import type { IdCardParsed } from './types'

/** 校验身份证号格式是否合法 */
export const isIdCardValid = (idCard: string): boolean => {
    if (idCard.length !== 18) return false
    // 前 17 位必须为数字
    if (!/^\d{17}$/.test(idCard.slice(0, 17))) return false
    // 第 18 位为数字或 X
    if (!/^[\dXx]$/.test(idCard[17])) return false
    return true
}

/** 解析身份证号，提取性别、年龄、生日 */
export const parseIdCard = (idCard: string): IdCardParsed => {
    const empty: IdCardParsed = { gender: '', age: '', birthday: '', sex: 0 }
    if (!isIdCardValid(idCard)) return empty

    // 第 17 位奇数为男，偶数为女
    const sexCode = parseInt(idCard[16], 10)
    const sex = sexCode % 2 === 1 ? 1 : 2

    // 第 7-14 位为生日 YYYYMMDD
    const year = parseInt(idCard.slice(6, 10), 10)
    const month = parseInt(idCard.slice(10, 12), 10)
    const day = parseInt(idCard.slice(12, 14), 10)

    // 计算年龄
    const now = new Date()
    let age = now.getFullYear() - year
    if (now.getMonth() < month - 1 || (now.getMonth() === month - 1 && now.getDate() < day)) {
        age--
    }

    return {
        gender: sex === 1 ? '男' : '女',
        age: String(age),
        birthday: `${year}-${String(month).padStart(2, '0')}-${String(day).padStart(2, '0')}`,
        sex,
    }
}

/** 从生日字符串（YYYY-MM-DD）计算周岁 */
export const calcAge = (birthday: string): number => {
    if (!birthday) return 0
    const parts = birthday.split('-').map(Number)
    const [year, month, day] = parts
    if (!year || !month || !day) return 0
    const now = new Date()
    let age = now.getFullYear() - year
    const nowMonth = now.getMonth() + 1
    const nowDay = now.getDate()
    if (nowMonth < month || (nowMonth === month && nowDay < day)) age -= 1
    return Math.max(0, age)
}