Google Sheets as a REST API in Flutter (Dart)

# pubspec.yaml
dependencies:
  flutter:
    sdk: flutter
  http: ^1.2.1

// lib/models/sheet_response.dart
class SheetMeta {
  final int total;
  final int limit;
  final int offset;
 
  const SheetMeta({
    required this.total,
    required this.limit,
    required this.offset,
  });
 
  factory SheetMeta.fromJson(Map<String, dynamic> json) => SheetMeta(
        total: json['total'] as int,
        limit: json['limit'] as int,
        offset: json['offset'] as int,
      );
}
 
class SheetResponse<T> {
  final List<T> data;
  final SheetMeta meta;
 
  const SheetResponse({required this.data, required this.meta});
}
 
class Product {
  final String name;
  final String price;
  final String category;
 
  const Product({
    required this.name,
    required this.price,
    required this.category,
  });
 
  factory Product.fromJson(Map<String, dynamic> json) => Product(
        name: json['name'] as String? ?? '',
        price: json['price'] as String? ?? '',
        category: json['category'] as String? ?? '',
      );
}

// lib/services/sheets_service.dart
import 'dart:convert';
import 'package:http/http.dart' as http;
import '../models/sheet_response.dart';
 
const _base = 'https://sheetsapi.gkit.mreshank.com/api/spreadsheets';
 
class SheetsService {
  final String userKey;
  final String? apiKey;
 
  const SheetsService({required this.userKey, this.apiKey});
 
  Map<String, String> get _headers => {
        if (apiKey != null) 'Authorization': 'Bearer $apiKey',
      };
 
  Future<SheetResponse<T>> query<T>({
    required String sheet,
    required T Function(Map<String, dynamic>) fromJson,
    int limit = 20,
    int offset = 0,
    String? search,
    String? sort,
    String? fields,
  }) async {
    final params = {
      'limit': '$limit',
      'offset': '$offset',
      if (search != null) 'search': search,
      if (sort != null) 'sort': sort,
      if (fields != null) 'fields': fields,
    };
 
    final uri = Uri.https(
      'sheetsapi.gkit.mreshank.com',
      '/api/spreadsheets/$userKey/$sheet',
      params,
    );
 
    final response = await http.get(uri, headers: _headers);
 
    if (response.statusCode != 200) {
      throw Exception('SheetsAPI ${response.statusCode}: ${response.body}');
    }
 
    final json = jsonDecode(response.body) as Map<String, dynamic>;
    final rawData = json['data'] as List<dynamic>;
 
    return SheetResponse<T>(
      data: rawData
          .map((item) => fromJson(item as Map<String, dynamic>))
          .toList(),
      meta: SheetMeta.fromJson(json['meta'] as Map<String, dynamic>),
    );
  }
}

// lib/screens/products_screen.dart
import 'package:flutter/material.dart';
import '../models/sheet_response.dart';
import '../services/sheets_service.dart';
 
final _service = SheetsService(
  userKey: 'YOUR_USER_KEY',
  apiKey: 'sk_your_api_key_here',
);
 
class ProductsScreen extends StatefulWidget {
  const ProductsScreen({super.key});
 
  @override
  State<ProductsScreen> createState() => _ProductsScreenState();
}
 
class _ProductsScreenState extends State<ProductsScreen> {
  late Future<SheetResponse<Product>> _future;
 
  @override
  void initState() {
    super.initState();
    _load();
  }
 
  void _load({String? search}) {
    _future = _service.query<Product>(
      sheet: 'Products',
      fromJson: Product.fromJson,
      limit: 50,
      sort: 'name',
      search: search,
    );
  }
 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Products')),
      body: FutureBuilder<SheetResponse<Product>>(
        future: _future,
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.waiting) {
            return const Center(child: CircularProgressIndicator());
          }
          if (snapshot.hasError) {
            return Center(child: Text('Error: ${snapshot.error}'));
          }
 
          final resp = snapshot.data!;
          return Column(
            children: [
              Padding(
                padding: const EdgeInsets.all(8),
                child: Text('${resp.meta.total} products'),
              ),
              Expanded(
                child: ListView.builder(
                  itemCount: resp.data.length,
                  itemBuilder: (context, i) {
                    final p = resp.data[i];
                    return ListTile(
                      title: Text(p.name),
                      subtitle: Text(p.category),
                      trailing: Text(p.price),
                    );
                  },
                ),
              ),
            ],
          );
        },
      ),
    );
  }
}

class _ProductsScreenState extends State<ProductsScreen> {
  late Future<SheetResponse<Product>> _future;
  final _searchCtrl = TextEditingController();
 
  @override
  void initState() {
    super.initState();
    _load();
  }
 
  void _load({String? search}) {
    setState(() {
      _future = _service.query<Product>(
        sheet: 'Products',
        fromJson: Product.fromJson,
        sort: 'name',
        search: search != null && search.isNotEmpty ? 'name:$search' : null,
      );
    });
  }
 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: TextField(
          controller: _searchCtrl,
          decoration: const InputDecoration(
            hintText: 'Search products…',
            border: InputBorder.none,
          ),
          onChanged: (q) => _load(search: q),
        ),
      ),
      body: FutureBuilder<SheetResponse<Product>>(
        future: _future,
        builder: (context, snapshot) {
          // ... same as before
          return const SizedBox.shrink();
        },
      ),
    );
  }
}

class _PaginatedProductsState extends State<PaginatedProducts> {
  final List<Product> _items = [];
  int _offset = 0;
  bool _loading = false;
  bool _done = false;
 
  @override
  void initState() {
    super.initState();
    _fetchNext();
  }
 
  Future<void> _fetchNext() async {
    if (_loading || _done) return;
    setState(() => _loading = true);
    final resp = await _service.query<Product>(
      sheet: 'Products',
      fromJson: Product.fromJson,
      limit: 30,
      offset: _offset,
      sort: 'name',
    );
    setState(() {
      _items.addAll(resp.data);
      _offset += 30;
      _done = _offset >= resp.meta.total;
      _loading = false;
    });
  }
 
  @override
  Widget build(BuildContext context) {
    return NotificationListener<ScrollEndNotification>(
      onNotification: (n) {
        if (n.metrics.extentAfter < 200) _fetchNext();
        return false;
      },
      child: ListView.builder(
        itemCount: _items.length + (_done ? 0 : 1),
        itemBuilder: (context, i) {
          if (i == _items.length) {
            return const Center(child: CircularProgressIndicator());
          }
          final p = _items[i];
          return ListTile(title: Text(p.name), trailing: Text(p.price));
        },
      ),
    );
  }
}