package com.spineview.dec;

import java.io.BufferedWriter;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.ClassNode;
import org.objectweb.asm.tree.InvokeDynamicInsnNode;
import org.objectweb.asm.tree.MethodNode;

/**
 * 把每个 invokedynamic 站点的**加密串**按 BSM 自己的算法解出真实目标：
 *   (类名, 方法名, 描述符)  ——  静态还是虚调用看首字符 0xB8=static、0xB6=virtual。
 *
 * 为什么要它：`rewrite_source.py` 只按"混淆名 → 类.方法"改名，**丢描述符**，
 * 于是 `SelectBox.getSelected()` 和 `SelectBox.setSelected(String)` 都被写成 `KP.B`，
 * 读源码时就会以为是同一个方法（这是之前把 KP.B 误当"建对象 API"的根因）。
 *
 * 用法：
 *   java -cp "asm.jar:本工具:已全 public 化的载荷.zip" com.spineview.dec.DumpSites <载荷> <out.tsv> [类名...]
 */
public final class DumpSites {
  private static final String BSM_DESC =
      "(Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;";

  public static void main(String[] args) throws Exception {
    Path payload = Paths.get(args[0]);
    Path out = Paths.get(args[1]);
    List<String> filters = new ArrayList<String>();
    for (int i = 2; i < args.length; i++) filters.add(args[i]);

    List<String[]> rows = new ArrayList<String[]>();
    try (ZipFile zip = new ZipFile(payload.toFile())) {
      Enumeration<? extends ZipEntry> entries = zip.entries();
      while (entries.hasMoreElements()) {
        ZipEntry entry = entries.nextElement();
        if (!entry.getName().endsWith(".class")) continue;
        ClassNode node;
        try {
          node = parse(readAll(zip.getInputStream(entry)));
        } catch (Throwable error) {
          continue;
        }
        if (!filters.isEmpty() && !filters.contains(node.name)) continue;
        for (MethodNode method : node.methods) {
          for (AbstractInsnNode insn = method.instructions.getFirst(); insn != null;
              insn = insn.getNext()) {
            if (!(insn instanceof InvokeDynamicInsnNode)) continue;
            InvokeDynamicInsnNode indy = (InvokeDynamicInsnNode) insn;
            if (!BSM_DESC.equals(indy.bsm.getDesc())) continue;
            if (indy.bsmArgs.length == 0 || !(indy.bsmArgs[0] instanceof String)) continue;
            String decoded = decode(indy.name, (String) indy.bsmArgs[0]);
            String caller = node.name + "." + method.name + method.desc;
            // 顺带把"最近压栈的那个 ldc 常量"当成描述文本，方便在源码里定位。
            String hint = nearestLdc(method, insn);
            rows.add(new String[] { caller, indy.name, indy.desc, decoded, hint });
          }
        }
      }
    }
    try (BufferedWriter writer = Files.newBufferedWriter(out, StandardCharsets.UTF_8)) {
      writer.write("caller\tindyName\tsiteDesc\tdecoded\tnearbyLdc\n");
      for (String[] row : rows) {
        for (int i = 0; i < row.length; i++) {
          if (i > 0) writer.write('\t');
          writer.write(escape(row[i]));
        }
        writer.write('\n');
      }
    }
    System.out.println("站点 " + rows.size() + " -> " + out);
  }

  private static String nearestLdc(MethodNode method, AbstractInsnNode site) {
    AbstractInsnNode node = site;
    for (int i = 0; i < 12 && node != null; i++) {
      node = node.getPrevious();
      if (node instanceof org.objectweb.asm.tree.LdcInsnNode) {
        Object value = ((org.objectweb.asm.tree.LdcInsnNode) node).cst;
        if (value instanceof String) return printable((String) value);
      }
    }
    return "";
  }

  private static String printable(String text) {
    StringBuilder builder = new StringBuilder();
    for (int i = 0; i < text.length(); i++) {
      char c = text.charAt(i);
      if (c >= 0x20 && c < 0x7F) builder.append(c);
      else builder.append('.');
    }
    return builder.toString();
  }

  /** 完全按 BSM 字节码里的算法复刻；先用已知站点自校验过。 */
  static String decode(String indyName, String cipher) {
    char[] name = indyName.toCharArray();
    int[] seed = new int[4];
    seed[0] = (name[1] << 16) | name[0];
    seed[1] = (name[3] << 16) | name[2];
    seed[2] = (name[5] << 16) | name[4];
    seed[3] = (name[7] << 16) | name[6];
    char[] out = cipher.toCharArray();
    int n4 = 0, n5 = 0, n6 = 0, n7 = 0;
    for (int i = 0; i < out.length; i++) {
      if (i % 8 == 0) {
        for (int k = 0; k < 48; k++) {
          int s = seed[k % 4] + k;
          n5 += n4 + ((n4 << 6) ^ (n4 >> 8)) + s;
          n4 += n5 + ((n5 << 6) ^ (n5 >> 8)) + s;
          n7 += n6 + ((n6 << 6) ^ (n6 >> 8)) + s;
          n6 += n7 + ((n7 << 6) ^ (n7 >> 8)) + s;
        }
      }
      int key;
      switch (i % 8) {
        case 0: case 4: key = n4 >> 16; break;
        case 1: case 5: key = n5; break;
        case 2: case 6: key = n6 >> 16; break;
        default: key = n7; break;
      }
      out[i] = (char) (key ^ out[i]);
    }
    // [0]=调用种类(0xB8 静态 / 0xB6 虚) [1]=类名长度 类名 [n]=方法名长度 方法名 描述符
    boolean isStatic = out[0] == '\u00b8';
    int classLength = out[1];
    String className = new String(out, 2, classLength);
    int nameLength = out[classLength + 2];
    String methodName = new String(out, classLength + 3, nameLength);
    String descriptor = new String(out, classLength + nameLength + 3,
        out.length - classLength - nameLength - 3);
    return (isStatic ? "static " : "virtual ") + className + "." + methodName + descriptor;
  }

  private static String escape(String text) {
    StringBuilder builder = new StringBuilder(text.length() + 8);
    for (int i = 0; i < text.length(); i++) {
      char c = text.charAt(i);
      if (c == '\t') builder.append("\\t");
      else if (c >= 0x20 && c <= 0x7E) builder.append(c);
      else builder.append(String.format("\\u%04x", Integer.valueOf(c)));
    }
    return builder.toString();
  }

  private static ClassNode parse(byte[] raw) {
    ClassNode node = new ClassNode();
    new ClassReader(raw).accept(node, ClassReader.SKIP_DEBUG | ClassReader.SKIP_FRAMES);
    return node;
  }

  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();
  }
}