stage1/ml9: create mixin bootstrap

Author: Sychic

stage1/modlauncher9/src/main/java/gg/essential/loader/stage1/EssentialMixinPluginLoader.java

@@ -0,0 +1,37 @@
+package gg.essential.loader.stage1;
+
+import cpw.mods.modlauncher.Launcher;
+import cpw.mods.modlauncher.api.IEnvironment;
+import cpw.mods.modlauncher.api.TypesafeMap;
+import net.minecraftforge.fml.loading.FMLLoader;
+
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+@SuppressWarnings("unused")
+public class EssentialMixinPluginLoader {
+    private static final String KEY_LOADED = "gg.essential.loader.stage1.loaded";
+
+    public EssentialMixinPluginLoader() throws Exception {
+        // Check if another stage1 loader has already loaded stage2 (we do not want to load it twice)
+        final TypesafeMap blackboard = Launcher.INSTANCE.blackboard();
+        final TypesafeMap.Key<Object> LOADED =
+                TypesafeMap.Key.getOrCreate(blackboard, KEY_LOADED, Object.class);
+        if (blackboard.get(LOADED).isPresent()) {
+            return;
+        }
+        // We are doing it
+        blackboard.computeIfAbsent(LOADED, __ -> this);
+
+        final Path gameDir = Launcher.INSTANCE.environment()
+                .getProperty(IEnvironment.Keys.GAMEDIR.get())
+                .orElse(Paths.get("."));
+
+        EssentialLoader loader = EssentialLoader.getInstance("modlauncher", "forge_" + FMLLoader.versionInfo().mcVersion());
+        loader.load(gameDir);
+
+        loader.getStage2().getClass()
+                .getMethod("loadFromMixin", Path.class)
+                .invoke(loader.getStage2(), gameDir);
+    }
+}