New way to handle conditional fields in packets

Some packets have conditional fields. The previous way to handle
those was to provide a single condition for each packet type
which determined if additional fields are appended to the packet.
Unfortunately this is not enough for some packets: They have
complex conditions that cannot be expressed this way.

This diff changes the way conditional fields are handled: For
each field in each packet there is a new optional 'condition'
function which will be called with the packet data. Only if
the 'condition' function returns true, the field is de/encoded.

This diff also adds new (previously missing) conditions.

lib/protocol.js

@@ -360,7 +360,10 @@ var packets = {
     { name: "inventoryType", type: "byte" },
     { name: "windowTitle", type: "string" },
     { name: "slotCount", type: "byte" },
-    { name: "useProvidedTitle", type: "bool" }
+    { name: "useProvidedTitle", type: "bool" },
+    { name: "entityId", type: "int", condition: function(field_values) {
+      return field_values['inventoryType'] == 11;
+    } }
   ],
   0x65: [
     { name: "windowId", type: "byte" }
@@ -462,8 +465,12 @@ var packets = {
   0xcf: [
     { name: "itemName", type: "string" },
     { name: "remove", type: "bool" },
-    { name: "scoreName", type: "string" },
+    { name: "scoreName", type: "string", condition: function(field_values) {
-    { name: "value", type: "int" }
+      return !field_values['remove']
+    } },
+    { name: "value", type: "int", condition: function(field_values) {
+      return !field_values['remove']
+    } }
   ],
   0xd0: [
     { name: "position", type: "byte" },
@@ -472,11 +479,21 @@ var packets = {
   0xd1: [
     { name: "team", type: "string" },
     { name: "mode", type: "byte" },
-    { name: "name", type: "string" },
+    { name: "name", type: "string", condition: function(field_values) {
-    { name: "prefix", type: "string" },
+      return field_values['mode'] == 0 || field_values['mode'] == 2;
-    { name: "suffix", type: "string" },
+    } },
-    { name: "friendlyFire", type: "byte" },
+    { name: "prefix", type: "string", condition: function(field_values) {
-    { name: "players", type: "stringArray" }
+      return field_values['mode'] == 0 || field_values['mode'] == 2;
+    } },
+    { name: "suffix", type: "string", condition: function(field_values) {
+      return field_values['mode'] == 0 || field_values['mode'] == 2;
+    } },
+    { name: "friendlyFire", type: "byte", condition: function(field_values) {
+      return field_values['mode'] == 0 || field_values['mode'] == 2;
+    } },
+    { name: "players", type: "stringArray", condition: function(field_values) {
+      return field_values['mode'] == 0 || field_values['mode'] == 3 || field_values['mode'] == 4;
+    } }
   ],
   0xfa: [
     { name: "channel", type: "string" },
@@ -505,17 +522,6 @@ var packets = {
   ]
 };
 
-packet_optional_fields = {
-  0x64: {
-    condition: function(field_values) {
-      return field_values["inventoryType"] === 11;
-    },
-    fields: [
-      { name: "entityId", type: "int" }
-    ]
-  }
-};
-
 var types = {
   'int': [readInt, writeInt, 4],
   'short': [readShort, writeShort, 2],
@@ -1393,18 +1399,17 @@ function createPacketBuffer(packetId, params, isServer) {
   var packet = get(packetId, !isServer);
   assert.notEqual(packet, null);
   packet.forEach(function(fieldInfo) {
+    var condition = fieldInfo.condition;
+    if (typeof condition != "undefined" && !condition(params))
+      return;
     size += sizeOf(fieldInfo.type, params[fieldInfo.name]);
   });
-  var optionalFields, i;
-  if (packet_optional_fields[packetId] && packet_optional_fields[packetId].condition && packet_optional_fields[packetId].condition(params)) {
-    optionalFields = packet_optional_fields[packetId].fields;
-    for (i = 0; i < optionalFields.length; ++i) {
-      size += sizeOf(optionalFields[i].type, params[optionalFields[i].name]);
-    }
-  }
   var buffer = new Buffer(size);
   var offset = writeUByte(packetId, buffer, 0);
   packet.forEach(function(fieldInfo) {
+    var condition = fieldInfo.condition;
+    if (typeof condition != "undefined" && !condition(params))
+      return;
     var write = types[fieldInfo.type][1];
     var value = params[fieldInfo.name];
     if(typeof value === "undefined") value = 0;
@@ -1444,6 +1449,9 @@ function parsePacket(buffer, isServer) {
   var i, fieldInfo, readResults;
   for (i = 0; i < packetInfo.length; ++i) {
     fieldInfo = packetInfo[i];
+    var condition = fieldInfo.condition;
+    if (typeof condition != "undefined" && !condition(results))
+      continue;
     readResults = readPacketField(fieldInfo);
     if (!readResults || readResults.error) {
       return readResults;
@@ -1451,17 +1459,6 @@ function parsePacket(buffer, isServer) {
     results[fieldInfo.name] = readResults.value;
     size += readResults.size;
   }
-  if (packet_optional_fields[packetId] && packet_optional_fields[packetId].condition(results)) {
-    for (i = 0; i < packet_optional_fields[packetId].fields.length; ++i) {
-      fieldInfo = packet_optional_fields[packetId].fields[i];
-      readResults = readPacketField(fieldInfo);
-      if (!readResults || readResults.error) {
-        return readResults;
-      }
-      results[fieldInfo.name] = readResults.value;
-      size += readResults.size;
-    }
-  }
   debug(results);
   return {
     size: size,