<?php

namespace App\Services;

use App\Models\DictItem;
use Carbon\Carbon;
use Carbon\CarbonInterface;

/**
 * 星级 → 下次跟进日规则（对齐 prototype teachers.html / teacher-detail.html）。
 */
class TeacherFollowPlanService
{
    /**
     * 根据星级字典项 value 计算下次跟进日；待定返回 null。
     */
    public function nextFollowDateFromStar(?DictItem $starItem, ?CarbonInterface $base = null): ?Carbon
    {
        if (! $starItem) {
            return null;
        }

        $days = $this->daysByStarValue((string) $starItem->value);
        if ($days === null) {
            return null;
        }

        $base = $base ? Carbon::parse($base) : Carbon::today();

        return $base->copy()->addDays($days);
    }

    /**
     * @return int|null 追加天数；null 表示不生成下次跟进日
     */
    public function daysByStarValue(string $value): ?int
    {
        return match ($value) {
            '1' => 365,
            '2', '3' => 180,
            '4', '5' => 90,
            default => null,
        };
    }

    public function starLabelToValue(string $label): ?string
    {
        return match ($label) {
            '一星' => '1',
            '二星' => '2',
            '三星' => '3',
            '四星' => '4',
            '五星' => '5',
            '待定' => 'pending',
            default => null,
        };
    }
}