using System.Text.Json.Serialization;

namespace FileShare_Common.Core
{
    /// <summary>
    /// 统一端点响应契约。
    /// </summary>
    public interface IApiResponse
    {
        /// <summary>是否成功。</summary>
        bool Success { get; }

        /// <summary>业务状态码。</summary>
        int Code { get; }
    }

    /// <summary>
    /// 统一 API 返回格式。
    /// 所有接口的返回都包装为此格式，确保前端收到一致的数据结构。
    /// </summary>
    /// <typeparam name="T">业务数据类型</typeparam>
    public class ApiResponse<T> : IApiResponse
    {
        /// <summary>是否成功</summary>
        [JsonPropertyName("success")]
        public bool Success { get; set; }

        /// <summary>HTTP 状态码</summary>
        [JsonPropertyName("code")]
        public int Code { get; set; }

        /// <summary>消息（成功时可为 null，失败时包含错误描述）</summary>
        [JsonPropertyName("message")]
        public string? Message { get; set; }

        /// <summary>业务数据</summary>
        [JsonPropertyName("data")]
        public T? Data { get; set; }

        /// <summary>时间戳</summary>
        [JsonPropertyName("timestamp")]
        public DateTime Timestamp { get; set; } = DateTime.Now;

        /// <summary>请求追踪 ID（用于排查问题）</summary>
        [JsonPropertyName("traceId")]
        public string? TraceId { get; set; }

        // ---- 快捷工厂方法 ----

        /// <summary>成功返回（有数据）</summary>
        public static ApiResponse<T> Ok(T data, string? message = null)
        {
            return new ApiResponse<T>
            {
                Success = true,
                Code = 200,
                Message = message,
                Data = data,
            };
        }

        /// <summary>失败返回</summary>
        public static ApiResponse<T> Fail(int code, string message, T? data = default)
        {
            return new ApiResponse<T>
            {
                Success = false,
                Code = code,
                Message = message,
                Data = data,
            };
        }

        /// <summary>400 参数错误</summary>
        public static ApiResponse<T> BadRequest(string message = "参数错误")
            => Fail(400, message);

        /// <summary>401 未授权</summary>
        public static ApiResponse<T> Unauthorized(string message = "未授权")
            => Fail(401, message);

        /// <summary>403 无权限</summary>
        public static ApiResponse<T> Forbidden(string message = "无权限")
            => Fail(403, message);

        /// <summary>404 未找到</summary>
        public static ApiResponse<T> NotFound(string message = "资源不存在")
            => Fail(404, message);

        /// <summary>500 服务器内部错误</summary>
        public static ApiResponse<T> ServerError(string message = "服务器内部错误")
            => Fail(500, message);
    }

    /// <summary>
    /// 无数据的统一返回格式（object? 版本）。
    /// </summary>
    public class ApiResponse : ApiResponse<object?>
    {
        /// <summary>成功返回（无数据）</summary>
        public static ApiResponse Succeed(string? message = null)
        {
            return new ApiResponse
            {
                Success = true,
                Code = 200,
                Message = message,
                Data = null,
            };
        }

        /// <summary>失败返回</summary>
        public static ApiResponse Failure(int code, string message)
        {
            return new ApiResponse
            {
                Success = false,
                Code = code,
                Message = message,
                Data = null,
            };
        }
    }

    /// <summary>
    /// 分页返回格式
    /// </summary>
    public class PagedResponse<T> : IApiResponse
    {
        /// <summary>
        /// 获取或设置操作是否成功。
        /// </summary>
        [JsonPropertyName("success")]
        public bool Success { get; set; } = true;

        /// <summary>
        /// 获取或设置业务状态码，默认 200。
        /// </summary>
        [JsonPropertyName("code")]
        public int Code { get; set; } = 200;

        /// <summary>
        /// 获取或设置分页数据项列表。
        /// </summary>
        [JsonPropertyName("items")]
        public List<T> Items { get; set; } = new();

        /// <summary>
        /// 获取或设置数据总条数。
        /// </summary>
        [JsonPropertyName("total")]
        public int Total { get; set; }

        /// <summary>
        /// 获取或设置当前页码，从 1 开始。
        /// </summary>
        [JsonPropertyName("page")]
        public int Page { get; set; } = 1;

        /// <summary>
        /// 获取或设置每页条数，默认 20。
        /// </summary>
        [JsonPropertyName("pageSize")]
        public int PageSize { get; set; } = 20;

        /// <summary>
        /// 获取总页数（根据 Total 和 PageSize 自动计算）。
        /// </summary>
        [JsonPropertyName("totalPages")]
        public int TotalPages => PageSize > 0 ? (int)Math.Ceiling((double)Total / PageSize) : 0;

        /// <summary>
        /// 从数据列表和分页参数创建分页响应。
        /// </summary>
        /// <param name="items">当前页数据项。</param>
        /// <param name="total">数据总条数。</param>
        /// <param name="page">当前页码。</param>
        /// <param name="pageSize">每页条数。</param>
        /// <returns>分页响应实例。</returns>
        public static PagedResponse<T> From(List<T> items, int total, int page, int pageSize)
        {
            return new PagedResponse<T>
            {
                Items = items,
                Total = total,
                Page = page,
                PageSize = pageSize,
            };
        }
    }

    /// <summary>
    /// 端点返回辅助方法 —— 在 AppEndpoints 中快捷构建统一响应。
    /// </summary>
    public static class ResponseHelper
    {
        /// <summary>成功返回</summary>
        public static ApiResponse<T> Ok<T>(T data, string? message = null)
            => ApiResponse<T>.Ok(data, message);

        /// <summary>成功返回（无数据）</summary>
        public static ApiResponse Succeed(string? message = null)
            => ApiResponse.Succeed(message);

        /// <summary>失败返回</summary>
        public static ApiResponse<T> Fail<T>(int code, string message, T? data = default)
            => ApiResponse<T>.Fail(code, message, data);

        /// <summary>失败返回（无数据）</summary>
        public static ApiResponse Failure(int code, string message)
            => ApiResponse.Failure(code, message);

        /// <summary>分页返回</summary>
        public static PagedResponse<T> Paged<T>(List<T> items, int total, int page, int pageSize)
            => PagedResponse<T>.From(items, total, page, pageSize);
    }
}