Refactor genai package to new modular interface

Reorganized the genai package by removing legacy LLM-related files and introducing a new modular interface under the 'interface' directory. Added provider-specific model classes, centralized constants, and updated the example to use the new API and data structures. Updated exports in genai.dart and improved dependency management.

packages/genai/lib/utils/ai_request_utils.dart

@@ -0,0 +1,149 @@
+import 'dart:async';
+import 'dart:convert';
+import 'package:better_networking/better_networking.dart';
+import 'package:flutter/foundation.dart';
+import 'package:nanoid/nanoid.dart';
+import '../models/models.dart';
+
+Future<String?> executeGenAIRequest(AIRequestModel? aiRequestModel) async {
+  final httpRequestModel = aiRequestModel?.httpRequestModel;
+  if (httpRequestModel == null) {
+    debugPrint("executeGenAIRequest -> httpRequestModel is null");
+    return null;
+  }
+  final (response, _, _) = await sendHttpRequest(
+    nanoid(),
+    APIType.rest,
+    httpRequestModel,
+  );
+  if (response == null) return null;
+  if (response.statusCode == 200) {
+    final data = jsonDecode(response.body);
+    return aiRequestModel?.getFormattedOutput(data);
+  } else {
+    debugPrint('LLM_EXCEPTION: ${response.statusCode}\n${response.body}');
+    return null;
+  }
+}
+
+Future<Stream<String?>> streamGenAIRequest(
+  AIRequestModel? aiRequestModel,
+) async {
+  final httpRequestModel = aiRequestModel?.httpRequestModel;
+  final streamController = StreamController<String?>();
+  if (httpRequestModel == null) {
+    debugPrint("streamGenAIRequest -> httpRequestModel is null");
+  } else {
+    final httpStream = await streamHttpRequest(
+      nanoid(),
+      APIType.rest,
+      httpRequestModel,
+    );
+
+    final subscription = httpStream.listen(
+      (dat) {
+        if (dat == null) {
+          streamController.addError('STREAMING ERROR: NULL DATA');
+          return;
+        }
+
+        final chunk = dat.$2;
+        final error = dat.$4;
+
+        if (chunk == null) {
+          streamController.addError(error ?? 'NULL ERROR');
+          return;
+        }
+
+        final ans = chunk.body;
+
+        final lines = ans.split('\n');
+        for (final line in lines) {
+          if (!line.startsWith('data: ') || line.contains('[DONE]')) continue;
+          final jsonStr = line.substring(6).trim();
+          try {
+            final jsonData = jsonDecode(jsonStr);
+            final formattedOutput = aiRequestModel?.getFormattedStreamOutput(
+              jsonData,
+            );
+            streamController.sink.add(formattedOutput);
+          } catch (e) {
+            debugPrint(
+              '⚠️ JSON decode error in SSE: $e\nSending as Regular Text',
+            );
+            streamController.sink.add(jsonStr);
+          }
+        }
+      },
+      onError: (error) {
+        streamController.addError('STREAM ERROR: $error');
+        streamController.close();
+      },
+      onDone: () {
+        streamController.close();
+      },
+      cancelOnError: true,
+    );
+    streamController.onCancel = () async {
+      await subscription.cancel();
+    };
+  }
+  return streamController.stream;
+}
+
+Future<void> callGenerativeModel(
+  AIRequestModel? aiRequestModel, {
+  required Function(String?) onAnswer,
+  required Function(dynamic) onError,
+}) async {
+  final modelRequestData = aiRequestModel?.modelRequestData;
+  if (modelRequestData != null) {
+    try {
+      if (modelRequestData.stream ?? false) {
+        final answerStream = await streamGenAIRequest(aiRequestModel);
+        processGenAIStreamOutput(answerStream, (w) {
+          onAnswer('$w ');
+        }, onError);
+      } else {
+        final answer = await executeGenAIRequest(aiRequestModel);
+        onAnswer(answer);
+      }
+    } catch (e) {
+      onError(e);
+    }
+  }
+}
+
+void processGenAIStreamOutput(
+  Stream<String?> stream,
+  Function(String) onWord,
+  Function(dynamic) onError,
+) {
+  String buffer = '';
+  stream.listen(
+    (chunk) {
+      if (chunk == null || chunk.isEmpty) return;
+      buffer += chunk;
+      // Split on spaces but preserve last partial word
+      final parts = buffer.split(RegExp(r'\s+'));
+      if (parts.length > 1) {
+        // Keep the last part in buffer (it may be incomplete)
+        buffer = parts.removeLast();
+        for (final word in parts) {
+          if (word.trim().isNotEmpty) {
+            onWord(word);
+          }
+        }
+      }
+    },
+    onDone: () {
+      // Print any remaining word when stream is finished
+      if (buffer.trim().isNotEmpty) {
+        onWord(buffer);
+      }
+    },
+    onError: (e) {
+      onError(e);
+    },
+  );
+}