import {
  useMemo,
  useState,
  type ComponentProps
} from 'react';
import {
  Pressable,
  ScrollView,
  StyleSheet,
  View
} from 'react-native';
import { Image } from 'expo-image';
import { Ionicons } from '@expo/vector-icons';
import { FlashList } from '@shopify/flash-list';
import { useLocalSearchParams, useRouter } from 'expo-router';
import { useSafeAreaInsets } from 'react-native-safe-area-context';
import { Screen } from '@/components/Screen';
import { Text } from '@/components/Text';
import { AstraLogo } from '@/components/AstraLogo';
import { TrackRow } from '@/components/library/TrackRow';
import { TrackActionsSheet } from '@/components/library/TrackActionsSheet';
import { CollapsingHeader, useDetailCollapse } from '@/components/library/CollapsingDetail';
import {
  fontSize,
  radius,
  spacing,
} from '@/theme';
import { createThemedStyles, useColors } from '@/theme/themed';
import { SCROLL_PRESS_DELAY, useRipple } from '@/theme/ripple';
import type { Palette } from '@/theme/palettes';
import { usePlayerStore } from '@/stores/playerStore';
import { useSettingsStore } from '@/stores/settingsStore';
import { playLibraryQuery } from '@/audio/playbackController';
import { artworkThumbUri, artworkUri } from '@/library/artwork';
import {
  buildArtistDetail,
  type ArtistAlbum,
  type ArtistDetail
} from '@/library/artistDetail';
import {
  useNativeArtistAlbums,
  useNativeArtistDetail,
} from '@/library/nativePages';
import { useLibraryDetailBack } from '@/navigation/useLibraryDetailBack';
import type { DbTrack } from '@/types/library';

type IconName = ComponentProps<typeof Ionicons>['name'];
type ArtistSectionTarget = 'songs' | 'albums' | 'appearances';

const SONG_PREVIEW_LIMIT = 5;
const ALBUM_PREVIEW_LIMIT = 8;
const APPEARANCE_PREVIEW_LIMIT = 5;

type ArtistPageItem =
  | {
      key: string;
      type: 'section';
      title: string;
      trailing: string;
      target?: ArtistSectionTarget;
    }
  | { key: 'albums'; type: 'albums' }
  | { key: string; type: 'track'; track: DbTrack; section: 'appearances' | 'songs'; index: number }
  | { key: 'empty'; type: 'empty' };

export default function ArtistScreen() {
  const styles = useStyles();
  const colors = useColors();
  const router = useRouter();
  const { name = 'Artist', credit } = useLocalSearchParams<{
    name: string;
    credit?: string;
  }>();
  const { goBack, backLabel } = useLibraryDetailBack();
  const insets = useSafeAreaInsets();
  const { scrollY, heroFaded, collapsed, onScroll, scrollEventThrottle, expandedHeight, onHeroBlockLayout } =
    useDetailCollapse();
  const groupingMode = useSettingsStore((s) => s.artistGroupingMode);
  const detailGroupingMode = credit === '1' ? 'astra' : groupingMode;
  const currentPath = usePlayerStore((s) => s.currentTrack?.path);
  const [actionTrack, setActionTrack] = useState<DbTrack | null>(null);

  const allPage = useNativeArtistDetail(name, detailGroupingMode, 'all');
  const songsPage = useNativeArtistDetail(name, detailGroupingMode, 'songs');
  const appearancesPage = useNativeArtistDetail(name, detailGroupingMode, 'appearances');
  const albumsPage = useNativeArtistAlbums(name, detailGroupingMode);
  const detail = useMemo(() => {
    const base = buildArtistDetail(allPage.items, name, detailGroupingMode);
    return {
      ...base,
      albums: albumsPage.items.map((album) => ({
        ...album,
        duration: album.total_duration ?? 0,
      })),
      tracks: allPage.items,
      playbackTracks: allPage.items,
      songTracks: songsPage.items,
      appearanceTracks: appearancesPage.items,
      showAppearances: appearancesPage.totalCount > 0,
      artworkHashes: allPage.summary?.artwork_hashes ?? base.artworkHashes,
    };
  }, [
    allPage.items,
    allPage.summary,
    albumsPage.items,
    appearancesPage.items,
    appearancesPage.totalCount,
    detailGroupingMode,
    name,
    songsPage.items,
  ]);

  const listItems = useMemo(
    () => buildListItems(detail, songsPage.totalCount, appearancesPage.totalCount),
    [appearancesPage.totalCount, detail, songsPage.totalCount]
  );

  const playTrackListFrom = (
    tracks: readonly DbTrack[],
    index: number,
    section: 'songs' | 'appearances' | 'all',
  ) => {
    if (tracks.length === 0) return;
    void playLibraryQuery({
      kind: 'artist',
      artistKey: name,
      groupingMode: detailGroupingMode,
      section,
    }, {
      anchorPath: tracks[index]?.path,
      source: { kind: 'artist', label: name },
    });
  };

  const playArtist = () => playTrackListFrom(detail.playbackTracks, 0, 'all');
  const shuffleArtist = () => {
    if (detail.playbackTracks.length === 0) return;
    void playLibraryQuery({
      kind: 'artist',
      artistKey: name,
      groupingMode: detailGroupingMode,
      section: 'all',
    }, {
      shuffle: true,
      source: { kind: 'artist', label: name },
    });
  };

  const openSection = (target: ArtistSectionTarget) => {
    router.push({
      pathname: `/library/artist/[name]/${target}`,
      params: { name, ...(credit === '1' ? { credit: '1' } : {}) },
    });
  };

  const renderItem = ({ item }: { item: ArtistPageItem }) => {
    switch (item.type) {
      case 'section': {
        const target = item.target;
        return (
          <SectionHeader
            title={item.title}
            trailing={item.trailing}
            onPress={target ? () => openSection(target) : undefined}
          />
        );
      }
      case 'albums':
        return (
          <AlbumRail
            albums={detail.albums.slice(0, ALBUM_PREVIEW_LIMIT)}
            onAlbumPress={(album) =>
              router.push({
                pathname: '/library/album/[key]',
                params: { key: album.identity_key },
              })
            }
          />
        );
      case 'track': {
        const sourceTracks =
          item.section === 'appearances' ? detail.appearanceTracks : detail.songTracks;
        return (
          <TrackRow
            track={item.track}
            subtitle={trackSubtitle(item.track, item.section)}
            active={item.track.path === currentPath}
            onPress={() =>
              playTrackListFrom(
                sourceTracks,
                item.index,
                item.section === 'appearances' ? 'appearances' : 'songs',
              )
            }
            onLongPress={() => setActionTrack(item.track)}
            onOpenActions={() => setActionTrack(item.track)}
          />
        );
      }
      case 'empty':
        return (
          <View style={styles.emptyState}>
            <Ionicons name="musical-notes" size={24} color={colors.textTertiary} />
            <Text variant="body" color={colors.textSecondary} style={styles.emptyText}>
              No tracks found for this artist.
            </Text>
          </View>
        );
    }
  };

  const backdropHash = detail.artworkHashes[0] ?? null;
  const disabled = detail.playbackTracks.length === 0;

  return (
    <Screen padded={false} style={styles.screen}>
      <FlashList
        data={listItems}
        keyExtractor={(item) => item.key}
        showsVerticalScrollIndicator={false}
        renderItem={renderItem}
        onScroll={onScroll}
        scrollEventThrottle={scrollEventThrottle}
        contentContainerStyle={{
          paddingTop: insets.top + expandedHeight,
          paddingHorizontal: spacing.lg,
          paddingBottom: spacing.xxl,
        }}
      />
      <CollapsingHeader
        artwork={artistArtwork(detail.artworkHashes, colors, styles)}
        backdropUri={backdropHash ? artworkThumbUri(backdropHash) : null}
        title={name}
        heroMeta={
          <View style={styles.stats}>
            {(allPage.summary?.album_count ?? detail.albums.length) > 0 ? (
              <StatChip
                icon="albums-outline"
                label={formatCount(allPage.summary?.album_count ?? detail.albums.length, 'album')}
              />
            ) : null}
            <StatChip icon="musical-notes-outline" label={formatCount(allPage.totalCount, 'track')} />
            {detail.totalDuration > 0 ? (
              <StatChip icon="time-outline" label={formatRuntime(detail.totalDuration)} />
            ) : null}
          </View>
        }
        disabled={disabled}
        onBack={goBack}
        backLabel={backLabel}
        onPlay={playArtist}
        onShuffle={shuffleArtist}
        scrollY={scrollY}
        heroFaded={heroFaded}
        collapsed={collapsed}
        expandedHeight={expandedHeight}
        onHeroBlockLayout={onHeroBlockLayout}
      />
      <TrackActionsSheet track={actionTrack} onClose={() => setActionTrack(null)} />
    </Screen>
  );
}

function buildListItems(
  detail: ArtistDetail,
  songCount: number,
  appearanceCount: number
): ArtistPageItem[] {
  const items: ArtistPageItem[] = [];

  if (detail.tracks.length === 0) {
    items.push({ key: 'empty', type: 'empty' });
    return items;
  }

  if (detail.albums.length > 0) {
    items.push({
      key: 'section-albums',
      type: 'section',
      title: 'Albums',
      trailing: formatCount(detail.albums.length, 'album'),
      target: 'albums',
    });
    items.push({ key: 'albums', type: 'albums' });
  }

  items.push({
    key: 'section-songs',
    type: 'section',
    title: 'Songs',
    trailing: formatCount(songCount, 'track'),
    target: 'songs',
  });
  detail.songTracks.slice(0, SONG_PREVIEW_LIMIT).forEach((track, index) => {
    items.push({ key: `song-${track.id}`, type: 'track', track, section: 'songs', index });
  });

  if (detail.showAppearances) {
    items.push({
      key: 'section-appearances',
      type: 'section',
      title: 'Appears On',
      trailing: formatCount(appearanceCount, 'track'),
      target: 'appearances',
    });
    detail.appearanceTracks.slice(0, APPEARANCE_PREVIEW_LIMIT).forEach((track, index) => {
      items.push({
        key: `appearance-${track.id}`,
        type: 'track',
        track,
        section: 'appearances',
        index,
      });
    });
  }

  return items;
}

/** Inner artwork for the collapsing header: 2x2 album mosaic, single cover, or fallback. */
function artistArtwork(
  hashes: string[],
  colors: Palette,
  styles: ReturnType<typeof useStyles>,
) {
  const useMosaic = hashes.length >= 4;
  const display = useMosaic ? hashes.slice(0, 4) : hashes.slice(0, 1);

  if (display.length === 0) {
    return <Ionicons name="person" size={60} color={colors.textTertiary} />;
  }
  if (useMosaic) {
    return (
      <View style={styles.mosaic}>
        {display.map((hash) => (
          <Image
            key={hash}
            source={{ uri: artworkUri(hash) }}
            style={styles.mosaicTile}
            contentFit="cover"
            transition={120}
          />
        ))}
      </View>
    );
  }
  return (
    <Image source={{ uri: artworkUri(display[0]) }} style={styles.artFill} contentFit="cover" transition={120} />
  );
}

function SectionHeader({
  title,
  trailing,
  onPress,
}: {
  title: string;
  trailing: string;
  onPress?: () => void;
}) {
  const styles = useStyles();
  const ripple = useRipple();
  const colors = useColors();
  return (
    <View style={styles.sectionHeader}>
      <View style={styles.sectionTitleGroup}>
        <Text variant="heading" style={styles.sectionTitle}>
          {title}
        </Text>
        <Text variant="label" numberOfLines={1}>
          {trailing}
        </Text>
      </View>
      {onPress ? (
        <Pressable android_ripple={ripple.bounded} unstable_pressDelay={SCROLL_PRESS_DELAY} style={styles.seeAllButton} onPress={onPress} accessibilityRole="button">
          <Text variant="label" color={colors.accentText}>
            See all
          </Text>
          <Ionicons name="chevron-forward" size={14} color={colors.accentText} />
        </Pressable>
      ) : null}
    </View>
  );
}

function AlbumRail({
  albums,
  onAlbumPress,
}: {
  albums: ArtistAlbum[];
  onAlbumPress: (album: ArtistAlbum) => void;
}) {
  const styles = useStyles();
  const ripple = useRipple();
  return (
    <ScrollView
      horizontal
      showsHorizontalScrollIndicator={false}
      contentContainerStyle={styles.albumRail}
    >
      {albums.map((album) => (
        <Pressable android_ripple={ripple.bounded} unstable_pressDelay={SCROLL_PRESS_DELAY}
          key={album.identity_key}
          style={styles.albumCard}
          onPress={() => onAlbumPress(album)}
          accessibilityRole="button"
        >
          <View style={styles.albumArt}>
            {album.artwork_hash ? (
              <Image
                source={{ uri: artworkUri(album.artwork_hash) }}
                style={styles.albumArtImage}
                contentFit="cover"
                transition={120}
              />
            ) : (
              <AstraLogo size={34} />
            )}
          </View>
          <Text variant="body" numberOfLines={2} style={styles.albumTitle}>
            {album.album}
          </Text>
          <Text variant="label" numberOfLines={1}>
            {[album.year ? String(album.year) : null, formatCount(album.track_count, 'track')]
              .filter(Boolean)
              .join(' - ')}
          </Text>
        </Pressable>
      ))}
    </ScrollView>
  );
}

function StatChip({ icon, label }: { icon: IconName; label: string }) {
  const styles = useStyles();
  const colors = useColors();
  return (
    <View style={styles.statChip}>
      <Ionicons name={icon} size={13} color={colors.accentText} />
      <Text variant="caption" color={colors.accentText} numberOfLines={1} style={styles.statLabel}>
        {label}
      </Text>
    </View>
  );
}

function formatCount(count: number, noun: string): string {
  return `${count} ${count === 1 ? noun : `${noun}s`}`;
}

function formatRuntime(seconds: number): string {
  const totalMinutes = seconds > 0 ? Math.max(1, Math.round(seconds / 60)) : 0;
  if (totalMinutes < 60) return `${totalMinutes}m`;

  const hours = Math.floor(totalMinutes / 60);
  const minutes = totalMinutes % 60;
  return minutes > 0 ? `${hours}h ${minutes}m` : `${hours}h`;
}

function trackSubtitle(track: DbTrack, section: 'appearances' | 'songs'): string {
  if (section === 'appearances') return `${track.artist} - ${track.album}`;
  return track.album;
}

const useStyles = createThemedStyles((colors) => ({
  // The backdrop runs behind the status bar; content pads itself instead.
  screen: {
    paddingTop: 0,
  },
  mosaic: {
    width: '100%',
    height: '100%',
    flexDirection: 'row',
    flexWrap: 'wrap',
  },
  mosaicTile: {
    width: '50%',
    height: '50%',
  },
  artFill: {
    width: '100%',
    height: '100%',
  },
  stats: {
    flexDirection: 'row',
    flexWrap: 'wrap',
    justifyContent: 'center',
    gap: spacing.xs,
  },
  statChip: {
    minHeight: 28,
    maxWidth: '100%',
    flexDirection: 'row',
    alignItems: 'center',
    gap: spacing.xs,
    paddingHorizontal: spacing.sm,
    paddingVertical: spacing.xs,
    borderRadius: radius.pill,
    backgroundColor: colors.glassHighlight,
    borderColor: colors.glassBorder,
    borderWidth: StyleSheet.hairlineWidth,
  },
  statLabel: {
    maxWidth: 180,
  },
  sectionHeader: {
    minHeight: 36,
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'space-between',
    gap: spacing.md,
    marginTop: spacing.lg,
    marginBottom: spacing.sm,
  },
  sectionTitleGroup: {
    flex: 1,
    minWidth: 0,
  },
  sectionTitle: {
    fontSize: fontSize.md,
  },
  seeAllButton: {
    minHeight: 32,
    flexDirection: 'row',
    alignItems: 'center',
    gap: 2,
    paddingLeft: spacing.sm,
  },
  albumRail: {
    gap: spacing.md,
    paddingRight: spacing.lg,
    paddingBottom: spacing.sm,
  },
  albumCard: {
    width: 132,
  },
  albumArt: {
    width: 132,
    height: 132,
    borderRadius: radius.md,
    backgroundColor: colors.bgTertiary,
    borderColor: colors.glassBorder,
    borderWidth: StyleSheet.hairlineWidth,
    alignItems: 'center',
    justifyContent: 'center',
    overflow: 'hidden',
    marginBottom: spacing.sm,
  },
  albumArtImage: {
    width: '100%',
    height: '100%',
  },
  albumTitle: {
    minHeight: 38,
    fontSize: 14,
    lineHeight: 19,
  },
  emptyState: {
    alignItems: 'center',
    justifyContent: 'center',
    gap: spacing.sm,
    paddingVertical: spacing.xxl,
  },
  emptyText: {
    textAlign: 'center',
  },
}));