Utils/BukkitUtils/src/main/java/eu/mikroskeem/utils/bukkit/ServerUtils.java

package eu.mikroskeem.utils.bukkit;

import eu.mikroskeem.shuriken.instrumentation.validate.ClassDescriptor;
import eu.mikroskeem.shuriken.instrumentation.validate.FieldDescriptor;
import eu.mikroskeem.shuriken.instrumentation.validate.Validate;
import eu.mikroskeem.shuriken.reflect.Reflect;
import eu.mikroskeem.shuriken.reflect.wrappers.ClassWrapper;
import eu.mikroskeem.shuriken.reflect.wrappers.FieldWrapper;
import org.bukkit.Bukkit;
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.plugin.java.JavaPluginLoader;
import org.jetbrains.annotations.Nullable;

import java.lang.reflect.InvocationTargetException;
import java.util.List;
import java.util.Map;
import java.util.Optional;

import static com.google.common.base.Preconditions.checkNotNull;

public class ServerUtils {
    /**
     * Get server's TPS
     *
     * Will use PaperSpigot's API if available, reflection otherwise
     * @return double array of TPS (not rounded!), values are -1 if reflection failed
     */
    @SuppressWarnings("unchecked")
    public static <C> double[] getTPS(){
        Class<C> _t = (Class<C>)double[].class;
        try {
            return Reflect.wrapClass(Bukkit.class).invokeMethod("getTPS", double[].class);
        } catch (NoSuchMethodException | InvocationTargetException | IllegalAccessException e) {
            try {
                Optional<ClassWrapper<?>> minecraftServerClassOpt = Reflect.getClass(String.format(
                        "net.minecraft.server.%s.MinecraftServer", getNmsVersion()
                ));
                if (minecraftServerClassOpt.isPresent()) {
                    ClassWrapper<?> minecraftServerClass = minecraftServerClassOpt.get();
                        minecraftServerClass.invokeMethod("getServer", minecraftServerClass.getWrappedClass());
                    Optional<FieldWrapper<C>> recentTpsOpt = minecraftServerClass.getField("recentTps", _t);
                    if(recentTpsOpt.isPresent())
                        return (double[]) recentTpsOpt.get().read();
                }
            }
            catch (NoSuchMethodException|NoSuchFieldException|InvocationTargetException|IllegalAccessException ignored){}
        }
        return new double[]{-1, -1, -1};
    }

    /**
     * Get plugin class loader. Useful when you want to add new classes on runtime
     *
     * @param plugin Plugin which will be used to get plugin ClassLoader
     * @return Plugin ClassLoader
     */
    @SuppressWarnings("unchecked")
    @Nullable
    public static ClassLoader getPluginClassLoader(JavaPlugin plugin){
        /*
         * Note: CB/Spigot has PluginClassLoader package-private, PaperSpigot has public
         * So *DO NOT* try to cast this ClassLoader to PluginClassLoader, if you aim to be
         * compatible with other Bukkit-based servers
         * I repeat, *DO NOT USE* PluginClassLoader!
         */
        JavaPluginLoader pl = (JavaPluginLoader) plugin.getPluginLoader();
        try {
            Optional<FieldWrapper<Object>> loadersFieldOpt = Reflect
                    .wrapClass(pl.getClass())
                    .setClassInstance(pl)
                    .getField("loaders", Object.class);
            if(loadersFieldOpt.isPresent()) {
                FieldWrapper<Object> loadersField = loadersFieldOpt.get();
                switch (ServerUtils.getNmsVersion()){
                    case "v1_8_R3":
                    case "v1_9_R1":
                    case "v1_9_R2":
                        Map<String, ClassLoader> loaderMap = (Map<String, ClassLoader>) loadersField.read();
                        return loaderMap.get(plugin.getName());
                    case "v1_10_R1":
                    case "v1_11_R1":
                        Optional<ClassWrapper<?>> pluginClassLoaderOpt = Reflect
                                .getClass("org.bukkit.plugin.java.PluginClassLoader");
                        if(pluginClassLoaderOpt.isPresent()){
                            List<ClassLoader> loaders = (List<ClassLoader>) loadersField.read();
                            return loaders.stream().filter(loader -> {
                                try {
                                    String pluginName = Reflect.wrapInstance(loader)
                                            .getField("plugin", JavaPlugin.class)
                                            .get()
                                            .read()
                                            .getName();
                                    return pluginName.equals(plugin.getName());
                                }
                                catch (NoSuchFieldException|IllegalAccessException|NullPointerException ignored){}
                                return false;
                            }).findFirst().orElse(null);
                        }
                        break;
                }
            }
        }
        catch (NoSuchFieldException|IllegalAccessException ignored){}
        return null;
    }

    /**
     * Get PluginClassLoader classes map
     * @param classLoader PluginClassLoader instance
     * @return Classes map
     */
    @SuppressWarnings("unchecked")
    @Nullable
    public static Map<String, Class<?>> getClassesMap(ClassLoader classLoader){
        Class<?> clClass = classLoader.getClass();
        try {
            ClassWrapper<?> pluginClassLoader = checkNotNull(Reflect
                    .getClass("org.bukkit.plugin.java.PluginClassLoader").orElse(null),
                    "Couldn't find org.bukkit.plugin.java.PluginClassLoader class")
                    .setClassInstance(classLoader);
            Validate.checkFields(pluginClassLoader, FieldDescriptor.of("classes", Map.class));
            Validate.checkClass(ClassDescriptor.ofWrapped(clClass, pluginClassLoader));
            return (Map<String, Class<?>>) checkNotNull(pluginClassLoader.getField("classes", Map.class)
                    .orElse(null),
                    "Failed to get classes field").read();
        } catch(NoSuchFieldException|IllegalAccessException|NullPointerException e){
            e.printStackTrace();
        }
        return null;
    }

    /**
     * Get NMS version of current running server
     * @return NMS version or 0 length string
     */
    public static String getNmsVersion(){
        try {
            String bukkitPackageName = Bukkit.getServer().getClass().getPackage().getName();
            return bukkitPackageName.substring(bukkitPackageName.lastIndexOf(".") + 1);
        } catch (NullPointerException e){
            return "";
        }
    }
}