// Kyoo - A portable and vast media library solution.
// Copyright (c) Kyoo.
//
// See AUTHORS.md and LICENSE file in the project root for full license information.
//
// Kyoo is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// any later version.
//
// Kyoo is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Kyoo. If not, see <https://www.gnu.org/licenses/>.

using System;
using System.Collections.Generic;
using System.IdentityModel.Tokens.Jwt;
using System.Linq;
using System.Security.Claims;
using System.Text;
using System.Threading.Tasks;
using Kyoo.Abstractions.Models;
using Kyoo.Authentication.Models;
using Microsoft.IdentityModel.Tokens;

namespace Kyoo.Authentication
{
	/// <summary>
	/// The service that controls jwt creation and validation.
	/// </summary>
	public class TokenController : ITokenController
	{
		/// <summary>
		/// The options that this controller will use.
		/// </summary>
		private readonly AuthenticationOption _options;

		/// <summary>
		/// Create a new <see cref="TokenController"/>.
		/// </summary>
		/// <param name="options">The options that this controller will use.</param>
		public TokenController(AuthenticationOption options)
		{
			_options = options;
		}

		/// <inheritdoc />
		public string CreateAccessToken(User user, out TimeSpan expireIn)
		{
			expireIn = new TimeSpan(1, 0, 0);

			SymmetricSecurityKey key = new(Encoding.UTF8.GetBytes(_options.Secret));
			SigningCredentials credential = new(key, SecurityAlgorithms.HmacSha256Signature);
			string permissions = user.Permissions != null
				? string.Join(',', user.Permissions)
				: string.Empty;
			List<Claim> claims = new()
			{
				new Claim(Claims.Id, user.Id.ToString()),
				new Claim(Claims.Name, user.Username),
				new Claim(Claims.Permissions, permissions),
				new Claim(Claims.Type, "access")
			};
			if (user.Email != null)
				claims.Add(new Claim(Claims.Email, user.Email));
			JwtSecurityToken token = new(
				signingCredentials: credential,
				claims: claims,
				expires: DateTime.UtcNow.Add(expireIn)
			);
			return new JwtSecurityTokenHandler().WriteToken(token);
		}

		/// <inheritdoc />
		public Task<string> CreateRefreshToken(User user)
		{
			SymmetricSecurityKey key = new(Encoding.UTF8.GetBytes(_options.Secret));
			SigningCredentials credential = new(key, SecurityAlgorithms.HmacSha256Signature);
			JwtSecurityToken token = new(
				signingCredentials: credential,
				claims: new[]
				{
					new Claim(Claims.Id, user.Id.ToString()),
					new Claim(Claims.Guid, Guid.NewGuid().ToString()),
					new Claim(Claims.Type, "refresh")
				},
				expires: DateTime.UtcNow.AddYears(1)
			);
			// TODO: refresh keys are unique (thanks to the guid) but we could store them in DB to invalidate them if requested by the user.
			return Task.FromResult(new JwtSecurityTokenHandler().WriteToken(token));
		}

		/// <inheritdoc />
		public Guid GetRefreshTokenUserID(string refreshToken)
		{
			SymmetricSecurityKey key = new(Encoding.UTF8.GetBytes(_options.Secret));
			JwtSecurityTokenHandler tokenHandler = new();
			ClaimsPrincipal principal;
			try
			{
				principal = tokenHandler.ValidateToken(refreshToken, new TokenValidationParameters
				{
					ValidateIssuer = false,
					ValidateAudience = false,
					ValidateIssuerSigningKey = true,
					ValidateLifetime = true,
					IssuerSigningKey = key
				}, out SecurityToken _);
			}
			catch (Exception)
			{
				throw new SecurityTokenException("Invalid refresh token");
			}

			if (principal.Claims.First(x => x.Type == Claims.Type).Value != "refresh")
				throw new SecurityTokenException("Invalid token type. The token should be a refresh token.");
			Claim identifier = principal.Claims.First(x => x.Type == Claims.Id);
			if (Guid.TryParse(identifier.Value, out Guid id))
				return id;
			throw new SecurityTokenException("Token not associated to any user.");
		}
	}
}