public LinkPreviewService()
{
_client = new InternalHttpClient();
//following https://developers.whatismybrowser.com/learn/browser-detection/user-agents/user-agent-best-practices
var assembly = this.GetType().Assembly;
string libUserAgentString = $"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.71 Safari/537.36 Edg/97.0.1072.55 {assembly.GetName().Name}/{assembly.GetName().Version.ToString()}";
_configWithCompression = new HttpClientConfiguration()
{
AcceptHeader = "text/html",
CustomUserAgentString = libUserAgentString,
AllowRedirect = false,
UseCookies = false,
UseCompression = true,
Timeout = TimeSpan.FromSeconds(30)
};
_configWithOutCompression = new HttpClientConfiguration()
{
AcceptHeader = "text/html",
CustomUserAgentString = libUserAgentString,
AllowRedirect = false,
UseCookies = false,
UseCompression = false,
Timeout = TimeSpan.FromSeconds(30)
};
_httpClientInstance = _client.GetStaticClient(_configWithCompression);
}
public HttpClient GetStaticClient(HttpClientConfiguration configuration)
{
if (_httpClientInstance == null)
{
var handler = new HttpClientHandler()
{
AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate,
AllowAutoRedirect = configuration.AllowRedirect,
UseCookies = configuration.UseCookies
};
_httpClientInstance = new HttpClient(handler);
if (configuration.ModifiedSince.HasValue)
{
_httpClientInstance.DefaultRequestHeaders.IfModifiedSince = new DateTimeOffset(configuration.ModifiedSince.Value);
}
if (configuration.UseCompression)
{
_httpClientInstance.DefaultRequestHeaders.AcceptEncoding.Add(new StringWithQualityHeaderValue("gzip"));
_httpClientInstance.DefaultRequestHeaders.AcceptEncoding.Add(new StringWithQualityHeaderValue("deflate"));
}
_httpClientInstance.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue(configuration.AcceptHeader));
_httpClientInstance.DefaultRequestHeaders.AcceptCharset.Add(new StringWithQualityHeaderValue(configuration.AcceptCharsetHeader));
_httpClientInstance.Timeout = configuration.Timeout;
if (string.IsNullOrEmpty(configuration.CustomUserAgentString))
{
var assembly = this.GetType().Assembly;
_httpClientInstance.DefaultRequestHeaders.UserAgent.Add(
new ProductInfoHeaderValue(string.IsNullOrEmpty(configuration.DefaultUserAgent) ? assembly.GetName().Name : configuration.DefaultUserAgent,
string.IsNullOrEmpty(configuration.UserAgentVersion) ? assembly.GetName().Version.ToString() : configuration.UserAgentVersion));
}
else
{
_httpClientInstance.DefaultRequestHeaders.Add("user-agent", configuration.CustomUserAgentString);
}
}
return(_httpClientInstance);
}