using Telegram.Bot.SpaceApi.Backend.Utils;

namespace Telegram.Bot.SpaceApi.Backend;

public class SpaceApiClient {
	private readonly string     _apiUrl;
	private readonly HttpClient _client;

	public SpaceApiClient(string apiUrl) {
		_apiUrl = apiUrl;
		_client = new HttpClient();
	}

	public SpaceApiClient(string apiUrl, string overrideAddress) {
		_apiUrl = apiUrl;
		_client = new HttpClient(new DnsHandler(new CustomDnsResolver(overrideAddress)));
	}

	public bool IsOpen() {
		using var rq = new HttpRequestMessage(HttpMethod.Get, _apiUrl);
		rq.Headers.ConnectionClose = true;
		rq.Headers.UserAgent.ParseAdd($"Mozilla/5.0 (compatible; {ApplicationInformation.Project}/1.0; +{ApplicationInformation.Repository})");
		rq.Headers.Host = new Uri(_apiUrl).Host;

		using var resp = _client.SendAsync(rq, HttpCompletionOption.ResponseContentRead).Result;

		return SpaceApiResponse.FromJson(resp.Content.ReadAsStringAsync().Result).State.Open ?? false;
	}

	private class DnsHandler : HttpClientHandler {
		private readonly CustomDnsResolver _dnsResolver;

		public DnsHandler(CustomDnsResolver dnsResolver) {
			_dnsResolver = dnsResolver;
		}

		protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) {
			var host = request.RequestUri!.Host;
			var ip   = _dnsResolver.Resolve(host);

			var builder = new UriBuilder(request.RequestUri) { Host = ip };

			request.RequestUri = builder.Uri;

			return base.SendAsync(request, cancellationToken);
		}
	}

	private class CustomDnsResolver {
		private readonly string _address;

		public CustomDnsResolver(string address) => _address = address;

		public string Resolve(string host) {
			return _address;
		}
	}
}