From 3d099792206d1703a001fdce7340679e6cf34258 Mon Sep 17 00:00:00 2001
From: artdeell <ultramaksim@gmail.com>
Date: Sat, 29 Apr 2023 23:53:20 +0300
Subject: [PATCH] Automatically pick runtime version for Mod Installer based on
 the main class file verion

---
 app_pojavlauncher/build.gradle                |  2 +-
 .../pojavlaunch/JavaGUILauncherActivity.java  | 42 ++++++++++++++++++-
 .../main/java/net/kdt/pojavlaunch/Tools.java  |  9 ++++
 3 files changed, 51 insertions(+), 2 deletions(-)

diff --git a/app_pojavlauncher/build.gradle b/app_pojavlauncher/build.gradle
index 99632e3a4..d3f1273d3 100644
--- a/app_pojavlauncher/build.gradle
+++ b/app_pojavlauncher/build.gradle
@@ -144,7 +144,7 @@ dependencies {
     // implementation 'com.intuit.ssp:ssp-android:1.0.5'
 
     implementation 'org.tukaani:xz:1.8'
-    implementation 'com.github.PojavLauncherTeam:exp4j:master-SNAPSHOT'
+    implementation 'com.github.PojavLauncherTeam:exp4j:60eaec6f78'
     // implementation 'net.sourceforge.streamsupport:streamsupport-cfuture:1.7.0'
     implementation fileTree(dir: 'libs', include: ['*.jar'])
 }
diff --git a/app_pojavlauncher/src/main/java/net/kdt/pojavlaunch/JavaGUILauncherActivity.java b/app_pojavlauncher/src/main/java/net/kdt/pojavlaunch/JavaGUILauncherActivity.java
index db1e63e98..3b7c1a487 100644
--- a/app_pojavlauncher/src/main/java/net/kdt/pojavlaunch/JavaGUILauncherActivity.java
+++ b/app_pojavlauncher/src/main/java/net/kdt/pojavlaunch/JavaGUILauncherActivity.java
@@ -11,7 +11,10 @@ import android.widget.*;
 import androidx.activity.OnBackPressedCallback;
 
 import java.io.*;
+import java.nio.ByteBuffer;
 import java.util.*;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipFile;
 
 import net.kdt.pojavlaunch.customcontrols.keyboard.AwtCharSender;
 import net.kdt.pojavlaunch.customcontrols.keyboard.TouchCharInput;
@@ -123,13 +126,20 @@ public class JavaGUILauncherActivity extends BaseActivity implements View.OnTouc
         });
 
         try {
-            MultiRTUtils.setRuntimeNamed(LauncherPreferences.PREF_DEFAULT_RUNTIME);
 
             placeMouseAt(CallbackBridge.physicalWidth / 2, CallbackBridge.physicalHeight / 2);
             
             final File modFile = (File) getIntent().getExtras().getSerializable("modFile");
             final String javaArgs = getIntent().getExtras().getString("javaArgs");
 
+            int javaVersion = getJavaVersion(modFile);
+            String jreName = javaVersion == -1 ? null : MultiRTUtils.getNearestJreName(javaVersion);
+            if(jreName != null) {
+                MultiRTUtils.setRuntimeNamed(jreName);
+            }else{
+                MultiRTUtils.setRuntimeNamed(LauncherPreferences.PREF_DEFAULT_RUNTIME);
+            }
+
             mSkipDetectMod = getIntent().getExtras().getBoolean("skipDetectMod", false);
             if (mSkipDetectMod) {
                 new Thread(() -> launchJavaRuntime(modFile, javaArgs), "JREMainThread").start();
@@ -309,4 +319,34 @@ public class JavaGUILauncherActivity extends BaseActivity implements View.OnTouc
     public void toggleKeyboard(View view) {
         mTouchCharInput.switchKeyboardState();
     }
+    public int getJavaVersion(File modFile) {
+        try (ZipFile zipFile = new ZipFile(modFile)){
+            ZipEntry manifest = zipFile.getEntry("META-INF/MANIFEST.MF");
+            if(manifest == null) return -1;
+            String manifestString = Tools.read(zipFile.getInputStream(manifest));
+            String mainClass = Tools.extractUntilCharacter(manifestString, "Main-Class:", '\n');
+            if(mainClass == null) return -1;
+            mainClass = mainClass.trim().replace('.', '/') + ".class";
+            ZipEntry mainClassFile = zipFile.getEntry(mainClass);
+            if(mainClassFile == null) return -1;
+            InputStream classStream = zipFile.getInputStream(mainClassFile);
+            byte[] bytesWeNeed = new byte[8];
+            int readCount = classStream.read(bytesWeNeed);
+            if(readCount < 8) return -1;
+            classStream.close();
+            ByteBuffer byteBuffer = ByteBuffer.wrap(bytesWeNeed);
+            if(byteBuffer.getInt() != 0xCAFEBABE) return -1;
+            short minorVersion = byteBuffer.getShort();
+            short majorVersion = byteBuffer.getShort();
+            Log.i("JavaGUILauncher", majorVersion+","+minorVersion);
+            return classVersionToJavaVersion(majorVersion);
+        }catch (Exception e) {
+            e.printStackTrace();
+            return -1;
+        }
+    }
+    public static int classVersionToJavaVersion(int majorVersion) {
+        if(majorVersion < 46) return 2; // there isn't even an arm64 port of jre 1.1 (or anything before 1.8 in fact)
+        return majorVersion - 44;
+    }
 }
diff --git a/app_pojavlauncher/src/main/java/net/kdt/pojavlaunch/Tools.java b/app_pojavlauncher/src/main/java/net/kdt/pojavlaunch/Tools.java
index bae59ab7a..2e2e01b46 100644
--- a/app_pojavlauncher/src/main/java/net/kdt/pojavlaunch/Tools.java
+++ b/app_pojavlauncher/src/main/java/net/kdt/pojavlaunch/Tools.java
@@ -967,4 +967,13 @@ public final class Tools {
             }
         });
     }
+
+    public static String extractUntilCharacter(String input, String whatFor, char terminator) {
+        int whatForStart = input.indexOf(whatFor);
+        if(whatForStart == -1) return null;
+        whatForStart += whatFor.length();
+        int terminatorIndex = input.indexOf(terminator, whatForStart);
+        if(terminatorIndex == -1) return null;
+        return input.substring(whatForStart, terminatorIndex);
+    }
 }