// Section navigation from the keyboard (J/K/U/I/O) and from media keys —
// headset buttons, AirPods, the lock screen — via the Media Session API.
//
// J/K = previous/next section in time order, U/I = up/down the loudest-first
// ranking, O = open the current clip in the full file. Holding Shift jumps to
// the extreme in that direction: Shift+J/K = first/last section in time,
// Shift+U/I = loudest/quietest. The clip queue takes priority; with no queue
// armed, the keys step the playhead of the open full-file player instead.

import {fmtDur, fmtClock, fileStartEpoch, announce} from './util.js';
import {hasQueue, stepClip, openClipInFile, scoreOrder, nextInOrder} from './clips.js';
import {activePlayerIdx, setCutFields} from './player.js';
import {sectionMap, fileByIdx} from './store.js';
import {getPreroll} from './settings.js';

export function navigate(dir, byScore, jump) {
  if (hasQueue()) { stepClip(dir, byScore, jump); return; }

  // Per-file in-player navigation (full-file listening, no clip queue)
  const idx = activePlayerIdx;
  if (idx === null) return;
  const all = sectionMap.get(idx) || [];
  const audio = document.getElementById('aud-' + idx);
  if (!all.length || !audio) return;
  const preroll = getPreroll();
  const cur     = audio.currentTime;
  const epoch   = fileStartEpoch(fileByIdx(idx)?.date);

  const jumpTo = (s, i, n, word) => {
    audio.currentTime = Math.max(0, s.start - preroll);
    setCutFields(idx, s.start, s.end);
    const when = epoch != null
      ? `${fmtClock(epoch + s.start)} to ${fmtClock(epoch + s.end)}`
      : `${fmtDur(s.start)} to ${fmtDur(s.end)}`;
    announce(`${word} ${i + 1} of ${n}: ${when}`);
  };

  if (byScore) {
    // U/I walk the ranking; the anchor is the section the playhead sits in
    // (incl. its preroll lead-in). Anywhere else, I starts at the loudest.
    // Shift jumps straight to the loudest (Shift+U) or quietest (Shift+I).
    const order  = scoreOrder(all);
    const curIdx = all.findIndex(s => cur >= s.start - preroll - 0.5 && cur <= s.end + 0.5);
    const pos    = curIdx === -1 ? -1 : order.indexOf(curIdx);
    const next   = nextInOrder(order, pos, dir, jump);
    if (next === null) { announce(dir < 0 ? 'Loudest highlight reached' : 'End of highlights'); return; }
    jumpTo(all[order[next]], next, order.length, 'Highlight');
    return;
  }

  // Shift+J/K jump to the first/last section regardless of the playhead.
  if (jump) {
    const i = dir < 0 ? 0 : all.length - 1;
    jumpTo(all[i], i, all.length, 'Section');
    return;
  }

  if (dir < 0) {
    for (let i = all.length - 1; i >= 0; i--)
      if (all[i].start < cur - 1) { jumpTo(all[i], i, all.length, 'Section'); return; }
    announce('Beginning of sections');
  } else {
    for (let i = 0; i < all.length; i++)
      if (all[i].start > cur + preroll) { jumpTo(all[i], i, all.length, 'Section'); return; }
    announce('End of sections');
  }
}

export function initNav() {
  document.addEventListener('keydown', e => {
    const t = e.target;
    if (t.tagName === 'INPUT' || t.tagName === 'TEXTAREA' || t.tagName === 'SELECT' || t.isContentEditable) return;
    if (e.ctrlKey || e.metaKey || e.altKey) return;
    const key = e.key.toLowerCase();
    if (!['j', 'k', 'u', 'i', 'o'].includes(key)) return;
    e.preventDefault();
    if (key === 'o') { openClipInFile(); return; }
    navigate(key === 'j' || key === 'u' ? -1 : 1, key === 'u' || key === 'i', e.shiftKey);
  });

  // Previous/next track = J/K. Works from AirPods, the iOS lock screen and
  // Control Center, and the media keys on a Windows keyboard.
  if ('mediaSession' in navigator) {
    for (const [action, dir] of [['previoustrack', -1], ['nexttrack', 1]]) {
      try { navigator.mediaSession.setActionHandler(action, () => navigate(dir, false, false)); }
      catch { /* action not supported here */ }
    }
  }
}