using System.Security.Cryptography;
using System.Text;

namespace Common.Notify
{
    /// <summary>
    /// IM 机器人 Webhook 加签工具（钉钉/飞书）
    /// 供 IOT_API 直连推送与 AlertBridge 跨网转发程序共用，保证两种模式签名算法一致
    /// </summary>
    public static class ImWebhookSigner
    {
        /// <summary>
        /// 钉钉机器人加签：sign = UrlEncode(Base64(HmacSHA256(timestamp + "\n" + secret, key=secret)))
        /// </summary>
        /// <param name="timestampMs">毫秒时间戳</param>
        /// <param name="secret">加签密钥（SEC 开头）</param>
        /// <returns>URL 编码后的签名</returns>
        public static string DingTalkSign(long timestampMs, string secret)
        {
            string stringToSign = $"{timestampMs}\n{secret}";
            using var hmac = new HMACSHA256(Encoding.UTF8.GetBytes(secret));
            byte[] signData = hmac.ComputeHash(Encoding.UTF8.GetBytes(stringToSign));
            return Uri.EscapeDataString(Convert.ToBase64String(signData));
        }

        /// <summary>
        /// 飞书机器人加签：sign = Base64(HmacSHA256(空串, key=timestamp + "\n" + secret))
        /// 注意与钉钉相反：飞书以"时间戳\n密钥"为 key、对空内容签名
        /// </summary>
        /// <param name="timestampSec">秒级时间戳</param>
        /// <param name="secret">加签密钥</param>
        /// <returns>Base64 签名</returns>
        public static string FeishuSign(long timestampSec, string secret)
        {
            using var hmac = new HMACSHA256(Encoding.UTF8.GetBytes($"{timestampSec}\n{secret}"));
            byte[] signData = hmac.ComputeHash(Array.Empty<byte>());
            return Convert.ToBase64String(signData);
        }
    }
}