using System;
using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Reflection;
using System.Runtime.Loader;
using System.Text;
using System.Text.Json;
using System.Text.Json.Nodes;
using System.Threading;
using System.Windows.Forms;
using Sim.Host;

namespace Sim.Runner;

/// <summary>
/// 运行一个已编译的学生程序：在模拟的界面线程上执行 Main，主线程从标准输入读取浏览器的操作。
/// 这个类不能引用 Roslyn 的任何类型，否则运行模式也会加载编译器。
/// </summary>
internal static class StudentProgramHost
{
    public static int Run(string dir)
    {
        var processStart = Process.GetCurrentProcess().StartTime;
        SimHost.Initialize(Console.OpenStandardOutput());
        var console = new ConsoleForwarder();
        Console.SetOut(console);
        Console.SetIn(TextReader.Null); // 标准输入用于协议，学生的 Console.ReadLine 读不到内容

        // 和中文 Windows 一致：DateTime.ToString() 等按 zh-CN 格式输出。
        // Linux 上的区域数据把时间写成 09:05:03，中文 Windows 是 9:05:03（书上的截图也是）；长日期后面多了星期（2024年1月16日星期二），
        // 中文 Windows 的长日期不带星期（日期选择框的长日期格式窄，带上星期会被截掉）。这里都改成 Windows 的写法
        var zhCN = (CultureInfo)CultureInfo.GetCultureInfo("zh-CN").Clone();
        zhCN.DateTimeFormat.LongTimePattern = "H:mm:ss";
        zhCN.DateTimeFormat.ShortTimePattern = "H:mm";
        zhCN.DateTimeFormat.LongDatePattern = "yyyy'年'M'月'd'日'";
        zhCN.DateTimeFormat.FullDateTimePattern = "yyyy'年'M'月'd'日' H:mm:ss";
        zhCN = CultureInfo.ReadOnly(zhCN);
        CultureInfo.DefaultThreadCurrentCulture = zhCN;
        CultureInfo.DefaultThreadCurrentUICulture = zhCN;
        CultureInfo.CurrentCulture = zhCN;
        CultureInfo.CurrentUICulture = zhCN;

        UseWritableBaseDirectory(dir);

        var assembly = AssemblyLoadContext.Default.LoadFromStream(
            new MemoryStream(File.ReadAllBytes(Path.Combine(dir, CompileServer.AssemblyFile))),
            new MemoryStream(File.ReadAllBytes(Path.Combine(dir, CompileServer.PdbFile))));
        SimHost.StudentAssembly = assembly;
        var entryPoint = assembly.EntryPoint;
        if (entryPoint == null)
        {
            SimHost.Send(new JsonObject { ["type"] = "exception", ["message"] = "程序中找不到 Main 方法", ["detail"] = "" });
            return 1;
        }

        AppDomain.CurrentDomain.UnhandledException += (_, e) =>
        {
            // 学生创建的后台线程抛出未处理异常时，和真实程序一样整个程序结束
            if (e.ExceptionObject is Exception ex) SimHost.ReportException(ex);
            console.Flush();
        };

        var uiThread = new Thread(() =>
        {
            SimHost.Ui.BindToCurrentThread();
            SynchronizationContext.SetSynchronizationContext(new WindowsFormsSynchronizationContext());
            SimHost.Send(new JsonObject { ["type"] = "started", ["ms"] = (long)(DateTime.Now - processStart).TotalMilliseconds });
            try
            {
                var parameters = entryPoint.GetParameters().Length == 0 ? null : new object[] { Array.Empty<string>() };
                entryPoint.Invoke(null, parameters);
            }
            catch (Exception ex)
            {
                SimHost.ReportException(ex);
            }
            finally
            {
                console.Flush();
                SimHost.FlushChanges();
                Environment.Exit(0);
            }
        }) { Name = "UI" };
        uiThread.Start();

        ReadActions();
        // 服务器关闭了标准输入：结束运行
        Environment.Exit(0);
        return 0;
    }

    /// <summary>
    /// 学生程序的"程序所在目录"：和在 VS 里按 F5 一样是工程下的 bin/Debug/，也是当前目录，可以写文件
    /// （教材把摄像头照片存到 AppDomain.CurrentDomain.BaseDirectory + "Camera/"）。
    /// 沙箱里工程目录只读，改用沙箱自己的临时目录；两种情况下文件都在程序结束后清掉。
    /// </summary>
    private static void UseWritableBaseDirectory(string projectDir)
    {
        string baseDir;
        try
        {
            baseDir = Directory.CreateDirectory(Path.Combine(projectDir, "bin", "Debug")).FullName;
        }
        catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
        {
            baseDir = Directory.CreateDirectory(Path.Combine(Path.GetTempPath(), "StudentApp", "bin", "Debug")).FullName;
        }
        baseDir = Path.TrimEndingDirectorySeparator(baseDir) + Path.DirectorySeparatorChar;
        // 程序目录下的 Resources 文件夹指向素材库：教材用 BaseDirectory + "//Resources//ring.mp3" 播放铃声
        var resources = Path.Combine(baseDir, "Resources");
        if (!Path.Exists(resources)) Directory.CreateSymbolicLink(resources, ProjectResources.Directory);
        AppContext.SetData("APP_CONTEXT_BASE_DIRECTORY", baseDir);
        Directory.SetCurrentDirectory(baseDir);
        SimHost.AppBaseDirectory = baseDir;
    }

    /// <summary>读取浏览器发来的操作，排队到界面线程执行</summary>
    private static void ReadActions()
    {
        using var input = new StreamReader(Console.OpenStandardInput(), new UTF8Encoding(false));
        while (input.ReadLine() is { } line)
        {
            JsonObject? message;
            try
            {
                message = JsonNode.Parse(line) as JsonObject;
            }
            catch (JsonException)
            {
                continue;
            }
            switch ((string?)message?["type"])
            {
                case "action":
                    if (SimHost.FindControl((string?)message!["id"] ?? "") is { } control)
                    {
                        var action = UserAction.FromJson(message);
                        SimHost.Ui.Post(() => control.PerformUserAction(action));
                    }
                    break;
                case "board":
                    DeviceCtrlLibrary.TrainingBoard.Update(message!);
                    break;
                case "reply":
                    SimHost.CompleteRequest((int?)message!["requestId"] ?? 0, message["result"]?.DeepClone());
                    break;
                case "stop":
                    Environment.Exit(0);
                    break;
            }
        }
    }
}