import 'dart:async';

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

import '../../design/cookit_colors.dart';
import '../../design/cookit_nav_bar.dart';
import '../../design/herb_pattern.dart';
import '../../localization/app_localizations.dart';
import '../../recipes/recipe_list_provider.dart';
import '../../settings/settings_controller.dart';
import '../day.dart';
import '../day_format.dart';
import '../models/plan_entry.dart';
import '../plan_repository.dart';
import 'widgets/fill_week_sheet.dart';
import 'widgets/plan_actions.dart';
import 'widgets/plan_grid.dart';
import 'widgets/week_share_menu.dart';
import 'widgets/today_banner.dart';

/// The Week Plan: today's banner, then one week as a grid. Swipe (or ‹ ›) for
/// other weeks. While an entry is dragged, the week bar turns into drop zones
/// for the neighbouring weeks and the navigation bar into "remove".
class WeekPlanView extends StatefulWidget {
  const WeekPlanView({super.key, this.onDraggingChanged});

  /// Lets the home screen hide its navigation bar while an entry is dragged.
  final ValueChanged<bool>? onDraggingChanged;

  @override
  State<WeekPlanView> createState() => _WeekPlanViewState();
}

class _WeekPlanViewState extends State<WeekPlanView> {
  /// The page showing the current week; pages before it are past weeks.
  static const _origin = 10000;

  final _pages = PageController(initialPage: _origin);
  var _page = _origin;
  var _dragging = false;

  @override
  void dispose() {
    _pages.dispose();
    super.dispose();
  }

  DateTime get _thisWeek => weekStartOf(dayOf(DateTime.now()), context.read<SettingsController>().weekStart);

  DateTime _weekOf(int page) => addDays(_thisWeek, 7 * (page - _origin));

  void _goTo(int page) =>
      _pages.animateToPage(page, duration: const Duration(milliseconds: 300), curve: Curves.easeOutCubic);

  // A drag can outlive the cell it started in (the week flips under it), so it
  // ends with the finger, not with the cell's callbacks.
  void _setDragging(bool dragging) {
    if (_dragging == dragging) return;
    setState(() => _dragging = dragging);
    widget.onDraggingChanged?.call(dragging);
  }

  /// Dropped on "Vorige/Nächste Woche": same weekday and Meal in the week now
  /// shown, or in the neighbouring one if the week hasn't flipped yet.
  Future<void> _dropOnWeek(PlanEntry entry, int direction) async {
    final weekStart = context.read<SettingsController>().weekStart;
    final entryWeek = weekStartOf(entry.day, weekStart);
    var target = _weekOf(_page);
    if (target == entryWeek) target = addDays(target, 7 * direction);
    final day = addDays(target, (entry.day.weekday - weekStart) % 7);
    final page = _origin + target.difference(_thisWeek).inDays ~/ 7;
    await context.read<PlanRepository>().moveEntry(entry.id, day, entry.mealId);
    _goTo(page);
  }

  Future<void> _remove(PlanEntry entry) async {
    final recipes = context.read<RecipeListProvider>().allRecipes;
    final name = recipes.where((r) => r.id == entry.recipeId).firstOrNull?.name ?? entry.note ?? '';
    await removeEntryWithUndo(context, entry, name);
  }

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context);
    final c = CookItColors.of(context);
    context.watch<SettingsController>();
    final today = dayOf(DateTime.now());
    final topInset = MediaQuery.paddingOf(context).top;
    final bottomInset = MediaQuery.paddingOf(context).bottom;
    final shown = _weekOf(_page);

    return Listener(
      onPointerUp: (_) => _setDragging(false),
      onPointerCancel: (_) => _setDragging(false),
      // No Scaffold of its own: HomeView's is the one the SnackBars appear in.
      child: ColoredBox(
        color: c.background,
        child: Stack(
          children: [
            const Positioned.fill(child: ParallaxEdgePattern()),
            Column(
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: [
                Padding(
                  padding: EdgeInsets.fromLTRB(20, topInset + 16, 20, 8),
                  child: Row(
                    children: [
                      Expanded(
                        child: Text(
                          l10n.weekPlanTitle,
                          style: TextStyle(
                            fontFamily: 'Nunito',
                            fontWeight: FontWeight.w900,
                            fontSize: 32,
                            color: c.ink,
                          ),
                        ),
                      ),
                      FilledButton.tonalIcon(
                        onPressed: () => _goTo(_origin),
                        icon: const Icon(Icons.today_rounded, size: 18),
                        label: Text(l10n.jumpToToday),
                      ),
                    ],
                  ),
                ),
                const Padding(padding: EdgeInsets.symmetric(horizontal: 16), child: TodayBanner()),
                SizedBox(
                  height: 60,
                  child: _dragging
                      ? Padding(
                          padding: const EdgeInsets.fromLTRB(16, 8, 16, 8),
                          child: Row(
                            children: [
                              Expanded(
                                child: _WeekDropZone(
                                  label: l10n.previousWeek,
                                  icon: Icons.chevron_left_rounded,
                                  onFlip: () => _goTo(_page - 1),
                                  onDrop: (entry) => _dropOnWeek(entry, -1),
                                ),
                              ),
                              const SizedBox(width: 8),
                              Expanded(
                                child: _WeekDropZone(
                                  label: l10n.nextWeek,
                                  icon: Icons.chevron_right_rounded,
                                  iconAfter: true,
                                  onFlip: () => _goTo(_page + 1),
                                  onDrop: (entry) => _dropOnWeek(entry, 1),
                                ),
                              ),
                            ],
                          ),
                        )
                      : _WeekBar(
                          start: shown,
                          weeksAway: _page - _origin,
                          past: addDays(shown, 6).isBefore(today),
                          onPrevious: () => _goTo(_page - 1),
                          onNext: () => _goTo(_page + 1),
                        ),
                ),
                Expanded(
                  child: PageView.builder(
                    controller: _pages,
                    onPageChanged: (page) => setState(() => _page = page),
                    itemBuilder: (context, page) => SingleChildScrollView(
                      padding: EdgeInsets.fromLTRB(12, 0, 12, 32 + bottomInset + CookItNavBar.height),
                      child: PlanGrid(weekStart: _weekOf(page), today: today, onDragStarted: () => _setDragging(true)),
                    ),
                  ),
                ),
              ],
            ),
            if (_dragging)
              Positioned(
                left: 16,
                right: 16,
                bottom: 16 + bottomInset,
                height: CookItNavBar.height,
                child: DragTarget<PlanEntry>(
                  onAcceptWithDetails: (d) => _remove(d.data),
                  builder: (context, candidates, _) => Container(
                    alignment: Alignment.center,
                    decoration: BoxDecoration(
                      color: candidates.isEmpty ? c.tiles[2] : const Color(0xFFF4C4AE),
                      borderRadius: BorderRadius.circular(CookItNavBar.height / 2),
                      border: Border.all(color: const Color(0xFFC0563A), width: 2),
                    ),
                    padding: const EdgeInsets.symmetric(horizontal: 16),
                    child: FittedBox(
                      fit: BoxFit.scaleDown,
                      child: Row(
                        mainAxisSize: MainAxisSize.min,
                        children: [
                          const Icon(Icons.delete_outline_rounded, color: Color(0xFF8A2E17)),
                          const SizedBox(width: 8),
                          Text(
                            l10n.dropToRemove,
                            style: const TextStyle(
                              fontFamily: 'Nunito',
                              fontWeight: FontWeight.w900,
                              fontSize: 15,
                              color: Color(0xFF8A2E17),
                            ),
                          ),
                        ],
                      ),
                    ),
                  ),
                ),
              ),
          ],
        ),
      ),
    );
  }
}

class _WeekBar extends StatelessWidget {
  const _WeekBar({
    required this.start,
    required this.weeksAway,
    required this.past,
    required this.onPrevious,
    required this.onNext,
  });

  final DateTime start;
  final int weeksAway;
  final bool past;
  final VoidCallback onPrevious;
  final VoidCallback onNext;

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context);
    final c = CookItColors.of(context);
    final title = switch (weeksAway) {
      0 => l10n.thisWeek,
      1 => l10n.nextWeek,
      -1 => l10n.lastWeek,
      _ => l10n.calendarWeek(calendarWeek(start)),
    };
    final round = IconButton.styleFrom(
      backgroundColor: c.surface,
      foregroundColor: c.green,
      fixedSize: const Size(40, 40),
    );
    return Padding(
      padding: const EdgeInsets.fromLTRB(4, 0, 16, 0),
      child: Row(
        children: [
          // ‹ title › take what the buttons leave, the title shortening only if it must.
          Expanded(
            child: Row(
              children: [
                IconButton(
                  tooltip: l10n.previousWeek,
                  onPressed: onPrevious,
                  icon: Icon(Icons.chevron_left_rounded, color: c.green),
                ),
                Flexible(
                  child: Column(
                    mainAxisSize: MainAxisSize.min,
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      Text(
                        title,
                        maxLines: 1,
                        overflow: TextOverflow.ellipsis,
                        style: TextStyle(
                          fontFamily: 'Nunito',
                          fontWeight: FontWeight.w900,
                          fontSize: 17,
                          color: c.green,
                        ),
                      ),
                      Text(
                        dayRange(start, addDays(start, 6)),
                        maxLines: 1,
                        overflow: TextOverflow.ellipsis,
                        style: TextStyle(fontWeight: FontWeight.w700, fontSize: 12, color: c.inkMuted),
                      ),
                    ],
                  ),
                ),
                IconButton(
                  tooltip: l10n.nextWeek,
                  onPressed: onNext,
                  icon: Icon(Icons.chevron_right_rounded, color: c.green),
                ),
              ],
            ),
          ),
          IconButton(
            tooltip: l10n.shareMenu,
            onPressed: () => showWeekShareMenu(context, start),
            style: round,
            icon: const Icon(Icons.share_rounded, size: 20),
          ),
          if (!past) ...[
            const SizedBox(width: 6),
            IconButton(
              tooltip: l10n.fillWeek,
              onPressed: () => showFillWeekSheet(context, start),
              style: round,
              icon: const Icon(Icons.casino_outlined, size: 20),
            ),
          ],
        ],
      ),
    );
  }
}

/// "Vorige Woche" / "Nächste Woche" while dragging: holding an entry over it
/// flips the week (again every moment it stays there); dropping it there moves it.
class _WeekDropZone extends StatefulWidget {
  const _WeekDropZone({
    required this.label,
    required this.icon,
    required this.onFlip,
    required this.onDrop,
    this.iconAfter = false,
  });

  final String label;
  final IconData icon;
  final bool iconAfter;
  final VoidCallback onFlip;
  final ValueChanged<PlanEntry> onDrop;

  @override
  State<_WeekDropZone> createState() => _WeekDropZoneState();
}

class _WeekDropZoneState extends State<_WeekDropZone> {
  Timer? _flipping;

  void _stop() {
    _flipping?.cancel();
    _flipping = null;
  }

  @override
  void dispose() {
    _stop();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final c = CookItColors.of(context);
    return DragTarget<PlanEntry>(
      onWillAcceptWithDetails: (_) {
        _flipping ??= Timer.periodic(const Duration(milliseconds: 800), (_) => widget.onFlip());
        return true;
      },
      onLeave: (_) => _stop(),
      onAcceptWithDetails: (d) {
        _stop();
        widget.onDrop(d.data);
      },
      builder: (context, candidates, _) {
        final icon = Icon(widget.icon, size: 20, color: c.green);
        return Container(
          alignment: Alignment.center,
          decoration: BoxDecoration(
            color: candidates.isEmpty ? c.surface : c.navBar,
            borderRadius: BorderRadius.circular(16),
            border: Border.all(color: c.brand, width: 2),
          ),
          padding: const EdgeInsets.symmetric(horizontal: 6),
          child: FittedBox(
            fit: BoxFit.scaleDown,
            child: Row(
              mainAxisSize: MainAxisSize.min,
              children: [
                if (!widget.iconAfter) icon,
                Text(
                  widget.label,
                  style: TextStyle(fontFamily: 'Nunito', fontWeight: FontWeight.w900, fontSize: 14, color: c.green),
                ),
                if (widget.iconAfter) icon,
              ],
            ),
          ),
        );
      },
    );
  }
}