<?php
/**
 * 亲属关系表的读写。
 *
 * 只维护两种边（详见 Kinship 的头注释）：
 *   parent : from 是 to 的父/母
 *   spouse : from 与 to 是配偶（对称，只存一条）
 *
 * ⚠️ 血缘关系必须**防环**：如果把 A 设为 B 的父亲、又顺手把 B 设成 A 的父亲，
 *    家谱展开会变成死循环。addParent() 在写库前先检查。
 */

declare(strict_types=1);

namespace App;

final class Relations
{
    /** 给某人指定一位父/母 */
    public static function addParent(int $familyId, int $childId, int $parentId, string $role): array
    {
        $role = $role === 'mother' ? 'mother' : 'father';
        if ($childId === $parentId) {
            return ['ok' => false, 'error' => '不能把自己设成自己的父母。'];
        }
        if (self::wouldCycle($familyId, $parentId, $childId)) {
            return ['ok' => false, 'error' => '这样会让两个人互为祖辈，关系说不通，已拒绝。'];
        }
        // 同一位父母只能有一个「父亲」和一个「母亲」位
        $db = Database::get();
        $st = $db->prepare(
            'DELETE FROM relations WHERE family_id = ? AND to_id = ? AND kind = "parent" AND from_role = ?'
        );
        $st->execute([$familyId, $childId, $role]);

        $st = $db->prepare(
            'INSERT INTO relations (family_id, from_id, to_id, kind, from_role) VALUES (?,?,?,"parent",?)'
        );
        $st->execute([$familyId, $parentId, $childId, $role]);
        return ['ok' => true, 'error' => ''];
    }

    /** 互为配偶（对称，只存一条；若已存在反向的记录则视为重复） */
    public static function addSpouse(int $familyId, int $a, int $b): array
    {
        if ($a === $b) {
            return ['ok' => false, 'error' => '不能把自己设成自己的配偶。'];
        }
        $db = Database::get();
        $st = $db->prepare(
            'SELECT id FROM relations
             WHERE family_id = ? AND kind = "spouse"
               AND ((from_id = ? AND to_id = ?) OR (from_id = ? AND to_id = ?))'
        );
        $st->execute([$familyId, $a, $b, $b, $a]);
        if ($st->fetchColumn()) {
            return ['ok' => true, 'error' => ''];
        }
        $st = $db->prepare(
            'INSERT INTO relations (family_id, from_id, to_id, kind) VALUES (?,?,?,"spouse")'
        );
        $st->execute([$familyId, $a, $b]);
        return ['ok' => true, 'error' => ''];
    }

    /** 解除某条关系（按 id） */
    public static function remove(int $familyId, int $id): void
    {
        Database::get()->prepare('DELETE FROM relations WHERE id = ? AND family_id = ?')
            ->execute([$id, $familyId]);
    }

    /** 解除两人之间的某种关系 */
    public static function detach(int $familyId, int $personId, string $kind, string $role = ''): void
    {
        $sql = 'DELETE FROM relations WHERE family_id = ? AND to_id = ? AND kind = ? AND from_role = ?';
        Database::get()->prepare($sql)->execute([$familyId, $personId, $kind, $role]);
    }

    /** 某人身上挂着的全部关系（详情页编辑用） */
    public static function forPerson(int $familyId, int $personId): array
    {
        $st = Database::get()->prepare(
            'SELECT r.*,
                    pf.name AS from_name, pt.name AS to_name
             FROM relations r
             JOIN persons pf ON pf.id = r.from_id
             JOIN persons pt ON pt.id = r.to_id
             WHERE r.family_id = ? AND (r.from_id = ? OR r.to_id = ?)
             ORDER BY r.kind, r.id'
        );
        $st->execute([$familyId, $personId, $personId]);
        return $st->fetchAll();
    }

    /**
     * 防环：若把 $maybeAncestor 挂到 $node 之上，会不会绕回自己？
     * 做法是顺着 parent 边从 $maybeAncestor 往上走，看能否走到 $node。
     */
    private static function wouldCycle(int $familyId, int $maybeAncestor, int $node): bool
    {
        $st = Database::get()->prepare(
            'SELECT from_id FROM relations WHERE family_id = ? AND to_id = ? AND kind = "parent"'
        );
        $stack = [$maybeAncestor];
        $seen  = [];
        while ($stack) {
            $cur = array_pop($stack);
            if ($cur === $node) {
                return true;
            }
            if (isset($seen[$cur])) {
                continue;
            }
            $seen[$cur] = true;
            $st->execute([$familyId, $cur]);
            foreach ($st->fetchAll(\PDO::FETCH_COLUMN) as $up) {
                $stack[] = (int)$up;
            }
        }
        return false;
    }

    /** 全家的关系条数（设置页/统计用） */
    public static function count(int $familyId): int
    {
        $st = Database::get()->prepare('SELECT COUNT(*) FROM relations WHERE family_id = ?');
        $st->execute([$familyId]);
        return (int)$st->fetchColumn();
    }
}