text: /*************************************************************************/
  /*  websocket_multiplayer_peer.cpp                                       */
  /*************************************************************************/
  /*                       This file is part of:                           */
  /*                           GODOT ENGINE                                */
  /*                      https://godotengine.org                          */
  /*************************************************************************/
  /* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
  /* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md).   */
  /*                                                                       */
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  /* a copy of this software and associated documentation files (the       */
  /* "Software"), to deal in the Software without restriction, including   */
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  /* distribute, sublicense, and/or sell copies of the Software, and to    */
  /* permit persons to whom the Software is furnished to do so, subject to */
  /* the following conditions:                                             */
  /*                                                                       */
  /* The above copyright notice and this permission notice shall be        */
  /* included in all copies or substantial portions of the Software.       */
  /*                                                                       */
  /* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
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  /* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
  /* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
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  /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
  /*************************************************************************/
  
  #include "websocket_multiplayer_peer.h"
  
  #include "core/os/os.h"
  
  WebSocketMultiplayerPeer::WebSocketMultiplayerPeer() {
  	_is_multiplayer = false;
  	_peer_id = 0;
  	_target_peer = 0;
  	_refusing = false;
  
  	_current_packet.source = 0;
  	_current_packet.destination = 0;
  	_current_packet.size = 0;
  	_current_packet.data = nullptr;
  }
  
  WebSocketMultiplayerPeer::~WebSocketMultiplayerPeer() {
  	_clear();
  }
  
  int WebSocketMultiplayerPeer::_gen_unique_id() const {
  	uint32_t hash = 0;
  
  	while (hash == 0 || hash == 1) {
  		hash = hash_djb2_one_32(
  				(uint32_t)OS::get_singleton()->get_ticks_usec());
  		hash = hash_djb2_one_32(
  				(uint32_t)OS::get_singleton()->get_unix_time(), hash);
  		hash = hash_djb2_one_32(
  				(uint32_t)OS::get_singleton()->get_data_path().hash64(), hash);
  		hash = hash_djb2_one_32(
  				(uint32_t)((uint64_t)this), hash); //rely on aslr heap
  		hash = hash_djb2_one_32(
  				(uint32_t)((uint64_t)&hash), hash); //rely on aslr stack
  		hash = hash & 0x7FFFFFFF; // make it compatible with unsigned, since negatie id is used for exclusion
  	}
  
  	return hash;
  }
  void WebSocketMultiplayerPeer::_clear() {
  	_peer_map.clear();
  	if (_current_packet.data != nullptr) {
  		memfree(_current_packet.data);
  	}
  
  	for (List<Packet>::Element *E = _incoming_packets.front(); E; E = E->next()) {
  		memfree(E->get().data);
  		E->get().data = nullptr;
  	}
  
  	_incoming_packets.clear();
  }
  
  void WebSocketMultiplayerPeer::_bind_methods() {
  	ClassDB::bind_method(D_METHOD("set_buffers", "input_buffer_size_kb", "input_max_packets", "output_buffer_size_kb", "output_max_packets"), &WebSocketMultiplayerPeer::set_buffers);
  	ClassDB::bind_method(D_METHOD("get_peer", "peer_id"), &WebSocketMultiplayerPeer::get_peer);
  
  	ADD_SIGNAL(MethodInfo("peer_packet", PropertyInfo(Variant::INT, "peer_source")));
  }
  
  //
  // PacketPeer
  //
  int WebSocketMultiplayerPeer::get_available_packet_count() const {
  	ERR_FAIL_COND_V_MSG(!_is_multiplayer, 0, "Please use get_peer(ID).get_available_packet_count to get available packet count from peers when not using the MultiplayerAPI.");
  
  	return _incoming_packets.size();
  }
  
  Error WebSocketMultiplayerPeer::get_packet(const uint8_t **r_buffer, int &r_buffer_size) {
  	ERR_FAIL_COND_V_MSG(!_is_multiplayer, ERR_UNCONFIGURED, "Please use get_peer(ID).get_packet/var to communicate with peers when not using the MultiplayerAPI.");
  
  	r_buffer_size = 0;
  
  	if (_current_packet.data != nullptr) {
  		memfree(_current_packet.data);
  		_current_packet.data = nullptr;
  	}
  
  	ERR_FAIL_COND_V(_incoming_packets.size() == 0, ERR_UNAVAILABLE);
  
  	_current_packet = _incoming_packets.front()->get();
  	_incoming_packets.pop_front();
  
  	*r_buffer = _current_packet.data;
  	r_buffer_size = _current_packet.size;
  
  	return OK;
  }
  
  Error WebSocketMultiplayerPeer::put_packet(const uint8_t *p_buffer, int p_buffer_size) {
  	ERR_FAIL_COND_V_MSG(!_is_multiplayer, ERR_UNCONFIGURED, "Please use get_peer(ID).put_packet/var to communicate with peers when not using the MultiplayerAPI.");
  
  	PoolVector<uint8_t> buffer = _make_pkt(SYS_NONE, get_unique_id(), _target_peer, p_buffer, p_buffer_size);
  
  	if (is_server()) {
  		return _server_relay(1, _target_peer, &(buffer.read()[0]), buffer.size());
  	} else {
  		return get_peer(1)->put_packet(&(buffer.read()[0]), buffer.size());
  	}
  }
  
  //
  // NetworkedMultiplayerPeer
  //
  void WebSocketMultiplayerPeer::set_transfer_mode(TransferMode p_mode) {
  	// Websocket uses TCP, reliable
  }
  
  NetworkedMultiplayerPeer::TransferMode WebSocketMultiplayerPeer::get_transfer_mode() const {
  	// Websocket uses TCP, reliable
  	return TRANSFER_MODE_RELIABLE;
  }
  
  void WebSocketMultiplayerPeer::set_target_peer(int p_target_peer) {
  	_target_peer = p_target_peer;
  }
  
  int WebSocketMultiplayerPeer::get_packet_peer() const {
  	ERR_FAIL_COND_V_MSG(!_is_multiplayer, 1, "This function is not available when not using the MultiplayerAPI.");
  	ERR_FAIL_COND_V(_incoming_packets.size() == 0, 1);
  
  	return _incoming_packets.front()->get().source;
  }
  
  int WebSocketMultiplayerPeer::get_unique_id() const {
  	return _peer_id;
  }
  
  void WebSocketMultiplayerPeer::set_refuse_new_connections(bool p_enable) {
  	_refusing = p_enable;
  }
  
  bool WebSocketMultiplayerPeer::is_refusing_new_connections() const {
  	return _refusing;
  }
  
  void WebSocketMultiplayerPeer::_send_sys(Ref<WebSocketPeer> p_peer, uint8_t p_type, int32_t p_peer_id) {
  	ERR_FAIL_COND(!p_peer.is_valid());
  	ERR_FAIL_COND(!p_peer->is_connected_to_host());
  
  	PoolVector<uint8_t> message = _make_pkt(p_type, 1, 0, (uint8_t *)&p_peer_id, 4);
  	p_peer->put_packet(&(message.read()[0]), message.size());
  }
  
  PoolVector<uint8_t> WebSocketMultiplayerPeer::_make_pkt(uint8_t p_type, int32_t p_from, int32_t p_to, const uint8_t *p_data, uint32_t p_data_size) {
  	PoolVector<uint8_t> out;
  	out.resize(PROTO_SIZE + p_data_size);
  
  	PoolVector<uint8_t>::Write w = out.write();
  	memcpy(&w[0], &p_type, 1);
  	memcpy(&w[1], &p_from, 4);
  	memcpy(&w[5], &p_to, 4);
  	memcpy(&w[PROTO_SIZE], p_data, p_data_size);
  
  	return out;
  }
  
  void WebSocketMultiplayerPeer::_send_add(int32_t p_peer_id) {
  	// First of all, confirm the ID!
  	_send_sys(get_peer(p_peer_id), SYS_ID, p_peer_id);
  
  	// Then send the server peer (which will trigger connection_succeded in client)
  	_send_sys(get_peer(p_peer_id), SYS_ADD, 1);
  
  	for (Map<int, Ref<WebSocketPeer>>::Element *E = _peer_map.front(); E; E = E->next()) {
  		int32_t id = E->key();
  		if (p_peer_id == id) {
  			continue; // Skip the newwly added peer (already confirmed)
  		}
  
  		// Send new peer to others
  		_send_sys(get_peer(id), SYS_ADD, p_peer_id);
  		// Send others to new peer
  		_send_sys(get_peer(p_peer_id), SYS_ADD, id);
  	}
  }
  
  void WebSocketMultiplayerPeer::_send_del(int32_t p_peer_id) {
  	for (Map<int, Ref<WebSocketPeer>>::Element *E = _peer_map.front(); E; E = E->next()) {
  		int32_t id = E->key();
  		if (p_peer_id != id) {
  			_send_sys(get_peer(id), SYS_DEL, p_peer_id);
  		}
  	}
  }
  
  void WebSocketMultiplayerPeer::_store_pkt(int32_t p_source, int32_t p_dest, const uint8_t *p_data, uint32_t p_data_size) {
  	Packet packet;
  	packet.data = (uint8_t *)memalloc(p_data_size);
  	packet.size = p_data_size;
  	packet.source = p_source;
  	packet.destination = p_dest;
  	memcpy(packet.data, &p_data[PROTO_SIZE], p_data_size);
  	_incoming_packets.push_back(packet);
  	emit_signal("peer_packet", p_source);
  }
  
  Error WebSocketMultiplayerPeer::_server_relay(int32_t p_from, int32_t p_to, const uint8_t *p_buffer, uint32_t p_buffer_size) {
  	if (p_to == 1) {
  		return OK; // Will not send to self
  
  	} else if (p_to == 0) {
  		for (Map<int, Ref<WebSocketPeer>>::Element *E = _peer_map.front(); E; E = E->next()) {
  			if (E->key() != p_from) {
  				E->get()->put_packet(p_buffer, p_buffer_size);
  			}
  		}
  		return OK; // Sent to all but sender
  
  	} else if (p_to < 0) {
  		for (Map<int, Ref<WebSocketPeer>>::Element *E = _peer_map.front(); E; E = E->next()) {
  			if (E->key() != p_from && E->key() != -p_to) {
  				E->get()->put_packet(p_buffer, p_buffer_size);
  			}
  		}
  		return OK; // Sent to all but sender and excluded
  
  	} else {
  		ERR_FAIL_COND_V(p_to == p_from, FAILED);
  
  		Ref<WebSocketPeer> peer_to = get_peer(p_to);
  		ERR_FAIL_COND_V(peer_to.is_null(), FAILED);
  
  		return peer_to->put_packet(p_buffer, p_buffer_size); // Sending to specific peer
  	}
  }
  
  void WebSocketMultiplayerPeer::_process_multiplayer(Ref<WebSocketPeer> p_peer, uint32_t p_peer_id) {
  	ERR_FAIL_COND(!p_peer.is_valid());
  
  	const uint8_t *in_buffer;
  	int size = 0;
  	int data_size = 0;
  
  	Error err = p_peer->get_packet(&in_buffer, size);
  
  	ERR_FAIL_COND(err != OK);
  	ERR_FAIL_COND(size < PROTO_SIZE);
  
  	data_size = size - PROTO_SIZE;
  
  	uint8_t type = 0;
  	uint32_t from = 0;
  	int32_t to = 0;
  	memcpy(&type, in_buffer, 1);
  	memcpy(&from, &in_buffer[1], 4);
  	memcpy(&to, &in_buffer[5], 4);
  
  	if (is_server()) { // Server can resend
  
  		ERR_FAIL_COND(type != SYS_NONE); // Only server sends sys messages
  		ERR_FAIL_COND(from != p_peer_id); // Someone is cheating
  
  		if (to == 1) { // This is for the server
  
  			_store_pkt(from, to, in_buffer, data_size);
  
  		} else if (to == 0) {
  			// Broadcast, for us too
  			_store_pkt(from, to, in_buffer, data_size);
  
  		} else if (to < 0) {
  			// All but one, for us if not excluded
  			if (_peer_id != -(int32_t)p_peer_id) {
  				_store_pkt(from, to, in_buffer, data_size);
  			}
  		}
  		// Relay if needed (i.e. "to" includes a peer that is not the server)
  		_server_relay(from, to, in_buffer, size);
  
  	} else {
  		if (type == SYS_NONE) { // Payload message
  
  			_store_pkt(from, to, in_buffer, data_size);
  			return;
  		}
  
  		// System message
  		ERR_FAIL_COND(data_size < 4);
  		int id = 0;
  		memcpy(&id, &in_buffer[PROTO_SIZE], 4);
  
  		switch (type) {
  			case SYS_ADD: // Add peer
  				_peer_map[id] = Ref<WebSocketPeer>();
  				emit_signal("peer_connected", id);
  				if (id == 1) { // We just connected to the server
  					emit_signal("connection_succeeded");
  				}
  				break;
  
  			case SYS_DEL: // Remove peer
  				_peer_map.erase(id);
  				emit_signal("peer_disconnected", id);
  				break;
  			case SYS_ID: // Helo, server assigned ID
  				_peer_id = id;
  				break;
  			default:
  				ERR_FAIL_MSG("Invalid multiplayer message.");
  				break;
  		}
  	}
  }
  