extends Node
## Transport and RPC surface. This is the only autoload in the project.
##
## It has to be an autoload because Godot routes an RPC by node path: the sender
## and receiver must agree on where the node lives, and `/root/Net` is the one
## path that exists identically on a dedicated server and on every client.
##
## The naming rule here is load-bearing: `c_*` is client -> server, `s_*` is
## server -> client. The `s_*` methods are annotated "authority", so the engine
## itself drops any attempt by a client to fake one.

signal state_changed(new_state: State)

enum State { OFFLINE, CONNECTING, ONLINE, FAILED }

## Peer id the engine gives the host. On a listen server this is also a real
## player, which is why every send goes through the helpers below.
const LOCAL_PEER := 1

var state: State = State.OFFLINE
var server: ServerRuntime = null
var client: ClientRuntime = null
var last_error: String = ""


func _set_state(s: State) -> void:
	state = s
	state_changed.emit(s)


# --- Lifecycle --------------------------------------------------------------

func host(port: int) -> Error:
	shutdown()
	var peer := ENetMultiplayerPeer.new()
	var err := peer.create_server(port, Protocol.MAX_CLIENTS, Protocol.CHANNEL_COUNT)
	if err != OK:
		last_error = "could not bind port %d (error %d)" % [port, err]
		GameLog.error("net", last_error)
		_set_state(State.FAILED)
		return err
	multiplayer.multiplayer_peer = peer
	multiplayer.peer_connected.connect(_on_peer_connected)
	multiplayer.peer_disconnected.connect(_on_peer_disconnected)
	server = ServerRuntime.new()
	server.name = "Server"
	add_child(server)
	_set_state(State.ONLINE)
	GameLog.info("net", "listening on %d" % port)
	return OK


func join(address: String, port: int) -> Error:
	shutdown()
	var peer := ENetMultiplayerPeer.new()
	var err := peer.create_client(address, port, Protocol.CHANNEL_COUNT)
	if err != OK:
		last_error = "could not reach %s:%d (error %d)" % [address, port, err]
		GameLog.error("net", last_error)
		_set_state(State.FAILED)
		return err
	multiplayer.multiplayer_peer = peer
	multiplayer.connected_to_server.connect(_on_connected)
	multiplayer.connection_failed.connect(_on_connect_failed)
	multiplayer.server_disconnected.connect(_on_server_disconnected)
	client = ClientRuntime.new()
	client.name = "Client"
	add_child(client)
	# Nothing is simulated until the server says hello back; on_welcome turns
	# the physics process on.
	client.set_physics_process(false)
	_set_state(State.CONNECTING)
	GameLog.info("net", "connecting to %s:%d" % [address, port])
	return OK


func shutdown() -> void:
	if multiplayer.multiplayer_peer != null \
			and multiplayer.multiplayer_peer is not OfflineMultiplayerPeer:
		multiplayer.multiplayer_peer.close()
	multiplayer.multiplayer_peer = null
	for sig in [multiplayer.peer_connected, multiplayer.peer_disconnected,
			multiplayer.connected_to_server, multiplayer.connection_failed,
			multiplayer.server_disconnected]:
		for c in sig.get_connections():
			sig.disconnect(c["callable"])
	if server != null:
		server.queue_free()
		server = null
	if client != null:
		client.queue_free()
		client = null
	_set_state(State.OFFLINE)


func kick(peer_id: int) -> void:
	if multiplayer.multiplayer_peer is ENetMultiplayerPeer:
		(multiplayer.multiplayer_peer as ENetMultiplayerPeer).disconnect_peer(peer_id)


func is_server() -> bool:
	return server != null


# --- Transport signals ------------------------------------------------------

func _on_peer_connected(peer_id: int) -> void:
	if server != null:
		server.on_peer_connected(peer_id)


func _on_peer_disconnected(peer_id: int) -> void:
	if server != null:
		server.on_peer_disconnected(peer_id)


func _on_connected() -> void:
	_set_state(State.ONLINE)
	c_hello.rpc_id(1, Protocol.VERSION, GameOpts.player_name)


func _on_connect_failed() -> void:
	last_error = "connection refused"
	GameLog.error("net", last_error)
	_set_state(State.FAILED)


func _on_server_disconnected() -> void:
	last_error = "server closed the connection"
	GameLog.warn("net", last_error)
	shutdown()


## Start a client inside the hosting process. The result is a listen server:
## the host plays through exactly the same code path as a remote player, sending
## input and learning outcomes from snapshots, with the transport short-circuited
## to a function call. No simulation code knows the difference.
func start_local_client() -> void:
	if server == null:
		GameLog.error("net", "start_local_client called with no server")
		return
	client = ClientRuntime.new()
	client.name = "Client"
	add_child(client)
	server.on_hello(LOCAL_PEER, Protocol.VERSION, GameOpts.player_name)


func _is_local(peer_id: int) -> bool:
	return peer_id == LOCAL_PEER and client != null


# --- Send helpers -----------------------------------------------------------
# Every server -> client message goes through one of these rather than calling
# rpc_id directly, so the listen server's own player is reachable too.

func send_welcome(peer_id: int) -> void:
	if _is_local(peer_id):
		client.on_welcome(peer_id)
	else:
		s_welcome.rpc_id(peer_id, peer_id, Protocol.VERSION)


func send_enter_instance(peer_id: int, id: int, kind: int, server_tick: int,
		boss_id: String, spawn: Vector2) -> void:
	if _is_local(peer_id):
		client.on_enter_instance(id, kind, server_tick, boss_id, spawn)
	else:
		s_enter_instance.rpc_id(peer_id, id, kind, server_tick, boss_id, spawn)


func send_snapshot(peer_id: int, data: PackedByteArray) -> void:
	if _is_local(peer_id):
		client.on_snapshot(data)
	else:
		s_snapshot.rpc_id(peer_id, data)


func send_events(peer_id: int, data: PackedByteArray) -> void:
	if _is_local(peer_id):
		client.on_events(data)
	else:
		s_events.rpc_id(peer_id, data)


func send_reject(peer_id: int, reason: String) -> void:
	if _is_local(peer_id):
		GameLog.error("net", "local client rejected: %s" % reason)
	else:
		s_reject.rpc_id(peer_id, reason)


func send_input(data: PackedByteArray) -> void:
	if server != null:
		server.on_input(LOCAL_PEER, data)   # listen server: no transport at all
	elif state == State.ONLINE and client != null:
		c_input.rpc_id(1, data)


# --- Client -> server -------------------------------------------------------

@rpc("any_peer", "call_remote", "reliable", 1)
func c_hello(version: int, display_name: String) -> void:
	if server == null:
		return
	server.on_hello(multiplayer.get_remote_sender_id(), version, display_name)


@rpc("any_peer", "call_remote", "unreliable_ordered", 4)
func c_input(data: PackedByteArray) -> void:
	if server == null:
		return
	server.on_input(multiplayer.get_remote_sender_id(), data)


# --- Server -> client -------------------------------------------------------

@rpc("authority", "call_remote", "reliable", 1)
func s_welcome(peer_id: int, _version: int) -> void:
	if client == null:
		return
	client.on_welcome(peer_id)
	client.set_physics_process(true)


@rpc("authority", "call_remote", "reliable", 1)
func s_enter_instance(id: int, kind: int, server_tick: int, boss_id: String,
		spawn: Vector2) -> void:
	if client == null:
		return
	client.on_enter_instance(id, kind, server_tick, boss_id, spawn)


@rpc("authority", "call_remote", "reliable", 1)
func s_reject(reason: String) -> void:
	last_error = reason
	GameLog.error("net", "rejected by server: %s" % reason)
	_set_state(State.FAILED)


@rpc("authority", "call_remote", "unreliable", 2)
func s_snapshot(data: PackedByteArray) -> void:
	if client != null:
		client.on_snapshot(data)


@rpc("authority", "call_remote", "reliable", 3)
func s_events(data: PackedByteArray) -> void:
	if client != null:
		client.on_events(data)