using IdentityModel;
using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.AspNetCore.Authorization;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.IdentityModel.Tokens;
using System;
using System.Threading.Tasks;
using System.Security.Claims;
using System.IdentityModel.Tokens.Jwt;
using System.Collections.Generic;
using System.Text;

namespace TEAMModelOS.SDK.Extension
{
    public static class JwtAuthExtension
    {
        public static string CreateAuthToken(string issuer, string userID, string salt, string[] roles = null, string[] permissions = null, int expire = 1)
        {
            // 設定要加入到 JWT Token 中的聲明資訊(Claims)
            var claims = new List<Claim>();
            // 在 RFC 7519 規格中(Section#4)，總共定義了 7 個預設的 Claims
            claims.Add(new Claim(JwtRegisteredClaimNames.Iss, issuer)); //發行者
            claims.Add(new Claim(JwtRegisteredClaimNames.Sub, userID)); // 用戶ID            
            claims.Add(new Claim(JwtRegisteredClaimNames.Exp, DateTimeOffset.UtcNow.AddHours(expire).ToUnixTimeSeconds().ToString())); // 到期的時間，必須為數字

            // 擴充 "roles" 加入登入者的角色，角色類型 (USER、HABOOK) 
            foreach (var role in roles)
            {
                claims.Add(new Claim("roles", role));
            }
            // 擴充 "permissions" 加入登入者的權限請求  

            foreach (var role in permissions)
            {
                claims.Add(new Claim("permissions", role));
            }           

            // 建立一組對稱式加密的金鑰，主要用於 JWT 簽章之用
            var securityKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(salt));
            // HmacSha256 有要求必須要大於 128 bits，所以 salt 不能太短，至少要 16 字元以上
            // https://stackoverflow.com/questions/47279947/idx10603-the-algorithm-hs256-requires-the-securitykey-keysize-to-be-greater
            var signingCredentials = new SigningCredentials(securityKey, SecurityAlgorithms.HmacSha256Signature);
            // 建立 SecurityTokenDescriptor
            var tokenDescriptor = new SecurityTokenDescriptor
            {                
                Issuer = issuer,
                Subject = new ClaimsIdentity(claims),
                Expires = DateTime.Now.AddHours(expire),
                SigningCredentials = signingCredentials
            };

            // 產出所需要的 JWT securityToken 物件，並取得序列化後的 Token 結果(字串格式)
            var tokenHandler = new JwtSecurityTokenHandler();
            var securityToken = tokenHandler.CreateToken(tokenDescriptor);
            var serializeToken = tokenHandler.WriteToken(securityToken);

            return serializeToken;
        }

        public static bool ValidateAuthToken(string token, string salt)
        {
            try
            {
                var handler = new JwtSecurityTokenHandler();
                var validationParameters = new TokenValidationParameters
                {
                    RequireExpirationTime = true,
                    ValidateIssuer = false,
                    ValidateAudience = false,
                    IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(salt)),
                    ValidateLifetime = false,
                    //LifetimeValidator = LifetimeValidator,
                    ClockSkew = TimeSpan.Zero
                };
                ClaimsPrincipal principal = handler.ValidateToken(token, validationParameters, out SecurityToken securityToken);
                return true;
            }
            catch (Exception ex)
            {
                //Trace.WriteLine(ex.Message);
                return false;
            }
        }
    }
}