/**************************************************************************/
/*  enet_multiplayer_peer.cpp                                             */
/**************************************************************************/
/*                         This file is part of:                          */
/*                             GODOT ENGINE                               */
/*                        https://godotengine.org                         */
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
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#include "enet_multiplayer_peer.h"

#include "core/io/ip.h"
#include "core/io/marshalls.h"
#include "core/os/os.h"

void ENetMultiplayerPeer::set_target_peer(int p_peer) {
	target_peer = p_peer;
}

int ENetMultiplayerPeer::get_packet_peer() const {
	ERR_FAIL_COND_V_MSG(!_is_active(), 1, "The multiplayer instance isn't currently active.");
	ERR_FAIL_COND_V(incoming_packets.is_empty(), 1);

	return incoming_packets.front()->get().from;
}

MultiplayerPeer::TransferMode ENetMultiplayerPeer::get_packet_mode() const {
	ERR_FAIL_COND_V_MSG(!_is_active(), TRANSFER_MODE_RELIABLE, "The multiplayer instance isn't currently active.");
	ERR_FAIL_COND_V(incoming_packets.is_empty(), TRANSFER_MODE_RELIABLE);
	return incoming_packets.front()->get().transfer_mode;
}

int ENetMultiplayerPeer::get_packet_channel() const {
	ERR_FAIL_COND_V_MSG(!_is_active(), 1, "The multiplayer instance isn't currently active.");
	ERR_FAIL_COND_V(incoming_packets.is_empty(), 1);
	int ch = incoming_packets.front()->get().channel;
	if (ch >= SYSCH_MAX) { // First 2 channels are reserved.
		return ch - SYSCH_MAX + 1;
	}
	return 0;
}

Error ENetMultiplayerPeer::create_server(int p_port, int p_max_clients, int p_max_channels, int p_in_bandwidth, int p_out_bandwidth) {
	ERR_FAIL_COND_V_MSG(_is_active(), ERR_ALREADY_IN_USE, "The multiplayer instance is already active.");
	set_refuse_new_connections(false);
	Ref<ENetConnection> host;
	host.instantiate();
	Error err = host->create_host_bound(bind_ip, p_port, p_max_clients, 0, p_max_channels > 0 ? p_max_channels + SYSCH_MAX : 0, p_out_bandwidth);
	if (err != OK) {
		return err;
	}

	active_mode = MODE_SERVER;
	unique_id = 1;
	connection_status = CONNECTION_CONNECTED;
	hosts[0] = host;
	return OK;
}

Error ENetMultiplayerPeer::create_client(const String &p_address, int p_port, int p_channel_count, int p_in_bandwidth, int p_out_bandwidth, int p_local_port) {
	ERR_FAIL_COND_V_MSG(_is_active(), ERR_ALREADY_IN_USE, "The multiplayer instance is already active.");
	set_refuse_new_connections(false);
	Ref<ENetConnection> host;
	host.instantiate();
	Error err;
	if (p_local_port) {
		err = host->create_host_bound(bind_ip, p_local_port, 1, 0, p_in_bandwidth, p_out_bandwidth);
	} else {
		err = host->create_host(1, 0, p_in_bandwidth, p_out_bandwidth);
	}
	if (err != OK) {
		return err;
	}

	unique_id = generate_unique_id();

	Ref<ENetPacketPeer> peer = host->connect_to_host(p_address, p_port, p_channel_count > 0 ? p_channel_count + SYSCH_MAX : 0, unique_id);
	if (peer.is_null()) {
		host->destroy();
		ERR_FAIL_V_MSG(ERR_CANT_CREATE, "Couldn't connect to the ENet multiplayer server.");
	}

	// Need to wait for CONNECT event.
	connection_status = CONNECTION_CONNECTING;
	active_mode = MODE_CLIENT;
	peers[1] = peer;
	hosts[0] = host;

	return OK;
}

Error ENetMultiplayerPeer::create_mesh(int p_id) {
	ERR_FAIL_COND_V_MSG(p_id <= 0, ERR_INVALID_PARAMETER, "The unique ID must be greater then 0");
	ERR_FAIL_COND_V_MSG(_is_active(), ERR_ALREADY_IN_USE, "The multiplayer instance is already active.");
	active_mode = MODE_MESH;
	unique_id = p_id;
	connection_status = CONNECTION_CONNECTED;
	return OK;
}

Error ENetMultiplayerPeer::add_mesh_peer(int p_id, Ref<ENetConnection> p_host) {
	ERR_FAIL_COND_V(p_host.is_null(), ERR_INVALID_PARAMETER);
	ERR_FAIL_COND_V_MSG(active_mode != MODE_MESH, ERR_UNCONFIGURED, "The multiplayer instance is not configured as a mesh. Call 'create_mesh' first.");
	List<Ref<ENetPacketPeer>> host_peers;
	p_host->get_peers(host_peers);
	ERR_FAIL_COND_V_MSG(host_peers.size() != 1 || host_peers.front()->get()->get_state() != ENetPacketPeer::STATE_CONNECTED, ERR_INVALID_PARAMETER, "The provided host must have exactly one peer in the connected state.");
	hosts[p_id] = p_host;
	peers[p_id] = host_peers.front()->get();
	emit_signal(SNAME("peer_connected"), p_id);
	return OK;
}

void ENetMultiplayerPeer::_store_packet(int32_t p_source, ENetConnection::Event &p_event) {
	Packet packet;
	packet.packet = p_event.packet;
	packet.channel = p_event.channel_id;
	packet.from = p_source;
	if (p_event.packet->flags & ENET_PACKET_FLAG_RELIABLE) {
		packet.transfer_mode = TRANSFER_MODE_RELIABLE;
	} else if (p_event.packet->flags & ENET_PACKET_FLAG_UNSEQUENCED) {
		packet.transfer_mode = TRANSFER_MODE_UNRELIABLE;
	} else {
		packet.transfer_mode = TRANSFER_MODE_UNRELIABLE_ORDERED;
	}
	packet.packet->referenceCount++;
	incoming_packets.push_back(packet);
}

void ENetMultiplayerPeer::_disconnect_inactive_peers() {
	HashSet<int> to_drop;
	for (const KeyValue<int, Ref<ENetPacketPeer>> &E : peers) {
		if (E.value->is_active()) {
			continue;
		}
		to_drop.insert(E.key);
	}
	for (const int &P : to_drop) {
		peers.erase(P);
		if (hosts.has(P)) {
			hosts.erase(P);
		}
		ERR_CONTINUE(active_mode == MODE_CLIENT && P != TARGET_PEER_SERVER);
		emit_signal(SNAME("peer_disconnected"), P);
	}
}

void ENetMultiplayerPeer::poll() {
	ERR_FAIL_COND_MSG(!_is_active(), "The multiplayer instance isn't currently active.");

	_pop_current_packet();

	_disconnect_inactive_peers();

	switch (active_mode) {
		case MODE_CLIENT: {
			if (!peers.has(1)) {
				close();
				return;
			}
			ENetConnection::Event event;
			ENetConnection::EventType ret = hosts[0]->service(0, event);
			do {
				if (ret == ENetConnection::EVENT_CONNECT) {
					connection_status = CONNECTION_CONNECTED;
					emit_signal(SNAME("peer_connected"), 1);
				} else if (ret == ENetConnection::EVENT_DISCONNECT) {
					if (connection_status == CONNECTION_CONNECTED) {
						// Client just disconnected from server.
						emit_signal(SNAME("peer_disconnected"), 1);
					}
					close();
				} else if (ret == ENetConnection::EVENT_RECEIVE) {
					_store_packet(1, event);
				} else if (ret != ENetConnection::EVENT_NONE) {
					close(); // Error.
				}
			} while (hosts.has(0) && hosts[0]->check_events(ret, event) > 0);
		} break;
		case MODE_SERVER: {
			ENetConnection::Event event;
			ENetConnection::EventType ret = hosts[0]->service(0, event);
			do {
				if (ret == ENetConnection::EVENT_CONNECT) {
					if (is_refusing_new_connections()) {
						event.peer->reset();
						continue;
					}
					// Client joined with invalid ID, probably trying to exploit us.
					if (event.data < 2 || peers.has((int)event.data)) {
						event.peer->reset();
						continue;
					}
					int id = event.data;
					event.peer->set_meta(SNAME("_net_id"), id);
					peers[id] = event.peer;
					emit_signal(SNAME("peer_connected"), id);
				} else if (ret == ENetConnection::EVENT_DISCONNECT) {
					int id = event.peer->get_meta(SNAME("_net_id"));
					if (!peers.has(id)) {
						// Never fully connected.
						continue;
					}
					emit_signal(SNAME("peer_disconnected"), id);
					peers.erase(id);
				} else if (ret == ENetConnection::EVENT_RECEIVE) {
					int32_t source = event.peer->get_meta(SNAME("_net_id"));
					_store_packet(source, event);
				} else if (ret != ENetConnection::EVENT_NONE) {
					close(); // Error
				}
			} while (hosts.has(0) && hosts[0]->check_events(ret, event) > 0);
		} break;
		case MODE_MESH: {
			HashSet<int> to_drop;
			for (KeyValue<int, Ref<ENetConnection>> &E : hosts) {
				ENetConnection::Event event;
				ENetConnection::EventType ret = E.value->service(0, event);
				do {
					if (ret == ENetConnection::EVENT_CONNECT) {
						event.peer->reset();
					} else if (ret == ENetConnection::EVENT_RECEIVE) {
						_store_packet(E.key, event);
					} else if (ret == ENetConnection::EVENT_NONE) {
						break; // Keep polling the others.
					} else {
						to_drop.insert(E.key); // Error or disconnect.
						break; // Keep polling the others.
					}
				} while (E.value->check_events(ret, event) > 0);
			}
			for (const int &P : to_drop) {
				if (peers.has(P)) {
					emit_signal(SNAME("peer_disconnected"), P);
					peers.erase(P);
				}
				hosts.erase(P);
			}
		} break;
		default:
			return;
	}
}

bool ENetMultiplayerPeer::is_server() const {
	return active_mode == MODE_SERVER;
}

bool ENetMultiplayerPeer::is_server_relay_supported() const {
	return active_mode == MODE_SERVER || active_mode == MODE_CLIENT;
}

void ENetMultiplayerPeer::disconnect_peer(int p_peer, bool p_force) {
	ERR_FAIL_COND(!_is_active() || !peers.has(p_peer));
	peers[p_peer]->peer_disconnect(0); // Will be removed during next poll.
	if (active_mode == MODE_CLIENT || active_mode == MODE_SERVER) {
		hosts[0]->flush();
	} else {
		ERR_FAIL_COND(!hosts.has(p_peer));
		hosts[p_peer]->flush();
	}
	if (p_force) {
		peers.erase(p_peer);
		if (hosts.has(p_peer)) {
			hosts.erase(p_peer);
		}
		if (active_mode == MODE_CLIENT) {
			hosts.clear(); // Avoid flushing again.
			close();
		}
	}
}

void ENetMultiplayerPeer::close() {
	if (!_is_active()) {
		return;
	}

	_pop_current_packet();

	for (KeyValue<int, Ref<ENetPacketPeer>> &E : peers) {
		if (E.value.is_valid() && E.value->get_state() == ENetPacketPeer::STATE_CONNECTED) {
			E.value->peer_disconnect_now(0);
		}
	}
	for (KeyValue<int, Ref<ENetConnection>> &E : hosts) {
		E.value->flush();
	}

	active_mode = MODE_NONE;
	incoming_packets.clear();
	peers.clear();
	hosts.clear();
	unique_id = 0;
	connection_status = CONNECTION_DISCONNECTED;
	set_refuse_new_connections(false);
}

int ENetMultiplayerPeer::get_available_packet_count() const {
	return incoming_packets.size();
}

Error ENetMultiplayerPeer::get_packet(const uint8_t **r_buffer, int &r_buffer_size) {
	ERR_FAIL_COND_V_MSG(incoming_packets.is_empty(), ERR_UNAVAILABLE, "No incoming packets available.");

	_pop_current_packet();

	current_packet = incoming_packets.front()->get();
	incoming_packets.pop_front();

	*r_buffer = (const uint8_t *)(current_packet.packet->data);
	r_buffer_size = current_packet.packet->dataLength;

	return OK;
}

Error ENetMultiplayerPeer::put_packet(const uint8_t *p_buffer, int p_buffer_size) {
	ERR_FAIL_COND_V_MSG(!_is_active(), ERR_UNCONFIGURED, "The multiplayer instance isn't currently active.");
	ERR_FAIL_COND_V_MSG(connection_status != CONNECTION_CONNECTED, ERR_UNCONFIGURED, "The multiplayer instance isn't currently connected to any server or client.");
	ERR_FAIL_COND_V_MSG(target_peer != 0 && !peers.has(ABS(target_peer)), ERR_INVALID_PARAMETER, vformat("Invalid target peer: %d", target_peer));
	ERR_FAIL_COND_V(active_mode == MODE_CLIENT && !peers.has(1), ERR_BUG);

	int packet_flags = 0;
	int channel = SYSCH_RELIABLE;
	int tr_channel = get_transfer_channel();
	switch (get_transfer_mode()) {
		case TRANSFER_MODE_UNRELIABLE: {
			packet_flags = ENET_PACKET_FLAG_UNSEQUENCED | ENET_PACKET_FLAG_UNRELIABLE_FRAGMENT;
			channel = SYSCH_UNRELIABLE;
		} break;
		case TRANSFER_MODE_UNRELIABLE_ORDERED: {
			packet_flags = ENET_PACKET_FLAG_UNRELIABLE_FRAGMENT;
			channel = SYSCH_UNRELIABLE;
		} break;
		case TRANSFER_MODE_RELIABLE: {
			packet_flags = ENET_PACKET_FLAG_RELIABLE;
			channel = SYSCH_RELIABLE;
		} break;
	}
	if (tr_channel > 0) {
		channel = SYSCH_MAX + tr_channel - 1;
	}

#ifdef DEBUG_ENABLED
	if ((packet_flags & ENET_PACKET_FLAG_UNRELIABLE_FRAGMENT) && p_buffer_size > ENET_HOST_DEFAULT_MTU) {
		WARN_PRINT_ONCE(vformat("Sending %d bytes unreliably which is above the MTU (%d), this will result in higher packet loss", p_buffer_size, ENET_HOST_DEFAULT_MTU));
	}
#endif

	ENetPacket *packet = enet_packet_create(nullptr, p_buffer_size, packet_flags);
	memcpy(&packet->data[0], p_buffer, p_buffer_size);

	if (is_server()) {
		if (target_peer == 0) {
			hosts[0]->broadcast(channel, packet);

		} else if (target_peer < 0) {
			// Send to all but one and make copies for sending.
			int exclude = -target_peer;
			for (KeyValue<int, Ref<ENetPacketPeer>> &E : peers) {
				if (E.key == exclude) {
					continue;
				}
				E.value->send(channel, packet);
			}
			_destroy_unused(packet);
		} else {
			peers[target_peer]->send(channel, packet);
		}
		ERR_FAIL_COND_V(!hosts.has(0), ERR_BUG);
		hosts[0]->flush();

	} else if (active_mode == MODE_CLIENT) {
		peers[1]->send(channel, packet); // Send to server for broadcast.
		ERR_FAIL_COND_V(!hosts.has(0), ERR_BUG);
		hosts[0]->flush();

	} else {
		if (target_peer <= 0) {
			int exclude = ABS(target_peer);
			for (KeyValue<int, Ref<ENetPacketPeer>> &E : peers) {
				if (E.key == exclude) {
					continue;
				}
				E.value->send(channel, packet);
				ERR_CONTINUE(!hosts.has(E.key));
				hosts[E.key]->flush();
			}
			_destroy_unused(packet);
		} else {
			peers[target_peer]->send(channel, packet);
			ERR_FAIL_COND_V(!hosts.has(target_peer), ERR_BUG);
			hosts[target_peer]->flush();
		}
	}

	return OK;
}

int ENetMultiplayerPeer::get_max_packet_size() const {
	return 1 << 24; // Anything is good
}

void ENetMultiplayerPeer::_pop_current_packet() {
	if (current_packet.packet) {
		current_packet.packet->referenceCount--;
		_destroy_unused(current_packet.packet);
		current_packet.packet = nullptr;
		current_packet.from = 0;
		current_packet.channel = -1;
	}
}

MultiplayerPeer::ConnectionStatus ENetMultiplayerPeer::get_connection_status() const {
	return connection_status;
}

int ENetMultiplayerPeer::get_unique_id() const {
	ERR_FAIL_COND_V_MSG(!_is_active(), 0, "The multiplayer instance isn't currently active.");
	return unique_id;
}

void ENetMultiplayerPeer::set_refuse_new_connections(bool p_enabled) {
#ifdef GODOT_ENET
	if (_is_active()) {
		for (KeyValue<int, Ref<ENetConnection>> &E : hosts) {
			E.value->refuse_new_connections(p_enabled);
		}
	}
#endif
	MultiplayerPeer::set_refuse_new_connections(p_enabled);
}

Ref<ENetConnection> ENetMultiplayerPeer::get_host() const {
	ERR_FAIL_COND_V(!_is_active(), nullptr);
	ERR_FAIL_COND_V(active_mode == MODE_MESH, nullptr);
	return hosts[0];
}

Ref<ENetPacketPeer> ENetMultiplayerPeer::get_peer(int p_id) const {
	ERR_FAIL_COND_V(!_is_active(), nullptr);
	ERR_FAIL_COND_V(!peers.has(p_id), nullptr);
	ERR_FAIL_COND_V(active_mode == MODE_CLIENT && p_id != 1, nullptr);
	return peers[p_id];
}

void ENetMultiplayerPeer::_destroy_unused(ENetPacket *p_packet) {
	if (p_packet->referenceCount == 0) {
		enet_packet_destroy(p_packet);
	}
}

void ENetMultiplayerPeer::_bind_methods() {
	ClassDB::bind_method(D_METHOD("create_server", "port", "max_clients", "max_channels", "in_bandwidth", "out_bandwidth"), &ENetMultiplayerPeer::create_server, DEFVAL(32), DEFVAL(0), DEFVAL(0), DEFVAL(0));
	ClassDB::bind_method(D_METHOD("create_client", "address", "port", "channel_count", "in_bandwidth", "out_bandwidth", "local_port"), &ENetMultiplayerPeer::create_client, DEFVAL(0), DEFVAL(0), DEFVAL(0), DEFVAL(0));
	ClassDB::bind_method(D_METHOD("create_mesh", "unique_id"), &ENetMultiplayerPeer::create_mesh);
	ClassDB::bind_method(D_METHOD("add_mesh_peer", "peer_id", "host"), &ENetMultiplayerPeer::add_mesh_peer);
	ClassDB::bind_method(D_METHOD("set_bind_ip", "ip"), &ENetMultiplayerPeer::set_bind_ip);

	ClassDB::bind_method(D_METHOD("get_host"), &ENetMultiplayerPeer::get_host);
	ClassDB::bind_method(D_METHOD("get_peer", "id"), &ENetMultiplayerPeer::get_peer);

	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "host", PROPERTY_HINT_RESOURCE_TYPE, "ENetConnection", PROPERTY_USAGE_NONE), "", "get_host");
}

ENetMultiplayerPeer::ENetMultiplayerPeer() {
	bind_ip = IPAddress("*");
}

ENetMultiplayerPeer::~ENetMultiplayerPeer() {
	if (_is_active()) {
		close();
	}
}

// Sets IP for ENet to bind when using create_server or create_client
// if no IP is set, then ENet bind to ENET_HOST_ANY
void ENetMultiplayerPeer::set_bind_ip(const IPAddress &p_ip) {
	ERR_FAIL_COND_MSG(!p_ip.is_valid() && !p_ip.is_wildcard(), vformat("Invalid bind IP address: %s", String(p_ip)));

	bind_ip = p_ip;
}