<?php
/**
 * AKSRT Follow — 关注系统
 *
 * 使用专用表 {prefix}aksrt_follow 存储关注关系。
 * 支持：关注、取消关注、计数、是否已关注。
 *
 * @package AKSRT
 */

defined('ABSPATH') || exit;

class AKSRT_Follow {

    private static $instance = null;

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

    private function table(): string {
        return AKSRT_DB_Migrator::table('follow');
    }

    /**
     * 关注用户
     *
     * @param int $follower_id  关注者 ID
     * @param int $following_id 被关注者 ID
     * @return bool
     */
    public function follow(int $follower_id, int $following_id): bool {
        if ($follower_id <= 0 || $following_id <= 0 || $follower_id === $following_id) {
            return false;
        }

        // 已关注则跳过
        if ($this->is_following($follower_id, $following_id)) {
            return true;
        }

        global $wpdb;
        $result = $wpdb->insert($this->table(), [
            'follower_id'  => $follower_id,
            'following_id' => $following_id,
            'created_at'   => current_time('mysql'),
        ], ['%d', '%d', '%s']);

        return $result !== false;
    }

    /**
     * 取消关注
     */
    public function unfollow(int $follower_id, int $following_id): bool {
        if ($follower_id <= 0 || $following_id <= 0) return false;

        global $wpdb;
        $result = $wpdb->delete($this->table(), [
            'follower_id'  => $follower_id,
            'following_id' => $following_id,
        ], ['%d', '%d']);

        return $result !== false;
    }

    /**
     * 切换关注状态
     *
     * @return bool true=已关注, false=已取消
     */
    public function toggle(int $follower_id, int $following_id): bool {
        if ($this->is_following($follower_id, $following_id)) {
            $this->unfollow($follower_id, $following_id);
            return false;
        }
        $this->follow($follower_id, $following_id);
        return true;
    }

    /**
     * 是否已关注
     */
    public function is_following(int $follower_id, int $following_id): bool {
        if ($follower_id <= 0 || $following_id <= 0) return false;

        global $wpdb;
        $exists = $wpdb->get_var($wpdb->prepare(
            "SELECT id FROM {$this->table()} WHERE follower_id = %d AND following_id = %d LIMIT 1",
            $follower_id, $following_id
        ));

        return (int) $exists > 0;
    }

    /**
     * 获取粉丝数（谁关注了 target_id）
     */
    public function get_follower_count(int $user_id): int {
        if ($user_id <= 0) return 0;

        global $wpdb;
        return (int) $wpdb->get_var($wpdb->prepare(
            "SELECT COUNT(*) FROM {$this->table()} WHERE following_id = %d",
            $user_id
        ));
    }

    /**
     * 获取关注数（target_id 关注了谁）
     */
    public function get_following_count(int $user_id): int {
        if ($user_id <= 0) return 0;

        global $wpdb;
        return (int) $wpdb->get_var($wpdb->prepare(
            "SELECT COUNT(*) FROM {$this->table()} WHERE follower_id = %d",
            $user_id
        ));
    }

    /**
     * 获取粉丝列表
     */
    public function get_followers(int $user_id, int $page = 1, int $per_page = 20): array {
        return $this->get_user_list($user_id, 'following_id', $page, $per_page);
    }

    /**
     * 获取关注列表
     */
    public function get_following(int $user_id, int $page = 1, int $per_page = 20): array {
        return $this->get_user_list($user_id, 'follower_id', $page, $per_page);
    }

    /**
     * 通用用户列表查询
     */
    private function get_user_list(int $user_id, string $where_field, int $page, int $per_page): array {
        global $wpdb;

        $other_field = $where_field === 'follower_id' ? 'following_id' : 'follower_id';
        $offset = max(0, ($page - 1) * $per_page);

        $total = (int) $wpdb->get_var($wpdb->prepare(
            "SELECT COUNT(*) FROM {$this->table()} WHERE {$where_field} = %d",
            $user_id
        ));

        $rows = $wpdb->get_results($wpdb->prepare(
            "SELECT {$other_field} as user_id, created_at
             FROM {$this->table()}
             WHERE {$where_field} = %d
             ORDER BY created_at DESC
             LIMIT %d OFFSET %d",
            $user_id, $per_page, $offset
        ), ARRAY_A);

        $items = [];
        foreach ((array) $rows as $row) {
            $uid = (int) $row['user_id'];
            $user = get_userdata($uid);
            $items[] = [
                'user_id'      => $uid,
                'display_name' => $user ? $user->display_name : '',
                'avatar_url'   => $user ? get_avatar_url($uid, ['size' => 48]) : '',
                'created_at'   => $row['created_at'] ?? '',
            ];
        }

        return [
            'items'       => $items,
            'total'       => $total,
            'page'        => $page,
            'total_pages' => max(1, (int) ceil($total / $per_page)),
        ];
    }
}