import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import 'package:intl/intl.dart';
import '../../config/app_config.dart';
import '../../models/document_model.dart';
import '../../main.dart';
import 'pending_documents_provider.dart';
import '../editor/pdf_service.dart';
import '../../core/network/api_client.dart';
import 'pending_document_card.dart';
import 'document_card.dart';
import '../camera/scan_mode_provider.dart';
import 'documents_tab_switcher.dart';
import 'documents_empty_state.dart';
import 'document_sync_merge.dart';

class DocumentsScreen extends ConsumerStatefulWidget {
  const DocumentsScreen({super.key});

  @override
  ConsumerState<DocumentsScreen> createState() => _DocumentsScreenState();
}

class _DocumentsScreenState extends ConsumerState<DocumentsScreen> {
  final _searchController = TextEditingController();
  List<DocumentModel> _allDocuments = [];
  List<DocumentModel> _filteredDocuments = [];
  Set<String> _unsyncedDocIds = {};
  // _selectedTab removed in task 8.1 -- scanModeProvider is the single source
  // of truth for the active tab, shared with CameraDrawer / CameraDrawerModeToggle.
  // Caching it locally (and seeding from the provider in initState) caused mode
  // desync when the camera drawer changed the mode after this screen was open.
  // See docs/api-contract-map.md G11, plans/next-enhancements.md §8.1.

  @override
  void initState() {
    super.initState();
    _loadDocuments();
    _searchController.addListener(_onSearchChanged);
  }

  Future<void> _loadDocuments() async {
    final localStorage = ref.read(localStorageProvider);
    final docs = localStorage.getAllDocuments();

    setState(() {
      _allDocuments = docs;
      _filteredDocuments = docs;
    });

    try {
      final apiClient = ref.read(apiClientProvider);
      final response = await apiClient.client.get(AppConfig.fetchDocumentsEndpoint);
      final List serverData = response.data['data'] ?? [];
      final List<DocumentModel> serverDocs = serverData
          .map((json) => DocumentModel.fromJson(Map<String, dynamic>.from(json)))
          .toList();

      // A document whose editor save PUT failed (syncFailed) still has its
      // corrected version saved locally - don't let the server's stale
      // pre-edit copy silently overwrite it on refresh (see
      // docs/api-contract-map.md G6).
      final unsyncedOverrides = <String, DocumentModel>{
        for (final pending in ref.read(pendingDocumentsProvider))
          if (pending.status == PendingDocumentStatus.syncFailed && pending.document != null)
            pending.document!.id: pending.document!,
      };
      final merged = mergeDocumentsWithUnsyncedOverrides(
        serverDocs: serverDocs,
        unsyncedOverrides: unsyncedOverrides,
      );

      await localStorage.documentBox.clear();
      for (var doc in merged.docs) {
        await localStorage.saveDocument(doc);
      }

      final updatedDocs = localStorage.getAllDocuments();
      if (mounted) {
        setState(() {
          _allDocuments = updatedDocs;
          _filteredDocuments = updatedDocs;
          _unsyncedDocIds = merged.unsyncedIds;
        });
      }
    } catch (e) {
      debugPrint('Offline or failed fetching: $e');
    }
  }

  void _onSearchChanged() {
    final query = _searchController.text.toLowerCase();
    setState(() {
      _filteredDocuments = _allDocuments.where((doc) {
        return doc.noDo.toLowerCase().contains(query) ||
               doc.noPo.toString().contains(query) ||
               doc.noSo.toString().contains(query) ||
               doc.tanggal.toLowerCase().contains(query) ||
               doc.kepadaYth.toLowerCase().contains(query);
      }).toList();
    });
  }

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

  Future<void> _printReceipt(DocumentModel doc) async {
    ScaffoldMessenger.of(context).showSnackBar(
      const SnackBar(content: Text('Membuat PDF...'), duration: Duration(seconds: 1), backgroundColor: AppConfig.secondaryColor),
    );
    await PdfService.generateAndPrintReceipt(doc);
  }

  @override
  Widget build(BuildContext context) {
    final pendingDocs = ref.watch(pendingDocumentsProvider);
    // Single source of truth for the active tab -- shared with CameraDrawer
    // via scanModeProvider (task 8.1, docs/api-contract-map.md G11).
    final selectedTab = ref.watch(scanModeProvider);

    final tabFilteredPendingDocs = pendingDocs.where((doc) {
      final isProduct = doc.scanMode == 'Product';
      if (selectedTab == 'DO') return !isProduct;
      if (selectedTab == 'Product') return isProduct;
      return true;
    }).toList();

    final tabFilteredDocs = _filteredDocuments.where((doc) {
      final isProduct = doc.docType == 'Product';
      if (selectedTab == 'DO') return !isProduct;
      if (selectedTab == 'Product') return isProduct;
      return true;
    }).toList();

    final Map<String, List<DocumentModel>> groupedDocs = {};
    for (var doc in tabFilteredDocs) {
      final date = doc.createdAt;
      final monthYearStr = DateFormat('MMMM yyyy').format(date);
      if (!groupedDocs.containsKey(monthYearStr)) {
        groupedDocs[monthYearStr] = [];
      }
      groupedDocs[monthYearStr]!.add(doc);
    }

    final List<Widget> listItems = [];

    if (tabFilteredPendingDocs.isNotEmpty) {
      listItems.add(
        Padding(
          padding: const EdgeInsets.only(bottom: AppConfig.spaceSmall),
          child: Text('Tertunda & Diproses', style: AppConfig.h3),
        ),
      );
      listItems.addAll(tabFilteredPendingDocs.map((doc) => PendingDocumentCard(
        doc: doc,
        onReload: () { if (mounted) _loadDocuments(); },
      )));
      listItems.add(const SizedBox(height: AppConfig.spaceLarge));
      listItems.add(const Divider());
      listItems.add(const SizedBox(height: AppConfig.spaceLarge));
    }

    if (groupedDocs.isNotEmpty) {
      groupedDocs.forEach((monthYear, docs) {
        listItems.add(
          Padding(
            padding: const EdgeInsets.only(top: AppConfig.spaceLarge, bottom: AppConfig.spaceSmall),
            child: Text(
              monthYear,
              style: AppConfig.bodyMedium.copyWith(
                fontWeight: FontWeight.bold,
                color: AppConfig.textSecondary,
              ),
            ),
          ),
        );
        listItems.addAll(docs.map((doc) => DocumentCard(
          doc: doc,
          onPrint: _printReceipt,
          isUnsynced: _unsyncedDocIds.contains(doc.id),
        )));
      });
    }

    return Scaffold(
      appBar: AppBar(
        title: const Text('Dokumen'),
        leading: IconButton(icon: const Icon(Icons.arrow_back), onPressed: () => context.go('/camera')),
      ),
      body: Column(
        children: [
          Container(
            padding: AppConfig.paddingLarge,
            color: AppConfig.surfaceColor,
            child: TextField(
              controller: _searchController,
              decoration: const InputDecoration(
                hintText: 'Cari berdasarkan No PO, No SO, DO, Tanggal...',
                prefixIcon: Icon(Icons.search),
              ),
            ),
          ),
          DocumentsTabSwitcher(
            selectedTab: selectedTab,
            onTabChanged: (tab) =>
                ref.read(scanModeProvider.notifier).state = tab,
          ),
          Expanded(
            child: (tabFilteredPendingDocs.isEmpty && tabFilteredDocs.isEmpty)
              ? const DocumentsEmptyState()
              : ListView(
                  padding: const EdgeInsets.symmetric(horizontal: AppConfig.spaceLarge),
                  children: listItems,
                ),
          ),
        ],
      ),
    );
  }
}