// Alphabet index for a library grid: sticky per-letter section headings
// inside the grid itself, plus a right-edge A-Z rail to jump straight to
// one - see docs/architecture.md. Library-only for now (that's the only
// page that asked), but nothing below assumes anything Library-specific
// beyond the two elements it measures (.libraryHeader, shell/Shell.html's
// .bottomStack) - reusable elsewhere later without change.
import './alphaIndex.css';
import { tileHtml } from './tiles';
import type { CleanupFn } from './router';
import type { ItemDto } from './types';

const ALL_BUCKETS = ['#', ...Array.from({ length: 26 }, (_, i) => String.fromCharCode(65 + i))];

/**
 * An item's index bucket: the first letter of its `sortName` - NOT
 * `name` - with accents folded to their base (so "Écho" lands on "E",
 * matching how a French speaker would expect the index to group it, not
 * off in its own "É"/"#" bucket). Anything else (a digit, empty) falls
 * back to "#".
 *
 * `sortName`, deliberately, not the display name: `items` arrives in
 * Emby's own SortName order (getLibraryItems/getArtists both request
 * `SortBy: SortName`), and that order strips leading articles ("Le
 * Voyage" sorts as "Voyage") - bucketing by the raw display name instead
 * put a "L" heading in the middle of a "V" run the one time an article
 * did that, reported directly as headers in no sensible order at all.
 * Bucketing by the exact same key Emby used to order the array is what
 * guarantees a bucket is always one contiguous run, not a guess that it
 * happens to line up.
 */
function bucketFor(item: ItemDto): string {
  const base = (item.sortName || item.name || '').trim().normalize('NFD').replace(/[̀-ͯ]/g, '');
  const c = base.charAt(0).toUpperCase();
  return c >= 'A' && c <= 'Z' ? c : '#';
}

/**
 * Same job as tiles.ts's renderTilesInChunks (chunked insertAdjacentHTML,
 * not one big innerHTML write - see that function's own comment for why
 * that matters on a 1000+-item library), plus a `.letterHeading` inserted
 * right before the first tile of each new bucket. `items` is assumed
 * already ordered by `sortName` (see bucketFor) - a chunk boundary
 * landing mid-bucket is fine, it's still one contiguous run either way.
 */
export function renderGroupedTilesInChunks(container: HTMLElement, items: ItemDto[], chunkSize = 40): void {
  container.innerHTML = '';
  let i = 0;
  let lastBucket: string | null = null;
  function renderNextChunk(): void {
    const chunk = items.slice(i, i + chunkSize);
    if (!chunk.length) return;
    let html = '';
    for (const item of chunk) {
      const bucket = bucketFor(item);
      if (bucket !== lastBucket) {
        html += `<div class="letterHeading" data-letter-anchor="${bucket}">${bucket}</div>`;
        lastBucket = bucket;
      }
      html += tileHtml(item);
    }
    container.insertAdjacentHTML('beforeend', html);
    i += chunkSize;
    if (i < items.length) setTimeout(renderNextChunk, 0);
  }
  renderNextChunk();
}

/**
 * Hides a `.letterHeading` whenever every tile in its run is currently
 * `.hide`'d by tiles.ts's wireSearchFilter - without this, searching
 * down to matches in only one bucket would leave every other bucket's
 * heading floating above nothing. Call once, after wireSearchFilter
 * itself is wired to the same input (listener order = registration
 * order, so this always runs after .hide has already been updated).
 */
export function wireSectionSearchSync(input: HTMLInputElement, grid: HTMLElement): void {
  input.addEventListener('input', () => {
    grid.querySelectorAll<HTMLElement>('.letterHeading').forEach((heading) => {
      let sib = heading.nextElementSibling;
      let anyVisible = false;
      while (sib && !sib.classList.contains('letterHeading')) {
        if (!sib.classList.contains('hide')) { anyVisible = true; break; }
        sib = sib.nextElementSibling;
      }
      heading.classList.toggle('hide', !anyVisible);
    });
  });
}

/**
 * The right-edge A-Z rail: tap or drag it to jump the page scroll to a
 * letter's section heading, with a big center-screen bubble showing the
 * current letter while doing so (fades out on release) - same
 * pointerdown/move/up-on-a-dedicated-element and touch-action: none shape
 * as shell/Shell.ts's own nav-sheet grabber handle, so a vertical drag
 * here doesn't get read as the browser's pull-to-refresh either. Letters
 * with nothing in `items` render dimmed and inert.
 *
 * The rail and every letterHeading's sticky offset are measured live off
 * .libraryHeader and .bottomStack rather than hardcoded: .bottomStack
 * (the music bar) can appear/resize while this page stays open - a
 * listen party starting - and it floats above the grid on desktop too,
 * not just mobile, so both need to stay clear of it regardless of
 * breakpoint. `getComputedStyle(libraryHeader).top` picks up whichever
 * of Library.css's own two breakpoint values is active without this
 * module needing to duplicate that 720px rule itself.
 *
 * Returns a CleanupFn (see router.ts) - the two ResizeObservers and the
 * window-level scroll/resize listeners this sets up would otherwise keep
 * running after the user navigates away, the exact leak class
 * docs/architecture.md already documents this app getting bitten by
 * once before.
 */
export function wireAlphaRail(root: HTMLElement, grid: HTMLElement, items: ItemDto[]): CleanupFn {
  const present = new Set(items.map((it) => bucketFor(it)));
  const libraryHeader = root.querySelector('.libraryHeader') as HTMLElement;
  const bottomStack = document.querySelector('.bottomStack') as HTMLElement | null;

  const rail = document.createElement('div');
  rail.className = 'alphaRail';
  rail.innerHTML = ALL_BUCKETS.map((letter) => {
    const has = present.has(letter);
    return `<span class="railLetter${has ? '' : ' railLetterEmpty'}" data-letter="${letter}" role="button" aria-label="Aller à ${letter}" aria-disabled="${!has}">${letter}</span>`;
  }).join('');
  root.appendChild(rail);

  const bubble = document.createElement('div');
  bubble.className = 'alphaBubble';
  root.appendChild(bubble);

  function recomputeOffsets(): void {
    const top = parseFloat(getComputedStyle(libraryHeader).top) || 0;
    const stickyBottom = top + libraryHeader.offsetHeight;
    grid.style.setProperty('--section-sticky-top', `${stickyBottom}px`);
    rail.style.top = `${stickyBottom}px`;
    rail.style.bottom = `${bottomStack ? bottomStack.offsetHeight : 0}px`;
  }
  recomputeOffsets();

  const resizeObserver = new ResizeObserver(recomputeOffsets);
  resizeObserver.observe(libraryHeader);
  if (bottomStack) resizeObserver.observe(bottomStack);
  window.addEventListener('resize', recomputeOffsets);

  let bubbleFadeTimer: ReturnType<typeof setTimeout> | null = null;
  function showBubble(letter: string): void {
    bubble.textContent = letter;
    bubble.classList.add('show');
    if (bubbleFadeTimer) clearTimeout(bubbleFadeTimer);
  }
  function scheduleHideBubble(): void {
    if (bubbleFadeTimer) clearTimeout(bubbleFadeTimer);
    bubbleFadeTimer = setTimeout(() => bubble.classList.remove('show'), 260);
  }

  function setActive(letter: string): void {
    rail.querySelectorAll('.railLetter').forEach((el) => {
      el.classList.toggle('active', el.getAttribute('data-letter') === letter);
    });
  }

  function letterAt(clientY: number): string {
    const rect = rail.getBoundingClientRect();
    const ratio = Math.min(1, Math.max(0, (clientY - rect.top) / rect.height));
    return ALL_BUCKETS[Math.min(ALL_BUCKETS.length - 1, Math.floor(ratio * ALL_BUCKETS.length))] as string;
  }

  function jumpTo(letter: string): void {
    setActive(letter);
    showBubble(letter);
    const target = grid.querySelector(`[data-letter-anchor="${letter}"]`);
    if (target) target.scrollIntoView({ block: 'start' });
  }

  let dragging = false;
  function onPointerDown(e: PointerEvent): void {
    dragging = true;
    rail.setPointerCapture(e.pointerId);
    jumpTo(letterAt(e.clientY));
  }
  function onPointerMove(e: PointerEvent): void {
    if (!dragging) return;
    jumpTo(letterAt(e.clientY));
  }
  function endDrag(): void {
    if (!dragging) return;
    dragging = false;
    scheduleHideBubble();
  }
  rail.addEventListener('pointerdown', onPointerDown);
  rail.addEventListener('pointermove', onPointerMove);
  rail.addEventListener('pointerup', endDrag);
  rail.addEventListener('pointercancel', endDrag);

  let scrollSpyScheduled = false;
  function onWindowScroll(): void {
    if (dragging || scrollSpyScheduled) return;
    scrollSpyScheduled = true;
    requestAnimationFrame(() => {
      scrollSpyScheduled = false;
      const stickyBottom = parseFloat(grid.style.getPropertyValue('--section-sticky-top')) || 0;
      let current = ALL_BUCKETS[0] as string;
      grid.querySelectorAll<HTMLElement>('[data-letter-anchor]').forEach((el) => {
        if (el.getBoundingClientRect().top - stickyBottom <= 4) current = el.getAttribute('data-letter-anchor') as string;
      });
      setActive(current);
    });
  }
  window.addEventListener('scroll', onWindowScroll, { passive: true });
  setActive(ALL_BUCKETS[0] as string);

  return () => {
    resizeObserver.disconnect();
    window.removeEventListener('resize', recomputeOffsets);
    window.removeEventListener('scroll', onWindowScroll);
    if (bubbleFadeTimer) clearTimeout(bubbleFadeTimer);
  };
}