using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;

namespace CRD.Utils;

public class ChallengeDetector{
    private static readonly HashSet<string> CloudflareServerNames = new HashSet<string>{
        "cloudflare",
        "cloudflare-nginx",
        "ddos-guard"
    };

    /// <summary>
    /// Checks if clearance is required.
    /// </summary>
    /// <param name="response">The HttpResponseMessage to check.</param>
    /// <returns>True if the site requires clearance</returns>
    public static bool IsClearanceRequired(HttpResponseMessage response) => IsCloudflareProtected(response);

    /// <summary>
    /// Checks if the site is protected by Cloudflare
    /// </summary>
    /// <param name="response">The HttpResponseMessage to check.</param>
    /// <returns>True if the site is protected</returns>
    private static bool IsCloudflareProtected(HttpResponseMessage response){
        // check response headers
        if (!response.Headers.Server.Any(i =>
                i.Product != null && CloudflareServerNames.Contains(i.Product.Name.ToLower())))
            return false;

        // detect CloudFlare and DDoS-GUARD
        if (response.StatusCode.Equals(HttpStatusCode.ServiceUnavailable) ||
            response.StatusCode.Equals(HttpStatusCode.Forbidden)){
            var responseHtml = response.Content.ReadAsStringAsync().Result;
            if (responseHtml.Contains("<title>Just a moment...</title>") || // Cloudflare
                responseHtml.Contains("<title>Access denied</title>") || // Cloudflare Blocked
                responseHtml.Contains("<title>Attention Required! | Cloudflare</title>") || // Cloudflare Blocked
                responseHtml.Trim().Equals("error code: 1020") || // Cloudflare Blocked
                responseHtml.IndexOf("<title>DDOS-GUARD</title>", StringComparison.OrdinalIgnoreCase) > -1) // DDOS-GUARD
                return true;
        }

        // detect Custom CloudFlare for EbookParadijs, Film-Paleis, MuziekFabriek and Puur-Hollands
        if (response.Headers.Vary.ToString() == "Accept-Encoding,User-Agent" &&
            response.Content.Headers.ContentEncoding.ToString() == "" &&
            response.Content.ReadAsStringAsync().Result.ToLower().Contains("ddos"))
            return true;

        return false;
    }
}