*In-progress, doesn't work (yet).* A simpler sync system for Godot.

Sync.gd

class_name JamminSync extends Node

# In-progress, doesn't work (yet).
# A simpler sync system for Godot.
# Add as an autoload named "Sync" or let JamminSync handle it.
# Usage:
# Sync.sync_prop_reliable(self, "prop_name")
# Sync.sync_prop_unreliable(self, "prop_name")

@export var log_syncs: bool = true
@export var log_missing_nodes: bool = true

var _synced_props: Dictionary = {}

# TODO: make this not run on the physics process, but rather call_deferred
func should_sync(obj_path: NodePath, prop: StringName, every: int = 1, sync_mode: StringName = &"on_change") -> bool:
	if every < 1: return false
	
	var frames = Engine.get_physics_frames()
	var is_on_tick = frames % every == 0
	
	# Always sync means always (on ticks)
	if sync_mode == &"always": return is_on_tick
	
	# Initialize cached values
	if not _synced_props.has(obj_path): _synced_props[obj_path] = { prop: { &"last_value": null } }
	if not _synced_props[obj_path].has(prop): _synced_props[obj_path][prop] = { &"last_value": null }
	var is_changed = _synced_props[obj_path][prop][&"last_value"] != get(prop)
	
	# Don't do a sync, even though it's changed, if we're not on the tick
	if sync_mode == &"on_change" and not is_changed: return false

	if is_changed:
		_synced_props[obj_path][prop][&"last_changed"] = frames
		_synced_props[obj_path][prop][&"last_value"] = get(prop)
		_synced_props[obj_path][prop][&"every"] = every
		return true
	
	# No change, so no sync
	if sync_mode == &"on_change": return false

	# Dynamic mode!
	# In this mode, we sync when the value changes, and fairly quickly for
	# a while, but then less and less often, until it changes again.
	var last_changed = _synced_props[obj_path][prop][&"last_changed"]
	var time_since_last_change = frames - last_changed
	var should_update = time_since_last_change % _synced_props[obj_path][prop][&"every"] == 0
	
	# Gradually increase the sync delay over time
	if should_update and _synced_props[obj_path][prop][&"every"] < every * 10: _synced_props[obj_path][prop][&"every"] += 1

	return should_update

func sync_prop_reliable(obj: Node, prop: StringName, every: int = 1, sync_mode: StringName = &"on_change"):
	if not Lobby.is_authority(obj): return
	# print("Syncing %s.%s" % [obj.get_path(), prop])
	var should = should_sync(obj.get_path(), prop, every, sync_mode)
	if should: print("Should sync: %s.%s = %s" % [obj.get_path(), prop, should])
	if should: remote_sync_prop_reliable.rpc(obj.get_path(), prop, get(prop))

func sync_prop_unreliable(obj: Node, prop: StringName, every: int = 1, sync_mode: StringName = &"on_change"):
	if not Lobby.is_authority(obj): return
	if should_sync(obj.get_path(), prop, every, sync_mode): remote_sync_prop_unreliable.rpc(obj.get_path(), prop, get(prop))

@rpc("call_local", "reliable", "authority")
func remote_sync_prop_reliable(obj_path: NodePath, prop: StringName, value: Variant):
	push_error("Rel Sync: %s.%s = %s" % [obj_path, prop, value])
	# TODO: allow optionally lerping to the new value quickly
	var obj = get_node(obj_path)
	if not obj:
		if log_missing_nodes: push_error("Sync: missing node %s" % obj_path)
		return
	obj.set(prop, value)

@rpc("call_local", "unreliable", "authority")
func remote_sync_prop_unreliable(obj_path: NodePath, prop: StringName, value: Variant):
	push_error("Unr Sync: %s.%s = %s" % [obj_path, prop, value])
	# TODO: allow optionally lerping to the new value quickly
	var obj = get_node(obj_path)
	if not obj:
		if log_missing_nodes: push_error("Sync: missing node %s" % obj_path)
		return
	obj.set(prop, value)