using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using Jose;

namespace Sony.Filtr.AppleMusic
{
    public class AppleMusicTokenGenerator
    {
        private readonly string _privateKey;
        private readonly string _kid;
        private readonly string _iss;

        public AppleMusicTokenGenerator(string privateKey, string kid, string iss)
        {
            _privateKey = privateKey;
            _kid = kid;
            _iss = iss;
        }

        public string GetJwtToken()
        {

            var headers = new Dictionary<string, object>()
            {
                { "alg", "ES256" },
                { "kid", _kid },
            };


            var issued = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
            var expiresAt = DateTimeOffset.UtcNow.AddMonths(3).ToUnixTimeSeconds();

            var payload = new Dictionary<string, object>()
            {
                { "iss", _iss },
                { "iat", issued },
                { "exp", expiresAt }
            };

            var secretKey = CngKey.Import(Convert.FromBase64String(_privateKey), CngKeyBlobFormat.Pkcs8PrivateBlob);

            return JWT.Encode(payload, secretKey, JwsAlgorithm.ES256, headers);
        }
    }
}