using Avalonia.Controls;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Reflection;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;

namespace Avalonia_PC.Views
{
    /// <summary>
    /// 主窗口，承载 WebView2 控件并管理前后端 Bridge 通信。
    /// </summary>
    public partial class MainWindow : Window
    {
        /// <summary>
        /// 自定义协议方案名称。
        /// </summary>
        private const string AppScheme = "app";
        /// <summary>
        /// 在线模式下的前端启动 URL。
        /// </summary>
        private const string? OnlineStartupUrl = "http://localhost:51240";
        //private const string? OnlineStartupUrl = null;
        /// <summary>
        /// 离线模式下的前端本地文件路径，为空则使用在线模式。
        /// </summary>
        private const string? LocalStartupPath = null;
        private static readonly JsonSerializerOptions BridgeJsonSerializerOptions = new()
        {
            PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        };

        /// <summary>
        /// WebView2 原生控件实例。
        /// </summary>
        private NativeWebView? _webView;
        /// <summary>
        /// 标记 WebView 事件是否已绑定。
        /// </summary>
        private bool _eventsAttached;
        /// <summary>
        /// WebView 适配器对象。
        /// </summary>
        private object? _webViewAdapter;
        /// <summary>
        /// 本地 HTTP 服务器实例（离线模式）。
        /// </summary>
        private HttpListener? _localHttpServer;
        /// <summary>
        /// 本地 HTTP 服务器的取消令牌源。
        /// </summary>
        private CancellationTokenSource? _localHttpServerCts;
        /// <summary>
        /// 本地 HTTP 服务器的基础 URL。
        /// </summary>
        private string? _localHttpBaseUrl;
        /// <summary>
        /// 本地 HTTP 服务器的根目录路径。
        /// </summary>
        private string? _localHttpRoot;

        #region 生命周期与 WebView 事件

        /// <summary>
        /// 初始化窗口并注册生命周期事件。
        /// </summary>
        public MainWindow(IServiceProvider services)
        {
            _services = services;
            InitializeComponent();
            Opened += OnOpened;
            Closed += OnClosed;

            RegisterRoutes();
        }

        /// <summary>
        /// 窗口打开后初始化 WebView、挂载事件并加载入口页面。
        /// </summary>
        private async void OnOpened(object? sender, EventArgs e)
        {
            if (_eventsAttached)
            {
                return;
            }

            _webView = this.FindControl<NativeWebView>("WebView");
            if (_webView is null)
            {
                return;
            }

            _eventsAttached = true;
            _webView.NavigationCompleted += OnNavigationCompleted;
            _webView.WebMessageReceived += OnWebMessageReceived;
            _webView.AdapterCreated += OnAdapterCreated;

            await LoadInitialContentAsync();
        }

        /// <summary>
        /// WebView 适配器创建后缓存实例，用于后续打开开发者工具。
        /// </summary>
        private void OnAdapterCreated(object? sender, WebViewAdapterEventArgs e)
        {
            _webViewAdapter = e.GetType().GetProperty("Adapter")?.GetValue(e);
        }

        /// <summary>
        /// 窗口关闭时解绑事件并释放本地资源。
        /// </summary>
        private void OnClosed(object? sender, EventArgs e)
        {
            if (_webView is not null)
            {
                _webView.NavigationCompleted -= OnNavigationCompleted;
                _webView.WebMessageReceived -= OnWebMessageReceived;
                _webView.AdapterCreated -= OnAdapterCreated;
            }

            _webViewAdapter = null;
            StopLocalHttpServer();
        }

        /// <summary>
        /// 页面导航完成后注入 JS 桥接脚本。
        /// </summary>
        private async void OnNavigationCompleted(object? sender, WebViewNavigationCompletedEventArgs e)
        {
            await InjectBridgeScriptAsync();
        }

        #endregion

        #region 前端桥接与页面加载

        /// <summary>
        /// 接收前端消息并进行分发（打开调试工具 / 处理 app 请求）。
        /// </summary>
        private async void OnWebMessageReceived(object? sender, WebMessageReceivedEventArgs e)
        {
            var messageJson = e.Body;
            if (string.IsNullOrWhiteSpace(messageJson))
            {
                return;
            }

            AppResponse? response = null;

            try
            {
                using var document = JsonDocument.Parse(messageJson);
                var root = document.RootElement;

                if (!root.TryGetProperty("kind", out var kindProperty))
                {
                    return;
                }

                var kind = kindProperty.GetString();
                if (string.Equals(kind, "app-open-devtools", StringComparison.OrdinalIgnoreCase))
                {
                    TryOpenDevTools();
                    return;
                }

                if (!string.Equals(kind, "app-request", StringComparison.OrdinalIgnoreCase))
                {
                    return;
                }

                response = await HandleAppRequestAsync(root);
            }
            catch (Exception ex)
            {
                response = new AppResponse
                {
                    Kind = "app-response",
                    Id = TryGetRequestId(messageJson),
                    StatusCode = 500,
                    StatusMessage = "Internal Server Error",
                    Body = JsonSerializer.Serialize(new { success = false, error = ex.Message }),
                    Headers = CreateJsonHeaders(),
                };
            }

            if (_webView is not null && response is not null)
            {
                var responseJson = JsonSerializer.Serialize(response, BridgeJsonSerializerOptions);
                var responseJsonLiteral = JsonSerializer.Serialize(responseJson);
                await _webView.InvokeScript($"window.__dispatchAppResponse({responseJsonLiteral})");
            }
        }

        /// <summary>
        /// 加载初始页面：优先在线地址，其次本地路径（通过本地 HTTP 服务托管）。
        /// </summary>
        private async Task LoadInitialContentAsync()
        {
            if (_webView is null)
            {
                return;
            }

            var onlineUrl = GetConfiguredOnlineStartupUrl();
            if (onlineUrl is not null)
            {
                StopLocalHttpServer();
                _webView.Source = onlineUrl;
                return;
            }

            var localHtmlPath = GetConfiguredLocalStartupPath();
            if (string.IsNullOrWhiteSpace(localHtmlPath) || !File.Exists(localHtmlPath))
            {
                return;
            }

            var localRoot = Path.GetDirectoryName(localHtmlPath);
            if (string.IsNullOrWhiteSpace(localRoot))
            {
                return;
            }

            await EnsureLocalHttpServerStartedAsync(localRoot);
            if (string.IsNullOrWhiteSpace(_localHttpBaseUrl))
            {
                _webView.Source = new Uri(localHtmlPath);
                return;
            }

            _webView.Source = new Uri(new Uri(_localHttpBaseUrl), Path.GetFileName(localHtmlPath));
        }

        /// <summary>
        /// 向页面注入桥接脚本，接管 app:// 请求并回传到 C# 处理。
        /// </summary>
        private async Task InjectBridgeScriptAsync()
        {
            if (_webView is null)
            {
                return;
            }

            await _webView.InvokeScript(BridgeScript);
        }

        #endregion

        #region 请求分发与通用响应

        /// <summary>
        /// 解析前端请求消息并转发到统一请求处理入口。
        /// </summary>
        private async Task<AppResponse> HandleAppRequestAsync(JsonElement request)
        {
            var id = request.TryGetProperty("id", out var idProperty) ? idProperty.GetString() : null;
            var url = request.TryGetProperty("url", out var urlProperty) ? urlProperty.GetString() : null;
            var method = request.TryGetProperty("method", out var methodProperty) ? methodProperty.GetString() : "GET";
            var body = request.TryGetProperty("body", out var bodyProperty) ? bodyProperty.GetString() : null;
            var headers = ExtractHeaders(request);

            return await HandleAppRequestAsync(id, url, method, body, headers);
        }

        /// <summary>
        /// 统一请求处理：构建上下文、处理 OPTIONS、使用统一端点适配器分发。
        /// </summary>
        private async Task<AppResponse> HandleAppRequestAsync(
            string? id,
            string? rawUrl,
            string? method,
            string? body,
            Dictionary<string, string> headers)
        {
            var response = new AppResponse
            {
                Kind = "app-response",
                Id = id,
                StatusCode = 200,
                StatusMessage = "OK",
                Headers = CreateJsonHeaders(),
            };

            try
            {
                var uri = new Uri(rawUrl ?? throw new InvalidOperationException("请求地址不能为空。"));

                if (string.Equals(method, "OPTIONS", StringComparison.OrdinalIgnoreCase))
                {
                    response.StatusCode = 200;
                    response.StatusMessage = "OK";
                    response.Body = JsonSerializer.Serialize(new { success = true });
                    return response;
                }

                // 使用统一端点适配器处理请求
                var (normalizedPath, queryParams) = ParseRequestUri(uri);

                var routeResult = await _endpointAdapter.HandleRequestAsync(
                    path: normalizedPath,
                    method: method ?? "GET",
                    body: body,
                    headers: headers,
                    query: queryParams);

                if (routeResult.IsMatched)
                {
                    response.StatusCode = routeResult.StatusCode;
                    response.StatusMessage = routeResult.StatusMessage;
                    response.Body = BuildSuccessResponseBody(routeResult.Data);
                    foreach (var kvp in routeResult.ResponseHeaders)
                    {
                        response.Headers[kvp.Key] = kvp.Value;
                    }
                    return response;
                }

                response.StatusCode = 404;
                response.StatusMessage = "Not Found";
                response.Body = JsonSerializer.Serialize(new { success = false, error = "API not found" });
                return response;
            }
            catch (Exception ex)
            {
                response.StatusCode = 500;
                response.StatusMessage = "Internal Server Error";
                response.Body = JsonSerializer.Serialize(new { success = false, error = ex.Message });
                return response;
            }
        }

        /// <summary>
        /// 从 URI 解析规范化路径和查询参数（供统一端点适配器使用）。
        /// </summary>
        private static (string normalizedPath, Dictionary<string, string> query) ParseRequestUri(Uri uri)
        {
            var host = uri.Host ?? string.Empty;
            var absolutePath = uri.AbsolutePath ?? string.Empty;
            var combinedPath = $"{host}/{absolutePath}";

            var pathSegments = combinedPath
                .Split('/', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries)
                .Select(Uri.UnescapeDataString)
                .ToArray();

            var normalizedPath = string.Join('/', pathSegments);
            var query = ParseQueryParameters(uri.Query);

            return (normalizedPath, query);
        }

        /// <summary>
        /// 统一构建成功响应体，保持前后端响应结构一致。
        /// </summary>
        private static string BuildSuccessResponseBody(object? data)
        {
            return JsonSerializer.Serialize(new { success = true, data });
        }

        /// <summary>
        /// 解析查询字符串为忽略大小写的字典。
        /// </summary>
        private static Dictionary<string, string> ParseQueryParameters(string? queryString)
        {
            var query = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
            if (string.IsNullOrWhiteSpace(queryString))
            {
                return query;
            }

            var raw = queryString.TrimStart('?');
            foreach (var pair in raw.Split('&', StringSplitOptions.RemoveEmptyEntries))
            {
                var separatorIndex = pair.IndexOf('=');
                if (separatorIndex < 0)
                {
                    query[Uri.UnescapeDataString(pair)] = string.Empty;
                    continue;
                }

                var key = Uri.UnescapeDataString(pair[..separatorIndex]);
                var value = Uri.UnescapeDataString(pair[(separatorIndex + 1)..]);
                query[key] = value;
            }

            return query;
        }


        /// <summary>
        /// 创建桥接响应的默认 JSON/CORS 头。
        /// </summary>
        private static Dictionary<string, string> CreateJsonHeaders() => new()
        {
            ["Content-Type"] = "application/json; charset=utf-8",
            ["Access-Control-Allow-Origin"] = "*",
            ["Access-Control-Allow-Methods"] = "GET, POST, OPTIONS",
            ["Access-Control-Allow-Headers"] = "Content-Type, Authorization",
        };

        /// <summary>
        /// 从前端请求消息中提取请求头。
        /// </summary>
        private static Dictionary<string, string> ExtractHeaders(JsonElement request)
        {
            if (!request.TryGetProperty("headers", out var headersElement) ||
                headersElement.ValueKind != JsonValueKind.Object)
            {
                return new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
            }

            var headers = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
            foreach (var property in headersElement.EnumerateObject())
            {
                headers[property.Name] = property.Value.GetString() ?? string.Empty;
            }

            return headers;
        }

        /// <summary>
        /// 获取授权头，供鉴权逻辑扩展使用。
        /// </summary>
        private static string? GetAuthorizationHeader(Dictionary<string, string> headers)
        {
            return headers.FirstOrDefault(
                entry => string.Equals(entry.Key, "Authorization", StringComparison.OrdinalIgnoreCase)).Value;
        }

        /// <summary>
        /// 在异常情况下尝试提取请求 id，确保前端可收到对应错误响应。
        /// </summary>
        private static string? TryGetRequestId(string messageJson)
        {
            try
            {
                using var document = JsonDocument.Parse(messageJson);
                return document.RootElement.TryGetProperty("id", out var idProperty) ? idProperty.GetString() : null;
            }
            catch
            {
                return null;
            }
        }

        #endregion

        #region 页面地址配置与本地静态服务

        /// <summary>
        /// 获取在线启动地址配置（仅允许 http/https）。
        /// </summary>
        private static Uri? GetConfiguredOnlineStartupUrl()
        {
            if (string.IsNullOrWhiteSpace(OnlineStartupUrl))
            {
                return null;
            }

            if (!Uri.TryCreate(OnlineStartupUrl, UriKind.Absolute, out var uri))
            {
                return null;
            }

            return uri.Scheme is "http" or "https" ? uri : null;
        }

        /// <summary>
        /// 获取本地启动文件路径，未配置时默认使用输出目录 www/index.html。
        /// </summary>
        private static string? GetConfiguredLocalStartupPath()
        {
            if (!string.IsNullOrWhiteSpace(LocalStartupPath))
            {
                return Path.GetFullPath(LocalStartupPath);
            }

            return Path.Combine(AppContext.BaseDirectory, "www", "index.html");
        }

        /// <summary>
        /// 确保本地 HTTP 静态服务已启动；根目录变化时会重启。
        /// </summary>
        private async Task EnsureLocalHttpServerStartedAsync(string localRoot)
        {
            if (!string.IsNullOrWhiteSpace(_localHttpBaseUrl) &&
                _localHttpServer is not null &&
                string.Equals(_localHttpRoot, localRoot, StringComparison.OrdinalIgnoreCase))
            {
                return;
            }

            StopLocalHttpServer();

            var port = GetAvailableTcpPort();
            var prefix = $"http://127.0.0.1:{port}/";

            _localHttpServerCts = new CancellationTokenSource();
            _localHttpServer = new HttpListener();
            _localHttpServer.Prefixes.Add(prefix);
            _localHttpServer.Start();
            _localHttpBaseUrl = prefix;
            _localHttpRoot = localRoot;

            _ = Task.Run(() => RunLocalHttpServerLoopAsync(_localHttpServer, _localHttpServerCts.Token, localRoot));
        }

        /// <summary>
        /// 本地静态服务主循环，持续接收并分发请求。
        /// </summary>
        private static async Task RunLocalHttpServerLoopAsync(HttpListener listener, CancellationToken cancellationToken, string wwwRoot)
        {
            try
            {
                while (!cancellationToken.IsCancellationRequested)
                {
                    var context = await listener.GetContextAsync();
                    _ = Task.Run(() => HandleLocalHttpRequest(context, wwwRoot), cancellationToken);
                }
            }
            catch
            {
            }
        }

        /// <summary>
        /// 处理本地静态资源请求并返回文件内容。
        /// </summary>
        private static async Task HandleLocalHttpRequest(HttpListenerContext context, string wwwRoot)
        {
            try
            {
                var relativePath = context.Request.Url?.AbsolutePath.TrimStart('/') ?? string.Empty;
                if (string.IsNullOrWhiteSpace(relativePath))
                {
                    relativePath = "index.html";
                }

                relativePath = relativePath.Replace('/', Path.DirectorySeparatorChar);
                var fullPath = Path.GetFullPath(Path.Combine(wwwRoot, relativePath));
                var fullRoot = Path.GetFullPath(wwwRoot);

                if (!fullPath.StartsWith(fullRoot, StringComparison.OrdinalIgnoreCase) || !File.Exists(fullPath))
                {
                    context.Response.StatusCode = 404;
                    context.Response.Close();
                    return;
                }

                context.Response.ContentType = GetContentType(fullPath);
                await using var input = File.OpenRead(fullPath);
                context.Response.ContentLength64 = input.Length;
                await input.CopyToAsync(context.Response.OutputStream);
                context.Response.OutputStream.Close();
            }
            catch
            {
                try
                {
                    context.Response.StatusCode = 500;
                    context.Response.Close();
                }
                catch
                {
                }
            }
        }

        /// <summary>
        /// 根据后缀返回静态资源 Content-Type。
        /// </summary>
        private static string GetContentType(string filePath)
        {
            return Path.GetExtension(filePath).ToLowerInvariant() switch
            {
                ".html" => "text/html; charset=utf-8",
                ".js" => "application/javascript; charset=utf-8",
                ".css" => "text/css; charset=utf-8",
                ".json" => "application/json; charset=utf-8",
                _ => "application/octet-stream",
            };
        }

        /// <summary>
        /// 获取一个可用本地端口，用于启动本地静态服务。
        /// </summary>
        private static int GetAvailableTcpPort()
        {
            var listener = new TcpListener(IPAddress.Loopback, 0);
            listener.Start();
            var port = ((IPEndPoint)listener.LocalEndpoint).Port;
            listener.Stop();
            return port;
        }

        /// <summary>
        /// 尝试打开 WebView 开发者工具（兼容不同适配器方法名）。
        /// </summary>
        private void TryOpenDevTools()
        {
            if (_webViewAdapter is null)
            {
                return;
            }

            var adapterType = _webViewAdapter.GetType();
            var method = adapterType.GetMethod("OpenDevTools", BindingFlags.Public | BindingFlags.Instance) ??
                         adapterType.GetMethod("ShowDevTools", BindingFlags.Public | BindingFlags.Instance);
            method?.Invoke(_webViewAdapter, null);
        }

        /// <summary>
        /// 停止并释放本地静态服务资源。
        /// </summary>
        private void StopLocalHttpServer()
        {
            try
            {
                _localHttpServerCts?.Cancel();
                _localHttpServer?.Stop();
                _localHttpServer?.Close();
            }
            catch
            {
            }
            finally
            {
                _localHttpServerCts?.Dispose();
                _localHttpServerCts = null;
                _localHttpServer = null;
                _localHttpBaseUrl = null;
                _localHttpRoot = null;
            }
        }

        #endregion

        #region DTO / 路由上下文模型

        /// <summary>
        /// Bridge 通信响应 DTO，用于序列化返回给前端的数据。
        /// </summary>
        private sealed class AppResponse
        {
            /// <summary>
            /// 获取或设置响应类型标识。
            /// </summary>
            public string Kind { get; set; } = string.Empty;

            /// <summary>
            /// 获取或设置请求 ID（对应前端请求）。
            /// </summary>
            public string? Id { get; set; }

            /// <summary>
            /// 获取或设置 HTTP 状态码。
            /// </summary>
            public int StatusCode { get; set; }

            /// <summary>
            /// 获取或设置状态描述文本。
            /// </summary>
            public string StatusMessage { get; set; } = string.Empty;

            /// <summary>
            /// 获取或设置响应体 JSON 字符串。
            /// </summary>
            public string Body { get; set; } = string.Empty;

            /// <summary>
            /// 获取或设置响应头字典。
            /// </summary>
            public Dictionary<string, string> Headers { get; set; } = new();
        }

        #endregion
    }
}