// 对拍比较：把两批截图逐对做差值，给出"改完到底有没有动到画面"的判定。
// 用法：node tools/compare.mjs <A目录> <B目录> [--tag A] [--tag B] [--threshold 1.0]
// 例：  node tools/compare.mjs before after

import { spawn } from "node:child_process";
import { readdir } from "node:fs/promises";
import { resolve } from "node:path";

const argv = process.argv.slice(2);
const [dirA, dirB] = argv;
if (!dirA || !dirB) {
  console.error("usage: node tools/compare.mjs <dirA> <dirB> [--threshold 1.0]");
  process.exit(2);
}
const opt = (name, dflt) => {
  const i = argv.indexOf(`--${name}`);
  return i >= 0 ? argv[i + 1] : dflt;
};
const threshold = Number(opt("threshold", "1.0"));

function run(cmd, args) {
  return new Promise((resolve) => {
    const p = spawn(cmd, args, { stdio: ["ignore", "pipe", "pipe"] });
    let out = "";
    p.stdout.on("data", (d) => (out += d));
    p.stderr.on("data", (d) => (out += d));
    p.on("close", () => resolve(out));
  });
}

const A = resolve("tools/shots", dirA);
const B = resolve("tools/shots", dirB);
const files = (await readdir(A)).filter((f) => f.endsWith(".png") && !f.endsWith(".ref.png")).sort();

let worst = 0;
let worstName = "";
let failed = 0;

for (const f of files) {
  const a = resolve(A, f);
  const b = resolve(B, f);
  const out = await run(process.execPath, ["tools/diff.mjs", a, b]);
  const m = out.match(/mean\|diff\|=([\d.]+)/);
  const mean = m ? Number(m[1]) : NaN;
  const verdict = Number.isNaN(mean) ? "MISSING" : mean < threshold ? "same" : "CHANGED";
  if (Number.isNaN(mean)) failed++;
  else if (mean > worst) {
    worst = mean;
    worstName = f;
  }
  console.log(`${f.padEnd(28)} mean|diff|=${String(mean).padStart(7)}   ${verdict}`);
}

console.log(`\n${dirA} → ${dirB}：${files.length} 对；最大差异 ${worst.toFixed(3)}/255（${worstName || "无"}）；判定阈值 ${threshold}`);
if (failed) {
  console.log(`${failed} 对缺少对照文件`);
  process.exit(1);
}