using System;
using System.Net;
using System.Collections.Specialized;
using System.Web;
using System.Security.Cryptography;
using System.Diagnostics;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace GetWalletTransactions
{
    class Program
    {
        static void Main(string[] args)
        {
            // Based on "OAuth 2.0 for Mobile or Desktop Applications" from https://docs.esi.evetech.net/docs/sso/native_sso_flow.html

            // Step 2
            const string clientId = "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"; // Dummy Client ID

            string authorizeUrl = @"https://login.eveonline.com/v2/oauth/authorize/";
            const string callback = @"http://127.0.0.1:12500/callback/";

            // Prepare Code Challenge
            Random random = new Random();
            const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
            string codeChallenge = new String(Enumerable.Repeat(chars, 32).Select(s => s[random.Next(s.Length)]).ToArray());
            string origEncodedCodeChallenge = urlSafeBase64Encode(codeChallenge);
            string encodedCodeChallenge = ComputeSha256Hash(origEncodedCodeChallenge);
            encodedCodeChallenge = urlSafeBase64Encode(encodedCodeChallenge);

            // Prepare Request for Authorization Code
            string[] queryStringParameters =
            {
                "response_type=code",
                "redirect_uri=" + HttpUtility.UrlEncode(callback),
                "client_id=" + clientId,
                "scope=" + HttpUtility.UrlEncode("esi-wallet.read_character_wallet.v1"),
                "code_challenge=" + encodedCodeChallenge,
                "code_challenge_method=S256",
                "state=" + HttpUtility.UrlEncode("XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX") // Dummy Secret
            };

            string queryParameters = String.Join("&", queryStringParameters);

            authorizeUrl += "?" + queryParameters;


            // Setup Listener for Authorization Code Response
            HttpListener listener = new HttpListener();
            listener.Prefixes.Add(callback);
            listener.Start();
            Console.Write("Listening...");


            // Send Request for Authorization Code
            Process.Start("chrome.exe", authorizeUrl);

            Console.WriteLine(listener.IsListening);

            HttpListenerContext context = listener.GetContext();
            HttpListenerRequest request = context.Request;

            Uri uri = new Uri(request.Url.AbsoluteUri);
            NameValueCollection parameters = HttpUtility.ParseQueryString(uri.Query);
            Console.WriteLine("Returned string: {0}", uri.Query);

            string authCode = parameters["code"];
            Console.WriteLine("Auth code: {0}", authCode);


            // Prepare Request for Access Token
            const string authBaseUrl = "https://login.eveonline.com/v2/oauth/token/";

            NameValueCollection post_params = new NameValueCollection();
            post_params.Add("grant_type", "authorization_code");
            post_params.Add("code", authCode);
            post_params.Add("client_id", clientId);
            post_params.Add("code_verifier", origEncodedCodeChallenge);

            using (WebClient client = new WebClient())
            {
                client.Encoding = Encoding.UTF8;
                client.Headers.Clear();
                client.Headers.Add("Content-Type", "application/x-www-form-urlencoded");
                client.Headers.Add("Host", "login.eveonline.com");

                Console.WriteLine();
                Console.WriteLine($"Authorization URL: {authBaseUrl}");

                try
                {
                    byte[] response = client.UploadValues(authBaseUrl, "POST", post_params);
                    Console.WriteLine(Encoding.UTF8.GetString(response));
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex);
                }
            }

            Console.ReadKey();
        }

        public static string urlSafeBase64Encode(string input)
        {
            byte[] byteArray = Encoding.UTF8.GetBytes(input);
            string working = Convert.ToBase64String(byteArray).TrimEnd('=');

            return working;
        }

        // This function was taken from: https://www.c-sharpcorner.com/article/compute-sha256-hash-in-c-sharp/
        public static string ComputeSha256Hash(string rawData)
        {
            using (SHA256 sha256Hash = SHA256.Create())
            {
                // ComputeHash - returns byte array
                byte[] bytes = sha256Hash.ComputeHash(Encoding.UTF8.GetBytes(rawData));

                // Convert byte array to a string
                StringBuilder builder = new StringBuilder();
                for (int i = 0; i < bytes.Length; i++)
                {
                    builder.Append(bytes[i].ToString("x2"));
                }

                return builder.ToString();
            }
        }
    }
}