<?php
/**
 * AKSRT AI — AI 子系统核心
 *
 * 统一管理 AI provider 调用、速率限制和输出处理。
 * 默认关闭，需管理员显式启用。
 *
 * @package AKSRT
 */

defined('ABSPATH') || exit;

class AKSRT_AI {

    private static $instance = null;

    const PROVIDER_NONE   = 'none';
    const PROVIDER_OPENAI = 'openai';

    public static function get_instance(): self {
        if (null === self::$instance) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    /**
     * 获取 AI 配置
     */
    public function get_config(): array {
        $defaults = [
            'enabled'    => false,
            'provider'   => self::PROVIDER_NONE,
            'api_key'    => '',
            'api_base'   => 'https://api.openai.com/v1',
            'model'      => 'gpt-3.5-turbo',
            'max_tokens' => 1000,
            'rate_limit' => 10, // 每分钟最大调用次数
        ];

        $saved = get_option('aksrt_ai_settings', []);
        if (!is_array($saved)) $saved = [];

        return array_merge($defaults, $saved);
    }

    /**
     * 更新 AI 配置
     */
    public function update_config(array $config): bool {
        $current = $this->get_config();
        $merged = array_merge($current, $config);

        // 如果 api_key 为掩码，保留原值
        if (isset($config['api_key']) && $config['api_key'] === '***') {
            $merged['api_key'] = $current['api_key'];
        }

        return update_option('aksrt_ai_settings', $merged);
    }

    /**
     * 检查 AI 是否可用
     */
    public function is_available(): bool {
        $config = $this->get_config();
        return !empty($config['enabled'])
            && $config['provider'] !== self::PROVIDER_NONE
            && !empty($config['api_key']);
    }

    /**
     * 获取 AI 状态
     */
    public function get_status(): array {
        $config = $this->get_config();

        return [
            'enabled'     => !empty($config['enabled']),
            'provider'    => $config['provider'],
            'configured'  => !empty($config['api_key']),
            'model'       => $config['model'],
            'api_key'     => !empty($config['api_key']) ? '***' : '',
            'rate_limit'  => $config['rate_limit'],
            'available'   => $this->is_available(),
        ];
    }

    /**
     * 调用 AI 生成
     *
     * @param string $prompt 提示词
     * @param array  $options 选项
     * @return array{success: bool, content?: string, message?: string}
     */
    public function generate(string $prompt, array $options = []): array {
        if (!$this->is_available()) {
            return ['success' => false, 'message' => 'AI 服务未启用或未配置'];
        }

        // 速率限制检查
        if (!$this->check_rate_limit()) {
            return ['success' => false, 'message' => '请求过于频繁，请稍后再试'];
        }

        $config = $this->get_config();
        $max_tokens = (int) ($options['max_tokens'] ?? $config['max_tokens']);
        $temperature = (float) ($options['temperature'] ?? 0.7);

        $response = wp_remote_post($config['api_base'] . '/chat/completions', [
            'headers' => [
                'Content-Type'  => 'application/json',
                'Authorization' => 'Bearer ' . $config['api_key'],
            ],
            'body' => wp_json_encode([
                'model'       => $config['model'],
                'messages'    => [
                    ['role' => 'system', 'content' => '你是一个内容助手，提供建议性内容。输出仅作为参考建议，不会自动应用到线上内容。'],
                    ['role' => 'user', 'content' => $prompt],
                ],
                'max_tokens'  => $max_tokens,
                'temperature' => $temperature,
            ]),
            'timeout' => 30,
        ]);

        // 记录调用
        $this->record_call();

        if (is_wp_error($response)) {
            return ['success' => false, 'message' => 'API 请求失败: ' . $response->get_error_message()];
        }

        $body = json_decode(wp_remote_retrieve_body($response), true);
        $status_code = wp_remote_retrieve_response_code($response);

        if ($status_code !== 200) {
            $error_msg = $body['error']['message'] ?? '未知错误';
            return ['success' => false, 'message' => 'API 错误 (' . $status_code . '): ' . $error_msg];
        }

        $message = $body['choices'][0]['message'] ?? [];
        $content = $message['content'] ?? '';

        // 兼容推理模型（如 mimo-v2.5-pro）：content 为空时取 reasoning_content
        if (empty($content) && !empty($message['reasoning_content'])) {
            $content = $message['reasoning_content'];
        }

        if (empty($content)) {
            return ['success' => false, 'message' => 'AI 返回内容为空（可能 max_tokens 不足）'];
        }

        return [
            'success'         => true,
            'content'         => trim($content),
            'reasoning'       => $message['reasoning_content'] ?? '',
            'usage'           => $body['usage'] ?? [],
            'finish_reason'   => $body['choices'][0]['finish_reason'] ?? '',
        ];
    }

    /**
     * 速率限制检查
     */
    private function check_rate_limit(): bool {
        $config = $this->get_config();
        $limit = (int) $config['rate_limit'];
        if ($limit <= 0) return true;

        $key = 'aksrt_ai_rate_' . get_current_user_id();
        $count = (int) get_transient($key);

        return $count < $limit;
    }

    /**
     * 记录调用
     */
    private function record_call(): void {
        $key = 'aksrt_ai_rate_' . get_current_user_id();
        $count = (int) get_transient($key);
        set_transient($key, $count + 1, MINUTE_IN_SECONDS);
    }
}