VillagerTradeHelper.java

package cyano.basemetals.util;

import net.minecraft.entity.passive.EntityVillager;
import net.minecraft.util.ResourceLocation;
import net.minecraftforge.fml.common.registry.VillagerRegistry;

import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.Arrays;

/**
 * Created by Chris on 3/30/2016.
 */
public class VillagerTradeHelper {

	private static final ResourceLocation[] professionList = {
			new ResourceLocation("minecraft:farmer"),
			new ResourceLocation("minecraft:librarian"),
			new ResourceLocation("minecraft:priest"),
			new ResourceLocation("minecraft:smith"),
			new ResourceLocation("minecraft:butcher")
	};

	/**
	 * Inserts one or more trades to the defaul villager trade table using dark magic (aka java reflection).
	 * @param professionID Villager profession ID (0-4)
	 * @param careerID Villager career ID (1-3)
	 * @param tradeLevel Level of trade (1+)
	 * @param trades Trades to add to the given level
	 * @throws NoSuchFieldException Thrown if java reflection has been disabled for security reasons
	 * @throws IllegalAccessException Thrown if java reflection has been disabled for security reasons
	 */
	public static void insertTrades(int professionID, int careerID, int tradeLevel, EntityVillager.ITradeList... trades) throws NoSuchFieldException, IllegalAccessException {
		ResourceLocation profession = professionList[professionID];
		insertTrades(profession,careerID,tradeLevel,trades);
		/*
		FMLLog.info("%s: injecting villager trades %s into default trade array table at position [%s][%s][%s][*]", BaseMetals.MODID, Arrays.toString(trades), professionID, careerID-1, tradeLevel-1);
		Field vanillaTradeField = getTradeArrayFromClass(EntityVillager.class);
		unlockPrivateFinalField(vanillaTradeField);
		Object tradeTable = vanillaTradeField.get(null); // is static
		appendToMultidimensionalArray(trades,tradeTable,professionID,Math.max(0,careerID-1),Math.max(0,tradeLevel-1));
		*/
	}

	/**
	 * Inserts one or more trades to the defaul villager trade table using dark magic (aka java reflection).
	 * @param profession Villager profession
	 * @param careerID Villager career ID (1-3)
	 * @param tradeLevel Level of trade (1+)
	 * @param trades Trades to add to the given level
	 */
	public static void insertTrades(ResourceLocation profession, int careerID, int tradeLevel, EntityVillager.ITradeList... trades) {
		for(EntityVillager.ITradeList trade : trades) {
			VillagerRegistry.instance().getRegistry().getValue(profession).getCareer(careerID-1).addTrade(tradeLevel, trade);
		}
	}

	public static void appendToMultidimensionalArray(Object append, Object array, int... indices){
		appendToMultidimensionalArray(Arrays.asList(append).toArray(),array,indices);
	}

	public static void appendToMultidimensionalArray(Object[] append, Object array, int... indices){
		// get the lowest level array
		Object prevArray = null;
		int i = 0;
		while( i < indices.length){
			int index = indices[i];
			prevArray = array;
			array = Array.get(array, index);
			i++;
			// make sure the next array is long enough
			if(i < indices.length){
				int nextIndex = indices[i];
				if(Array.getLength(array) <= nextIndex){
					Object pad;
					if(array.getClass().getComponentType().isArray()){
						pad = Array.newInstance(array.getClass().getComponentType().getComponentType(),0);
					} else {
						// this shouldn't happen
						pad = null;
					}
					Object newArray = expandArray(array,nextIndex+1,pad);
					Array.set(prevArray,index,newArray);
					array = newArray;
				}
			}
		}

		// expand lowest level array to new size
		Class aType = array.getClass().getComponentType();
		if(!aType.isAssignableFrom(append.getClass().getComponentType())){
			throw new IllegalArgumentException("Class type "+append.getClass().getComponentType().getCanonicalName()+" cannot be appended to "+aType.getCanonicalName()+" array");
		}
		Object newArray = expandArray(array,Array.getLength(array)+append.length,null);
		System.arraycopy(append,0,newArray,Array.getLength(array),append.length);
		Array.set(prevArray,indices[indices.length - 1],newArray);
	}

	public static Object expandArray(Object array, int newSize, Object fill){
		Object newArray = Array.newInstance(array.getClass().getComponentType(),newSize);
		if(Array.getLength(array) == 0) return newArray;
		System.arraycopy(array,0,newArray,0,Array.getLength(array));
		for (int i = Array.getLength(array); i < newSize; i++){
			Array.set(newArray,i,fill);
		}
		return newArray;
	}

	public static void unlockPrivateFinalField(Field v) throws NoSuchFieldException, IllegalAccessException {
		v.setAccessible(true);
		Field modField = Field.class.getDeclaredField("modifiers");
		modField.setAccessible(true);
		modField.setInt(v, v.getModifiers() & ~Modifier.FINAL);
	}

	public static Field getTradeArrayFromClass(Class c){
		// search for 4D array of ITradeList objects
		for(Field f : c.getDeclaredFields()){
			if(f.getType().isArray() // D1
					&& f.getType().getComponentType().isArray() // D2
					&& f.getType().getComponentType().getComponentType().isArray() // D3
					&& f.getType().getComponentType().getComponentType().getComponentType().isArray() // D4
					&& f.getType().getComponentType().getComponentType().getComponentType().getComponentType().isAssignableFrom(EntityVillager.ITradeList.class)) {
				return f;
			}
		}
		return null;
	}
}