<script lang="ts">
  import { pageTitle } from '$lib/branding';
  import { createArtistsQuery } from '$lib/api/queries';
  import ArtistCard from '$lib/components/ArtistCard.svelte';
  import AlphabeticalGrid from '$lib/components/AlphabeticalGrid.svelte';
  import ApiErrorBanner from '$lib/components/ApiErrorBanner.svelte';
  import InfiniteScrollSentinel from '$lib/components/InfiniteScrollSentinel.svelte';
  import QuickFilter from '$lib/components/QuickFilter.svelte';
  import EmptyState from '$lib/components/EmptyState.svelte';
  import { useDelayed } from '$lib/utils/useDelayed.svelte';
  import type { ArtistRef } from '$lib/api/types';

  const queryStore = $derived(createArtistsQuery('alpha'));
  const query = $derived($queryStore);
  const artists = $derived(query.data?.pages?.flatMap((p) => p.items) ?? []);
  const total = $derived(query.data?.pages?.[0]?.total ?? 0);
  const showSkeleton = useDelayed(() => query.isPending);

  let filter = $state('');
  const filtered = $derived.by(() => {
    const q = filter.trim().toLowerCase();
    if (!q) return artists;
    return artists.filter((a) => a.name.toLowerCase().includes(q));
  });
</script>

<svelte:head><title>{pageTitle('Library · Artists')}</title></svelte:head>

<div class="space-y-4">
  <header class="flex flex-wrap items-end justify-between gap-3">
    <div>
      <h1 class="font-display text-2xl font-medium text-text-primary">Artists</h1>
      {#if !query.isPending && !query.isError}
        <p class="text-sm text-text-secondary">
          {total} {total === 1 ? 'artist' : 'artists'}
        </p>
      {/if}
    </div>
    {#if artists.length > 0}
      <QuickFilter bind:value={filter} placeholder="Filter artists" />
    {/if}
  </header>

  {#if query.isError}
    <ApiErrorBanner error={query.error} onRetry={query.refetch} />
  {:else if showSkeleton.value && artists.length === 0}
    <p class="text-text-secondary">Loading…</p>
  {:else if !query.isPending && total === 0}
    <EmptyState
      title="No artists yet"
      hint="Once a library folder has been scanned, artists will appear here."
    >
      {#snippet actions()}
        <a
          href="/settings"
          class="inline-flex items-center rounded-md bg-action-secondary px-4 py-2 text-sm text-action-fg hover:opacity-90"
        >
          Open settings
        </a>
      {/snippet}
    </EmptyState>
  {:else if filter.trim() && filtered.length === 0}
    <p class="text-text-secondary">
      No artists in your loaded library match
      <span class="font-medium">'{filter.trim()}'</span>.
      <a href={`/search/artists?q=${encodeURIComponent(filter.trim())}`} class="text-accent hover:underline">
        Search the full library →
      </a>
    </p>
  {:else}
    <AlphabeticalGrid
      items={filtered}
      getKey={(a: ArtistRef) => a.sort_name || a.name}
      hasMore={!!query.hasNextPage}
      onLoadMore={() => query.fetchNextPage()}
    >
      {#snippet item(a: ArtistRef)}
        <ArtistCard artist={a} />
      {/snippet}
    </AlphabeticalGrid>

    {#if query.hasNextPage}
      <InfiniteScrollSentinel
        enabled={!query.isFetchingNextPage}
        onIntersect={() => query.fetchNextPage()}
      />
      {#if query.isFetchingNextPage}
        <p class="py-2 text-center text-sm text-text-secondary">Loading more…</p>
      {/if}
    {:else if artists.length > 0}
      <p class="py-2 text-center text-sm text-text-secondary">End of library</p>
    {/if}
  {/if}
</div>
