import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.jar.JarEntry;
import java.util.jar.JarInputStream;
import java.util.jar.JarOutputStream;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;

/**
 * 在 Spine 3.8.99 的 launcher.jar 里插一条调用：
 *   com.esotericsoftware.spine.editor.launcher.Launcher.main(String[])
 * 的第一行改成先调 com.spineview.SceneScan.main(String[])，
 * 并把我们编译好的类一起打进 jar。
 *
 * 因为 3.8.99 是明文的，这么做之后我们的代码就和编辑器处在同一个类加载器里，
 * 不再有"跨加载器看不到 TextButton"的问题。
 */
public final class Patcher {
  /** 目标类 / 方法 / 描述符，从命令行传（args[3..5]）。 */
  private static String targetClass;
  private static String targetEntry;
  private static String hookMethod;
  private static String hookDesc;
  private static final String HOOK_OWNER = "com/spineview/SceneScan";

  public static void main(String[] args) throws Exception {
    Path source = Paths.get(args[0]);
    Path target = Paths.get(args[1]);
    Path classesDir = Paths.get(args[2]);
    targetClass = args.length > 3 ? args[3] : "com/esotericsoftware/spine/editor/launcher/Launcher";
    String methodName = args.length > 4 ? args[4] : "main";
    hookMethod = args.length > 5 ? args[5] : "main";
    hookDesc = args.length > 6 ? args[6] : "([Ljava/lang/String;)V";
    targetEntry = targetClass + ".class";

    Map<String, byte[]> entries = new LinkedHashMap<String, byte[]>();
    try (JarInputStream in = new JarInputStream(Files.newInputStream(source))) {
      JarEntry entry;
      while ((entry = in.getNextJarEntry()) != null) {
        if (entry.isDirectory()) continue;
        entries.put(entry.getName(), readAll(in));
      }
    }
    System.out.println("原 jar 条目数 = " + entries.size());

    byte[] original = entries.get(targetEntry);
    if (original == null) throw new IllegalStateException("找不到 " + targetEntry);
    entries.put(targetEntry, patch(original, methodName));
    System.out.println("已给 " + targetClass + "." + methodName + " 插入了 " + HOOK_OWNER + "." + hookMethod);

    int added = 0;
    try (java.util.stream.Stream<Path> stream = Files.walk(classesDir)) {
      for (Path path : (Iterable<Path>) stream::iterator) {
        if (!Files.isRegularFile(path)) continue;
        String relative = classesDir.relativize(path).toString();
        if (!relative.endsWith(".class")) continue;
        entries.put(relative.replace('\\', '/'), Files.readAllBytes(path));
        added++;
      }
    }
    System.out.println("加进 jar 的类 = " + added);

    try (JarOutputStream out = new JarOutputStream(Files.newOutputStream(target))) {
      for (Map.Entry<String, byte[]> entry : entries.entrySet()) {
        JarEntry jarEntry = new JarEntry(entry.getKey());
        jarEntry.setTime(0L);
        out.putNextEntry(jarEntry);
        out.write(entry.getValue());
        out.closeEntry();
      }
    }
    System.out.println("已写出 " + target);
  }

  private static byte[] patch(byte[] original, final String methodName) {
    ClassReader reader = new ClassReader(original);
    ClassWriter writer = new ClassWriter(0);
    ClassVisitor visitor = new ClassVisitor(Opcodes.ASM9, writer) {
      @Override
      public MethodVisitor visitMethod(int access, String name, String descriptor,
          String signature, String[] exceptions) {
        MethodVisitor next = super.visitMethod(access, name, descriptor, signature, exceptions);
        if (!methodName.equals(name) || !hookDesc.equals(descriptor)) return next;
        return new MethodVisitor(Opcodes.ASM9, next) {
          @Override
          public void visitCode() {
            super.visitCode();
            // 我们的钩子是 ()V，不需要压任何参数；栈平衡保持不变。
            visitMethodInsn(Opcodes.INVOKESTATIC, HOOK_OWNER, hookMethod, hookDesc, false);
          }
        };
      }
    };
    reader.accept(visitor, 0);
    return writer.toByteArray();
  }

  private static byte[] readAll(InputStream in) throws Exception {
    ByteArrayOutputStream buffer = new ByteArrayOutputStream();
    byte[] chunk = new byte[16384];
    int read;
    while ((read = in.read(chunk)) > 0) buffer.write(chunk, 0, read);
    return buffer.toByteArray();
  }
}