<?php
/**
 * AKSRT AI — AI 子系统核心
 *
 * 统一管理 AI 调用：优先 WordPress AI Client（Connectors），
 * 回退主题 OpenAI 兼容配置。默认关闭，需管理员显式启用主题 provider
 * 或配置核心 Connectors。
 *
 * @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（主题侧 provider）
     */
    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,
        ];

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

        // Preserve existing key when client sends the masked placeholder.
        if (isset($config['api_key']) && $config['api_key'] === '***') {
            $merged['api_key'] = $current['api_key'];
        }

        $merged['enabled']    = !empty($merged['enabled']);
        $merged['provider']   = sanitize_key((string) ($merged['provider'] ?? self::PROVIDER_NONE));
        $merged['api_key']    = (string) ($merged['api_key'] ?? '');
        $merged['api_base']   = esc_url_raw((string) ($merged['api_base'] ?? 'https://api.openai.com/v1'));
        $merged['model']      = sanitize_text_field((string) ($merged['model'] ?? 'gpt-3.5-turbo'));
        $merged['max_tokens'] = max(100, min(4000, (int) ($merged['max_tokens'] ?? 1000)));
        $merged['rate_limit'] = max(1, min(100, (int) ($merged['rate_limit'] ?? 10)));

        // Persist only the known keys so shape stays stable.
        $to_store = [
            'enabled'    => $merged['enabled'],
            'provider'   => $merged['provider'],
            'api_key'    => $merged['api_key'],
            'api_base'   => $merged['api_base'],
            'model'      => $merged['model'],
            'max_tokens' => $merged['max_tokens'],
            'rate_limit' => $merged['rate_limit'],
        ];

        $before  = get_option('aksrt_ai_settings', []);
        $updated = update_option('aksrt_ai_settings', $to_store);
        if ($updated) {
            return true;
        }

        // update_option returns false when the value is unchanged — treat as success.
        if (is_array($before)) {
            $before_normalized = array_merge([
                '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,
            ], $before);
            $before_normalized['enabled']    = !empty($before_normalized['enabled']);
            $before_normalized['provider']   = sanitize_key((string) ($before_normalized['provider'] ?? self::PROVIDER_NONE));
            $before_normalized['api_key']    = (string) ($before_normalized['api_key'] ?? '');
            $before_normalized['api_base']   = esc_url_raw((string) ($before_normalized['api_base'] ?? 'https://api.openai.com/v1'));
            $before_normalized['model']      = sanitize_text_field((string) ($before_normalized['model'] ?? 'gpt-3.5-turbo'));
            $before_normalized['max_tokens'] = max(100, min(4000, (int) ($before_normalized['max_tokens'] ?? 1000)));
            $before_normalized['rate_limit'] = max(1, min(100, (int) ($before_normalized['rate_limit'] ?? 10)));

            return maybe_serialize($before_normalized) === maybe_serialize($to_store)
                || $before_normalized == $to_store;
        }

        return maybe_serialize($before) === maybe_serialize($to_store);
    }

    /**
     * WordPress 核心 AI Client 是否真正可用。
     *
     * 仅有函数存根不够：没有 Connectors / wp_supports_ai=false 时不应抢占主题 provider。
     */
    public function is_wp_ai_available(): bool {
        if (!function_exists('wp_ai_client_prompt')) {
            return false;
        }
        // Prefer the official capability gate when present.
        if (function_exists('wp_supports_ai')) {
            return (bool) wp_supports_ai();
        }
        // Without wp_supports_ai, do not claim availability (avoids false-positive 400s).
        return false;
    }

    /**
     * 主题 OpenAI 兼容 provider 是否可用。
     */
    public function is_theme_provider_available(): bool {
        $config = $this->get_config();
        $provider = sanitize_key((string) ($config['provider'] ?? self::PROVIDER_NONE));
        $api_key = trim((string) ($config['api_key'] ?? ''));
        $api_base = trim((string) ($config['api_base'] ?? ''));

        return !empty($config['enabled'])
            && $provider !== self::PROVIDER_NONE
            && $provider !== ''
            && $api_key !== ''
            && $api_base !== '';
    }

    /**
     * 任一后端可用即可生成。
     */
    public function is_available(): bool {
        return $this->is_theme_provider_available() || $this->is_wp_ai_available();
    }

    /**
     * 当前优先后端标识。
     *
     * Theme provider wins when explicitly configured — WP AI stubs often exist
     * without a working connector and previously produced opaque 400 failures.
     */
    public function resolve_backend(): string {
        if ($this->is_theme_provider_available()) {
            return 'theme';
        }
        if ($this->is_wp_ai_available()) {
            return 'wp_ai';
        }
        return 'none';
    }

    /**
     * 获取 AI 状态（不回显完整密钥）。
     */
    public function get_status(): array {
        $config = $this->get_config();
        $seo    = class_exists('AKSRT_Settings') ? AKSRT_Settings::get_seo_settings() : [];

        return [
            'enabled'         => !empty($config['enabled']),
            'provider'        => (string) ($config['provider'] ?? self::PROVIDER_NONE),
            'configured'      => !empty($config['api_key']) || $this->is_wp_ai_available(),
            'model'           => (string) ($config['model'] ?? ''),
            'api_base'        => (string) ($config['api_base'] ?? ''),
            'api_key'         => !empty($config['api_key']) ? '***' : '',
            'max_tokens'      => (int) ($config['max_tokens'] ?? 1000),
            'rate_limit'      => (int) ($config['rate_limit'] ?? 10),
            'available'       => $this->is_available(),
            'backend'         => $this->resolve_backend(),
            'wp_ai_available' => $this->is_wp_ai_available(),
            'theme_available' => $this->is_theme_provider_available(),
            'seo_enabled'     => !empty($seo['seo_enabled']),
            'seo_ai_enabled'  => !empty($seo['seo_ai_enabled']),
            'write_assist'    => $this->is_available(),
        ];
    }

    /**
     * 统一文本生成出口。
     *
     * @param string $prompt  用户提示 / 上下文
     * @param array  $options system_instruction, max_tokens, temperature
     * @return array{success:bool,content?:string,message?:string,backend?:string}
     */
    public function generate_text(string $prompt, array $options = []): array {
        if (!$this->is_available()) {
            return [
                'success' => false,
                'message' => __('AI 服务未启用或未配置。请配置 WordPress AI Connectors，或在「扩展 → AI 辅助」填写 API Key。', 'aksrt'),
            ];
        }

        if (!$this->check_rate_limit()) {
            return [
                'success' => false,
                'message' => __('请求过于频繁，请稍后再试', 'aksrt'),
            ];
        }

        $system = isset($options['system_instruction'])
            ? (string) $options['system_instruction']
            : __('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。', 'aksrt');

        $last_error = [
            'success' => false,
            'message' => __('AI 服务未启用或未配置。请配置 WordPress AI Connectors，或在「扩展 → AI 辅助」填写 API Key。', 'aksrt'),
        ];

        // 1) Prefer explicitly configured theme OpenAI-compatible provider.
        if ($this->is_theme_provider_available()) {
            $theme_result = $this->generate_via_theme($prompt, $system, $options);
            $this->record_call();
            if (!empty($theme_result['success'])) {
                $theme_result['backend'] = 'theme';
                return $theme_result;
            }
            $last_error = $theme_result;
            // Fall through to WP AI if available.
        }

        // 2) WordPress AI Client (Connectors).
        if ($this->is_wp_ai_available()) {
            $wp_result = $this->generate_via_wp_ai($prompt, $system, $options);
            $this->record_call();
            if (!empty($wp_result['success'])) {
                $wp_result['backend'] = 'wp_ai';
                return $wp_result;
            }
            $last_error = $wp_result;
        }

        return $last_error;
    }

    /**
     * 兼容旧调用。
     */
    public function generate(string $prompt, array $options = []): array {
        return $this->generate_text($prompt, $options);
    }

    private function generate_via_wp_ai(string $prompt, string $system, array $options): array {
        try {
            $builder = wp_ai_client_prompt($prompt);
            if (is_object($builder) && method_exists($builder, 'using_system_instruction') && $system !== '') {
                $builder = $builder->using_system_instruction($system);
            }
            if (!is_object($builder) || !method_exists($builder, 'generate_text')) {
                return [
                    'success' => false,
                    'message' => __('WordPress AI Client 接口不可用', 'aksrt'),
                ];
            }
            $text = $builder->generate_text();
            if (is_wp_error($text)) {
                return [
                    'success' => false,
                    'message' => $text->get_error_message(),
                ];
            }
            $text = is_string($text) ? trim($text) : '';
            if ($text === '') {
                return [
                    'success' => false,
                    'message' => __('AI 未返回任何文本', 'aksrt'),
                ];
            }
            return [
                'success' => true,
                'content' => $text,
            ];
        } catch (Throwable $t) {
            return [
                'success' => false,
                'message' => $t->getMessage() ?: __('WordPress AI Client 调用失败', 'aksrt'),
            ];
        }
    }

    private function generate_via_theme(string $prompt, string $system, array $options): array {
        $config      = $this->get_config();
        $max_tokens  = (int) ($options['max_tokens'] ?? $config['max_tokens']);
        $temperature = (float) ($options['temperature'] ?? 0.7);
        $api_base    = rtrim((string) $config['api_base'], '/');

        $response = wp_remote_post($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' => $system],
                    ['role' => 'user', 'content' => $prompt],
                ],
                'max_tokens'  => $max_tokens,
                'temperature' => $temperature,
            ]),
            'timeout' => 45,
        ]);

        if (is_wp_error($response)) {
            return [
                'success' => false,
                'message' => sprintf(
                    /* translators: %s: error message */
                    __('API 请求失败: %s', 'aksrt'),
                    $response->get_error_message()
                ),
            ];
        }

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

        if ($status_code !== 200) {
            $error_msg = is_array($body) ? ($body['error']['message'] ?? __('未知错误', 'aksrt')) : __('未知错误', 'aksrt');
            return [
                'success' => false,
                'message' => sprintf(
                    /* translators: 1: HTTP status, 2: error message */
                    __('API 错误 (%1$d): %2$s', 'aksrt'),
                    $status_code,
                    $error_msg
                ),
            ];
        }

        $message = is_array($body) ? ($body['choices'][0]['message'] ?? []) : [];
        $content = is_array($message) ? (string) ($message['content'] ?? '') : '';

        if ($content === '' && is_array($message) && !empty($message['reasoning_content'])) {
            $content = (string) $message['reasoning_content'];
        }

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

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

    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;
    }

    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);
    }
}