// Display formatters — units, durations, dates, states.

export function bytes(n, dp = 1) {
  if (n == null || isNaN(n)) return '–';
  if (n === 0) return '0 B';
  const u = ['B', 'KiB', 'MiB', 'GiB', 'TiB', 'PiB'];
  const i = Math.min(u.length - 1, Math.floor(Math.log(n) / Math.log(1024)));
  return `${(n / 1024 ** i).toFixed(i === 0 ? 0 : dp)} ${u[i]}`;
}

export function rate(n) {
  if (!n) return '–';
  return `${bytes(n)}/s`;
}

export function eta(sec) {
  if (sec == null || sec >= 8640000 || sec < 0) return '∞';
  if (sec < 1) return '0s';
  const d = Math.floor(sec / 86400);
  const h = Math.floor((sec % 86400) / 3600);
  const m = Math.floor((sec % 3600) / 60);
  const s = Math.floor(sec % 60);
  if (d) return `${d}d ${h}h`;
  if (h) return `${h}h ${m}m`;
  if (m) return `${m}m ${s}s`;
  return `${s}s`;
}

export function duration(sec) {
  if (sec == null || sec < 0) return '–';
  const d = Math.floor(sec / 86400);
  const h = Math.floor((sec % 86400) / 3600);
  const m = Math.floor((sec % 3600) / 60);
  if (d) return `${d}d ${h}h ${m}m`;
  if (h) return `${h}h ${m}m`;
  return `${m}m`;
}

export function pct(p) { return `${(p * 100).toFixed(1)}%`; }

export function ratio(r) {
  if (r == null) return '–';
  if (r >= 9999) return '∞';
  return r.toFixed(2);
}

// Timestamps from the backend are Unix epoch SECONDS; 0/negative means "unset".
export function date(sec) {
  if (!sec || sec < 0) return '–';
  const d = new Date(sec * 1000);
  return d.toLocaleString(undefined, { year: '2-digit', month: 'short', day: '2-digit', hour: '2-digit', minute: '2-digit' });
}

export function ago(sec) {
  if (!sec || sec < 0) return '–';
  const s = Date.now() / 1000 - sec;
  if (s < 60) return 'just now';
  if (s < 3600) return `${Math.floor(s / 60)}m ago`;
  if (s < 86400) return `${Math.floor(s / 3600)}h ago`;
  return `${Math.floor(s / 86400)}d ago`;
}

const STATE_LABEL = {
  downloading: 'Downloading', forcedDL: '[F] Downloading', metaDL: 'Fetching metadata',
  stalledDL: 'Stalled (DL)', uploading: 'Seeding', forcedUP: '[F] Seeding',
  stalledUP: 'Seeding (idle)', pausedDL: 'Paused', pausedUP: 'Completed',
  checkingDL: 'Checking', checkingUP: 'Checking', moving: 'Moving',
  queuedDL: 'Queued', queuedUP: 'Queued', error: 'Error', missingFiles: 'Missing files',
};
export function stateLabel(s) { return STATE_LABEL[s] || s; }

const STATE_COLOR = {
  downloading: 'var(--dl)', forcedDL: 'var(--dl)', metaDL: 'var(--dl)',
  uploading: 'var(--up)', forcedUP: 'var(--up)',
  stalledDL: 'var(--txt-dim)', stalledUP: 'var(--txt-dim)',
  pausedDL: 'var(--pause)', pausedUP: 'var(--pause)',
  checkingDL: 'var(--check)', checkingUP: 'var(--check)', moving: 'var(--check)',
  queuedDL: 'var(--queue)', queuedUP: 'var(--queue)',
  error: 'var(--err)', missingFiles: 'var(--err)',
};
export function stateColor(s) { return STATE_COLOR[s] || 'var(--txt-dim)'; }

const PRIO_LABEL = { 0: 'Do not download', 1: 'Normal', 6: 'High', 7: 'Maximum' };
export function filePrio(p) { return PRIO_LABEL[p] ?? 'Normal'; }

export function esc(s) {
  return String(s ?? '').replace(/[&<>"']/g, (c) => ({ '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#39;' }[c]));
}