Via Mapping Utilities

MappingsGenerator.java

import com.google.gson.*;

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.nio.file.Files;
import java.util.Map;

public final class MappingsGenerator {

    public static void main(final String[] args) throws IOException {
        new File("generated").delete();

        net.minecraft.data.Main.main(new String[]{"--reports"});

        String content = new String(Files.readAllBytes(new File("generated/reports/blocks.json").toPath()));

        final Gson gson = new GsonBuilder().setPrettyPrinting().disableHtmlEscaping().create();
        JsonObject object = gson.fromJson(content, JsonObject.class);

        final JsonObject viaMappings = new JsonObject();
        final JsonObject blockstates = new JsonObject();
        final JsonObject blocks = new JsonObject();
        viaMappings.add("blockstates", blockstates);
        viaMappings.add("blocks", blocks);

        String lastBlock = "";
        int id = 0;
        for (final Map.Entry<String, JsonElement> blocksEntry : object.entrySet()) {
            final JsonObject block = blocksEntry.getValue().getAsJsonObject();
            final JsonArray states = block.getAsJsonArray("states");
            for (final JsonElement state : states) {
                final StringBuilder value = new StringBuilder(blocksEntry.getKey());
                if (!lastBlock.equals(blocksEntry.getKey())) {
                    lastBlock = blocksEntry.getKey();
                    blocks.add(Integer.toString(id++), new JsonPrimitive(lastBlock.replace("minecraft:", "")));
                }
                if (state.getAsJsonObject().has("properties")) {
                    value.append("[");
                    final JsonObject properties = state.getAsJsonObject().getAsJsonObject("properties");
                    boolean first = true;
                    for (final Map.Entry<String, JsonElement> propertyEntry : properties.entrySet()) {
                        if (first) {
                            first = false;
                        } else {
                            value.append(',');
                        }
                        value.append(propertyEntry.getKey()).append('=').append(propertyEntry.getValue().getAsJsonPrimitive().getAsString());
                    }
                    value.append("]");
                }
                blockstates.add(state.getAsJsonObject().get("id").getAsString(), new JsonPrimitive(value.toString()));
            }
        }

        content = new String(Files.readAllBytes(new File("generated/reports/registries.json").toPath()));
        object = gson.fromJson(content, JsonObject.class);

        final JsonObject items = new JsonObject();
        viaMappings.add("items", items);

        for (final Map.Entry<String, JsonElement> itemsEntry : object.getAsJsonObject("minecraft:item").getAsJsonObject("entries").entrySet()) {
            items.add(String.valueOf(itemsEntry.getValue().getAsJsonObject().getAsJsonPrimitive("protocol_id").getAsInt()), new JsonPrimitive(itemsEntry.getKey()));
        }

        final JsonArray sounds = new JsonArray();
        viaMappings.add("sounds", sounds);

        int i = 0;
        for (final Map.Entry<String, JsonElement> soundEntry : object.getAsJsonObject("minecraft:sound_event").getAsJsonObject("entries").entrySet()) {
            if (soundEntry.getValue().getAsJsonObject().getAsJsonPrimitive("protocol_id").getAsInt() != i) {
                throw new IllegalStateException();
            }
            sounds.add(new JsonPrimitive(soundEntry.getKey().replace("minecraft:", "")));
            i++;
        }

        try (final PrintWriter out = new PrintWriter("mapping-1.16.json")) {
            out.print(gson.toJson(viaMappings));
        }
    }
}

ViaItemMapHelper.java

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;

import java.io.File;
import java.nio.file.Files;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

public final class ViaItemMapHelper {

    public static void main(final String[] args) throws Exception {
        final Gson gson = new GsonBuilder().create();
        final String oldVer = "1.15";
        final String newVer = "1.16";
        // requires mapping files (shipped with ViaVersion)
        final JsonObject oldMapping = gson.fromJson(Files.readString(new File("mapping-" + oldVer + ".json").toPath()), JsonObject.class);
        final JsonObject newMapping = gson.fromJson(Files.readString(new File("mapping-" + newVer + ".json").toPath()), JsonObject.class);
        final JsonObject missing = new JsonObject();

        final Set<String> oldItems = new HashSet<>();
        for (final Map.Entry<String, JsonElement> entry : oldMapping.getAsJsonObject("items").entrySet()) {
            oldItems.add(entry.getValue().getAsString());
        }

        for (final Map.Entry<String, JsonElement> entry : newMapping.getAsJsonObject("items").entrySet()) {
            final String namespacedKey = entry.getValue().getAsString();
            if (oldItems.contains(namespacedKey)) continue;

            final JsonObject object = new JsonObject();
            object.addProperty("id", ""); // to be added manually case by case
            object.addProperty("name", newVer + " " + createNiceString(namespacedKey));
            missing.add(namespacedKey, object);
        }

        System.out.println(missing);
    }

    public static String createNiceString(String s) {
        s = s.replace("minecraft:", "");
        String result = "";
        for (final String split : s.split("_")) {
            result = result + " " + Character.toUpperCase(split.charAt(0)) + split.substring(1);
        }
        return result.substring(1);
    }
}

ViaTranslation.java

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;

import java.io.File;
import java.nio.file.Files;
import java.util.LinkedHashMap;
import java.util.Map;

public final class ViaTranslation {

    public static void main(final String[] args) throws Exception {
        final String oldVer = "15.2";
        final String newVer = "16";
        final Gson gson = new GsonBuilder().setLenient().create();

        final Map<String, String> newTranslations = new LinkedHashMap<>();
        final JsonObject object = gson.fromJson(Files.readString(new File("en_us" + newVer + ".json").toPath()), JsonObject.class);
        for (final Map.Entry<String, JsonElement> entry : object.entrySet()) {
            newTranslations.put(entry.getKey(), entry.getValue().getAsString());
        }

        final Map<String, String> oldTranslations = new LinkedHashMap<>();
        final JsonObject oldObject = gson.fromJson(Files.readString(new File("en_us" + oldVer + ".json").toPath()), JsonObject.class);
        for (final Map.Entry<String, JsonElement> entry : oldObject.entrySet()) {
            oldTranslations.put(entry.getKey(), entry.getValue().getAsString());
        }

        final JsonObject diff = new JsonObject();
        for (final Map.Entry<String, String> entry : newTranslations.entrySet()) {
            if (!oldTranslations.containsKey(entry.getKey())) {
                diff.addProperty(entry.getKey(), entry.getValue());
            }
        }

        System.out.println(diff);
    }
}