namespace Monitor.Backend.Application;

/// <summary>
/// 把「ASN 和组织名」归成几个常见的国内运营商：mobile / telecom / unicom / broadnet；别的是 other（显示组织名）。
/// 只用来挑展示用的图标和中文名。
/// </summary>
public static class IspClassifier
{
    public const string Mobile = "mobile";
    public const string Telecom = "telecom";
    public const string Unicom = "unicom";
    public const string Broadnet = "broadnet";
    public const string Other = "other";

    private static readonly HashSet<int> s_mobile = [9808, 24400, 24445, 56040, 56041, 56042, 56044, 56046, 56047, 56048, 132525, 138407];
    private static readonly HashSet<int> s_telecom = [4134, 4809, 4811, 4812, 4813, 9394, 17638, 23724, 38283, 58466, 58519, 136188, 137693];
    private static readonly HashSet<int> s_unicom = [4808, 4837, 9929, 10099, 17621, 17622, 17623, 17816, 136958, 138421];
    private static readonly HashSet<int> s_broadnet = [63838, 140061];

    public static (string Key, string Name) Classify(int? asn, string? organization)
    {
        if (asn is { } a)
        {
            if (s_mobile.Contains(a))
            {
                return (Mobile, "中国移动");
            }

            if (s_telecom.Contains(a))
            {
                return (Telecom, "中国电信");
            }

            if (s_unicom.Contains(a))
            {
                return (Unicom, "中国联通");
            }

            if (s_broadnet.Contains(a))
            {
                return (Broadnet, "中国广电");
            }
        }

        string org = organization ?? string.Empty;
        if (Has(org, "china mobile") || Has(org, "cmnet") || Has(org, "中国移动"))
        {
            return (Mobile, "中国移动");
        }

        if (Has(org, "china telecom") || Has(org, "chinanet") || Has(org, "中国电信"))
        {
            return (Telecom, "中国电信");
        }

        if (Has(org, "china unicom") || Has(org, "cncgroup") || Has(org, "中国联通"))
        {
            return (Unicom, "中国联通");
        }

        if (Has(org, "china broadnet") || Has(org, "中国广电"))
        {
            return (Broadnet, "中国广电");
        }

        return (Other, Shorten(org));
    }

    private static bool Has(string text, string needle) => text.Contains(needle, StringComparison.OrdinalIgnoreCase);

    /// <summary>组织名常常很长（「Hangzhou Alibaba Advertising Co.,Ltd.」）：去掉公司后缀，最多留 28 个字符。</summary>
    internal static string Shorten(string organization)
    {
        string name = organization.Trim();
        foreach (string suffix in new[] { ", Inc.", " Inc.", ", LLC", " LLC", " Co.,Ltd.", " Co., Ltd.", " Co.,Ltd", " Co., Ltd", " Ltd.", " Ltd", " Corporation", " Corp.", " Limited", " GmbH", " B.V.", " S.A." })
        {
            if (name.EndsWith(suffix, StringComparison.OrdinalIgnoreCase))
            {
                name = name[..^suffix.Length].TrimEnd(',', ' ');
                break;
            }
        }

        return name.Length > 28 ? name[..28].TrimEnd() : name;
    }
}