using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace BaronSoftware.SSO
{
    internal static class PKCEUtil
    {
        public static string NewVerifier() => B64Url(RandomNumberGenerator.GetBytes(32));
        public static string RandomToken() => B64Url(RandomNumberGenerator.GetBytes(16));
        public static string Challenge(string verifier) => B64Url(SHA256.HashData(Encoding.ASCII.GetBytes(verifier)));
        private static string B64Url(byte[] bytes) => Convert.ToBase64String(bytes).TrimEnd('=').Replace('+', '-').Replace('/', '_');
        public static Dictionary<string, string> ParseQuery(string uri)
        {
            var result = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
            var query = new Uri(uri).Query.TrimStart('?');
            foreach (var pair in query.Split('&', StringSplitOptions.RemoveEmptyEntries))
            {
                var kv = pair.Split('=', 2);
                result[Uri.UnescapeDataString(kv[0])] = kv.Length > 1 ? Uri.UnescapeDataString(kv[1]) : string.Empty;
            }
            return result;
        }
    }
}