/** 可读化时差 （date2 - date1）
 * @param options.fuzzy 模糊化大于“天”以内内的时间，都显示为 “不久前”，如 “40 分钟” 前会显示为 “不久前”
 * @example
 * readableDateDiff(new Date(), new Date('2020-01-01')) // 1 年前
 * readableDateDiff(new Date(), new Date('2020-01-01')) // 12 天前
 * readableDateDiff(new Date(), new Date('2020-01-01')) // 3 月前
 *
 */

const I18N = {
    zh: {
        y: " 年前",
        M: " 月前",
        d: " 天前",
        h: " 小时前",
        m: " 分钟前",
        s: " 秒前",
        ss: "几秒前",
        fuzzy: "不久前",
        _y: " 年后",
        _M: " 月后",
        _d: " 天后",
        _h: " 小时后",
        _m: " 分钟后",
        _s: " 秒后",
        _ss: "几秒后",
        _fuzzy: "不久后",
    },
    en: {
        y: " years ago",
        M: " months ago",
        d: " days ago",
        h: " hours ago",
        m: " minutes ago",
        s: " seconds ago",
        fuzzy: "just now",
        _y: " years later",
        _M: " months later",
        _d: " days later",
        _h: " hours later",
        _m: " minutes later",
        _s: "seconds later",
        _fuzzy: "just later",
    },
}

export function readableDateDiff(
    date1: Date | string,
    date2: Date | string,
    options?: {
        /** 模糊 */
        fuzzy?: boolean
        /** 模糊秒 */
        fuzzySecond?: boolean
        /** i18n 语言 */
        i18n?: keyof typeof I18N
        /** 在 10 秒误差内, 保证 date1 > date2，用于客户端之间时间误差不会出现当前时间小于目标时间的情况*/
        ensureDate1Bigger?: boolean
    }
) {
    let t1 = new Date(date1).getTime()
    let t2 = new Date(date2).getTime()

    if (options?.ensureDate1Bigger && t1 < t2 && Math.abs(t1 - t2) < 10 * 1000) {
        t1 = t2
    }

    let diff = Math.abs(t1 - t2)
    let direction = t1 >= t2 ? "" : "_"

    let ms = diff
    let s = ms / 1000
    let m = s / 60
    let h = m / 60
    let d = h / 24
    let M = d / 30
    let y = M / 12

    let lang = options?.i18n || "zh"
    let Dict: any = I18N[lang]

    if (s < 60) {
        if (options?.fuzzy) {
            return Dict[direction + "fuzzy"]
        } else {
            let ft = Math.trunc(s)
            if (options?.fuzzySecond && ft < 60) {
                return Dict[direction + "ss"]
            } else {
                return Math.trunc(s) + Dict[direction + "s"]
            }
        }
    } else if (m < 60) {
        if (options?.fuzzy) {
            return Dict[direction + "fuzzy"]
        } else {
            return Math.trunc(m) + Dict[direction + "m"]
        }
    } else if (h < 24) {
        if (options?.fuzzy) {
            return Dict[direction + "fuzzy"]
        } else {
            return Math.trunc(h) + Dict[direction + "h"]
        }
    } else if (d < 30) {
        return Math.trunc(d) + Dict[direction + "d"]
    } else if (M < 12) {
        return Math.trunc(M) + Dict[direction + "M"]
    } else {
        return Math.trunc(y) + Dict[direction + "y"]
    }
}