===== ISTEM =====
Solve the following programming task.

TASK: TIK Register Machine

Write a function 'runTik(program)' that runs a program written in TIK, a small made-up language, and returns an array of the numbers it outputs.

Program text:
- Instructions are separated by newlines. Leading and trailing spaces on a line are ignored.
- Lines that are empty (or only spaces) and lines whose first non-space character is '#' are ignored and are not instructions.
- Within an instruction, tokens are separated by one or more spaces.

Machine:
- There are four registers named a, b, c and d. All start at 0.
- Every value stored in a register is reduced to the range 0..999 by taking it modulo 1000, always giving a non-negative result (for example -1 becomes 999 and 1003 becomes 3).
- An integer literal is an optional '-' followed by one or more digits ('+5' and '5.0' are not valid).
- An operand written as X below is either a register name or an integer literal. Its value is the register's value, or the literal reduced to 0..999 in the same way.

Instructions (R must be a register name, N must be an integer literal):
- set R X: R becomes the value of X.
- add R X: R becomes R plus the value of X.
- mul R X: R becomes R times the value of X.
- out X: appends the value of X to the output.
- jmp X N: if the value of X is not 0, the next instruction is the one N instructions away from this one (N may be negative; ignored lines are not counted). Otherwise execution continues with the next instruction.
Instruction names and register names are lowercase; anything else is invalid.

Running:
- Before running anything, check the whole program. If any line that is not ignored is not a valid instruction (unknown name, wrong number of operands, or an invalid register, literal or operand), throw an Error whose message is 'bad instruction at line K', where K is the 1-based line number of the first such line in the original text, counting ignored lines too. In that case nothing is run.
- Execution starts at the first instruction and stops normally when the next instruction position is before the first instruction or after the last one.
- A program may execute at most 10,000 instructions. If it has not stopped after executing 10,000 instructions, throw an Error with the message 'step limit'.

STARTER CODE (javascript):
function runTik(program) {
  // Write your code here
}

module.exports = { runTik };


RULES:
- Keep the function name and signature EXACTLY as given.
- Return working code only. No explanations.
- Put the code in a single ``` block.
- Try to solve it first. If you genuinely cannot, write only this single
  line instead of producing faulty code: CANNOT_SOLVE

===== HAM YANIT =====
```javascript
function runTik(program) {
  const lines = program.split(/\r?\n/);
  const instructions = [];
  const regNames = ['a', 'b', 'c', 'd'];

  // helper to check literal
  const isLiteral = (s) => /^-?\d+$/.test(s);

  // parse operand: register or literal
  const parseOperand = (token) => {
    if (regNames.includes(token)) return { type: 'reg', name: token };
    if (isLiteral(token)) return { type: 'lit', value: Number.parseInt(token, 10) };
    throw new Error();
  };

  // validation
  for (let i = 0; i < lines.length; i++) {
    const raw = lines[i];
    const trimmed = raw.trim();
    if (trimmed === '' || trimmed[0] === '#') continue; // ignored
    const tokens = trimmed.split(/\s+/);
    const name = tokens[0];

    try {
      switch (name) {
        case 'set':
        case 'add':
        case 'mul':
          if (tokens.length !== 3) throw new Error();
          if (!regNames.includes(tokens[1])) throw new Error();
          const opX = parseOperand(tokens[2]);
          instructions.push({ type: name, R: tokens[1], X: opX });
          break;
        case 'out':
          if (tokens.length !== 2) throw new Error();
          const opOut = parseOperand(tokens[1]);
          instructions.push({ type: 'out', X: opOut });
          break;
        case 'jmp':
          if (tokens.length !== 3) throw new Error();
          const opJmpX = parseOperand(tokens[1]);
          const tokN = tokens[2];
          if (!isLiteral(tokN)) throw new Error();
          const nVal = Number.parseInt(tokN, 10);
          instructions.push({ type: 'jmp', X: opJmpX, n: nVal });
          break;
        default:
          throw new Error();
      }
    } catch (_) {
      throw new Error(`bad instruction at line ${i + 1}`);
    }
  }

  // execution
  const regs = { a: 0, b: 0, c: 0, d: 0 };
  const output = [];
  const mod = (v) => ((v % 1000) + 1000) % 1000;
  const evalOperand = (op) => (op.type === 'reg' ? regs[op.name] : mod(op.value));

  let pc = 0;
  let steps = 0;
  while (pc >= 0 && pc < instructions.length) {
    if (steps >= 10000) throw new Error('step limit');
    const instr = instructions[pc];
    switch (instr.type) {
      case 'set':
        regs[instr.R] = evalOperand(instr.X);
        break;
      case 'add':
        regs[instr.R] = mod(regs[instr.R] + evalOperand(instr.X));
        break;
      case 'mul':
        regs[instr.R] = mod(regs[instr.R] * evalOperand(instr.X));
        break;
      case 'out':
        output.push(evalOperand(instr.X));
        break;
      case 'jmp':
        if (evalOperand(instr.X) !== 0) {
          pc += instr.n;
          steps++;
          continue;
        }
        break;
    }
    pc += 1;
    steps++;
  }

  return output;
}

module.exports = { runTik };
```