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

import '../../../app/providers.dart';
import '../../../core/theme/app_colors.dart';
import '../../../core/theme/app_dimens.dart';
import '../../../core/utils/formatters.dart';
import '../../../data/sync/sync_engine.dart';
import '../../sync/providers/sync_controller.dart';
import '../widgets/module_widgets.dart';

/// What this terminal has traded, and what has reached the server.
///
/// Read-only. Uploading is the sync engine's job — it pushes after every sale
/// and retries on its own — so this page reports rather than drives. The
/// warning banner at the top is the exception: a bill the engine has given up
/// on is the one thing here that needs a person to notice it.
class EventsView extends ConsumerWidget {
  const EventsView({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final report = ref.watch(todayReportProvider);
    final pending = ref.watch(unsyncedCountProvider).value ?? 0;
    final rows = ref.watch(orderSyncRowsProvider).value ?? const [];

    // The engine may not have emitted yet on a cold start, so fall back to
    // its current value rather than showing nothing. This is the same state
    // that drives the header pill — it is what actually knows whether the
    // automatic push right after a sale succeeded, not just what the manual
    // "Sync" button on this page last did.
    final engine = ref.watch(syncEngineStateProvider).value ??
        ref.watch(syncEngineProvider).state;

    final r = report.value;

    return ModulePage(
      children: [
        if (engine.lastError != null && pending > 0)
          _EngineWarningBanner(engine: engine),

        Wrap(
          spacing: AppSpacing.lg,
          runSpacing: AppSpacing.lg,
          children: [
            StatTile(
              label: 'Bills Today',
              value: '${r?.billCount ?? 0}',
              icon: Icons.receipt_long_rounded,
              caption: r?.firstBillAt == null
                  ? 'no sales yet'
                  : '${Formatters.time(r!.firstBillAt!)} – '
                      '${Formatters.time(r.lastBillAt!)}',
            ),
            StatTile(
              label: 'Items Sold',
              value: (r?.itemCount ?? 0).toStringAsFixed(0),
              icon: Icons.shopping_basket_rounded,
              color: AppColors.info,
              caption: 'units across all bills',
            ),
            StatTile(
              label: "Today's Sales",
              value: Formatters.money(r?.grossSales ?? 0),
              icon: Icons.payments_rounded,
              color: AppColors.success,
              caption: 'gross takings',
            ),
            StatTile(
              label: 'Awaiting Sync',
              value: '$pending',
              icon: Icons.cloud_off_rounded,
              color: pending > 0 ? AppColors.warning : AppColors.success,
              caption: pending > 0
                  ? 'held on this terminal'
                  : 'everything uploaded',
            ),
          ],
        ),
        const SizedBox(height: AppSpacing.lg),

        PanelCard(
          title: 'Orders',
          subtitle: '${rows.length} stored \u00b7 $pending awaiting upload',
          child: ResponsiveTable(
            columns: const [
              TableCol('Invoice', flex: 3),
              TableCol('Date & time', flex: 3, priority: 1),
              TableCol('Items', flex: 1, numeric: true, priority: 2),
              TableCol('Total', flex: 2, numeric: true),
              TableCol('Sync', flex: 2, numeric: true),
            ],
            rows: rows
                .map((o) => [
                      Cell(o.invoiceNumber, bold: true, mono: true),
                      // Date sits with the time because this table outlives the
                      // day it was rung on — bills stay on the terminal until
                      // they are purged, so a bare clock time is ambiguous the
                      // moment the shop opens again.
                      Cell(
                        '${Formatters.date(o.createdAt)} \u00b7 '
                        '${Formatters.time(o.createdAt)}',
                        color: AppColors.textTertiary,
                      ),
                      Cell(_units(o.itemCount), mono: true),
                      Cell(Formatters.money(o.total), mono: true, bold: true),
                      TagChip(
                        o.isSynced ? 'Synced' : 'Pending',
                        color:
                            o.isSynced ? AppColors.success : AppColors.warning,
                      ),
                    ],)
                .toList(),
          ),
        ),
      ],
    );
  }

  /// Units on a bill. Whole where they are whole — loose goods are sold by
  /// weight, so "2.5" is a real answer here and rounding it would be a lie.
  static String _units(double count) =>
      count % 1 == 0 ? count.toStringAsFixed(0) : count.toStringAsFixed(2);
}

/// Flags a bill that could not reach the server on its own.
///
/// Sits above everything else on the page because a bill stuck here is the
/// one thing on this screen that needs a person to notice it, rather than
/// just waiting for the next background retry.
class _EngineWarningBanner extends StatelessWidget {
  const _EngineWarningBanner({required this.engine});

  final SyncEngineState engine;

  @override
  Widget build(BuildContext context) {
    final halted = engine.isHalted;
    final color = halted ? AppColors.danger : AppColors.warning;
    final surface = halted ? AppColors.dangerSurface : AppColors.warningSurface;

    final retry = engine.nextAttemptAt;
    final retryNote = halted
        ? 'Retrying will not help until this is fixed.'
        : retry == null
            ? 'It will retry automatically.'
            : 'It will retry automatically at ${Formatters.time(retry)}.';

    return Container(
      margin: const EdgeInsets.only(bottom: AppSpacing.lg),
      padding: const EdgeInsets.all(AppSpacing.md),
      decoration: BoxDecoration(color: surface, borderRadius: AppRadius.brLg),
      child: Row(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Icon(Icons.wifi_off_rounded, size: 20, color: color),
          const SizedBox(width: AppSpacing.md),
          Expanded(
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Text(
                  halted
                      ? 'Sync halted — ${engine.pending} bill(s) not sent'
                      : "Couldn't reach the server — "
                          '${engine.pending} bill(s) not sent',
                  style: TextStyle(
                    fontSize: 14,
                    fontWeight: FontWeight.w700,
                    color: color,
                  ),
                ),
                const SizedBox(height: 2),
                Text(
                  engine.lastError ?? 'The last upload attempt failed.',
                  style: TextStyle(
                    fontSize: 12.5,
                    color: color,
                    height: 1.45,
                  ),
                ),
                const SizedBox(height: 4),
                Text(
                  '$retryNote Every bill is still safe on this terminal — '
                  'nothing is lost while it waits.',
                  style: const TextStyle(
                    fontSize: 12,
                    color: AppColors.textSecondary,
                    height: 1.45,
                  ),
                ),
              ],
            ),
          ),
        ],
      ),
    );
  }
}