using Authentication;
using Avalonia_Common.Core;
using Avalonia_Services.Core;
using Avalonia_Services.Services.AuthService;
using System;
using System.Text.Json;
using System.Threading.Tasks;

namespace Avalonia_PC.Authentication
{
    /// <summary>
    /// PC 端鉴权端点服务，实现 <see cref="IPcAuthEndpointService"/>，
    /// 处理授权码登录、Token 刷新和登出操作。
    /// </summary>
    public sealed class PcAuthEndpointService(PcGlobalTokenService tokenService) : IPcAuthEndpointService
    {
        private static readonly JsonSerializerOptions JsonOptions = new()
        {
            PropertyNameCaseInsensitive = true,
        };

        /// <inheritdoc />
        public async Task<object?> AuthorizeAsync(ServiceEndpointContext ctx)
        {
            var request = Deserialize<PcAuthorizeRequest>(ctx.Body);
            var token = await tokenService.AuthorizeAsync(request?.AuthorizationCode);
            if (token is null)
            {
                ctx.StatusCode = 401;
                return ResponseHelper.Failure(401, "授权失败");
            }

            return ResponseHelper.Ok(token, "授权成功");
        }

        /// <inheritdoc />
        public async Task<object?> RefreshAsync(ServiceEndpointContext ctx)
        {
            var request = Deserialize<PcRefreshRequest>(ctx.Body);
            var token = request?.Token ?? ExtractBearerToken(ctx.GetHeader("Authorization"));
            var refreshed = await tokenService.RefreshAsync(token);
            if (refreshed is null)
            {
                ctx.StatusCode = 401;
                return ResponseHelper.Failure(401, "授权已失效");
            }

            return ResponseHelper.Ok(refreshed, "刷新成功");
        }

        /// <inheritdoc />
        public Task<object?> LogoutAsync(ServiceEndpointContext ctx)
        {
            var request = Deserialize<PcLogoutRequest>(ctx.Body);
            var token = request?.Token ?? ExtractBearerToken(ctx.GetHeader("Authorization"));
            tokenService.Logout(token);
            return Task.FromResult<object?>(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 Authorization 头中提取 Bearer Token。
        /// </summary>
        /// <param name="authorization">Authorization 头的值。</param>
        /// <returns>提取的 Token 字符串；若无法提取则返回 null。</returns>
        private static string? ExtractBearerToken(string? authorization)
        {
            if (string.IsNullOrWhiteSpace(authorization))
            {
                return null;
            }

            /// <summary>
        /// Bearer Token 的前缀常量。
        /// </summary>
        const string prefix = "Bearer ";
            return authorization.StartsWith(prefix, StringComparison.OrdinalIgnoreCase)
                ? authorization[prefix.Length..].Trim()
                : authorization.Trim();
        }
    }
}