// Author: fruit.com.cn

import 'dart:async';

import 'package:flutter/material.dart';

import '../../../core/data/models/drama.dart';
import '../../../core/data/models/home_feed.dart';
import '../../../core/theme/app_colors.dart';
import '../../../core/widgets/remote_image.dart';

/// 推荐页顶部静态头图轮播：封面 + 底部剧名/简介 + 轮播点。
class HomeHeroCarousel extends StatefulWidget {
  const HomeHeroCarousel({
    super.key,
    required this.banners,
    required this.dramaFor,
    required this.onWatch,
    this.active = true,
  });

  final List<FeedBanner> banners;

  /// 按 banner 关联到的剧目；为空时只展示头图。
  final Drama? Function(FeedBanner banner) dramaFor;

  /// 点击头图进入播放。
  final ValueChanged<Drama> onWatch;

  final bool active;

  /// 固定轮播高度；后台按该比例（屏宽 : height）出图即可铺满不裁切。
  static const double height = 420;

  @override
  State<HomeHeroCarousel> createState() => _HomeHeroCarouselState();
}

class _HomeHeroCarouselState extends State<HomeHeroCarousel> {
  static const Duration _autoInterval = Duration(milliseconds: 4500);
  static const Duration _pageDuration = Duration(milliseconds: 480);
  static const double _dotSize = 4;
  static const double _dotGap = 9;

  /// 轮播点距底边的距离。
  static const double _dotBottom = 14;

  /// 文案区距底边：让出轮播点区域（底距 + 点直径）再留一段呼吸空间。
  static const double _copyBottomInset = _dotBottom + _dotSize + 18;

  /// 无限轮播：PageView 用虚拟大页码，取模映射到真实 banner，首尾天然相接。
  static const int _basePage = 1000;

  late final PageController _controller;
  Timer? _timer;
  int _page = 0;
  int _index = 0;
  bool _pressed = false;
  bool _tickerEnabled = true;

  /// 起始页码取 banner 数量的大倍数，向左右滑都不会到头。
  static int _initialPageOf(int bannerCount) =>
      bannerCount > 1 ? bannerCount * _basePage : 0;

  @override
  void initState() {
    super.initState();
    _page = _initialPageOf(widget.banners.length);
    _controller = PageController(initialPage: _page);
    WidgetsBinding.instance.addPostFrameCallback((_) => _syncTimer());
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    final enabled = TickerMode.valuesOf(context).enabled;
    if (enabled != _tickerEnabled) {
      _tickerEnabled = enabled;
      _syncTimer();
    }
  }

  @override
  void didUpdateWidget(covariant HomeHeroCarousel oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (oldWidget.banners.length != widget.banners.length) {
      // 首屏 banner 是异步到的：列表从空变有之后要把页码挪到虚拟起点，
      // 否则左滑第一下就到头了。
      _page = _initialPageOf(widget.banners.length);
      _index = 0;
      _jumpToBasePage();
    }
    if (oldWidget.banners.length != widget.banners.length ||
        oldWidget.active != widget.active) {
      _syncTimer();
    }
  }

  @override
  void dispose() {
    _timer?.cancel();
    _controller.dispose();
    super.dispose();
  }

  void _syncTimer() {
    _timer?.cancel();
    _timer = null;
    final canAdvance =
        mounted &&
        widget.active &&
        _tickerEnabled &&
        !_pressed &&
        widget.banners.length > 1;
    if (!canAdvance) return;
    _timer = Timer.periodic(_autoInterval, (_) => _advance());
  }

  void _advance() {
    if (!_controller.hasClients || widget.banners.length < 2) return;
    // 虚拟页码无限，直接翻下一页即可，不用在末尾跳回第 0 页。
    _controller.nextPage(duration: _pageDuration, curve: Curves.easeOutCubic);
  }

  /// 把 PageView 静默挪到虚拟起点：视觉上是同一张图，不会闪。
  void _jumpToBasePage() {
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (!mounted || !_controller.hasClients) return;
      if (_controller.page?.round() != _page) _controller.jumpToPage(_page);
    });
  }

  @override
  Widget build(BuildContext context) {
    if (widget.banners.isEmpty) return const SizedBox.shrink();
    return SizedBox(
      key: const Key('home-hero-carousel'),
      height: HomeHeroCarousel.height,
      child: Listener(
        onPointerDown: (_) {
          _pressed = true;
          _timer?.cancel();
        },
        onPointerUp: (_) {
          _pressed = false;
          _syncTimer();
        },
        onPointerCancel: (_) {
          _pressed = false;
          _syncTimer();
        },
        child: Stack(
          fit: StackFit.expand,
          children: [
            PageView.builder(
              controller: _controller,
              // 数量大于 1 时用无限页码做无缝循环，取模映射到真实 banner。
              itemCount: widget.banners.length > 1
                  ? null
                  : widget.banners.length,
              onPageChanged: (value) => setState(() {
                _page = value;
                final count = widget.banners.length;
                _index = count == 0 ? 0 : value % count;
              }),
              itemBuilder: (context, page) =>
                  _bannerPage(context, page % widget.banners.length),
            ),
            Positioned(
              left: 0,
              right: 0,
              bottom: _dotBottom,
              child: _dots(context),
            ),
          ],
        ),
      ),
    );
  }

  Widget _bannerPage(BuildContext context, int index) {
    final banner = widget.banners[index];
    final drama = widget.dramaFor(banner);
    return Stack(
      fit: StackFit.expand,
      children: [
        RemoteImage(
          banner.imageUrl,
          fit: BoxFit.cover,
          fallbackColor: AppColors.contentSurface,
        ),
        const DecoratedBox(
          decoration: BoxDecoration(
            gradient: LinearGradient(
              begin: Alignment.topCenter,
              end: Alignment.bottomCenter,
              colors: [
                Color(0x99000000),
                Color(0x00000000),
                Color(0x66000000),
                Color(0xB3000000),
              ],
              stops: [0, 0.22, 0.62, 1],
            ),
          ),
        ),
        if (drama != null)
          Positioned(
            left: 28,
            right: 28,
            bottom: _copyBottomInset,
            child: _HeroCopy(key: Key('home-hero-copy-$index'), drama: drama),
          ),
        if (drama != null)
          Positioned.fill(
            child: Material(
              color: AppColors.transparent,
              child: InkWell(
                key: Key('home-hero-$index'),
                highlightColor: AppColors.transparent,
                onTap: () => widget.onWatch(drama),
              ),
            ),
          ),
      ],
    );
  }

  Widget _dots(BuildContext context) {
    if (widget.banners.length < 2) return const SizedBox.shrink();
    return ExcludeSemantics(
      child: Row(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          for (var index = 0; index < widget.banners.length; index++)
            Container(
              key: Key('home-hero-dot-$index'),
              width: _dotSize,
              height: _dotSize,
              margin: const EdgeInsets.symmetric(horizontal: _dotGap / 2),
              decoration: BoxDecoration(
                shape: BoxShape.circle,
                color: index == _index
                    ? AppColors.brandRed
                    : AppColors.textPrimary.withValues(alpha: 0.4),
              ),
            ),
        ],
      ),
    );
  }
}

/// Hero 底部居中文案：剧名 + 简介。
class _HeroCopy extends StatelessWidget {
  const _HeroCopy({super.key, required this.drama});

  final Drama drama;

  static const Color _titleCream = Color(0xFFE9D3B8);

  @override
  Widget build(BuildContext context) {
    final lang = Localizations.localeOf(context).languageCode;

    return Column(
      key: const Key('home-hero-copy'),
      mainAxisSize: MainAxisSize.min,
      children: [
        Text(
          drama.localizedTitle(lang),
          maxLines: 1,
          overflow: TextOverflow.ellipsis,
          textAlign: TextAlign.center,
          style: const TextStyle(
            color: _titleCream,
            fontSize: 22,
            fontWeight: FontWeight.w400,
            height: 1.15,
            shadows: [Shadow(color: Color(0x80000000), blurRadius: 12)],
          ),
        ),
        const SizedBox(height: 8),
        Text(
          drama.localizedSynopsis(lang),
          maxLines: 1,
          overflow: TextOverflow.ellipsis,
          textAlign: TextAlign.center,
          style: TextStyle(
            color: AppColors.textPrimary.withValues(alpha: 0.95),
            fontSize: 15,
            fontWeight: FontWeight.w400,
            shadows: const [Shadow(color: Color(0x80000000), blurRadius: 8)],
          ),
        ),
      ],
    );
  }
}