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.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;

/**
 * 给 Spine 3.8.99 的编辑器载荷加一个"正式视图"。
 *
 * 视图系统的情况（全部从字节码读出来的）：
 *   - us 是视图枚举：us("meshTools", 4, "Mesh Tools", MV.L, ut.B)
 *     <clinit> 里建好全部常量、组装 $VALUES（字段 B:[Lus;），再按 MV/ut 分成左右两组列表。
 *   - tD.<init> 给每个视图 new 一个 Actor 并挂到 us.X.D。
 *
 * 所以两处补丁：
 *   1) us：<clinit> 开头造一个新常量 "spineView"，并在 $VALUES 组装完之后把它追加进数组
 *      （必须在分组列表生成之前追加，否则 Views 菜单里看不到）。
 *   2) tD：<init> 里最后一个 us.X.D 赋值之后，插一条调用
 *      com.spineview.ViewInstaller.install()，由我们把面板 Actor 塞进 us.SPINEVIEW.D。
 *
 * 用法：java -cp asm.jar:... ViewPatcher <源载荷> <目标载荷>
 */
public final class ViewPatcher {
  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";

  public static void main(String[] args) throws Exception {
    Path source = Paths.get(args[0]);
    Path target = Paths.get(args[1]);
    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("载荷条目 " + entries.size());

    entries.put(VIEW_ENUM + ".class", patchEnum(entries.get(VIEW_ENUM + ".class")));
    entries.put(UI_CLASS + ".class", patchUi(entries.get(UI_CLASS + ".class")));

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

  /** 给 us 加一个新枚举常量。 */
  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);

      // 找到 $VALUES 的组装点（PUTSTATIC us.B:[Lus;），在它后面把新常量追加进数组
      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 的组装点");

      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.out.println("us.<clinit> 已插入新视图常量 " + VIEW_NAME);
    }

    ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_MAXS);
    node.accept(writer);
    return writer.toByteArray();
  }

  /** 在 tD.<init> 里最后一个 us.X.D 赋值之后，插一条调用去建我们视图的面板。 */
  private static byte[] patchUi(byte[] data) {
    ClassNode node = new ClassNode();
    new ClassReader(data).accept(node, 0);
    int inserted = 0;
    for (MethodNode method : node.methods) {
      AbstractInsnNode last = null;
      for (AbstractInsnNode insn = method.instructions.getFirst(); insn != null;
          insn = insn.getNext()) {
        if (insn instanceof FieldInsnNode) {
          FieldInsnNode field = (FieldInsnNode) insn;
          // 真正的写法是：getstatic us.StackMapTable:Lus; ... putfield us.D:Ldl;
          // 也就是"先取视图常量，再把面板 Actor 写进它的 D 字段"。
          if (field.getOpcode() == Opcodes.PUTFIELD && VIEW_ENUM.equals(field.owner)
              && "Ldl;".equals(field.desc)) {
            last = insn;
          }
        }
      }
      if (last == null) continue;
      InsnList hook = new InsnList();
      hook.add(new MethodInsnNode(Opcodes.INVOKESTATIC, "com/spineview/ViewInstaller",
          "install", "()V", false));
      method.instructions.insert(last, hook);
      inserted++;
      System.out.println("在 " + method.name + method.desc + " 里插入了调用");
    }
    if (inserted == 0) throw new IllegalStateException("tD 里没找到挂视图的地方");
    System.out.println("tD.<init> 已插入 ViewInstaller.install()");
    ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_MAXS);
    node.accept(writer);
    return writer.toByteArray();
  }

  private static byte[] readAll(InputStream in) throws java.io.IOException {
    ByteArrayOutputStream buffer = new ByteArrayOutputStream();
    byte[] chunk = new byte[65536];
    int n;
    while ((n = in.read(chunk)) > 0) buffer.write(chunk, 0, n);
    return buffer.toByteArray();
  }
}