refactor(artists): I.4 — split Artists.tsx 520 → 233 LOC across 6 files (#676)

* refactor(artists): extract helpers + constants

Pull ALL_SENTINEL / ALPHABET / ARTIST_LIST_* row-height estimates,
the ArtistListFlatRow union, CTP_COLORS palette, and the deterministic
nameColor / nameInitial helpers into utils/artistsHelpers.ts.

Artists.tsx: 520 → 496 LOC.

* refactor(artists): extract ArtistAvatars subcomponents

Pull ArtistCardAvatar (300px, grid view) and ArtistRowAvatar (64px, list
view) into components/artists/ArtistAvatars.tsx. Both fall back to a
hashed-Catppuccin monogram when artist images are off or no cover art
is available.

Artists.tsx: 496 → 436 LOC.

* refactor(artists): extract useArtistsFiltering hook

Bundle the letter/text/star filter pipeline, visible-slice memo,
group-by-letter, and the virtualizer flat-rows list into
hooks/useArtistsFiltering.ts. List-view-only outputs short-circuit when
grid view is active.

Artists.tsx: 436 → 386 LOC.

* refactor(artists): extract useArtistsInfiniteScroll hook

Bundle visibleCount + loadingMore state, the sentinel
IntersectionObserver, loadMore callback, and the filter-change reset
into hooks/useArtistsInfiniteScroll.ts. The observer no longer takes
hasMore — the sentinel element only mounts while there is more data,
so the observer attaches/detaches naturally with it.

Artists.tsx: 386 → 370 LOC.

* refactor(artists): extract ArtistsGridView + ArtistsListView

Move the grid card layout to components/artists/ArtistsGridView.tsx and
the dual-path list layout (non-virtualized fallback + virtualized stream)
to components/artists/ArtistsListView.tsx. Both paths now share an
internal ArtistListRow component so click + context-menu behaviour is
identical regardless of which renderer is active.

Artists.tsx: 370 → 233 LOC.

src/pages/Artists.tsx

@@ -1,109 +1,27 @@
-import { buildCoverArtUrl, coverArtCacheKey } from '../api/subsonicStreamUrl';
 import { getArtists } from '../api/subsonicArtists';
 import type { SubsonicArtist } from '../api/subsonicTypes';
-import React, { useEffect, useState, useCallback, useRef, useMemo } from 'react';
+import { useEffect, useState, useCallback } from 'react';
 import { useNavigate } from 'react-router-dom';
-import { LayoutGrid, List, Images, CheckSquare2, ListMusic, Check } from 'lucide-react';
+import { LayoutGrid, List, Images, CheckSquare2 } from 'lucide-react';
 import StarFilterButton from '../components/StarFilterButton';
 import { usePlayerStore } from '../store/playerStore';
 import { useAuthStore } from '../store/authStore';
-import CachedImage from '../components/CachedImage';
 import { useTranslation } from 'react-i18next';
 import { useVirtualizer } from '@tanstack/react-virtual';
 import { APP_MAIN_SCROLL_VIEWPORT_ID } from '../constants/appScroll';
 import { useElementClientHeightById } from '../hooks/useResizeClientHeight';
 import { usePerfProbeFlags } from '../utils/perfFlags';
-
-const ALL_SENTINEL = 'ALL';
-const ALPHABET = [ALL_SENTINEL, '#', ...'ABCDEFGHIJKLMNOPQRSTUVWXYZ'.split('')];
-
-/** Virtual row height guesses — letter heading vs dense rows vs last row in section (group gap). */
-const ARTIST_LIST_LETTER_ROW_EST = 48;
-const ARTIST_LIST_ROW_EST = 64;
-const ARTIST_LIST_LAST_IN_LETTER_EST = 88;
-
-type ArtistListFlatRow =
-  | { kind: 'letter'; letter: string }
-  | { kind: 'artist'; artist: SubsonicArtist; isLastInLetter: boolean };
-
-// Catppuccin accent colors — one is picked deterministically from the artist name
-const CTP_COLORS = [
-  'var(--ctp-rosewater)', 'var(--ctp-flamingo)', 'var(--ctp-pink)',    'var(--ctp-mauve)',
-  'var(--ctp-red)',       'var(--ctp-maroon)',    'var(--ctp-peach)',   'var(--ctp-yellow)',
-  'var(--ctp-green)',     'var(--ctp-teal)',      'var(--ctp-sky)',     'var(--ctp-sapphire)',
-  'var(--ctp-blue)',      'var(--ctp-lavender)',
-];
-
-function nameColor(name: string): string {
-  let h = 0;
-  for (let i = 0; i < name.length; i++) h = (h * 31 + name.charCodeAt(i)) >>> 0;
-  return CTP_COLORS[h % CTP_COLORS.length];
-}
-
-function nameInitial(name: string): string {
-  // \p{L} matches any Unicode letter — covers cyrillic, arabic, CJK, etc.
-  const letter = name.match(/\p{L}/u)?.[0];
-  if (letter) return letter.toUpperCase();
-  const alnum = name.match(/[0-9]/)?.[0];
-  return alnum ?? '?';
-}
-
-function ArtistCardAvatar({ artist, showImages }: { artist: SubsonicArtist; showImages: boolean }) {
-  const color = nameColor(artist.name);
-  const coverId = artist.coverArt || artist.id;
-  const { coverSrc, coverKey } = useMemo(
-    () => ({
-      coverSrc: coverId ? buildCoverArtUrl(coverId, 300) : '',
-      coverKey: coverId ? coverArtCacheKey(coverId, 300) : '',
-    }),
-    [coverId],
-  );
-  if (showImages && coverId) {
-    return (
-      <div className="artist-card-avatar">
-        <CachedImage
-          src={coverSrc}
-          cacheKey={coverKey}
-          alt={artist.name}
-        />
-      </div>
-    );
-  }
-  return (
-    <div className="artist-card-avatar artist-card-avatar-initial" style={{ borderColor: color }}>
-      <span style={{ color }}>{nameInitial(artist.name)}</span>
-    </div>
-  );
-}
-
-function ArtistRowAvatar({ artist, showImages }: { artist: SubsonicArtist; showImages: boolean }) {
-  const color = nameColor(artist.name);
-  const coverId = artist.coverArt || artist.id;
-  const { coverSrc, coverKey } = useMemo(
-    () => ({
-      coverSrc: coverId ? buildCoverArtUrl(coverId, 64) : '',
-      coverKey: coverId ? coverArtCacheKey(coverId, 64) : '',
-    }),
-    [coverId],
-  );
-  if (showImages && coverId) {
-    return (
-      <div className="artist-avatar">
-        <CachedImage
-          src={coverSrc}
-          cacheKey={coverKey}
-          alt={artist.name}
-          style={{ width: '100%', height: '100%', objectFit: 'cover', borderRadius: '50%' }}
-        />
-      </div>
-    );
-  }
-  return (
-    <div className="artist-avatar artist-avatar-initial" style={{ borderColor: color }}>
-      <span style={{ color }}>{nameInitial(artist.name)}</span>
-    </div>
-  );
-}
+import {
+  ALL_SENTINEL,
+  ALPHABET,
+  ARTIST_LIST_LAST_IN_LETTER_EST,
+  ARTIST_LIST_LETTER_ROW_EST,
+  ARTIST_LIST_ROW_EST,
+} from '../utils/artistsHelpers';
+import { useArtistsFiltering } from '../hooks/useArtistsFiltering';
+import { useArtistsInfiniteScroll } from '../hooks/useArtistsInfiniteScroll';
+import { ArtistsGridView } from '../components/artists/ArtistsGridView';
+import { ArtistsListView } from '../components/artists/ArtistsListView';
 
 export default function Artists() {
   const perfFlags = usePerfProbeFlags();
@@ -117,9 +35,14 @@ export default function Artists() {
 
   const showArtistImages = useAuthStore(s => s.showArtistImages);
   const PAGE_SIZE = showArtistImages ? 50 : 100; // Smaller with images to reduce I/O
-  const [visibleCount, setVisibleCount] = useState(PAGE_SIZE);
-  const [loadingMore, setLoadingMore] = useState(false);
-  const observerTarget = useRef<HTMLDivElement>(null);
+  const {
+    visibleCount,
+    loadingMore,
+    observerTarget,
+  } = useArtistsInfiniteScroll({
+    pageSize: PAGE_SIZE,
+    resetDeps: [filter, letterFilter, starredOnly, viewMode],
+  });
   const navigate = useNavigate();
   const openContextMenu = usePlayerStore(state => state.openContextMenu);
   const setShowArtistImages = useAuthStore(s => s.setShowArtistImages);
@@ -153,81 +76,9 @@ export default function Artists() {
     getArtists().then(data => { setArtists(data); setLoading(false); }).catch(() => setLoading(false));
   }, [musicLibraryFilterVersion]);
 
-  const loadMore = useCallback(() => {
-    if (loadingMore) return;
-    setLoadingMore(true);
-    setVisibleCount(prev => prev + PAGE_SIZE);
-    setTimeout(() => setLoadingMore(false), 100);
-  }, [loadingMore, PAGE_SIZE]);
-
-  // Reset infinite scroll when filters or image setting change
-  useEffect(() => {
-    setVisibleCount(PAGE_SIZE);
-  }, [filter, letterFilter, starredOnly, viewMode, PAGE_SIZE]);
-
-  const starredOverrides = usePlayerStore(s => s.starredOverrides);
-  // Filter pipeline — memoised so unrelated state changes (selection mode,
-  // viewMode, etc.) don't re-iterate the full artists array. With 5000+
-  // artists each re-render walked the list twice without this.
-  const filtered = useMemo(() => {
-    let out = artists;
-    if (letterFilter !== ALL_SENTINEL) {
-      out = out.filter(a => {
-        const first = a.name[0]?.toUpperCase() ?? '#';
-        const isAlpha = /^[A-Z]$/.test(first);
-        if (letterFilter === '#') return !isAlpha;
-        return first === letterFilter;
-      });
-    }
-    if (filter) {
-      const needle = filter.toLowerCase();
-      out = out.filter(a => a.name.toLowerCase().includes(needle));
-    }
-    if (starredOnly) {
-      out = out.filter(a => a.id in starredOverrides ? starredOverrides[a.id] : !!a.starred);
-    }
-    return out;
-  }, [artists, letterFilter, filter, starredOnly, starredOverrides]);
-
-  const visible = useMemo(() => filtered.slice(0, visibleCount), [filtered, visibleCount]);
-  const hasMore = visibleCount < filtered.length;
-
-  // Intersection Observer for infinite scroll (after hasMore declaration)
-  useEffect(() => {
-    const observer = new IntersectionObserver(
-      entries => { if (entries[0].isIntersecting) loadMore(); },
-      { rootMargin: '200px' }
-    );
-    if (observerTarget.current) observer.observe(observerTarget.current);
-    return () => observer.disconnect();
-  }, [loadMore, hasMore]);
-
-  // Group by first letter (for list view) — only recompute when the visible
-  // slice or the view mode actually changes. Skipped entirely in grid view.
-  const { groups, letters } = useMemo(() => {
-    if (viewMode !== 'list') return { groups: {} as Record<string, SubsonicArtist[]>, letters: [] as string[] };
-    const g: Record<string, SubsonicArtist[]> = {};
-    for (const a of visible) {
-      const letter = a.name[0]?.toUpperCase() ?? '#';
-      const key = /^[A-Z]$/.test(letter) ? letter : '#';
-      if (!g[key]) g[key] = [];
-      g[key].push(a);
-    }
-    return { groups: g, letters: Object.keys(g).sort() };
-  }, [visible, viewMode]);
-
-  const artistListFlatRows = useMemo((): ArtistListFlatRow[] => {
-    if (viewMode !== 'list') return [];
-    const out: ArtistListFlatRow[] = [];
-    for (const letter of letters) {
-      out.push({ kind: 'letter', letter });
-      const group = groups[letter];
-      for (let i = 0; i < group.length; i++) {
-        out.push({ kind: 'artist', artist: group[i], isLastInLetter: i === group.length - 1 });
-      }
-    }
-    return out;
-  }, [viewMode, letters, groups]);
+  const {
+    filtered, visible, hasMore, groups, letters, artistListFlatRows,
+  } = useArtistsFiltering({ artists, filter, letterFilter, starredOnly, visibleCount, viewMode });
 
   const mainScrollViewportHeight = useElementClientHeightById(APP_MAIN_SCROLL_VIEWPORT_ID);
   /** Mixed row heights; smallest typical step ≈ artist row — one viewport of extra indices each side. */
@@ -335,173 +186,35 @@ export default function Artists() {
       {loading && <div style={{ display: 'flex', justifyContent: 'center', padding: '3rem' }}><div className="spinner" /></div>}
 
       {!loading && viewMode === 'grid' && (
-        <div className="album-grid-wrap">
-          {visible.map(artist => (
-            <div
-              key={artist.id}
-              className={`artist-card${selectionMode && selectedIds.has(artist.id) ? ' selected' : ''}${selectionMode ? ' artist-card--selectable' : ''}`}
-              onClick={() => {
-                if (selectionMode) {
-                  toggleSelect(artist.id);
-                } else {
-                  navigate(`/artist/${artist.id}`);
-                }
-              }}
-              onContextMenu={(e) => {
-                e.preventDefault();
-                if (selectionMode && selectedIds.size > 0) {
-                  openContextMenu(e.clientX, e.clientY, selectedArtists, 'multi-artist');
-                } else {
-                  openContextMenu(e.clientX, e.clientY, artist, 'artist');
-                }
-              }}
-              style={selectionMode && selectedIds.has(artist.id) ? {
-                outline: '2px solid var(--accent)',
-                outlineOffset: '2px',
-                borderRadius: 'var(--radius-md)'
-              } : {}}
-            >
-              {selectionMode && (
-                <div className={`artist-card-select-check${selectedIds.has(artist.id) ? ' artist-card-select-check--on' : ''}`}>
-                  {selectedIds.has(artist.id) && <Check size={14} strokeWidth={3} />}
-                </div>
-              )}
-              <ArtistCardAvatar artist={artist} showImages={showArtistImages} />
-              <div style={{ textAlign: 'center' }}>
-                <div className="artist-card-name">{artist.name}</div>
-                {artist.albumCount != null && (
-                  <div className="artist-card-meta">{t('artists.albumCount', { count: artist.albumCount })}</div>
-                )}
-              </div>
-            </div>
-          ))}
-        </div>
+        <ArtistsGridView
+          visible={visible}
+          selectionMode={selectionMode}
+          selectedIds={selectedIds}
+          selectedArtists={selectedArtists}
+          showArtistImages={showArtistImages}
+          toggleSelect={toggleSelect}
+          navigate={navigate}
+          openContextMenu={openContextMenu}
+          t={t}
+        />
       )}
 
       {!loading && viewMode === 'list' && (
-        perfFlags.disableMainstageVirtualLists ? (
-          <>
-            {letters.map(letter => (
-              <div key={letter} style={{ marginBottom: '1.5rem' }}>
-                <h3 className="letter-heading">{letter}</h3>
-                <div className="artist-list">
-                  {groups[letter].map(artist => (
-                    <button
-                      key={artist.id}
-                      className={`artist-row${selectionMode && selectedIds.has(artist.id) ? ' selected' : ''}`}
-                      onClick={() => {
-                        if (selectionMode) {
-                          toggleSelect(artist.id);
-                        } else {
-                          navigate(`/artist/${artist.id}`);
-                        }
-                      }}
-                      onContextMenu={(e) => {
-                        e.preventDefault();
-                        if (selectionMode && selectedIds.size > 0) {
-                          openContextMenu(e.clientX, e.clientY, selectedArtists, 'multi-artist');
-                        } else {
-                          openContextMenu(e.clientX, e.clientY, artist, 'artist');
-                        }
-                      }}
-                      id={`artist-${artist.id}`}
-                      style={selectionMode && selectedIds.has(artist.id) ? {
-                        background: 'var(--accent-dim)',
-                        color: 'var(--accent)'
-                      } : {}}
-                    >
-                      <ArtistRowAvatar artist={artist} showImages={showArtistImages} />
-                      <div style={{ textAlign: 'left' }}>
-                        <div className="artist-name">{artist.name}</div>
-                        {artist.albumCount != null && (
-                          <div className="artist-meta">{t('artists.albumCount', { count: artist.albumCount })}</div>
-                        )}
-                      </div>
-                    </button>
-                  ))}
-                </div>
-              </div>
-            ))}
-          </>
-        ) : (
-          <div style={{ position: 'relative', width: '100%' }}>
-            <div
-              style={{
-                height: artistListFlatRows.length === 0 ? 0 : artistListVirtualizer.getTotalSize(),
-                width: '100%',
-                position: 'relative',
-              }}
-            >
-              {artistListVirtualizer.getVirtualItems().map(vi => {
-                const row = artistListFlatRows[vi.index];
-                if (!row) return null;
-                if (row.kind === 'letter') {
-                  return (
-                    <div
-                      key={vi.key}
-                      style={{
-                        position: 'absolute',
-                        top: 0,
-                        left: 0,
-                        width: '100%',
-                        transform: `translateY(${vi.start}px)`,
-                      }}
-                    >
-                      <h3 className="letter-heading">{row.letter}</h3>
-                    </div>
-                  );
-                }
-                const artist = row.artist;
-                return (
-                  <div
-                    key={vi.key}
-                    style={{
-                      position: 'absolute',
-                      top: 0,
-                      left: 0,
-                      width: '100%',
-                      transform: `translateY(${vi.start}px)`,
-                      paddingBottom: row.isLastInLetter ? '1.5rem' : undefined,
-                    }}
-                  >
-                    <button
-                      type="button"
-                      className={`artist-row${selectionMode && selectedIds.has(artist.id) ? ' selected' : ''}`}
-                      onClick={() => {
-                        if (selectionMode) {
-                          toggleSelect(artist.id);
-                        } else {
-                          navigate(`/artist/${artist.id}`);
-                        }
-                      }}
-                      onContextMenu={(e) => {
-                        e.preventDefault();
-                        if (selectionMode && selectedIds.size > 0) {
-                          openContextMenu(e.clientX, e.clientY, selectedArtists, 'multi-artist');
-                        } else {
-                          openContextMenu(e.clientX, e.clientY, artist, 'artist');
-                        }
-                      }}
-                      id={`artist-${artist.id}`}
-                      style={selectionMode && selectedIds.has(artist.id) ? {
-                        background: 'var(--accent-dim)',
-                        color: 'var(--accent)'
-                      } : {}}
-                    >
-                      <ArtistRowAvatar artist={artist} showImages={showArtistImages} />
-                      <div style={{ textAlign: 'left' }}>
-                        <div className="artist-name">{artist.name}</div>
-                        {artist.albumCount != null && (
-                          <div className="artist-meta">{t('artists.albumCount', { count: artist.albumCount })}</div>
-                        )}
-                      </div>
-                    </button>
-                  </div>
-                );
-              })}
-            </div>
-          </div>
-        )
+        <ArtistsListView
+          virtualized={!perfFlags.disableMainstageVirtualLists}
+          groups={groups}
+          letters={letters}
+          artistListFlatRows={artistListFlatRows}
+          artistListVirtualizer={artistListVirtualizer}
+          selectionMode={selectionMode}
+          selectedIds={selectedIds}
+          selectedArtists={selectedArtists}
+          showArtistImages={showArtistImages}
+          toggleSelect={toggleSelect}
+          navigate={navigate}
+          openContextMenu={openContextMenu}
+          t={t}
+        />
       )}
 
       {!loading && hasMore && (