Still some AI integration issues

2026-03-03 23:35:07 +08:00
parent 2e99ec1234
commit b5449f7842
11 changed files with 1893 additions and 565 deletions
@@ -0,0 +1,144 @@
+import 'dart:convert';
+
+import 'package:flutter_dotenv/flutter_dotenv.dart';
+import 'package:google_generative_ai/google_generative_ai.dart';
+import 'package:http/http.dart' as http;
+
+class GeminiService {
+  static final GeminiService _instance = GeminiService._internal();
+
+  late final String _apiKey;
+
+  /// Cache of valid model IDs (flash/lite, supporting generateContent).
+  List<String> _validModels = [];
+
+  factory GeminiService() => _instance;
+
+  GeminiService._internal() {
+    final apiKey = dotenv.env['GEMINI_API_KEY'];
+    if (apiKey == null || apiKey.isEmpty) {
+      throw Exception('GEMINI_API_KEY not found in .env file');
+    }
+    _apiKey = apiKey;
+  }
+
+  // ---------------------------------------------------------------------------
+  // Model discovery
+  // ---------------------------------------------------------------------------
+
+  /// Queries the Gemini REST API for available models and caches those that
+  ///  - support `generateContent`, AND
+  ///  - contain "flash" or "lite" in their name (free-tier / fast models).
+  ///
+  /// Returns a stable cached list on subsequent calls.
+  Future<List<String>> _getValidModels() async {
+    if (_validModels.isNotEmpty) return _validModels;
+
+    try {
+      final uri = Uri.parse(
+        'https://generativelanguage.googleapis.com/v1beta/models?key=$_apiKey',
+      );
+      final response = await http.get(uri);
+
+      if (response.statusCode == 200) {
+        final data = jsonDecode(response.body) as Map<String, dynamic>;
+        final rawModels = (data['models'] as List<dynamic>?) ?? [];
+
+        final discovered = <String>[];
+        for (final m in rawModels) {
+          final fullName = (m['name'] as String? ?? '');
+          final lower = fullName.toLowerCase();
+          final methods =
+              (m['supportedGenerationMethods'] as List<dynamic>?) ?? [];
+
+          if (methods.contains('generateContent') &&
+              (lower.contains('flash') || lower.contains('lite'))) {
+            // Strip the "models/" prefix so it can be passed directly to
+            // GenerativeModel(model: ...).
+            final id = fullName.startsWith('models/')
+                ? fullName.substring('models/'.length)
+                : fullName;
+            discovered.add(id);
+          }
+        }
+
+        // Sort descending so newer/more-capable models are tried first.
+        discovered.sort((a, b) => b.compareTo(a));
+        _validModels = discovered;
+      }
+    } catch (_) {
+      // Fall back to hard-coded list of known free-tier models below.
+    }
+
+    // If discovery failed or returned nothing, use safe known fallbacks.
+    if (_validModels.isEmpty) {
+      _validModels = [
+        'gemini-2.5-flash-lite',
+        'gemini-2.5-flash',
+        'gemini-2.0-flash',
+        'gemini-1.5-flash',
+      ];
+    }
+
+    return _validModels;
+  }
+
+  // ---------------------------------------------------------------------------
+  // Public API
+  // ---------------------------------------------------------------------------
+
+  /// Fixes spelling/grammar, improves clarity, and translates [text] to
+  /// professional English.
+  ///
+  /// Provide a custom [promptInstruction] to give Gemini field-specific
+  /// context (subject, description, action-taken).  If omitted a sensible
+  /// default is used.
+  ///
+  /// Automatically retries with the next available model on 429 / quota
+  /// errors to minimise wasted quota calls.
+  Future<String> enhanceText(String text, {String? promptInstruction}) async {
+    if (text.trim().isEmpty) return text;
+    final instruction =
+        promptInstruction ??
+        'Fix spelling and grammar, improve clarity, and translate to '
+            'professional English. Return ONLY the improved text, no explanations:';
+    final prompt = '$instruction\n\n"$text"';
+    return _generateWithRetry(prompt, fallback: text);
+  }
+
+  // ---------------------------------------------------------------------------
+  // Internal helpers
+  // ---------------------------------------------------------------------------
+
+  /// Sends [prompt] to Gemini, retrying across all valid models on 429 errors.
+  /// Returns the model response on success, or throws if all models fail.
+  Future<String> _generateWithRetry(
+    String prompt, {
+    required String fallback,
+  }) async {
+    final models = await _getValidModels();
+
+    for (int i = 0; i < models.length; i++) {
+      try {
+        final model = GenerativeModel(model: models[i], apiKey: _apiKey);
+        final response = await model.generateContent([Content.text(prompt)]);
+        return response.text ?? fallback;
+      } catch (e) {
+        final msg = e.toString().toLowerCase();
+        final is429 =
+            msg.contains('429') ||
+            msg.contains('quota') ||
+            msg.contains('resource_exhausted');
+
+        if (!is429 || i == models.length - 1) {
+          // Non-quota error or last model — give up.
+          throw Exception('Gemini request failed: $e');
+        }
+        // Quota hit — try the next model.
+      }
+    }
+
+    // Should not reach here, but safety fallback.
+    throw Exception('All Gemini models exhausted');
+  }
+}