feat: switch chatbot from Gemini to Groq (llama-3.3-70b, 14400 RPD free)

api/chat.php

@@ -25,10 +25,11 @@ $_SESSION['chat_requests'][] = $now;
 // Load DB connection which also loads environment variables
 require_once __DIR__ . '/../config/db.php';
 
-$apiKey = $_ENV['GEMINI_API_KEY'] ?? getenv('GEMINI_API_KEY') ?? '';
+// Load Groq API key (free tier: 14,400 req/day)
+$apiKey = $_ENV['GROQ_API_KEY'] ?? getenv('GROQ_API_KEY') ?? '';
 if (empty($apiKey)) {
     http_response_code(500);
-    echo json_encode(['error' => 'API Key configuration is missing. Please configure GEMINI_API_KEY in your .env file.']);
+    echo json_encode(['error' => 'API Key configuration is missing. Please set GROQ_API_KEY in your .env file.']);
     exit;
 }
 
@@ -121,49 +122,32 @@ $systemPrompt .= "3. If asked about contact options or hiring, point them to his
 $systemPrompt .= "4. Do not make up facts or external projects not listed in the context. If you don't know the answer, politely invite the user to contact Cris directly.\n";
 $systemPrompt .= "5. Format your output using simple markdown (like bolding or bullet points) to make it readable.\n";
 
-// Map chat history
-// Map chat history and prepend system instructions to the first user message
-$contents = [];
-$firstMsgPrepended = false;
+// Build Groq messages array (OpenAI-compatible format)
+// System prompt goes in its own 'system' role message
+$messages = [
+    ['role' => 'system', 'content' => $systemPrompt]
+];
 
+// Append chat history
 if (isset($inputData['history']) && is_array($inputData['history']) && !empty($inputData['history'])) {
-    foreach ($inputData['history'] as $index => $msg) {
+    foreach ($inputData['history'] as $msg) {
         if (isset($msg['role']) && isset($msg['text'])) {
-            $role = ($msg['role'] === 'user') ? 'user' : 'model';
-            $text = $msg['text'];
-            
-            // Prepend system prompt to the first user message in history
-            if (!$firstMsgPrepended && $role === 'user') {
-                $text = "System Context & Instructions:\n" . $systemPrompt . "\n\nUser Message: " . $text;
-                $firstMsgPrepended = true;
-            }
-            
-            $contents[] = [
-                'role' => $role,
-                'parts' => [['text' => $text]]
-            ];
+            $role = ($msg['role'] === 'user') ? 'user' : 'assistant';
+            $messages[] = ['role' => $role, 'content' => $msg['text']];
         }
     }
 }
 
-// Add the current user message (prepend system instructions if history was empty)
-$currentUserText = $userMessage;
-if (!$firstMsgPrepended) {
-    $currentUserText = "System Context & Instructions:\n" . $systemPrompt . "\n\nUser Message: " . $userMessage;
-}
+// Add the current user message
+$messages[] = ['role' => 'user', 'content' => $userMessage];
 
-$contents[] = [
-    'role' => 'user',
-    'parts' => [['text' => $currentUserText]]
-];
-
-// Setup request body without systemInstruction key
+// Groq request payload (OpenAI-compatible)
 $requestPayload = [
-    'contents' => $contents,
-    'generationConfig' => [
-        'temperature' => 0.7,
-        'maxOutputTokens' => 800
-    ]
+    'model'       => 'llama-3.3-70b-versatile', // 14,400 RPD free
+    'messages'    => $messages,
+    'temperature' => 0.7,
+    'max_tokens'  => 800,
+    'stream'      => false
 ];
 
 // Guard: cURL must be available
@@ -173,15 +157,18 @@ if (!function_exists('curl_init')) {
     exit;
 }
 
-// Call Gemini API via cURL
-// gemini-2.0-flash-lite: highest free-tier quota (1,500 req/day)
-$url = "https://generativelanguage.googleapis.com/v1beta/models/gemini-2.0-flash-lite:generateContent?key=" . urlencode($apiKey);
+// Call Groq API via cURL (OpenAI-compatible endpoint)
+// Model: llama-3.3-70b-versatile — free tier, 14,400 req/day
+$url = 'https://api.groq.com/openai/v1/chat/completions';
 
 $ch = curl_init($url);
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
 curl_setopt($ch, CURLOPT_POST, true);
 curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($requestPayload));
-curl_setopt($ch, CURLOPT_HTTPHEADER, ['Content-Type: application/json']);
+curl_setopt($ch, CURLOPT_HTTPHEADER, [
+    'Content-Type: application/json',
+    'Authorization: Bearer ' . $apiKey
+]);
 curl_setopt($ch, CURLOPT_TIMEOUT, 15);
 curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
 
@@ -200,18 +187,18 @@ curl_close($ch);
 if ($httpCode !== 200) {
     http_response_code($httpCode);
     $errorDetails = json_decode($response, true);
-    $errMsg = isset($errorDetails['error']['message']) ? $errorDetails['error']['message'] : 'Failed to retrieve response from Gemini.';
-    echo json_encode(['error' => $errMsg, 'raw' => $response]);
+    $errMsg = isset($errorDetails['error']['message']) ? $errorDetails['error']['message'] : 'Failed to retrieve response from Groq.';
+    echo json_encode(['error' => $errMsg]);
     exit;
 }
 
 $responseData = json_decode($response, true);
 $reply = '';
-if (isset($responseData['candidates'][0]['content']['parts'][0]['text'])) {
-    $reply = $responseData['candidates'][0]['content']['parts'][0]['text'];
+if (isset($responseData['choices'][0]['message']['content'])) {
+    $reply = $responseData['choices'][0]['message']['content'];
 } else {
     http_response_code(502);
-    echo json_encode(['error' => 'Invalid response structure from Gemini API.', 'raw' => $responseData]);
+    echo json_encode(['error' => 'Invalid response structure from Groq API.', 'raw' => $responseData]);
     exit;
 }