/**
 * Tencent Turing Captcha Chaos VM (TDC VM) Disassembler
 * --------------------------------------------------------
 * 依据 AGENTS.md §3.3 规范，将 TDC 混淆字节码反汇编为可读指令流与结构化操作。
 */

const fs = require("fs");
const path = require("path");
const parser = require("@babel/parser");
const generate = require("@babel/generator").default;

const OP_NAMES = {
  0: "PUSH_STR_CHAR",
  1: "IS_EXCEPTION",
  2: "DUP",
  3: "XOR",
  4: "EQ_STRICT",
  5: "MOD",
  6: "CALL_FUNC",
  8: "GET_GLOBAL_PROP",
  9: "MAKE_PROP_REF",
  10: "TYPEOF",
  11: "DELETE",
  12: "LOGICAL_NOT",
  13: "EQ_LOOSE",
  14: "SET_PROP",
  15: "GREATER_THAN",
  17: "SWAP",
  18: "IN",
  19: "RET_TRUE",
  20: "GREATER_EQ",
  22: "PUSH_IMM",
  23: "MUL",
  25: "LOAD_REG_INDIRECT",
  26: "ITER_NEXT",
  28: "BIND_THIS",
  29: "PUSH_NULL",
  30: "BITWISE_AND",
  31: "PUSH_IMM_ARRAY",
  32: "MAKE_REG_PROP_REF",
  33: "SUB",
  34: "CALL_METHOD",
  35: "SHR",
  36: "SHL",
  37: "JUMP_IF_TRUE",
  38: "FOR_IN_KEYS",
  39: "ADD",
  41: "NEW_METHOD",
  42: "PUSH_UNDEFINED",
  45: "PUSH_FALSE",
  46: "STORE_REG",
  47: "ALLOC_REG",
  48: "POP_TRY",
  49: "THROW",
  51: "POP",
  52: "DIV",
  53: "SET_STACK_LEN",
  54: "REVERSE_TOP2",
  55: "PUSH_EMPTY_STR",
  56: "PUSH_TRY",
  57: "CREATE_CLOSURE",
  59: "GET_PROP",
  60: "JUMP",
  61: "NEW_FUNC",
  62: "BITWISE_OR",
  64: "REPLACE_TOP_IMM",
  65: "SHR_UNSIGNED",
  66: "PUSH_TRUE",
  68: "LOAD_REG_IMM",
  69: "CLEAR_EXCEPTION",
};

function extractBytecode(tdcPath) {
  const code = fs.readFileSync(tdcPath, "utf-8");
  const ast = parser.parse(code, { sourceType: "script" });
  const fn = ast.program.body[3].declarations[0].init.callee;
  const iFuncCode = generate(fn.body.body[1]).code;
  const returnStmt = fn.body.body[2];
  const vmCall = returnStmt.argument.expressions ? returnStmt.argument.expressions[1] : returnStmt.argument;
  const zCall = vmCall.arguments[1];
  const zCallCode = generate(zCall).code;

  const runner = `
    ${iFuncCode}
    (${zCallCode});
  `;
  return eval(runner);
}

function disassemble(z) {
  let H = 0;
  const rawInstructions = [];
  const total = z.length;

  while (H < total) {
    const pc = H;
    const op = z[H++];
    const opName = OP_NAMES[op] || `UNKNOWN_${op}`;
    const args = [];

    switch (op) {
      case 0: // PUSH_STR_CHAR
      case 22: // PUSH_IMM
      case 31: // PUSH_IMM_ARRAY
      case 47: // ALLOC_REG
      case 53: // SET_STACK_LEN
      case 64: // REPLACE_TOP_IMM
      case 68: // LOAD_REG_IMM
        args.push(z[H++]);
        break;
      case 6: // CALL_FUNC
      case 17: // SWAP
      case 34: // CALL_METHOD
      case 41: // NEW_METHOD
      case 61: // NEW_FUNC
        args.push(`args=${z[H++]}`);
        break;
      case 37: // JUMP_IF_TRUE
      case 60: // JUMP
        args.push(`target=@${z[H++]}`);
        break;
      case 56: // PUSH_TRY
        args.push(`catchTarget=@${z[H++]}`);
        args.push(`catchVarReg=${z[H++]}`);
        break;
      case 57: { // CREATE_CLOSURE
        const targetPc = z[H++];
        const capCount = z[H++];
        const paramCount = z[H++];
        const captures = [];
        for (let m = 0; m < capCount; m++) {
          captures.push(`r${z[H++]}=r${z[H++]}`);
        }
        const params = [];
        for (let m = 0; m < paramCount; m++) {
          params.push(`p${m}->r${z[H++]}`);
        }
        args.push(`target=@${targetPc}`);
        args.push(`caps=[${captures.join(",")}]`);
        args.push(`params=[${params.join(",")}]`);
        break;
      }
      default:
        // no extra operand
        break;
    }

    rawInstructions.push({ pc, op, opName, args });
  }

  // Pass 2: Fold PUSH_EMPTY_STR + PUSH_STR_CHAR ... into PUSH_STR "..."
  const folded = [];
  for (let i = 0; i < rawInstructions.length; i++) {
    const ins = rawInstructions[i];
    if (ins.opName === "PUSH_EMPTY_STR") {
      let str = "";
      let j = i + 1;
      while (j < rawInstructions.length && rawInstructions[j].opName === "PUSH_STR_CHAR") {
        str += String.fromCharCode(rawInstructions[j].args[0]);
        j++;
      }
      if (j > i + 1) {
        folded.push({
          pc: ins.pc,
          op: 0,
          opName: "PUSH_STR",
          args: [JSON.stringify(str)],
        });
        i = j - 1;
        continue;
      }
    }
    folded.push(ins);
  }

  return folded;
}

// CLI usage
if (require.main === module) {
  const tdcFile = process.argv[2] || "tcaptcha/core_js/tdc_sample.js";
  console.log(`Extracting and disassembling ${tdcFile}...`);
  const z = extractBytecode(tdcFile);
  console.log(`Bytecode size: ${z.length} bytes`);
  const insts = disassemble(z);
  console.log(`Total instructions: ${insts.length}`);

  const outFile = tdcFile.replace(/\.js$/, ".disasm.txt");
  const lines = insts.map(
    (ins) => `@${ins.pc.toString().padStart(5, "0")}: ${ins.opName.padEnd(18)} ${ins.args.join(" ")}`
  );
  fs.writeFileSync(outFile, lines.join("\n"), "utf-8");
  console.log(`Disassembly written to ${outFile}`);

  // Preview first 30 instructions
  console.log("\n--- Preview first 30 instructions ---");
  lines.slice(0, 30).forEach((l) => console.log(l));
}

module.exports = { extractBytecode, disassemble, OP_NAMES };