Support Overriding World Seeds - Closes #350

Allows you to add to paper.yml

seed-overrides:
  world_name: some seed value

This will ignore every where a seed is set/created/loaded and force
a world to use the specified seed.

This seed will end up being saved to the world data file, so it is
a permanent change in that it won't go back if you remove it from paper.yml

Spigot-Server-Patches/0374-Support-Overriding-World-Seeds.patch

@@ -0,0 +1,102 @@
+From 9dd9a3abeb5338d4fa5733683634c6c22ee59f24 Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Mon, 17 Sep 2018 23:05:31 -0400
+Subject: [PATCH] Support Overriding World Seeds
+
+Allows you to add to paper.yml
+
+seed-overrides:
+  world_name: some seed value
+
+This will ignore every where a seed is set/created/loaded and force
+a world to use the specified seed.
+
+This seed will end up being saved to the world data file, so it is
+a permanent change in that it won't go back if you remove it from paper.yml
+
+diff --git a/src/main/java/com/destroystokyo/paper/PaperConfig.java b/src/main/java/com/destroystokyo/paper/PaperConfig.java
+index 54f088c242..4093fbeb63 100644
+--- a/src/main/java/com/destroystokyo/paper/PaperConfig.java
++++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java
+@@ -11,6 +11,7 @@ import java.lang.reflect.Modifier;
+ import java.util.HashMap;
+ import java.util.List;
+ import java.util.Map;
++import java.util.Set;
+ import java.util.concurrent.TimeUnit;
+ import java.util.logging.Level;
+ import java.util.logging.Logger;
+@@ -20,6 +21,7 @@ import com.google.common.collect.Lists;
+ import net.minecraft.server.MinecraftServer;
+ import org.bukkit.Bukkit;
+ import org.bukkit.command.Command;
++import org.bukkit.configuration.ConfigurationSection;
+ import org.bukkit.configuration.InvalidConfigurationException;
+ import org.bukkit.configuration.file.YamlConfiguration;
+ import co.aikar.timings.Timings;
+@@ -351,4 +353,23 @@ public class PaperConfig {
+         }
+         tabSpamLimit = getInt("settings.spam-limiter.tab-spam-limit", tabSpamLimit);
+     }
++
++    public static Map<String, Long> seedOverride = new java.util.HashMap<>();
++    private static void worldSeedOverrides() {
++        ConfigurationSection seeds = config.getConfigurationSection("seed-overrides");
++        if (seeds != null) {
++            TimingsManager.hiddenConfigs.add("seed-overrides");
++            for (String key : seeds.getKeys(false)) {
++                String seedString = seeds.getString(key);
++                long seed;
++                try {
++                    seed = Long.parseLong(seedString);
++                } catch (Exception e) {
++                    seed = (long) seedString.hashCode();
++                }
++                log("Seed Override: " + key + " => " + seed);
++                seedOverride.put(key, seed);
++            }
++        }
++    }
+ }
+diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
+index 81cda5df56..fb62320310 100644
+--- a/src/main/java/net/minecraft/server/MinecraftServer.java
++++ b/src/main/java/net/minecraft/server/MinecraftServer.java
+@@ -350,7 +350,7 @@ public abstract class MinecraftServer implements IAsyncTaskHandler, IMojangStati
+             this.convertWorld(name); // Run conversion now
+ 
+             org.bukkit.generator.ChunkGenerator gen = this.server.getGenerator(name);
+-            WorldSettings worldsettings = new WorldSettings(i, this.getGamemode(), this.getGenerateStructures(), this.isHardcore(), worldtype);
++            WorldSettings worldsettings = new WorldSettings(com.destroystokyo.paper.PaperConfig.seedOverride.getOrDefault(name, i), this.getGamemode(), this.getGenerateStructures(), this.isHardcore(), worldtype); // Paper
+             worldsettings.setGeneratorSettings(jsonelement);
+ 
+             if (j == 0) {
+diff --git a/src/main/java/net/minecraft/server/WorldData.java b/src/main/java/net/minecraft/server/WorldData.java
+index a98bc4d0e1..c108b97b9b 100644
+--- a/src/main/java/net/minecraft/server/WorldData.java
++++ b/src/main/java/net/minecraft/server/WorldData.java
+@@ -110,7 +110,7 @@ public class WorldData {
+             this.d = nbttagcompound2.getBoolean("Snapshot");
+         }
+ 
+-        this.e = nbttagcompound.getLong("RandomSeed");
++        this.e = com.destroystokyo.paper.PaperConfig.seedOverride.getOrDefault(nbttagcompound.getString("LevelName"), nbttagcompound.getLong("RandomSeed")); // Paper
+         if (nbttagcompound.hasKeyOfType("generatorName", 8)) {
+             String s = nbttagcompound.getString("generatorName");
+ 
+diff --git a/src/main/java/org/bukkit/craftbukkit/CraftServer.java b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+index bcf7a3b9d8..ba01e51b41 100644
+--- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
++++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+@@ -979,7 +979,7 @@ public final class CraftServer implements Server {
+         WorldData worlddata = sdm.getWorldData();
+         WorldSettings worldSettings = null;
+         if (worlddata == null) {
+-            worldSettings = new WorldSettings(creator.seed(), EnumGamemode.getById(getDefaultGameMode().getValue()), generateStructures, hardcore, type);
++            worldSettings = new WorldSettings(com.destroystokyo.paper.PaperConfig.seedOverride.getOrDefault(name, creator.seed()), EnumGamemode.getById(getDefaultGameMode().getValue()), generateStructures, hardcore, type); // Paper
+             JsonElement parsedSettings = new JsonParser().parse(creator.generatorSettings());
+             if (parsedSettings.isJsonObject()) {
+                 worldSettings.setGeneratorSettings(parsedSettings.getAsJsonObject());
+-- 
+2.19.0
+