// Compiles and evaluates one runtime.js bundle in isolation, with node:vm, and reports
// the median compile and evaluate time (ms) over several rounds, plus their ratio.
// runtime.js assigns to `self` at its top level (it is written for a worker global
// scope), so this script stands in a bare `self`; nothing else it touches at module
// evaluation time is missing from Node's global object.
// Needs --experimental-vm-modules. Usage: node --experimental-vm-modules
//   scripts/eval-budget.mjs [path/to/runtime.js] [rounds]
globalThis.self = globalThis;

import vm from "node:vm";
import { readFileSync } from "node:fs";

const path = process.argv[2] ?? "dist/runtime/runtime.js";
const rounds = Number(process.argv[3] ?? 40);
const source = readFileSync(path, "utf8");

function once() {
  const t0 = performance.now();
  const mod = new vm.SourceTextModule(source, {
    identifier: `eval-budget-${Math.random()}`,
    initializeImportMeta(meta) {
      meta.url = "file:///runtime.js";
    },
  });
  const t1 = performance.now();
  return mod.link(() => { throw new Error("runtime.js is bundled; it should import nothing"); }).then(() => {
    const t2 = performance.now();
    return mod.evaluate().then(() => {
      const t3 = performance.now();
      return { compile: t1 - t0, evaluate: t3 - t2 };
    });
  });
}

const compile = [];
const evaluate = [];
for (let i = 0; i < rounds; i++) {
  const r = await once();
  compile.push(r.compile);
  evaluate.push(r.evaluate);
}

function median(a) {
  const s = [...a].sort((x, y) => x - y);
  const n = s.length;
  return n % 2 ? s[(n - 1) / 2] : (s[n / 2 - 1] + s[n / 2]) / 2;
}

const compileMs = median(compile);
const evaluateMs = median(evaluate);
console.log(JSON.stringify({ path, rounds, compileMs, evaluateMs, ratio: evaluateMs / compileMs }));