import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.Instrumentation;
import java.security.ProtectionDomain;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.ClassNode;
import org.objectweb.asm.tree.FieldInsnNode;
import org.objectweb.asm.tree.FieldNode;
import org.objectweb.asm.tree.InsnList;
import org.objectweb.asm.tree.InsnNode;
import org.objectweb.asm.tree.IntInsnNode;
import org.objectweb.asm.tree.LdcInsnNode;
import org.objectweb.asm.tree.MethodInsnNode;
import org.objectweb.asm.tree.MethodNode;
import org.objectweb.asm.tree.TypeInsnNode;
import org.objectweb.asm.tree.VarInsnNode;

/**
 * 在**内存里**给编辑器加一个正式视图（"Spine View"），磁盘上的载荷一个字节都不改。
 *
 * 为什么必须走内存：编辑器启动时会自检——把它自己 jar 里所有类的 SHA1 和签名里的清单比对，
 * 一旦有出入就报 "Spine's integrity check failed."。所以任何磁盘改动都不行。
 *
 * 两处插桩（与 tools/patch_view/ViewPatcher 完全同源）：
 *   us.<clinit> ：造一个新枚举常量 spineView，并在 $VALUES 组装完之后追加进数组
 *                 （必须在分组列表生成之前，否则 Views 菜单里看不到它）
 *   tD.<init>   ：最后一个 `putfield us.D:Ldl;`（即给视图塞面板 Actor）之后，
 *                 插一条 com.spineview.ViewInstaller.install()
 */
public final class ViewAgent {
  private static final String VIEW_ENUM = "us";
  private static final String UI_CLASS = "tD";
  private static final String VIEW_NAME = "spineView";
  private static final String VIEW_TITLE = "Spine View";
  private static final String VIEW_FIELD = "SPINEVIEW";
  private static boolean enumDone;
  private static boolean uiDone;

  public static void premain(String arguments, Instrumentation instrumentation) {
    System.err.println("[view-agent] premain 已加载");
    instrumentation.addTransformer(new ClassFileTransformer() {
      @Override
      public byte[] transform(ClassLoader loader, String className, Class<?> beingRedefined,
          ProtectionDomain protectionDomain, byte[] classfileBuffer) {
        try {
          if (VIEW_ENUM.equals(className) && !enumDone
              && !"0".equals(System.getProperty("viewagent.enum"))) {
            enumDone = true;
            return patchEnum(classfileBuffer);
          }
          // 默认不再动 tD：这个混淆过的构造函数对插入指令极其敏感，
          // 插一条 NOP 没事，插任何带操作数的指令都会把它的初始化流程弄坏。
          // 视图面板改由 ViewInstaller 在编辑器起来之后从外部填进 us.spineView.D。
          if (UI_CLASS.equals(className) && !uiDone
              && "1".equals(System.getProperty("viewagent.ui"))) {
            uiDone = true;
            return patchUi(classfileBuffer);
          }
        } catch (Throwable error) {
          System.err.println("[view-agent] 插桩 " + className + " 失败: " + error);
        }
        return null;
      }
    });
  }

  private static byte[] patchEnum(byte[] data) {
    ClassNode node = new ClassNode();
    new ClassReader(data).accept(node, 0);
    boolean hasField = false;
    for (FieldNode field : node.fields) {
      if (VIEW_FIELD.equals(field.name)) hasField = true;
    }
    if (!hasField) {
      node.fields.add(new FieldNode(Opcodes.ACC_PUBLIC | Opcodes.ACC_STATIC, VIEW_FIELD,
          "L" + VIEW_ENUM + ";", null, null));
    }
    for (MethodNode method : node.methods) {
      if (!"<clinit>".equals(method.name)) continue;

      InsnList head = new InsnList();
      head.add(new TypeInsnNode(Opcodes.NEW, VIEW_ENUM));
      head.add(new InsnNode(Opcodes.DUP));
      head.add(new LdcInsnNode(VIEW_NAME));
      head.add(new IntInsnNode(Opcodes.BIPUSH, 16));
      head.add(new LdcInsnNode(VIEW_TITLE));
      head.add(new FieldInsnNode(Opcodes.GETSTATIC, "MV", "L", "I"));
      head.add(new FieldInsnNode(Opcodes.GETSTATIC, "ut", "B", "Lut;"));
      head.add(new MethodInsnNode(Opcodes.INVOKESPECIAL, VIEW_ENUM, "<init>",
          "(Ljava/lang/String;ILjava/lang/String;ILut;)V", false));
      head.add(new FieldInsnNode(Opcodes.PUTSTATIC, VIEW_ENUM, VIEW_FIELD,
          "L" + VIEW_ENUM + ";"));
      method.instructions.insert(head);

      AbstractInsnNode anchor = null;
      for (AbstractInsnNode insn = method.instructions.getFirst(); insn != null;
          insn = insn.getNext()) {
        if (insn instanceof FieldInsnNode) {
          FieldInsnNode field = (FieldInsnNode) insn;
          if (field.getOpcode() == Opcodes.PUTSTATIC && VIEW_ENUM.equals(field.owner)
              && "B".equals(field.name) && ("[L" + VIEW_ENUM + ";").equals(field.desc)) {
            anchor = insn;
          }
        }
      }
      if (anchor == null) throw new IllegalStateException("找不到 $VALUES 组装点");

      InsnList extend = new InsnList();
      extend.add(new FieldInsnNode(Opcodes.GETSTATIC, VIEW_ENUM, "B", "[L" + VIEW_ENUM + ";"));
      extend.add(new VarInsnNode(Opcodes.ASTORE, 40));
      extend.add(new VarInsnNode(Opcodes.ALOAD, 40));
      extend.add(new InsnNode(Opcodes.ARRAYLENGTH));
      extend.add(new InsnNode(Opcodes.ICONST_1));
      extend.add(new InsnNode(Opcodes.IADD));
      extend.add(new TypeInsnNode(Opcodes.ANEWARRAY, VIEW_ENUM));
      extend.add(new VarInsnNode(Opcodes.ASTORE, 41));
      extend.add(new VarInsnNode(Opcodes.ALOAD, 40));
      extend.add(new InsnNode(Opcodes.ICONST_0));
      extend.add(new VarInsnNode(Opcodes.ALOAD, 41));
      extend.add(new InsnNode(Opcodes.ICONST_0));
      extend.add(new VarInsnNode(Opcodes.ALOAD, 40));
      extend.add(new InsnNode(Opcodes.ARRAYLENGTH));
      extend.add(new MethodInsnNode(Opcodes.INVOKESTATIC, "java/lang/System", "arraycopy",
          "(Ljava/lang/Object;ILjava/lang/Object;II)V", false));
      extend.add(new VarInsnNode(Opcodes.ALOAD, 41));
      extend.add(new VarInsnNode(Opcodes.ALOAD, 40));
      extend.add(new InsnNode(Opcodes.ARRAYLENGTH));
      extend.add(new FieldInsnNode(Opcodes.GETSTATIC, VIEW_ENUM, VIEW_FIELD,
          "L" + VIEW_ENUM + ";"));
      extend.add(new InsnNode(Opcodes.AASTORE));
      extend.add(new VarInsnNode(Opcodes.ALOAD, 41));
      extend.add(new FieldInsnNode(Opcodes.PUTSTATIC, VIEW_ENUM, "B", "[L" + VIEW_ENUM + ";"));
      method.instructions.insert(anchor, extend);
      System.err.println("[view-agent] us.<clinit> 已插入视图常量 " + VIEW_NAME);
    }
    ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_MAXS);
    node.accept(writer);
    return writer.toByteArray();
  }

  private static byte[] patchUi(byte[] data) {
    ClassNode node = new ClassNode();
    ClassReader reader = new ClassReader(data);
    reader.accept(node, 0);
    for (MethodNode method : node.methods) {
      if (!"<init>".equals(method.name)) continue;
      // 插在构造函数最末尾（最后一条 return 之前）：那时皮肤、贴图都读完了，
      // 期间去加载别的类不会干扰编辑器自己的资源流。
      AbstractInsnNode end = method.instructions.getLast();
      while (end != null && end.getOpcode() != Opcodes.RETURN) end = end.getPrevious();
      if (end == null) continue;
      InsnList hook = new InsnList();
      if ("1".equals(System.getProperty("viewagent.mark"))) {
        // 只碰 JDK 类，不加载我们自己的任何类（判定实验）
        hook.add(new LdcInsnNode("spineview.tD"));
        hook.add(new LdcInsnNode("1"));
        hook.add(new MethodInsnNode(Opcodes.INVOKESTATIC, "java/lang/System", "setProperty",
            "(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;", false));
        hook.add(new InsnNode(Opcodes.POP));
      } else if ("1".equals(System.getProperty("viewagent.ping"))) {
        hook.add(new MethodInsnNode(Opcodes.INVOKESTATIC, "com/spineview/ViewInstaller",
            "ping", "()V", false));
      } else if (!"1".equals(System.getProperty("viewagent.nop"))) {
        hook.add(new MethodInsnNode(Opcodes.INVOKESTATIC, "com/spineview/ViewInstaller",
            "install", "()V", false));
      } else {
        hook.add(new InsnNode(Opcodes.NOP));
        System.err.println("[view-agent] 只插 NOP（判定实验）");
      }
      method.instructions.insertBefore(end, hook);
      // 用 ClassWriter(reader, 0) 时不重算 max_stack，必须自己抬高，
      // 否则插入的代码会把操作栈写爆（表现为编辑器初始化随机的 IOException）。
      // 多给几格，反正只影响这一帧的栈分配。
      method.maxStack += 8;
      System.err.println("[view-agent] " + method.name + method.desc
          + " 已插入 ViewInstaller.install()");
    }
    // 关键：用 ClassWriter(reader, 0)，未改动的部分原样复制原始字节码。
    // 之前用 COMPUTE_MAXS 全量重写这个 14 万字节、混淆得很厉害的类，
    // 会把它的初始化流程弄坏（表现为构造器里资源流出 IOException）。
    // 我们只插了一条净栈效果为 0 的 invokestatic，max_stack / 栈帧都不用动。
    ClassWriter writer = new ClassWriter(reader, 0);
    node.accept(writer);
    return writer.toByteArray();
  }
}