<?php

namespace App\Services\LLM;

use App\Models\GatewayUser;
use App\Models\GatewayUserCredential;
use App\Exceptions\{ProviderException, InsufficientBudgetException};
use Illuminate\Support\Facades\Log;

class GatewayService
{
    public function __construct(
        private CostCalculator $costCalculator,
        private RequestLogger $requestLogger,
    ) {}

    /**
     * Process a chat completion request through the gateway
     *
     * @param GatewayUser $user Gateway user making the request
     * @param string $provider Provider name (openai, anthropic, google, deepseek, mistral)
     * @param string $model Model name
     * @param array $messages Chat messages
     * @param array $options Optional parameters
     * @param string|null $ipAddress Client IP address
     * @param string|null $userAgent Client user agent
     * @return array Response with metadata
     * @throws ProviderException
     */
    public function chatCompletion(
        GatewayUser $user,
        string $provider,
        string $model,
        array $messages,
        array $options = [],
        ?string $ipAddress = null,
        ?string $userAgent = null
    ): array {
        $startTime = microtime(true);
        
        // 1. Get user's API credentials for the provider
        $credential = $this->getUserCredential($user, $provider);
        
        // 2. Create provider instance
        $providerInstance = ProviderFactory::create($provider, $credential->api_key);
        
        // 3. Build request payload for logging
        $requestPayload = [
            'provider' => $provider,
            'model' => $model,
            'messages' => $messages,
            'options' => $options,
        ];
        
        try {
            // 4. Make the API request to LLM provider
            $response = $providerInstance->chatCompletion($messages, array_merge($options, ['model' => $model]));
            
            // 5. Normalize response to standard format
            $normalized = $providerInstance->normalizeResponse($response);
            
            // 6. Calculate response time
            $responseTimeMs = (int) round((microtime(true) - $startTime) * 1000);
            
            // 7. Calculate costs based on token usage
            $costs = $this->costCalculator->calculate(
                $provider,
                $normalized['model'],
                $normalized['usage']['prompt_tokens'],
                $normalized['usage']['completion_tokens']
            );
            
            // 8. Log successful request
            $requestId = $this->requestLogger->logSuccess(
                $user->user_id,  // Gateway user ID
                $provider,
                $normalized['model'],
                $requestPayload,
                $normalized,
                $costs,
                $responseTimeMs,
                $ipAddress,
                $userAgent
            );
            
            // 9. Update user's spending budget
            $this->updateUserBudget($user, $costs['total_cost']);
            
            // 10. Return standardized response with metadata
            return [
                'success' => true,
                'request_id' => $requestId,
                'provider' => $provider,
                'model' => $normalized['model'],
                'content' => $normalized['content'],
                'role' => $normalized['role'],
                'finish_reason' => $normalized['finish_reason'],
                'usage' => $normalized['usage'],
                'cost' => $costs,
                'response_time_ms' => $responseTimeMs,
            ];
            
        } catch (ProviderException $e) {
            // Log failed request
            $this->requestLogger->logFailure(
                $user->user_id,
                $provider,
                $model,
                $requestPayload,
                $e->getMessage(),
                $e->getCode(),
                $ipAddress,
                $userAgent
            );
            
            throw $e;
        }
    }

    /**
     * Get user's credential for a specific provider
     *
     * @param GatewayUser $user
     * @param string $provider
     * @return GatewayUserCredential
     * @throws ProviderException
     */
    private function getUserCredential(GatewayUser $user, string $provider): GatewayUserCredential
    {
        $credential = GatewayUserCredential::where('gateway_user_id', $user->user_id)
            ->where('provider', $provider)
            ->where('is_active', true)
            ->first();
            
        if (!$credential) {
            throw new ProviderException(
                "No active API credentials found for provider: {$provider}",
                400
            );
        }
        
        // Update last used timestamp
        $credential->update(['last_used_at' => now()]);
        
        return $credential;
    }

    /**
     * Update user's budget with spending
     * Budget is now stored directly in gateway_users table
     *
     * @param GatewayUser $user
     * @param float $cost Cost to add to spending
     * @return void
     */
    private function updateUserBudget(GatewayUser $user, float $cost): void
    {
        // Increment spending using model method
        $user->incrementSpending($cost);
        
        // Check if user should receive budget alert
        if ($user->shouldSendBudgetAlert()) {
            // TODO: Dispatch budget alert notification
            Log::info("Budget alert: Gateway user {$user->user_id} has reached {$user->getBudgetUsagePercentage()}% of budget");
        }
        
        // Check if budget is now exceeded
        if ($user->hasExceededBudget()) {
            Log::warning("Budget exceeded: Gateway user {$user->user_id} has exceeded monthly budget");
        }
    }
}