<?php
/**
 * AKSRT AI SEO — SEO 字段生成（对齐 Zibll 闭环）
 *
 * @package AKSRT
 */

defined('ABSPATH') || exit;

class AKSRT_AI_SEO {

    private static $instance = null;

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

    /**
     * SEO AI 功能是否启用。
     */
    public function is_enabled(): bool {
        if (!class_exists('AKSRT_Settings')) {
            return false;
        }
        $seo = AKSRT_Settings::get_seo_settings();
        return !empty($seo['seo_enabled']) && !empty($seo['seo_ai_enabled']);
    }

    /**
     * 从已保存实体生成 SEO 三字段（Zibll 形状）。
     *
     * @return array{success:bool,data?:array,message?:string}
     */
    public function generate_fields(string $type, int $id): array {
        if (!$this->is_enabled()) {
            return [
                'success' => false,
                'message' => __('AI SEO 功能未启用', 'aksrt'),
            ];
        }

        if (!class_exists('AKSRT_AI') || !class_exists('AKSRT_AI_Prompt')) {
            return [
                'success' => false,
                'message' => __('AI 模块未加载', 'aksrt'),
            ];
        }

        $ai = AKSRT_AI::get_instance();
        if (!$ai->is_available()) {
            return [
                'success' => false,
                'message' => __('AI 服务未启用或未配置', 'aksrt'),
            ];
        }

        $type = $type === 'term' ? 'term' : 'post';
        if ($id <= 0) {
            return [
                'success' => false,
                'message' => __('请先保存后再生成 SEO', 'aksrt'),
            ];
        }

        $context = $type === 'term'
            ? $this->build_term_context($id)
            : $this->build_post_context($id);

        if (is_wp_error($context)) {
            return [
                'success' => false,
                'message' => $context->get_error_message(),
            ];
        }

        $prompt = AKSRT_AI_Prompt::get_instance();

        $title = $this->run_field(
            $ai,
            $context,
            $prompt->get_seo_title_system_instruction(),
            'title'
        );
        $keywords = $this->run_field(
            $ai,
            $context,
            $prompt->get_seo_keywords_system_instruction(),
            'keywords'
        );
        $description = $this->run_field(
            $ai,
            $context,
            $prompt->get_seo_description_system_instruction(),
            'description'
        );

        return [
            'success' => true,
            'data'    => [
                'title'       => $title,
                'keywords'    => $keywords,
                'description' => $description,
            ],
        ];
    }

    /**
     * 草稿场景：用传入 title/content 生成（兼容旧 /ai/seo-suggest）。
     */
    public function suggest(string $title, string $content = ''): array {
        if (!$this->is_enabled()) {
            return ['success' => false, 'message' => __('AI SEO 功能未启用', 'aksrt')];
        }

        if (!class_exists('AKSRT_AI') || !class_exists('AKSRT_AI_Prompt')) {
            return ['success' => false, 'message' => __('AI 模块未加载', 'aksrt')];
        }

        $ai = AKSRT_AI::get_instance();
        if (!$ai->is_available()) {
            return ['success' => false, 'message' => __('AI 服务未启用', 'aksrt')];
        }

        $title   = trim($title);
        $content = trim(wp_strip_all_tags($content));
        if ($title === '' && $content === '') {
            return [
                'success' => false,
                'message' => __('无可用内容，请先填写标题或正文', 'aksrt'),
            ];
        }

        $parts = [];
        if ($title !== '') {
            $parts[] = '标题: ' . $title;
        }
        if ($content !== '') {
            $content = wp_trim_words($content, 1500, '');
            $parts[] = "正文:\n" . $content;
        }
        $context = implode("\n\n", $parts);
        $prompt  = AKSRT_AI_Prompt::get_instance();

        $title_out = $this->run_field($ai, $context, $prompt->get_seo_title_system_instruction(), 'title');
        $kw_out    = $this->run_field($ai, $context, $prompt->get_seo_keywords_system_instruction(), 'keywords');
        $desc_out  = $this->run_field($ai, $context, $prompt->get_seo_description_system_instruction(), 'description');

        $keywords = [];
        if (!empty($kw_out['content'])) {
            $keywords = array_values(array_filter(array_map('trim', explode(',', $kw_out['content']))));
        }

        return [
            'success' => true,
            'data'    => [
                'suggested_title'       => (string) ($title_out['content'] ?? ''),
                'suggested_description' => (string) ($desc_out['content'] ?? ''),
                'suggested_keywords'    => $keywords,
                'fields'                => [
                    'title'       => $title_out,
                    'keywords'    => $kw_out,
                    'description' => $desc_out,
                ],
            ],
        ];
    }

    /**
     * @return string|WP_Error
     */
    public function build_post_context(int $post_id, int $word_limit = 1500) {
        $post = get_post($post_id);
        if (!$post) {
            return new WP_Error('no_post', __('内容不存在', 'aksrt'));
        }

        $title   = trim((string) $post->post_title);
        $excerpt = trim((string) $post->post_excerpt);
        $content = wp_strip_all_tags((string) $post->post_content);
        $content = trim(preg_replace('/\s+/u', ' ', $content) ?? $content);
        $content = wp_trim_words($content, max(50, $word_limit), '');

        if ($title === '' && $content === '' && $excerpt === '') {
            return new WP_Error('empty_content', __('无可用内容，请先填写标题、摘要或正文并保存', 'aksrt'));
        }

        $parts = [];
        if ($title !== '') {
            $parts[] = '标题: ' . $title;
        }
        if ($excerpt !== '') {
            $parts[] = '摘要: ' . $excerpt;
        }
        if ($content !== '') {
            $parts[] = "正文:\n" . $content;
        }

        return implode("\n\n", $parts);
    }

    /**
     * @return string|WP_Error
     */
    public function build_term_context(int $term_id) {
        $term = get_term($term_id);
        if (!$term || is_wp_error($term)) {
            return new WP_Error('no_term', __('分类/标签不存在', 'aksrt'));
        }

        $parts = [];
        if ($term->name !== '') {
            $parts[] = '标题: ' . $term->name;
        }
        if ($term->description !== '') {
            $parts[] = '描述: ' . wp_strip_all_tags((string) $term->description);
        }

        if (empty($parts)) {
            return new WP_Error('empty_term', __('没有可用的标题或描述', 'aksrt'));
        }

        return implode("\n\n", $parts);
    }

    /**
     * @return array{content?:string,error?:string}
     */
    private function run_field(AKSRT_AI $ai, string $context, string $system, string $field): array {
        $result = $ai->generate_text($context, [
            'system_instruction' => $system,
            'max_tokens'         => $field === 'description' ? 400 : 300,
            'temperature'        => 0.5,
        ]);

        if (empty($result['success'])) {
            return [
                'error' => (string) ($result['message'] ?? __('生成失败', 'aksrt')),
            ];
        }

        $raw = (string) ($result['content'] ?? '');
        return [
            'content' => $this->post_process_field($field, $raw),
        ];
    }

    private function post_process_field(string $field, string $raw): string {
        $raw = trim($raw);
        // Strip common wrappers
        $raw = preg_replace('/^["\'“”]+|["\'“”]+$/u', '', $raw) ?? $raw;
        $raw = trim($raw);

        if ($field === 'title') {
            $title = sanitize_text_field($raw);
            $seo   = class_exists('AKSRT_Settings') ? AKSRT_Settings::get_seo_settings() : [];
            $conn  = trim((string) ($seo['seo_connector'] ?? '-')) ?: '-';
            $site  = trim((string) get_bloginfo('name'));
            if ($site !== '' && $title !== '' && mb_stripos($title, $site) === false) {
                $title = $title . ' ' . $conn . ' ' . $site;
            }
            return $title;
        }

        if ($field === 'keywords') {
            $raw = str_replace(['、', '，', ';', '；', "\n", "\r"], ',', $raw);
            $parts = array_map('trim', explode(',', $raw));
            $parts = array_values(array_unique(array_filter($parts, static function ($p) {
                return $p !== '';
            })));
            $parts = array_map('sanitize_text_field', $parts);
            return implode(',', array_slice($parts, 0, 12));
        }

        // description
        $raw = preg_replace('/\s+/u', ' ', $raw) ?? $raw;
        return sanitize_text_field(trim($raw));
    }
}