import Foundation

/// 后端 ISO 8601 时间字符串 → 友好展示。后端 datetime 可能带/不带时区与微秒,逐档尝试解析。
enum AppDate {
    static func friendly(_ iso: String) -> String {
        guard let date = parse(iso) else { return String(iso.prefix(10)) }
        let f = DateFormatter()
        f.locale = Locale(identifier: "zh_CN")
        f.dateFormat = "M月d日"
        return f.string(from: date)
    }

    private static func parse(_ iso: String) -> Date? {
        let isoFmt = ISO8601DateFormatter()
        isoFmt.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
        if let d = isoFmt.date(from: iso) { return d }
        isoFmt.formatOptions = [.withInternetDateTime]
        if let d = isoFmt.date(from: iso) { return d }

        let df = DateFormatter()
        df.locale = Locale(identifier: "en_US_POSIX")
        df.timeZone = TimeZone(identifier: "Asia/Shanghai")
        for fmt in ["yyyy-MM-dd'T'HH:mm:ss.SSSSSS", "yyyy-MM-dd'T'HH:mm:ss.SSS", "yyyy-MM-dd'T'HH:mm:ss"] {
            df.dateFormat = fmt
            if let d = df.date(from: iso) { return d }
        }
        return nil
    }
}