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Refactor ForexRateAPI integration to load API key from .env file and enhance error handling

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Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>
This commit is contained in:
Hans Kokx
2026-03-19 23:48:26 +01:00
parent a775a20dd2
commit e6c16967f9
8 changed files with 244 additions and 81 deletions
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lib/services/open_exchange_service.dart
+100 -48
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@@ -1,5 +1,7 @@
import 'dart:convert';
import 'dart:async';
import 'package:flutter/foundation.dart';
import 'package:http/http.dart' as http;
import 'package:intl/intl.dart';
@@ -16,79 +18,129 @@ class ForexRateApiService {
final http.Client httpClient;
final String apiKey;
void _log(String message) {
if (kDebugMode) {
debugPrint('[ForexRateApiService] $message');
}
}
String _redactedUri(Uri uri) {
final redactedQuery = <String, String>{...uri.queryParameters};
if (redactedQuery.containsKey('access_key')) {
redactedQuery['access_key'] = '***REDACTED***';
}
return uri.replace(queryParameters: redactedQuery).toString();
}
bool _isRateLimitedResponse(http.Response response) {
if (response.statusCode == 429) {
return true;
}
try {
final parsed = jsonDecode(response.body) as Map<String, dynamic>;
final error = parsed['error'] as Map<String, dynamic>?;
final code = error?['code']?.toString().toLowerCase();
return code == 'rate_limit_reached';
} catch (_) {
return false;
}
}
Future<http.Response> _getWithRateLimitRetry(
Uri uri, {
required String operation,
}) async {
const maxAttempts = 3;
for (var attempt = 1; attempt <= maxAttempts; attempt++) {
final response = await httpClient.get(uri);
_log('$operation HTTP status: ${response.statusCode}');
_log('$operation raw response: ${response.body}');
final shouldRetry = _isRateLimitedResponse(response);
if (!shouldRetry || attempt == maxAttempts) {
return response;
}
final delayMs = 1200 * attempt;
_log(
'$operation rate limited; retrying in ${delayMs}ms (attempt ${attempt + 1}/$maxAttempts)',
);
await Future.delayed(Duration(milliseconds: delayMs));
}
throw StateError('Unexpected rate-limit retry flow for $operation.');
}
Future<double> fetchUsdToSekRate({required DateTime estDate}) async {
if (apiKey == 'REPLACE_WITH_YOUR_FOREXRATE_API_KEY') {
throw StateError('ForexRateAPI key is not configured.');
if (apiKey == 'REPLACE_WITH_YOUR_EXCHANGE_RATE_API_KEY') {
throw StateError('ExchangeratesAPI key is not configured.');
}
final date = DateFormat('yyyy-MM-dd').format(estDate);
final uri = Uri.https('api.forexrateapi.com', '/v1/$date', <String, String>{
'api_key': apiKey,
'base': 'USD',
'currencies': 'SEK',
});
final uri = Uri.https(
'api.exchangeratesapi.io',
'/v1/$date',
// Free-tier plans can restrict custom base currencies.
// We request EUR-based USD and SEK rates and derive USD->SEK via cross-rate.
<String, String>{'access_key': apiKey, 'symbols': 'USD,SEK'},
);
final response = await httpClient.get(uri);
_log('Daily rate request: ${_redactedUri(uri)}');
final response = await _getWithRateLimitRetry(uri, operation: 'Daily rate');
if (response.statusCode != 200) {
throw StateError('ForexRateAPI request failed (${response.statusCode}).');
throw StateError(
'ExchangeratesAPI request failed (${response.statusCode}).',
);
}
final json = jsonDecode(response.body) as Map<String, dynamic>;
final success = json['success'] as bool? ?? false;
if (!success) {
throw StateError('ForexRateAPI returned success=false.');
final error = json['error'];
_log('Daily rate success=false. error=$error');
throw StateError('ExchangeratesAPI returned success=false. error=$error');
}
final rates = json['rates'] as Map<String, dynamic>?;
final sek = rates?['SEK'];
if (sek == null) {
throw StateError('SEK rate was missing in API response.');
final usdPerEur = rates?['USD'];
final sekPerEur = rates?['SEK'];
if (usdPerEur == null || sekPerEur == null) {
throw StateError('USD/SEK rates were missing in API response.');
}
return (sek as num).toDouble();
final usdPerEurValue = (usdPerEur as num).toDouble();
final sekPerEurValue = (sekPerEur as num).toDouble();
if (usdPerEurValue == 0) {
throw StateError('USD rate was zero; cannot derive USD->SEK.');
}
final usdToSek = sekPerEurValue / usdPerEurValue;
_log(
'Daily rate parsed usdPerEur=$usdPerEurValue sekPerEur=$sekPerEurValue derivedUsdToSek=$usdToSek',
);
return usdToSek;
}
Future<ForexConversionResult> convertUsdToSek({
required DateTime estDate,
required double amount,
}) async {
if (apiKey == 'REPLACE_WITH_YOUR_FOREXRATE_API_KEY') {
throw StateError('ForexRateAPI key is not configured.');
if (apiKey == 'REPLACE_WITH_YOUR_EXCHANGE_RATE_API_KEY') {
throw StateError('ExchangeratesAPI key is not configured.');
}
final date = DateFormat('yyyy-MM-dd').format(estDate);
final uri =
Uri.https('api.forexrateapi.com', '/v1/convert', <String, String>{
'api_key': apiKey,
'from': 'USD',
'to': 'SEK',
'amount': amount.toStringAsFixed(2),
'date': date,
});
final quote = await fetchUsdToSekRate(estDate: estDate);
final result = quote * amount;
final response = await httpClient.get(uri);
if (response.statusCode != 200) {
throw StateError('ForexRateAPI convert failed (${response.statusCode}).');
}
final json = jsonDecode(response.body) as Map<String, dynamic>;
final success = json['success'] as bool? ?? false;
if (!success) {
throw StateError('ForexRateAPI convert returned success=false.');
}
final info = json['info'] as Map<String, dynamic>?;
final quote = info?['quote'];
final result = json['result'];
if (quote == null || result == null) {
throw StateError(
'ForexRateAPI convert response was missing quote/result.',
);
}
return ForexConversionResult(
quote: (quote as num).toDouble(),
result: (result as num).toDouble(),
_log(
'Computed conversion from daily rate quote=$quote result=$result amount=$amount date=${DateFormat('yyyy-MM-dd').format(estDate)}',
);
return ForexConversionResult(quote: quote, result: result);
}
}