calorimeter/lib/food_scan/food_fact_lookup.dart

import 'dart:convert';
import 'dart:developer';
import 'dart:io';

class FoodFactLookupClient {
  FoodFactLookupClient();

  static const String url = "https://world.openfoodfacts.org/api/v3/product/";

  String getProductUrl(String ean) {
    return "$url$ean.json";
  }

  Future<FoodFactResponse> retrieveFoodInfo(String ean) async {
    HttpClient client = HttpClient();
    String asString = "";

    try {
      var request = await client.getUrl(Uri.parse(getProductUrl(ean)));

      var response = await request.close();

      if (response.statusCode != HttpStatus.ok) {
        return FoodFactResponse(
            food: null, status: FoodFactResponseStatus.barcodeNotFound);
      }

      asString = await response.transform(utf8.decoder).join();
    } on SocketException {
      return FoodFactResponse(
          food: null,
          status: FoodFactResponseStatus.foodFactServerNotReachable);
    } catch (e) {
      log(e.toString());
    } finally {
      client.close();
    }

    return FoodFactResponse(
        food: FoodFactModel.fromJson(jsonDecode(asString)),
        status: FoodFactResponseStatus.ok);
  }
}

class FoodFactModel {
  final String name;
  final int kcalPer100g;

  FoodFactModel({required this.name, required this.kcalPer100g});

  factory FoodFactModel.fromJson(Map<String, dynamic> json) {
    return FoodFactModel(
        name: json['product']['product_name'],
        kcalPer100g: json['product']['nutriments']['energy-kcal_100g']);
  }
}

enum FoodFactResponseStatus {
  foodFactServerNotReachable,
  barcodeNotFound,
  ok,
}

class FoodFactResponse {
  final FoodFactModel? food;
  final FoodFactResponseStatus status;

  FoodFactResponse({required this.food, required this.status});
}