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

import '../../../../core/constants/enums.dart';
import '../../../../core/constants/route_constants.dart';
import '../../../../core/errors/failure.dart';
import '../../../../core/utils/formatters.dart';
import '../../../../shared/models/grn_model.dart';
import '../../../../shared/models/user_management_models.dart';
import '../../../../shared/providers/permissions_provider.dart';
import '../../../../shared/utils/file_download_helper.dart';
import '../../../../shared/widgets/app_text_field.dart';
import '../../../../shared/widgets/app_loading_view.dart';
import '../../../../shared/widgets/detail_overview_widgets.dart';
import '../../../../shared/widgets/error_view.dart';
import '../providers/grn_lookups_provider.dart';
import '../providers/grn_provider.dart';
import '../widgets/grn_attachments_card.dart';
import '../widgets/grn_line_items_editor.dart';
import '../widgets/grn_status_chip.dart';
import '../../../../shared/widgets/api_feedback.dart';
import '../../../../shared/widgets/app_toast.dart';

class GrnDetailScreen extends ConsumerStatefulWidget {
  const GrnDetailScreen({super.key, required this.grnId});

  final String grnId;

  @override
  ConsumerState<GrnDetailScreen> createState() => _GrnDetailScreenState();
}

class _GrnDetailScreenState extends ConsumerState<GrnDetailScreen> {
  bool _isWorking = false;
  bool _isDownloadingPdf = false;
  bool _requestedFreshLoad = false;

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    if (_requestedFreshLoad) return;
    _requestedFreshLoad = true;
    // Always hit GET /grn/{id} when opening view.
    ref.invalidate(grnDetailProvider(widget.grnId));
  }

  @override
  void didUpdateWidget(covariant GrnDetailScreen oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (oldWidget.grnId != widget.grnId) {
      ref.invalidate(grnDetailProvider(widget.grnId));
    }
  }

  @override
  Widget build(BuildContext context) {
    final detailAsync = ref.watch(grnDetailProvider(widget.grnId));
    final lookupsAsync = ref.watch(grnLookupsProvider);
    final canEdit = ref.can('grn', PermissionAction.update);
    final canDelete = ref.can('grn', PermissionAction.delete);
    final canExport = ref.can('grn', PermissionAction.export);

    return Scaffold(
      backgroundColor: Theme.of(context).colorScheme.surface,
      body: detailAsync.when(
        loading: () => const AppLoadingView(message: 'Loading Purchase Receipt...'),
        error: (e, _) => ErrorView.fromFailure(
          e is Failure ? e : Failure.unknown(message: e.toString()),
          onRetry: () => ref.invalidate(grnDetailProvider(widget.grnId)),
        ),
        data: (grn) {
          final lookups = lookupsAsync.asData?.value;
          return SingleChildScrollView(
            padding: const EdgeInsets.fromLTRB(16, 16, 16, 32),
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: [
                    _DetailHeader(
                      grn: grn,
                      isWorking: _isWorking,
                      isDownloadingPdf: _isDownloadingPdf,
                      canEdit: canEdit,
                      canExport: canExport,
                      onBack: () => context.go(RouteConstants.grn),
                      onPdf: () => _downloadPdf(grn),
                      onEdit: () => context.push(
                        '${RouteConstants.grn}/${grn.id}/edit',
                      ),
                      onCancel: () => _cancel(grn),
                    ),
                    if (grn.cancellationReason != null &&
                        grn.cancellationReason!.isNotEmpty) ...[
                      const SizedBox(height: 12),
                      _CancellationBanner(reason: grn.cancellationReason!),
                    ],
                    const SizedBox(height: 16),
                    _ReceiptDetailsCard(grn: grn, lookups: lookups),
                    const SizedBox(height: 16),
                    _LineItemsCard(grn: grn),
                    const SizedBox(height: 16),
                    GrnAttachmentsCard(
                      grn: grn,
                      canUpload: canEdit,
                      canDelete: canDelete,
                    ),
                    if (grn.remarks?.trim().isNotEmpty == true) ...[
                      const SizedBox(height: 16),
                      _SectionCard(
                        title: 'REMARKS',
                        child: Text(
                          grn.remarks!.trim(),
                          style: Theme.of(context).textTheme.bodyLarge,
                        ),
                      ),
                    ],
                    const SizedBox(height: 20),
                    _DetailFooter(grn: grn),
                  ],
            ),
          );
        },
      ),
    );
  }

  Future<void> _runWorkflow(
    Future<void> Function() action,
    String success,
  ) async {
    setState(() => _isWorking = true);
    try {
      await action();
      if (mounted) {
        showAppToastFromSnackBar(context, SnackBar(content: Text(success)));
      }
    } catch (e) {
      if (mounted) {
        showAppToastFromSnackBar(
          context,
          SnackBar(content: Text(errorDisplayMessage(e))),
        );
      }
    } finally {
      if (mounted) setState(() => _isWorking = false);
    }
  }

  Future<void> _cancel(GrnModel grn) async {
    final reasonController = TextEditingController();
    final confirmed = await showDialog<bool>(
      context: context,
      builder: (context) => AlertDialog(
        title: const Text('Cancel Purchase Receipt'),
        content: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Text(
              'Cancel ${grn.grnNumber ?? grn.id}? This will reverse PO receipts.',
            ),
            const SizedBox(height: 16),
            AppTextField(
              label: 'Cancellation Reason *',
              controller: reasonController,
              maxLines: 3,
            ),
          ],
        ),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(context, false),
            child: const Text('Close'),
          ),
          FilledButton(
            onPressed: () {
              if (reasonController.text.trim().isEmpty) return;
              Navigator.pop(context, true);
            },
            child: const Text('Cancel Purchase Receipt'),
          ),
        ],
      ),
    );
    if (confirmed != true || !mounted) return;

    await _runWorkflow(
      () => ref.read(grnDetailProvider(widget.grnId).notifier).cancel(
            cancellationReason: reasonController.text.trim(),
          ),
      'Purchase Receipt cancelled',
    );
    reasonController.dispose();
  }

  Future<void> _downloadPdf(GrnModel grn) async {
    setState(() => _isDownloadingPdf = true);
    try {
      final bytes = await ref
          .read(grnDetailProvider(widget.grnId).notifier)
          .downloadPdf();
      await downloadFile(
        bytes: bytes,
        fileName: '${grn.grnNumber ?? 'PurchaseReceipt-${grn.id}'}.pdf',
      );
      if (mounted) {
        showAppToastFromSnackBar(context, const SnackBar(content: Text('PDF downloaded')));
      }
    } catch (e) {
      if (mounted) {
        showAppToastFromSnackBar(
          context,
          SnackBar(content: Text(errorDisplayMessage(e))),
        );
      }
    } finally {
      if (mounted) setState(() => _isDownloadingPdf = false);
    }
  }
}

String _userLabel(List<FilterOptionModel>? users, int? userId) {
  if (userId == null || users == null) return '—';
  for (final user in users) {
    if (int.tryParse(user.id) == userId) return user.name;
  }
  return 'User #$userId';
}

String _displayOrDash(String? value) {
  final trimmed = value?.trim();
  if (trimmed == null || trimmed.isEmpty) return '—';
  return trimmed;
}

class _DetailHeader extends StatelessWidget {
  const _DetailHeader({
    required this.grn,
    required this.isWorking,
    required this.isDownloadingPdf,
    required this.canEdit,
    required this.canExport,
    required this.onBack,
    required this.onPdf,
    required this.onEdit,
    required this.onCancel,
  });

  final GrnModel grn;
  final bool isWorking;
  final bool isDownloadingPdf;
  final bool canEdit;
  final bool canExport;
  final VoidCallback onBack;
  final VoidCallback onPdf;
  final VoidCallback onEdit;
  final VoidCallback onCancel;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final subtitleParts = [
      if (grn.poNumber?.trim().isNotEmpty == true) 'PO ${grn.poNumber!.trim()}',
      if (grn.vendorName?.trim().isNotEmpty == true) grn.vendorName!.trim(),
      if (grn.locationName?.trim().isNotEmpty == true)
        grn.locationName!.trim(),
    ];

    final actions = Wrap(
      spacing: 8,
      runSpacing: 8,
      alignment: WrapAlignment.end,
      crossAxisAlignment: WrapCrossAlignment.center,
      children: [
        if (canExport)
          _HeaderActionButton(
            label: 'PDF',
            icon: Icons.description_outlined,
            isLoading: isDownloadingPdf,
            onPressed: (isWorking || isDownloadingPdf) ? null : onPdf,
          ),
        if (canEdit && grn.canEdit)
          _HeaderActionButton(
            label: 'Edit',
            icon: Icons.edit_outlined,
            onPressed: isWorking ? null : onEdit,
          ),
        if (canEdit && grn.canCancel)
          _HeaderActionButton(
            label: 'Cancel',
            icon: Icons.block_outlined,
            destructive: true,
            onPressed: isWorking ? null : onCancel,
          ),
      ],
    );

    final titleBlock = Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        Row(
          children: [
            Flexible(
              child: Text(
                grn.grnNumber ?? 'Purchase Receipt #${grn.id}',
                style: theme.textTheme.headlineSmall,
                overflow: TextOverflow.ellipsis,
              ),
            ),
            const SizedBox(width: 10),
            GrnStatusChip(status: grn.status, compact: true),
          ],
        ),
        if (subtitleParts.isNotEmpty) ...[
          const SizedBox(height: 4),
          Text(
            subtitleParts.join(' · '),
            style: theme.textTheme.bodyMedium?.copyWith(
              color: theme.colorScheme.onSurfaceVariant,
            ),
          ),
        ],
      ],
    );

    return LayoutBuilder(
      builder: (context, constraints) {
        final stack = constraints.maxWidth < 800;
        if (stack) {
          return Column(
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: [
              Row(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  IconButton(
                    tooltip: 'Back',
                    onPressed: onBack,
                    icon: const Icon(Icons.arrow_back),
                  ),
                  const SizedBox(width: 4),
                  Expanded(child: titleBlock),
                ],
              ),
              const SizedBox(height: 12),
              actions,
            ],
          );
        }

        return Row(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            IconButton(
              tooltip: 'Back',
              onPressed: onBack,
              icon: const Icon(Icons.arrow_back),
            ),
            const SizedBox(width: 4),
            Expanded(child: titleBlock),
            const SizedBox(width: 12),
            actions,
          ],
        );
      },
    );
  }
}

class _HeaderActionButton extends StatelessWidget {
  const _HeaderActionButton({
    required this.label,
    required this.icon,
    required this.onPressed,
    this.isLoading = false,
    this.destructive = false,
  });

  final String label;
  final IconData icon;
  final VoidCallback? onPressed;
  final bool isLoading;
  final bool destructive;

  static const double _height = 40;
  static const double _radius = 8;
  static const EdgeInsets _padding =
      EdgeInsets.symmetric(horizontal: 14, vertical: 0);

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final error = theme.colorScheme.error;

    final style = ButtonStyle(
      minimumSize: const WidgetStatePropertyAll(Size(0, _height)),
      fixedSize: const WidgetStatePropertyAll(Size.fromHeight(_height)),
      padding: const WidgetStatePropertyAll(_padding),
      shape: WidgetStatePropertyAll(
        RoundedRectangleBorder(borderRadius: BorderRadius.circular(_radius)),
      ),
      visualDensity: VisualDensity.standard,
      tapTargetSize: MaterialTapTargetSize.shrinkWrap,
    );

    final child = Row(
      mainAxisSize: MainAxisSize.min,
      children: [
        if (isLoading)
          SizedBox(
            width: 18,
            height: 18,
            child: CircularProgressIndicator(
              strokeWidth: 2,
              color: destructive ? error : null,
            ),
          )
        else
          Icon(icon, size: 18),
        const SizedBox(width: 8),
        Text(label),
      ],
    );

    if (destructive) {
      return OutlinedButton(
        onPressed: onPressed,
        style: style.copyWith(
          foregroundColor: WidgetStatePropertyAll(error),
          side: WidgetStatePropertyAll(BorderSide(color: error)),
        ),
        child: child,
      );
    }

    return OutlinedButton(
      onPressed: onPressed,
      style: style,
      child: child,
    );
  }
}

class _CancellationBanner extends StatelessWidget {
  const _CancellationBanner({required this.reason});

  final String reason;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Container(
      width: double.infinity,
      padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
      decoration: BoxDecoration(
        color: theme.colorScheme.errorContainer.withValues(alpha: 0.35),
        borderRadius: BorderRadius.circular(8),
        border: Border.all(
          color: theme.colorScheme.error.withValues(alpha: 0.35),
        ),
      ),
      child: Row(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Icon(Icons.info_outline, color: theme.colorScheme.error, size: 20),
          const SizedBox(width: 10),
          Expanded(
            child: Text(
              'Cancellation reason: $reason',
              style: theme.textTheme.bodyMedium?.copyWith(
                color: theme.colorScheme.error,
              ),
            ),
          ),
        ],
      ),
    );
  }
}

class _SectionCard extends StatelessWidget {
  const _SectionCard({
    required this.title,
    required this.child,
  });

  final String title;
  final Widget child;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Container(
      width: double.infinity,
      padding: const EdgeInsets.all(20),
      decoration: BoxDecoration(
        color: theme.colorScheme.surface,
        borderRadius: BorderRadius.circular(12),
        border: Border.all(
          color: theme.colorScheme.outline.withValues(alpha: 0.2),
        ),
      ),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          Text(
            title,
            style: theme.textTheme.labelMedium?.copyWith(
              color: theme.colorScheme.onSurfaceVariant,
              fontWeight: FontWeight.w600,
              letterSpacing: 0.8,
            ),
          ),
          const SizedBox(height: 16),
          child,
        ],
      ),
    );
  }
}

class _ReceiptDetailsCard extends StatelessWidget {
  const _ReceiptDetailsCard({
    required this.grn,
    required this.lookups,
  });

  final GrnModel grn;
  final GrnLookups? lookups;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final scheme = theme.colorScheme;
    final locationDisplay = _displayOrDash(
      [
        if (grn.locationName?.trim().isNotEmpty == true)
          grn.locationName!.trim(),
        if (grn.locationType?.trim().isNotEmpty == true)
          '(${grn.locationType!.trim()})',
      ].join(' ').trim(),
    );

    return _SectionCard(
      title: 'RECEIPT DETAILS',
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          DetailOverviewSection(
            title: 'Summary',
            child: DetailSummaryStrip(
              metrics: [
                DetailSummaryMetric(
                  icon: Icons.flag_outlined,
                  label: 'Status',
                  accent: scheme.secondary,
                  child: GrnStatusChip(status: grn.status, compact: true),
                ),
                DetailSummaryMetric(
                  icon: Icons.calendar_today_outlined,
                  label: 'Purchase Receipt Date',
                  child: Text(
                    DateFormatter.displayDate(grn.grnDate),
                    style: theme.textTheme.titleMedium?.copyWith(
                      fontWeight: FontWeight.w700,
                    ),
                  ),
                ),
                DetailSummaryMetric(
                  icon: Icons.receipt_long_outlined,
                  label: 'PO Number',
                  child: Text(
                    _displayOrDash(grn.poNumber),
                    style: theme.textTheme.titleMedium?.copyWith(
                      fontWeight: FontWeight.w700,
                    ),
                  ),
                ),
                DetailSummaryMetric(
                  icon: Icons.payments_outlined,
                  label: 'Invoice Amount',
                  accent: scheme.primary,
                  child: Text(
                    grn.vendorInvoiceAmount != null
                        ? CurrencyFormatter.format(grn.vendorInvoiceAmount!)
                        : '—',
                    style: theme.textTheme.titleMedium?.copyWith(
                      fontWeight: FontWeight.w800,
                    ),
                  ),
                ),
              ],
            ),
          ),
          DetailOverviewSection(
            title: 'Receipt',
            child: DetailInfoGrid(
              items: [
                DetailInfoItem('Vendor', _displayOrDash(grn.vendorName)),
                DetailInfoItem('Location', locationDisplay),
                DetailInfoItem(
                  'Vendor Invoice No',
                  _displayOrDash(grn.vendorInvoiceNo),
                ),
                DetailInfoItem(
                  'Vendor Invoice Date',
                  DateFormatter.displayDate(grn.vendorInvoiceDate),
                ),
                DetailInfoItem(
                  'Received By',
                  _userLabel(lookups?.users, grn.receivedBy),
                ),
                DetailInfoItem(
                  'Quality Checked By',
                  _userLabel(lookups?.users, grn.qualityCheckedBy),
                ),
              ],
            ),
          ),
          DetailOverviewSection(
            title: 'Transport',
            showDivider: false,
            child: DetailInfoGrid(
              items: [
                DetailInfoItem('Vehicle No', _displayOrDash(grn.vehicleNo)),
                DetailInfoItem('LR No', _displayOrDash(grn.lrNo)),
                DetailInfoItem(
                  'LR Date',
                  DateFormatter.displayDate(grn.lrDate),
                ),
              ],
            ),
          ),
        ],
      ),
    );
  }
}

class _LineItemsCard extends StatelessWidget {
  const _LineItemsCard({required this.grn});

  final GrnModel grn;

  @override
  Widget build(BuildContext context) {
    return _SectionCard(
      title: 'LINE ITEMS · ${grn.items.length}',
      child: GrnItemsTable(items: grn.items),
    );
  }
}

class _DetailFooter extends StatelessWidget {
  const _DetailFooter({required this.grn});

  final GrnModel grn;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final parts = <String>[
      if (grn.createdAt != null)
        'Created ${DateFormatter.displayDateTime(grn.createdAt)}',
      if (grn.updatedAt != null)
        'Updated ${DateFormatter.displayDateTime(grn.updatedAt)}',
    ];

    if (parts.isEmpty) return const SizedBox.shrink();

    return Text(
      parts.join(' · '),
      style: theme.textTheme.bodySmall?.copyWith(
        color: theme.colorScheme.onSurfaceVariant,
      ),
    );
  }
}