import http from 'k6/http';
import { check } from 'k6';
import { BASE, as, pick } from './lib.js';

// Listeners seeking: fifty at once asking for ranges of the same few episodes, as a player does
// on every seek and every few seconds of playback. Every range is checked against what the feed
// served, byte by byte at a sample of offsets, so a wrong offset fails, not only a wrong status.
export const options = {
  scenarios: { seeking: { executor: 'constant-vus', vus: 50, duration: '45s' } },
  thresholds: {
    http_req_failed: ['rate==0'],
    checks: ['rate==1'],
    // About four times its p95 on 2026-10-05, 48ms on SQLite and 45 on Postgres: a range is a
    // file read, little to vary.
    'http_req_duration{name:range}': ['p(95)<200'],
  },
};
// The generated file: ID3's ten bytes, then a byte its offset gives (run.js, mediaByte).
const SIZE = 2 * 1024 * 1024;
const byte = k => (k * 31 + 7) & 255;

export function setup() {
  const r = http.get(`${BASE}/api/entries?filter=downloaded&limit=50`, as('listener', 'setup'));
  const files = r.json().entries.flatMap(e => e.enclosures).filter(x => x.path).map(x => x.id);
  if (!files.length) throw new Error('the listener has no downloaded files to seek through');
  return { files };
}

export default function ({ files }) {
  const start = 10 + Math.floor(Math.random() * (SIZE - 11));
  const end = Math.min(SIZE - 1, start + Math.floor(Math.random() * 65536));
  const r = http.get(`${BASE}/media/${pick(files)}`, {
    headers: { 'X-Load-User': 'listener', Range: `bytes=${start}-${end}` },
    responseType: 'binary',
    tags: { name: 'range' },
  });
  const body = r.status === 206 ? new Uint8Array(r.body) : new Uint8Array(0);
  check(r, {
    'part of the file': r => r.status === 206,
    'the range asked for': r => r.headers['Content-Range'] === `bytes ${start}-${end}/${SIZE}`,
    'its bytes': () => {
      if (body.length !== end - start + 1) return false;
      for (const at of [0, body.length - 1, ...Array.from({ length: 30 }, () => Math.floor(Math.random() * body.length))])
        if (body[at] !== byte(start + at)) return false;
      return true;
    },
  });
}