// List every instruction in a game module's .text that uses one of the given
// immediate values (decimal or 0x-hex), e.g. to find hardcoded resolutions.
//
//   node tools/find-imm.mjs <exe> 1024 768 [...]
//   node tools/find-imm.mjs <exe> /96AB0h\]/      (regex on instruction text)
//
// Output: one line per hit, "address  instruction".

import { readFileSync } from "node:fs";
import { Decoder, DecoderOptions, Formatter, FormatterSyntax, OpKind } from "iced-x86";

const [exePath, ...valueTexts] = process.argv.slice(2);
if (!exePath || valueTexts.length === 0) {
  console.error("usage: node find-imm.mjs <exe> <value> [value...]");
  process.exit(1);
}
const textPattern = valueTexts.length === 1 && /^\/.*\/$/.test(valueTexts[0])
  ? new RegExp(valueTexts[0].slice(1, -1), "i")
  : null;
const wanted = textPattern ? new Set() : new Set(valueTexts.map((t) => BigInt(Number(t))));

const file = readFileSync(exePath);
const peOffset = file.readUInt32LE(0x3c);
const sectionCount = file.readUInt16LE(peOffset + 6);
const optionalSize = file.readUInt16LE(peOffset + 20);
const imageBase = file.readUInt32LE(peOffset + 24 + 28);
const sectionTable = peOffset + 24 + optionalSize;

let text = null;
for (let i = 0; i < sectionCount; i++) {
  const s = sectionTable + 40 * i;
  const name = file.toString("latin1", s, s + 8).replace(/\0+$/, "");
  if (name === ".text") {
    text = {
      virtualAddress: file.readUInt32LE(s + 12),
      rawSize: file.readUInt32LE(s + 16),
      rawOffset: file.readUInt32LE(s + 20),
    };
  }
}
if (!text) throw new Error("no .text section");

const bytes = file.subarray(text.rawOffset, text.rawOffset + text.rawSize);
const decoder = new Decoder(32, bytes, DecoderOptions.None);
decoder.ip = BigInt(imageBase + text.virtualAddress);
const formatter = new Formatter(FormatterSyntax.Intel);

const immediateKinds = new Set([
  OpKind.Immediate8, OpKind.Immediate16, OpKind.Immediate32,
  OpKind.Immediate8to16, OpKind.Immediate8to32,
]);

// Linear sweep: data embedded in .text can produce a few bogus hits.
while (decoder.canDecode) {
  const instruction = decoder.decode();
  if (textPattern) {
    const text = formatter.format(instruction);
    if (textPattern.test(text)) {
      console.log(`${Number(instruction.ip).toString(16).padStart(8, "0")}  ${text}`);
    }
    instruction.free();
    continue;
  }
  for (let op = 0; op < instruction.opCount; op++) {
    if (immediateKinds.has(instruction.opKind(op)) && wanted.has(instruction.immediate(op) & 0xffffffffn)) {
      console.log(`${Number(instruction.ip).toString(16).padStart(8, "0")}  ${formatter.format(instruction)}`);
      break;
    }
  }
  instruction.free();
}
decoder.free();
formatter.free();