using System;
using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using System.Security.Principal;
using System.Threading.Tasks;
using Microsoft.Extensions.Options;
using static BlueWest.WebApi.Context.Users.Constants;

namespace BlueWest.WebApi.Context.Users;

public class JwtFactory : IJwtFactory
{
    private readonly IJwtTokenHandler _jwtTokenHandler;
    private readonly JwtIssuerOptions _jwtOptions;

    public JwtFactory(IJwtTokenHandler jwtTokenHandler, IOptions<JwtIssuerOptions> jwtOptions)
    {
        _jwtTokenHandler = jwtTokenHandler;
        _jwtOptions = jwtOptions.Value;
        ThrowIfInvalidOptions(_jwtOptions);
    }

    public async Task<AccessToken> GenerateEncodedToken(string id, string userName)
    {
        var identity = GenerateClaimsIdentity(id, userName);

        var claims = new[]
        {
            new Claim(JwtRegisteredClaimNames.Sub, userName),
            new Claim(JwtRegisteredClaimNames.Jti, await _jwtOptions.JtiGenerator()),
            new Claim(JwtRegisteredClaimNames.Iat, ToUnixEpochDate(_jwtOptions.IssuedAt).ToString(),
                ClaimValueTypes.Integer64),
            identity.FindFirst(JwtClaimIdentifiers.Rol),
            identity.FindFirst(JwtClaimIdentifiers.Id)
        };

        // Create the JWT security token and encode it.
        var jwt = new JwtSecurityToken(
            _jwtOptions.Issuer,
            _jwtOptions.Audience,
            claims,
            _jwtOptions.NotBefore,
            _jwtOptions.Expiration,
            _jwtOptions.SigningCredentials);

        return new AccessToken(_jwtTokenHandler.WriteToken(jwt), (int)_jwtOptions.ValidFor.TotalSeconds);
    }

    private static ClaimsIdentity GenerateClaimsIdentity(string id, string userName)
    {
        return new ClaimsIdentity(new GenericIdentity(userName, "Token"), new[]
        {
            new Claim(JwtClaimIdentifiers.Id, id),
            new Claim(JwtClaimIdentifiers.Rol, JwtClaims.ApiAccess)
        });
    }

    /// <returns>Date converted to seconds since Unix epoch (Jan 1, 1970, midnight UTC).</returns>
    private static long ToUnixEpochDate(DateTime date)
        => (long)Math.Round((date.ToUniversalTime() -
                             new DateTimeOffset(1970, 1, 1, 0, 0, 0, TimeSpan.Zero))
            .TotalSeconds);

    private static void ThrowIfInvalidOptions(JwtIssuerOptions options)
    {
        if (options == null) throw new ArgumentNullException(nameof(options));

        if (options.ValidFor <= TimeSpan.Zero)
        {
            throw new ArgumentException("Must be a non-zero TimeSpan.", nameof(JwtIssuerOptions.ValidFor));
        }

        if (options.SigningCredentials == null)
        {
            throw new ArgumentNullException(nameof(JwtIssuerOptions.SigningCredentials));
        }

        if (options.JtiGenerator == null)
        {
            throw new ArgumentNullException(nameof(JwtIssuerOptions.JtiGenerator));
        }
    }
}