<?php

namespace app\service;

use app\model\AiModel;
use think\exception\HttpResponseException;

class OpenAIService
{
    public static function getModel(?int $modelId = null): AiModel
    {
        if ($modelId) {
            $model = AiModel::where('id', $modelId)->where('enabled', 1)->find();
        } else {
            $model = AiModel::where('is_default', 1)->where('enabled', 1)->find();
        }

        if (!$model) {
            $model = AiModel::where('enabled', 1)->order('sort_order')->find();
        }

        if (!$model) {
            throw new HttpResponseException(json([
                'code'    => 1,
                'message' => '未配置可用的 AI 模型',
                'data'    => null,
            ], 500));
        }

        return $model;
    }

    public static function streamChat(AiModel $model, array $messages, callable $onChunk): void
    {
        $url = rtrim($model->api_base_url, '/') . '/chat/completions';
        $payload = [
            'model'       => $model->model_id,
            'messages'    => $messages,
            'stream'      => true,
            'max_tokens'  => (int) $model->max_tokens,
            'temperature' => (float) $model->temperature,
        ];

        $ch = curl_init($url);
        curl_setopt_array($ch, [
            CURLOPT_POST           => true,
            CURLOPT_POSTFIELDS     => json_encode($payload),
            CURLOPT_HTTPHEADER     => [
                'Content-Type: application/json',
                'Authorization: Bearer ' . $model->api_key,
            ],
            CURLOPT_RETURNTRANSFER => false,
            CURLOPT_WRITEFUNCTION  => function ($ch, $data) use ($onChunk) {
                $lines = explode("\n", $data);
                foreach ($lines as $line) {
                    $line = trim($line);
                    if ($line === '' || $line === 'data: [DONE]') {
                        continue;
                    }
                    if (str_starts_with($line, 'data: ')) {
                        $json = json_decode(substr($line, 6), true);
                        if ($json) {
                            $onChunk($json);
                        }
                    }
                }
                return strlen($data);
            },
            CURLOPT_TIMEOUT        => 120,
            CURLOPT_SSL_VERIFYPEER => false,
        ]);

        $result = curl_exec($ch);
        if ($result === false) {
            $error = curl_error($ch);
            curl_close($ch);
            self::sseEvent('error', ['message' => 'AI 请求失败: ' . $error]);
            return;
        }
        curl_close($ch);
    }

    public static function chat(AiModel $model, array $messages): array
    {
        $url = rtrim($model->api_base_url, '/') . '/chat/completions';
        $payload = [
            'model'       => $model->model_id,
            'messages'    => $messages,
            'stream'      => false,
            'max_tokens'  => (int) $model->max_tokens,
            'temperature' => (float) $model->temperature,
        ];

        $ch = curl_init($url);
        curl_setopt_array($ch, [
            CURLOPT_POST           => true,
            CURLOPT_POSTFIELDS     => json_encode($payload),
            CURLOPT_HTTPHEADER     => [
                'Content-Type: application/json',
                'Authorization: Bearer ' . $model->api_key,
            ],
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_TIMEOUT        => 120,
            CURLOPT_SSL_VERIFYPEER => false,
        ]);

        $response = curl_exec($ch);
        $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        curl_close($ch);

        if ($httpCode !== 200) {
            throw new HttpResponseException(json([
                'code'    => 1,
                'message' => 'AI 请求失败: HTTP ' . $httpCode,
                'data'    => null,
            ], 502));
        }

        $data = json_decode($response, true);
        if (!$data) {
            throw new HttpResponseException(json([
                'code'    => 1,
                'message' => 'AI 响应解析失败',
                'data'    => null,
            ], 502));
        }

        return $data;
    }

    public static function sseHeaders(): void
    {
        header('Content-Type: text/event-stream');
        header('Cache-Control: no-cache');
        header('Connection: keep-alive');
        header('X-Accel-Buffering: no');
    }

    public static function sseEvent(string $event, mixed $data): void
    {
        echo "event: {$event}\n";
        echo 'data: ' . json_encode($data, JSON_UNESCAPED_UNICODE) . "\n\n";
        if (ob_get_level() > 0) {
            ob_flush();
        }
        flush();
    }
}