using Avalonia_Common.Core;
using Avalonia_EFCore.Database;
using Avalonia_EFCore.Models;
using Avalonia_Services.Core;
using Avalonia_Services.Services.AuthService;
using Microsoft.EntityFrameworkCore;
using System.Text.Json;

namespace Avalonia_API.Authentication
{
    /// <summary>
    /// API 鉴权端点服务，实现 <see cref="IApiAuthEndpointService"/>，
    /// 处理登录、刷新 Token 和登出操作，使用 JWT 与 Refresh Token 机制。
    /// </summary>
    public sealed class ApiAuthEndpointService(
        AppDataContext db,
        JwtTokenService jwtTokenService,
        RefreshTokenService refreshTokenService) : IApiAuthEndpointService
    {
        private static readonly JsonSerializerOptions JsonOptions = new()
        {
            PropertyNameCaseInsensitive = true,
        };

        /// <summary>
        /// 处理用户登录请求。根据账号（邮箱或用户名）查找或创建用户，
        /// 生成 JWT Access Token 和 Refresh Token 并返回。
        /// </summary>
        /// <param name="ctx">服务端点上下文，包含请求体、请求头等信息。</param>
        /// <returns>包含 AccessToken、RefreshToken 及过期时间的认证响应。</returns>
        public async Task<object?> LoginAsync(ServiceEndpointContext ctx)
        {
            var request = Deserialize<ApiLoginRequest>(ctx.Body);
            if (string.IsNullOrWhiteSpace(request?.Account))
            {
                ctx.StatusCode = 400;
                return ResponseHelper.Failure(400, "账号不能为空");
            }

            var user = await db.Users.FirstOrDefaultAsync(
                x => x.Email == request.Account || x.Name == request.Account);

            if (user is null)
            {
                user = new UserEntity
                {
                    Name = request.Account,
                    Email = request.Account.Contains('@') ? request.Account : null,
                };
                db.Users.Add(user);
                await db.SaveChangesAsync();
            }

            var roles = NormalizeRoles(request.Roles);
            var accessToken = jwtTokenService.CreateAccessToken(user, roles);
            var refreshToken = await refreshTokenService.CreateAsync(
                user.Id,
                ctx.GetHeader("User-Agent"),
                GetRemoteIpAddress(ctx));

            return ResponseHelper.Ok(new AuthTokenResponse(
                accessToken.Token,
                refreshToken.Token,
                accessToken.ExpiresAt,
                refreshToken.Entity.ExpiresAt,
                roles), "登录成功");
        }

        /// <summary>
        /// 使用 Refresh Token 轮换新的 Access Token 和 Refresh Token。
        /// 旧的 Refresh Token 会被撤销并替换。
        /// </summary>
        /// <param name="ctx">服务端点上下文，包含请求体中的 RefreshToken。</param>
        /// <returns>新的 Token 对；若 Refresh Token 无效则返回 401 错误。</returns>
        public async Task<object?> RefreshAsync(ServiceEndpointContext ctx)
        {
            var request = Deserialize<ApiRefreshTokenRequest>(ctx.Body);
            var rotated = await refreshTokenService.RotateAsync(
                request?.RefreshToken,
                ctx.GetHeader("User-Agent"),
                GetRemoteIpAddress(ctx));

            if (rotated is null)
            {
                ctx.StatusCode = 401;
                return ResponseHelper.Failure(401, "刷新 token 无效或已过期");
            }

            var user = await db.Users.FindAsync(rotated.Value.Entity.UserId);
            if (user is null)
            {
                ctx.StatusCode = 401;
                return ResponseHelper.Failure(401, "用户不存在");
            }

            var roles = new[] { "Admin" };
            var accessToken = jwtTokenService.CreateAccessToken(user, roles);

            return ResponseHelper.Ok(new AuthTokenResponse(
                accessToken.Token,
                rotated.Value.Token,
                accessToken.ExpiresAt,
                rotated.Value.Entity.ExpiresAt,
                roles), "刷新成功");
        }

        /// <summary>
        /// 处理用户登出请求，撤销指定的 Refresh Token。
        /// </summary>
        /// <param name="ctx">服务端点上下文，包含请求体中的 RefreshToken。</param>
        /// <returns>登出成功的响应。</returns>
        public async Task<object?> LogoutAsync(ServiceEndpointContext ctx)
        {
            var request = Deserialize<ApiLogoutRequest>(ctx.Body);
            await refreshTokenService.RevokeAsync(request?.RefreshToken);
            return ResponseHelper.Succeed("退出成功");
        }

        /// <summary>
        /// 将 JSON 请求体反序列化为指定类型。
        /// </summary>
        /// <typeparam name="T">目标类型。</typeparam>
        /// <param name="body">JSON 请求体字符串，可为空。</param>
        /// <returns>反序列化后的对象；若 body 为空则返回默认值。</returns>
        private static T? Deserialize<T>(string? body)
        {
            return string.IsNullOrWhiteSpace(body)
                ? default
                : JsonSerializer.Deserialize<T>(body, JsonOptions);
        }

        /// <summary>
        /// 从上下文的 Items 中提取 ASP.NET Core HttpContext，并获取客户端远程 IP 地址。
        /// </summary>
        /// <param name="ctx">服务端点上下文。</param>
        /// <returns>客户端 IP 地址字符串；若无法获取则返回 null。</returns>
        private static string? GetRemoteIpAddress(ServiceEndpointContext ctx)
        {
            return ctx.Items.TryGetValue("HttpContext", out var value) && value is HttpContext httpContext
                ? httpContext.Connection.RemoteIpAddress?.ToString()
                : null;
        }

        /// <summary>
        /// 规范化角色数组：去空白、去重（忽略大小写），为空时默认返回 Admin 角色。
        /// </summary>
        /// <param name="roles">原始角色数组，可为 null。</param>
        /// <returns>规范化后的角色数组。</returns>
        private static string[] NormalizeRoles(string[]? roles)
        {
            var normalized = roles?
                .Where(role => !string.IsNullOrWhiteSpace(role))
                .Select(role => role.Trim())
                .Distinct(StringComparer.OrdinalIgnoreCase)
                .ToArray();

            return normalized is { Length: > 0 } ? normalized : ["Admin"];
        }
    }
}