using FileShare_EFCore.Models;
using Microsoft.Extensions.Options;
using Microsoft.IdentityModel.Tokens;
using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using System.Text;

namespace FileShare_API.Authentication
{
    /// <summary>
    /// JWT Token 服务，负责创建包含用户声明和角色的 Access Token。
    /// </summary>
    public sealed class JwtTokenService(IOptions<JwtOptions> options)
    {
        /// <summary>
        /// JWT 配置选项。
        /// </summary>
        private readonly JwtOptions _options = options.Value;

        /// <summary>
        /// 创建包含用户声明和角色的 JWT Access Token。
        /// </summary>
        /// <param name="user">用户实体。</param>
        /// <param name="roles">角色集合。</param>
        /// <returns>包含 Token 字符串和过期时间的元组。</returns>
        public (string Token, DateTime ExpiresAt) CreateAccessToken(UserEntity user, IReadOnlyCollection<string> roles)
        {
            var expiresAt = DateTime.UtcNow.AddMinutes(_options.AccessTokenMinutes);
            var claims = new List<Claim>
            {
                new(JwtRegisteredClaimNames.Sub, user.Id.ToString()),
                new(ClaimTypes.NameIdentifier, user.Id.ToString()),
                new(ClaimTypes.Name, user.Name ?? user.Email ?? $"user-{user.Id}"),
                new("auth_type", "api-jwt"),
            };

            foreach (var role in roles.Where(role => !string.IsNullOrWhiteSpace(role)).Distinct(StringComparer.OrdinalIgnoreCase))
            {
                claims.Add(new Claim(ClaimTypes.Role, role));
            }

            var signingKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_options.SigningKey));
            var credentials = new SigningCredentials(signingKey, SecurityAlgorithms.HmacSha256);
            var jwt = new JwtSecurityToken(
                issuer: _options.Issuer,
                audience: _options.Audience,
                claims: claims,
                notBefore: DateTime.UtcNow,
                expires: expiresAt,
                signingCredentials: credentials);

            return (new JwtSecurityTokenHandler().WriteToken(jwt), expiresAt);
        }
    }
}