id = 1
	GameState.apply_snapshot(_valid_snapshot)
	assert_that(GameState.player_position).is_equal(Vector2(10, 15))

	# Apply snapshot with no entities — player position unchanged (no matching entity)
	GameState.apply_snapshot({"tick": 2})
	assert_that(GameState.player_position).is_equal(Vector2(10, 15))
	assert_that(GameState.current_tick).is_equal(2)

func test_sim_bridge_test_snapshot_deterministic() -> void:
	SimBridge._test_tick = 0
	var snap1 = SimBridge._test_snapshot()
	var snap2 = SimBridge._test_snapshot()

	assert_that(snap1.tick).is_equal(1)
	assert_that(snap2.tick).is_equal(2)
	# Snapshot matches Protocol format
	assert_that(snap1.has("tick")).is_true()
	assert_that(snap1.has("entities")).is_true()
	assert_that(snap1.entities.size()).is_greater(0)
	assert_that(snap1.entities[0].has("entity_id")).is_true()
	assert_that(snap1.entities[0].has("kind")).is_true()