using System.ComponentModel.DataAnnotations;
using System.Net;
using System.Text.Json;
using RestSharp;
using Store.Management.Api.Authentication;
using Store.Management.Api.Models;

namespace Store.Management.Api.Transport;

/// <summary>唯一 HTTP 出口；模块仅指定相对路由、请求数据与响应类型。</summary>
public sealed class ApiTransport : IDisposable
{
    private readonly RestClient _client;
    private readonly TokenSession _session;
    private readonly string _version;
    private static readonly JsonSerializerOptions Json = new(JsonSerializerDefaults.Web);

    internal ApiTransport(ApiClientOptions options, TokenSession session, HttpClient? httpClient)
    {
        options.Validate();
        _session = session;
        _version = options.Version;
        RestClientOptions settings = new RestClientOptions(new Uri(options.BaseUrl.AbsoluteUri.TrimEnd('/') + "/"))
        {
            Timeout = options.Timeout,
            FollowRedirects = false
        };
        _client = httpClient is null ? new RestClient(settings) : new RestClient(httpClient, settings, disposeHttpClient: false);
    }

    public async Task<T?> SendAsync<T>(string route, Method method, object? body = null,
        IReadOnlyDictionary<string, string?>? query = null, bool authenticated = true,
        CancellationToken cancellationToken = default)
    {
        cancellationToken.ThrowIfCancellationRequested();
        if (string.IsNullOrWhiteSpace(route) || route.StartsWith('/') || route.Contains("..") ||
            route.Contains(':') || route.Contains('?') || route.Contains('#') || route.Contains('\\'))
        {
            throw new ArgumentException("接口必须使用相对路由，例如 user/GetAllUser。", nameof(route));
        }
        if (body is not null)
        {
            Validator.ValidateObject(body, new ValidationContext(body), true);
        }
        string? token = authenticated ? _session.Token : null;
        if (authenticated && token is null)
        {
            throw new ApiException(ApiErrorKind.Unauthorized, "请先登录。", code: 401);
        }
        RestRequest request = new RestRequest($"{_version}/{route}", method);
        if (token is not null)
        {
            request.AddHeader("Authorization", $"Bearer {token}");
        }
        if (body is not null)
        {
            request.AddJsonBody(body);
        }
        if (query is not null)
        {
            foreach (KeyValuePair<string, string?> pair in query)
            {
                if (pair.Value is not null)
                {
                    request.AddQueryParameter(pair.Key, pair.Value);
                }
            }
        }
        RestResponse response = await _client.ExecuteAsync(request, cancellationToken).ConfigureAwait(false);
        cancellationToken.ThrowIfCancellationRequested();
        if (response.ResponseStatus == ResponseStatus.TimedOut)
        {
            throw new ApiException(ApiErrorKind.Timeout, "请求超时，请稍后重试。", innerException: response.ErrorException);
        }
        if ((int)response.StatusCode == 0)
        {
            throw new ApiException(ApiErrorKind.Network, "无法连接服务器，请检查网络与服务地址。", innerException: response.ErrorException);
        }

        // 先判断状态，再解析 data；错误响应的数据结构可能与成功响应不同。
        ApiResult<JsonElement>? result = null;
        JsonException? parseError = null;
        try
        {
            result = JsonSerializer.Deserialize<ApiResult<JsonElement>>(response.Content ?? "", Json);
        }
        catch (JsonException ex)
        {
            parseError = ex;
        }
        if (response.StatusCode == HttpStatusCode.Unauthorized || result?.Code == 401)
        {
            _session.ClearIfCurrent(token);
            throw new ApiException(ApiErrorKind.Unauthorized, result?.Msg ?? "登录已失效，请重新登录。",
                response.StatusCode, 401, result?.TraceId);
        }
        if (!response.IsSuccessful)
        {
            throw new ApiException(ApiErrorKind.Http, result?.Msg ?? $"服务器请求失败（{(int)response.StatusCode}）。",
                response.StatusCode, result?.Code, result?.TraceId);
        }
        if (result is null)
        {
            throw new ApiException(ApiErrorKind.InvalidResponse, "服务器响应格式无效。", response.StatusCode, innerException: parseError);
        }
        if (result.Code != 200)
        {
            throw new ApiException(ApiErrorKind.Business, result.Msg ?? "操作失败。", response.StatusCode, result.Code, result.TraceId);
        }
        if (result.Data.ValueKind is JsonValueKind.Null or JsonValueKind.Undefined)
        {
            return default;
        }
        try
        {
            return result.Data.Deserialize<T>(Json);
        }
        catch (JsonException ex)
        {
            throw new ApiException(ApiErrorKind.InvalidResponse, "服务器响应 data 格式无效。",
                response.StatusCode, result.Code, result.TraceId, ex);
        }
    }

    public async Task<T> GetRequiredAsync<T>(string route, Method method, object? body = null,
        IReadOnlyDictionary<string, string?>? query = null, bool authenticated = true, CancellationToken cancellationToken = default)
        where T : class
        => await SendAsync<T>(route, method, body, query, authenticated, cancellationToken).ConfigureAwait(false)
           ?? throw new ApiException(ApiErrorKind.InvalidResponse, "服务器响应缺少 data。");

    public void Dispose() => _client.Dispose();
}