using System;
using System.IdentityModel.Tokens.Jwt;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using FlexitimeAPI.Interfaces;
using FlexitimeAPI.Models;
using FlexitimeAPI.Services;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Options;
using Microsoft.IdentityModel.Tokens;

namespace FlexitimeAPI.Helpers
{
    public class JwtMiddleware
    {
        private readonly IApplicationSettings _appSettings;
        private readonly RequestDelegate _next;

        public JwtMiddleware(RequestDelegate next, IApplicationSettings appSettings)
        {
            _next = next;
            _appSettings = appSettings;
        }

        public async Task Invoke(HttpContext context, IUserService userService)
        {
            var token = context.Request.Headers["Authorization"].FirstOrDefault()?.Split(" ").Last();

            if (token != null)
                await AttachUserToContext(context, userService, token);

            await _next(context);
        }

        private async Task AttachUserToContext(HttpContext context, IUserService userService, string token)
        {
            try
            {
                var tokenHandler = new JwtSecurityTokenHandler();
                var key = Encoding.ASCII.GetBytes(_appSettings.Secret);
                tokenHandler.ValidateToken(token, new TokenValidationParameters
                {
                    ValidateIssuerSigningKey = true,
                    IssuerSigningKey = new SymmetricSecurityKey(key),
                    ValidateIssuer = false,
                    ValidateAudience = false,
                    // set clockskew to zero so tokens expire exactly at token expiration time (instead of 5 minutes later)
                    ClockSkew = TimeSpan.Zero
                }, out var validatedToken);

                var jwtToken = (JwtSecurityToken) validatedToken;
                var userId = Guid.Parse(jwtToken.Claims.First(x => x.Type == "id").Value);
                // attach user to context on successful jwt validation
                context.Items["User"] = await userService.GetById(userId);
            }
            catch(Exception ex)
            {
                // do nothing if jwt validation fails
                // user is not attached to context so request won't have access to secure routes
            }
        }
    }
}