private final UUID id; // 玩家UUID数据，它代表了玩家的唯一标识

private final String name; // 玩家名称

private final PropertyMap properties = new PropertyMap(); // 属性信息，这内部存储了皮肤信息

private boolean legacy; // 这个我也无法确定是干什么的>_<，有可能为区分老账号与新账号的

public GameProfile(UUID id, String name) {
	// 名称和UUID不能同时为空（在玩家刚进入服务器时可能找不到UUID）
	if (id == null && StringUtils.isBlank(name))
		throw new IllegalArgumentException("Name and ID cannot both be blank");
	this.id = id;
	this.name = name;
}

private final String name; // 属性名称，对于皮肤属性此项通常为"textures"
private final String value; // 皮肤数据，为被Base64加密的JSON数据
private final String signature; // 签名，此签名是以Yggdrasil API的RSA私钥加密的结果，用于校验正确性

{
	"timestamp":<这一项是Java的时间值，单位是ms>,
	"profileId":"<玩家的UUID>"，
	"profileName":"<玩家的名称>",
	"signatureRequired":true, // 当皮肤属性含有签名时才会含有这项，否则不含有此属性
	"textures":{
		"SKIN":{
			"url":"<皮肤所处的URL>",
			"metadata":{ // 如果为Steve皮肤则不含有此项
				"model":"slim"
			}
		},
		"CAPE":{ // 如果玩家没有披风，则没有此项
			"url":"<披风所处的URL>"
		}
	}
}

{
	"id":"<玩家UUID>"，
	"name":"<玩家名称>",
	"properties":[
      {
			"name":"textures",
			"value":"<Base64加密的皮肤数据>",
			"signature":"<Yggdrasil API的RSA私钥加密的value数据>" // 这项可能不存在
      }
	]
}

// com.mojang.authlib.yggdrasil.YggdrasilMinecraftSessionService#fillGameProfile
protected GameProfile fillGameProfile(GameProfile profile, boolean requireSecure) {
	try {
		URL url = HttpAuthenticationService
				.constantURL("https://sessionserver.mojang.com/session/minecraft/profile/" + UUIDTypeAdapter.fromUUID(profile.getId()));
		url = HttpAuthenticationService.concatenateURL(url, "unsigned=" + (!requireSecure ? 1 : 0));
		MinecraftProfilePropertiesResponse response = getAuthenticationService().makeRequest(url, null, MinecraftProfilePropertiesResponse.class);
		if (response == null) {
			LOGGER.debug("Couldn't fetch profile properties for " + profile + " as the profile does not exist");
			return profile;
		}
		GameProfile result = new GameProfile(response.getId(), response.getName());
		result.getProperties().putAll((Multimap) response.getProperties());
		profile.getProperties().putAll((Multimap) response.getProperties());
		LOGGER.debug("Successfully fetched profile properties for " + profile);
		return result;
	} catch (AuthenticationException e) {
		LOGGER.warn("Couldn't look up profile properties for " + profile, e);
		return profile;
	}
}

// com.mojang.authlib.yggdrasil.YggdrasilMinecraftSessionService#getTextures
public Map<MinecraftProfileTexture.Type, MinecraftProfileTexture> getTextures(GameProfile profile, boolean requireSecure) {
	MinecraftTexturesPayload result;
	Property textureProperty = (Property) Iterables.getFirst(profile.getProperties().get("textures"), null);
	if (textureProperty == null)
		return new HashMap<>();
	if (requireSecure) {
		if (!textureProperty.hasSignature()) {
			LOGGER.error("Signature is missing from textures payload");
			throw new InsecureTextureException("Signature is missing from textures payload");
		}
			if (!textureProperty.isSignatureValid(this.publicKey)) {
			LOGGER.error("Textures payload has been tampered with (signature invalid)");
			throw new InsecureTextureException("Textures payload has been tampered with (signature invalid)");
		}
	}
	try {
		String json = new String(Base64.decodeBase64(textureProperty.getValue()), Charsets.UTF_8);
		result = (MinecraftTexturesPayload) this.gson.fromJson(json, MinecraftTexturesPayload.class);
	} catch (JsonParseException e) {
		LOGGER.error("Could not decode textures payload", (Throwable) e);
		return new HashMap<>();
	}
	if (result == null || result.getTextures() == null)
		return new HashMap<>();
	for (Map.Entry<MinecraftProfileTexture.Type, MinecraftProfileTexture> entry : result.getTextures().entrySet()) {
		if (!isWhitelistedDomain(((MinecraftProfileTexture) entry.getValue()).getUrl())) {
			LOGGER.error("Textures payload has been tampered with (non-whitelisted domain)");
			return new HashMap<>();
		}
	}
	return result.getTextures();
}

// net.minecraft.network.protocol.game.ClientboundPlayerInfoPacket.Action#ADD_PLAYER#read
// 读取部分
protected ClientboundPlayerInfoPacket.PlayerUpdate read(FriendlyByteBuf buf) {
	GameProfile gameProfile = new GameProfile(buf.readUUID(), buf.readUtf(16));
	PropertyMap propertyMap = gameProfile.getProperties();
	buf.readWithCount(friendlyByteBuf -> {
		String name = friendlyByteBuf.readUtf();
		String value = friendlyByteBuf.readUtf();
		if (friendlyByteBuf.readBoolean()) {
			String signature = friendlyByteBuf.readUtf();
			gameProfile.put(name, new Property(name, value, signature));
		} else {
			gameProfile.put(name, new Property(name, value));
		} 
	});
	GameType gameType = GameType.byId(buf.readVarInt());
	int i = buf.readVarInt();
	Component component = ClientboundPlayerInfoPacket.readDisplayName(buf);
	return new ClientboundPlayerInfoPacket.PlayerUpdate(gameProfile, i, gameType, component);
}

// net.minecraft.client.multiplayer.ClientPacketListener#handlePlayerInfo
public void handlePlayerInfo(ClientboundPlayerInfoPacket packet) {
	PacketUtils.ensureRunningOnSameThread(packet, this, minecraft);
	for (ClientboundPlayerInfoPacket.PlayerUpdate playerUpdate : packet.getEntries()) {
		// 删除了一部分无关代码
		if (packet.getAction() == ClientboundPlayerInfoPacket.Action.ADD_PLAYER) {
			playerInfo = new PlayerInfo(playerUpdate);
			playerInfoMap.put(playerInfo.getProfile().getId(), playerInfo);
			minecraft.getPlayerSocialManager().addPlayer(playerInfo);
		} 
		// 删除了无关代码
	}
}

// net.minecraft.client.renderer.entity.player.PlayerRenderer#renderHand
private void renderHand(PoseStack stack, MultiBufferSource buffer, int i, AbstractClientPlayer player, ModelPart modelPart1, ModelPart modelPart2) {
	PlayerModel<AbstractClientPlayer> playerModel = getModel();
	setModelProperties(player);
	playerModel.attackTime = 0.0F;
	playerModel.crouching = false;
	playerModel.swimAmount = 0.0F;
	playerModel.setupAnim(player, 0.0F, 0.0F, 0.0F, 0.0F, 0.0F);
	modelPart1.xRot = 0.0F;
	modelPart1.render(stack, buffer.getBuffer(RenderType.entitySolid(player.getSkinTextureLocation())), i, OverlayTexture.NO_OVERLAY);
	modelPart2.xRot = 0.0F;
	modelPart2.render(stack, buffer.getBuffer(RenderType.entityTranslucent(player.getSkinTextureLocation())), i, OverlayTexture.NO_OVERLAY);
}

// net.minecraft.client.multiplayer.ClientPacketListener#handleAddPlayer
public void handleAddPlayer(ClientboundAddPlayerPacket packet) {
	PacketUtils.ensureRunningOnSameThread(packet, this, minecraft);
	double x = packet.getX();
	double y = packet.getY();
	double z = packet.getZ();
	float yRot = (packet.getyRot() * 360) / 256.0F;
	float xRot = (packet.getxRot() * 360) / 256.0F;
	int id = packet.getEntityId();
	RemotePlayer remotePlayer = new RemotePlayer(minecraft.level, getPlayerInfo(packet.getPlayerId()).getProfile());
	remotePlayer.setId(id);
	remotePlayer.setPacketCoordinates(x, y, z);
	remotePlayer.absMoveTo(x, y, z, yRot, xRot);
	remotePlayer.setOldPosAndRot();
	level.addPlayer(id, remotePlayer);
}

// net.minecraft.client.multiplayer.PlayerInfo#registerTextures
protected void registerTextures() {
	synchronized (this) {
		if (!pendingTextures) {
			pendingTextures = true;
			Minecraft.getInstance().getSkinManager().registerSkins(profile, (type, location, texture) -> {
				// 这里可能是并发线程加载   
				textureLocations.put(type, location);
				if (type == MinecraftProfileTexture.Type.SKIN) {
					skinModel = texture.getMetadata("model");
					if (skinModel == null)
						skinModel = "default"; 
				} 
			}, true);
		} 
	} 
}

// net.minecraft.client.resource.DefaultPlayerSkin#isAlexDefault
private static boolean isAlexDefault(UUID uuid) {
	return uuid.hashCode() & 0x1 == 1;
	// 这段代码的意义是：如果哈希码值为奇数则使用Alex皮肤，偶数则使用Steve皮肤
}

// net.minecraft.world.entity.player.Player#createPlayerUUID(String)
public static UUID createPlayerUUID(String name) {
	return UUID.nameUUIDFromBytes(("OfflinePlayer:" + name).getBytes(StandardCharsets.UTF_8));
}

// net.minecraft.server.network.ServerLoginPacketListenerImpl#createFakeProfile
protected GameProfile createFakeProfile(GameProfile profile) {
	UUID uUID = Player.createPlayerUUID(profile.getName());
	return new GameProfile(uUID, profile.getName());
	// 插入点可以放在RETURN上（Mixin）
}

// net.minecraft.client.Minecraft#<init>
public Minecraft(GameConfig config) {
	// ...
	proxy = config.user.proxy;
	YggdrasilAuthenticationService yggdrasilAuthenticationService = new YggdrasilAuthenticationService(proxy);
	// 在此处替换为代理的服务
	minecraftSessionService = yggdrasilAuthenticationService.createMinecraftSessionService();
	socialInteractionsService = createSocialInteractions(yggdrasilAuthenticationService, config);
	user = config.user.user;
	// ...
}