private static async Task<string?> GetDRMMPDPSSH(string mpdUrl, string policy, string signature, string kvp)
{
    try
    {
        HttpClient client = new HttpClient();
        var request = new HttpRequestMessage
        {
            RequestUri = new Uri(mpdUrl),
            Method = HttpMethod.Get,
        };
        request.Headers.Add("Accept", "application/dash+xml,video/vnd.mpeg.dash.mpd");
        request.Headers.Add("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.110 Safari/537.36");
        request.Headers.Add("Cookie", $"CloudFront-Policy={policy}; CloudFront-Signature={signature}; CloudFront-Key-Pair-Id={kvp}");

        var response = await client.SendAsync(request);
        response.EnsureSuccessStatusCode();

        string mpdContent = await response.Content.ReadAsStringAsync();
        XDocument mpdDoc = XDocument.Parse(mpdContent);
        XNamespace ns = "urn:mpeg:dash:schema:mpd:2011";
        var psshElement = mpdDoc.Descendants(ns + "PSSH").FirstOrDefault();

        return psshElement?.Value;
    }
    catch (Exception ex)
    {
        Log.Error("Error getting PSSH: {0}", ex.Message);
        return null;
    }
}

private static async Task<DateTime> GetDRMMPDLastModified(string mpdUrl, string policy, string signature, string kvp)
{
    try
    {
        HttpClient client = new HttpClient();
        var request = new HttpRequestMessage
        {
            RequestUri = new Uri(mpdUrl),
            Method = HttpMethod.Head,
        };
        request.Headers.Add("Accept", "application/dash+xml,video/vnd.mpeg.dash.mpd");
        request.Headers.Add("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.110 Safari/537.36");
        request.Headers.Add("Cookie", $"CloudFront-Policy={policy}; CloudFront-Signature={signature}; CloudFront-Key-Pair-Id={kvp}");

        var response = await client.SendAsync(request);
        response.EnsureSuccessStatusCode();

        return response.Content.Headers.LastModified?.DateTime ?? DateTime.Now;
    }
    catch (Exception ex)
    {
        Log.Error("Error getting MPD last modified date: {0}", ex.Message);
        return DateTime.Now;
    }
}

private static Dictionary<string, string> GetDynamicHeaders(string url, string queryParams)
{
    var headers = new Dictionary<string, string>();
    try
    {
        headers = auth.GetDynamicHeaders(url, queryParams);
    }
    catch (Exception ex)
    {
        Log.Error("Error getting dynamic headers: {0}", ex.Message);
    }
    return headers;
}

private static async Task<string> GetDecryptionKeyOFDL(Dictionary<string, string> drmHeaders, string licenseUrl, string pssh)
{
    try
    {
        var client = new HttpClient();
        var request = new HttpRequestMessage(HttpMethod.Post, "https://ofdl.tools/wv")
        {
            Content = new FormUrlEncodedContent(new Dictionary<string, string>
            {
                { "license_url", licenseUrl },
                { "headers", JsonConvert.SerializeObject(drmHeaders) },
                { "pssh", pssh },
                { "build_identifier", "windows_software_widevinecdm_win_x86_64" },
                { { "proxy", "" }
            })
        };

        var response = await client.SendAsync(request);
        response.EnsureSuccessStatusCode();

        var responseContent = await response.Content.ReadAsStringAsync();
        var jsonResponse = JObject.Parse(responseContent);
        return jsonResponse["keys"][0]["key"].ToString();
    }
    catch (Exception ex)
    {
        Log.Error("Error getting decryption key from OFDL: {0}", ex.Message);
        throw;
    }
}

private static async Task<string> GetDecryptionKeyCDM(Dictionary<string, string> drmHeaders, string licenseUrl, string pssh)
{
    try
    {
        var client = new WidevineClient.Widevine.CDMClient();
        return await client.GetContentKey(licenseUrl, drmHeaders, pssh);
    }
    catch (Exception ex)
    {
        Log.Error("Error getting decryption key from CDM: {0}", ex.Message);
        throw;
    }
}

private static async Task<bool> DownloadPurchasedMessageDRMVideo(
    string policy,
    string signature,
    string kvp,
    string url,
    string decryptionKey,
    string folder,
    DateTime lastModified,
    long media_id,
    string api_type,
    ProgressTask task,
    string filenameFormat,
    Purchased.List? messageInfo,
    Medium? messageMedia,
    User? fromUser,
    Dictionary<string, int> users)
{
    try
    {
        string filename = string.Empty;
        string customFileName = string.Empty;
        string path = string.Empty;

        if (messageInfo != null && messageMedia != null && fromUser != null)
        {
            filename = await DownloadHelper.GenerateFilename(filenameFormat, "Messages", messageInfo, messageMedia, fromUser, users, api_type);
            customFileName = filename.Split('.')[0];
            path = Path.Combine(folder, filename);
        }
        else
        {
            filename = $"{media_id}.mp4";
            path = Path.Combine(folder, filename);
        }

        if (File.Exists(path) && new FileInfo(path).Length > 0)
        {
            return false;
        }

        var downloader = new DownloadHelper.DRMVideoDownloader();
        await downloader.DownloadDRMVideo(
            url: url,
            decryptionKey: decryptionKey,
            folder: folder,
            lastModified: lastModified,
            policy: policy,
            signature: signature,
            kvp: kvp,
            customFileName: customFileName,
            task: task);

        return true;
    }
    catch (Exception ex)
    {
        Log.Error("Error downloading DRM video: {0}", ex.Message);
        return false;
    }
}

private static async Task<bool> DownloadPurchasedMedia(
    string url,
    string folder,
    long media_id,
    string api_type,
    ProgressTask task,
    string filenameFormat,
    Purchased.List? messageInfo,
    Medium? messageMedia,
    User? fromUser,
    Dictionary<string, int> users)
{
    try
    {
        string filename = string.Empty;
        string path = string.Empty;

        if (messageInfo != null && messageMedia != null && fromUser != null)
        {
            filename = await DownloadHelper.GenerateFilename(filenameFormat, "Messages", messageInfo, messageMedia, fromUser, users, api_type);
            path = Path.Combine(folder, filename);
        }
        else
        {
            filename = $"{media_id}.mp4";
            path = Path.Combine(folder, filename);
        }

        if (File.Exists(path) && new FileInfo(path).Length > 0)
        {
            return false;
        }

        var downloader = new DownloadHelper.MediaDownloader();
        await downloader.DownloadMedia(
            url: url,
            folder: folder,
            filename: filename,
            task: task);

        return true;
    }
    catch (Exception ex)
    {
        Log.Error("Error downloading media: {0}", ex.Message);
        return false;
    }
}