using System.Net.Http;
using System.Net.Http.Json;
using System.Security.Cryptography;
using System.Text;

namespace Admin.NET.Plugin.ApprovalFlow.Service;

/// <summary>
/// 钉钉推送（P4-16 - 首版 Webhook 机制）
/// 通过配置的群机器人 Webhook URL（含 access_token）推送文本消息。
/// 不做 DingTalk 应用消息（需要 DingId 与 AgentId，留待后续 P5 补齐 SysUser.DingId 字段）。
/// 若配置了 Secret 则按钉钉官方规范加签发送。
/// </summary>
public class DingTalkNotifyPusher : INotifyPusher, ITransient
{
    public string Channel => "DingTalk";

    private static readonly HttpClient _httpClient = new() { Timeout = TimeSpan.FromSeconds(5) };

    public bool IsEnabled(NotifyChannelConfig cfg) =>
        cfg?.DingTalk == true && !string.IsNullOrWhiteSpace(cfg.DingTalkWebhookUrl);

    public async Task<FlowNotifyPushResult> PushAsync(List<long> userIds, FlowNotification notification)
    {
        var cfg = App.GetConfig<NotifyChannelConfig>("ApprovalFlow:Notify");
        var url = cfg?.DingTalkWebhookUrl;
        if (string.IsNullOrWhiteSpace(url)) return FlowNotifyPushResult.Ok(0);

        if (!string.IsNullOrWhiteSpace(cfg.DingTalkSecret))
        {
            var ts = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
            var stringToSign = $"{ts}\n{cfg.DingTalkSecret}";
            using var hmac = new HMACSHA256(Encoding.UTF8.GetBytes(cfg.DingTalkSecret));
            var sign = Uri.EscapeDataString(
                Convert.ToBase64String(hmac.ComputeHash(Encoding.UTF8.GetBytes(stringToSign))));
            url += $"&timestamp={ts}&sign={sign}";
        }

        var content = $"【{notification.Title}】\n{notification.Content}\n实例: {notification.InstanceId}";
        var payload = new { msgtype = "text", text = new { content } };

        try
        {
            var resp = await _httpClient.PostAsJsonAsync(url, payload);
            var body = await resp.Content.ReadAsStringAsync();
            if (!resp.IsSuccessStatusCode)
                return FlowNotifyPushResult.Fail($"HTTP {(int)resp.StatusCode}: {body}");
            if (body.Contains("\"errcode\":0") || body.Contains("errcode\": 0"))
                return FlowNotifyPushResult.Ok(userIds.Count);
            return FlowNotifyPushResult.Fail($"DingTalk resp: {body}");
        }
        catch (Exception ex)
        {
            return FlowNotifyPushResult.Fail(ex.Message);
        }
    }
}