Add dPlayer.open_book mech

src/main/java/net/aufdemrand/denizen/objects/dPlayer.java

@@ -2208,6 +2208,19 @@ else if (split.length > 1) {
             PlayerSpectateEntity.setSpectating(getPlayerEntity(), value.asType(dEntity.class).getBukkitEntity());
         }
 
+        // <--[mechanism]
+        // @object dPlayer
+        // @name open_book
+        // @input None
+        // @description
+        // Forces the player to open the written book in their hand.
+        // The book can safely be removed from the player's hand
+        // without the player closing the book.
+        // -->
+        if (mechanism.matches("open_book")) {
+            OpenBook.openBook(getPlayerEntity());
+        }
+
         // Iterate through this object's properties' mechanisms
         for (Property property : PropertyParser.getProperties(this)) {
             property.adjust(mechanism);

src/main/java/net/aufdemrand/denizen/utilities/packets/OpenBook.java

@@ -0,0 +1,38 @@
+package net.aufdemrand.denizen.utilities.packets;
+
+import io.netty.buffer.Unpooled;
+import net.aufdemrand.denizen.utilities.debugging.dB;
+import net.minecraft.server.v1_8_R1.PacketDataSerializer;
+import net.minecraft.server.v1_8_R1.PacketPlayOutCustomPayload;
+import org.bukkit.entity.Player;
+
+import java.lang.reflect.Field;
+import java.util.Map;
+
+public class OpenBook {
+
+    private static final Field channel, packet_data;
+
+    static {
+        Map<String, Field> fields = PacketHelper.registerFields(PacketPlayOutCustomPayload.class);
+        channel = fields.get("a");
+        packet_data = fields.get("b");
+    }
+
+    public static PacketPlayOutCustomPayload getOpenBookPacket() {
+        PacketPlayOutCustomPayload customPayloadPacket = new PacketPlayOutCustomPayload();
+        try {
+            channel.set(customPayloadPacket, "MC|BOpen");
+            packet_data.set(customPayloadPacket, new PacketDataSerializer(Unpooled.buffer()));
+        } catch (Exception e) {
+            dB.echoError(e);
+        }
+        return customPayloadPacket;
+    }
+
+    public static void openBook(Player player) {
+        PacketPlayOutCustomPayload customPayloadPacket = getOpenBookPacket();
+        PacketHelper.sendPacket(player, customPayloadPacket);
+    }
+
+}