laravel-llm-gateway/laravel-app/app/Http/Controllers/Api/ChatCompletionController.php

<?php

namespace App\Http\Controllers\Api;

use App\Http\Controllers\Controller;
use App\Http\Requests\ChatCompletionRequest;
use App\Services\LLM\GatewayService;
use App\Exceptions\{ProviderException, InsufficientBudgetException, RateLimitExceededException};
use Illuminate\Http\JsonResponse;
use Illuminate\Support\Facades\Log;

class ChatCompletionController extends Controller
{
    public function __construct(
        private GatewayService $gatewayService
    ) {}

    /**
     * Create a chat completion
     * 
     * Send messages to an LLM provider and receive completions. This endpoint accepts OpenAI-compatible 
     * requests and routes them to the appropriate LLM provider (OpenAI, Anthropic, DeepSeek, Google Gemini, 
     * or Mistral AI).
     * 
     * The request uses the authenticated gateway user's provider credentials (API keys). Cost tracking, 
     * budget checking, and rate limiting are applied automatically based on the gateway user's configuration.
     * 
     * ## Authentication
     * 
     * Requires a valid API key in the Authorization header:
     * ```
     * Authorization: Bearer llmg_your_api_key_here
     * ```
     * 
     * ## Supported Providers
     * 
     * - `openai` - OpenAI models (GPT-4, GPT-3.5-turbo, etc.)
     * - `anthropic` - Anthropic Claude models (Claude 4, Claude 3.5 Sonnet, etc.)
     * - `google` - Google Gemini models (Gemini Pro, Gemini Flash, etc.)
     * - `deepseek` - DeepSeek models (DeepSeek Chat, DeepSeek Coder)
     * - `mistral` - Mistral AI models (Mistral Large, Mistral Medium, etc.)
     * 
     * ## Example Request
     * 
     * ```json
     * {
     *   "provider": "openai",
     *   "model": "gpt-4o-mini",
     *   "messages": [
     *     {
     *       "role": "system",
     *       "content": "You are a helpful assistant."
     *     },
     *     {
     *       "role": "user",
     *       "content": "Hello, how are you?"
     *     }
     *   ],
     *   "temperature": 0.7,
     *   "max_tokens": 150
     * }
     * ```
     * 
     * ## Example Response
     * 
     * ```json
     * {
     *   "success": true,
     *   "request_id": "req_abc123xyz",
     *   "provider": "openai",
     *   "model": "gpt-4o-mini",
     *   "content": "Hello! I'm doing well, thank you for asking. How can I help you today?",
     *   "role": "assistant",
     *   "finish_reason": "stop",
     *   "usage": {
     *     "prompt_tokens": 23,
     *     "completion_tokens": 18,
     *     "total_tokens": 41
     *   },
     *   "cost": {
     *     "prompt_cost": 0.000023,
     *     "completion_cost": 0.000054,
     *     "total_cost": 0.000077
     *   },
     *   "response_time_ms": 1245
     * }
     * ```
     * 
     * ## Error Responses
     * 
     * ### Budget Exceeded (402)
     * ```json
     * {
     *   "success": false,
     *   "error": "budget_exceeded",
     *   "message": "Monthly budget limit exceeded"
     * }
     * ```
     * 
     * ### Rate Limit Exceeded (429)
     * ```json
     * {
     *   "success": false,
     *   "error": "rate_limit_exceeded",
     *   "message": "Rate limit exceeded. Please try again later.",
     *   "retry_after": 3600
     * }
     * ```
     * 
     * ### Provider Error (400-500)
     * ```json
     * {
     *   "success": false,
     *   "error": "provider_error",
     *   "message": "Invalid API key for provider"
     * }
     * ```
     * 
     * @tags Chat
     * 
     * @param ChatCompletionRequest $request
     * @return JsonResponse
     */
    public function create(ChatCompletionRequest $request): JsonResponse
    {
        try {
            $user = $request->user();
            
            $result = $this->gatewayService->chatCompletion(
                user: $user,
                provider: $request->input('provider'),
                model: $request->input('model'),
                messages: $request->input('messages'),
                options: $request->only(['temperature', 'max_tokens', 'top_p', 'frequency_penalty', 'presence_penalty', 'stop']),
                ipAddress: $request->ip(),
                userAgent: $request->userAgent()
            );
            
            return response()->json($result, 200);
            
        } catch (InsufficientBudgetException $e) {
            return response()->json([
                'success' => false,
                'error' => 'budget_exceeded',
                'message' => $e->getMessage(),
            ], 402); // Payment Required
            
        } catch (RateLimitExceededException $e) {
            return response()->json([
                'success' => false,
                'error' => 'rate_limit_exceeded',
                'message' => $e->getMessage(),
                'retry_after' => $e->getRetryAfter(),
            ], 429);
            
        } catch (ProviderException $e) {
            Log::error('Provider error in chat completion', [
                'user_id' => $request->user()->user_id,
                'provider' => $request->input('provider'),
                'error' => $e->getMessage(),
            ]);
            
            return response()->json([
                'success' => false,
                'error' => 'provider_error',
                'message' => $e->getMessage(),
            ], $e->getCode() ?: 500);
            
        } catch (\Exception $e) {
            Log::error('Unexpected error in chat completion', [
                'user_id' => $request->user()->user_id,
                'error' => $e->getMessage(),
                'trace' => $e->getTraceAsString(),
            ]);
            
            return response()->json([
                'success' => false,
                'error' => 'internal_error',
                'message' => 'An unexpected error occurred. Please try again.',
            ], 500);
        }
    }
}