using System;
using System.Diagnostics;
using System.IO;
using System.Threading;
using System.Threading.Tasks;

namespace MacTranslocator {
    class TranslocateHandler {
        /// <summary>
        /// This is the name of the game, the name of the folder in local storage where the game will be run from,
        /// and the name of the .app folder that contains the game.
        /// It is not the name of the executable file, use Platform_FilenameExecutable for that.
        /// </summary>
        public const string APPLICATION_NAME = "MacTranslocator";

        private readonly Action<string> _ShowMessage;
        private readonly Action _OnFail;
        private readonly Action _OnSuccess;

        /// <summary>
        /// This mode will show an update screen while it checks for patches and then downloads any updates.
        /// Normally this will only run on compiled versions, not in the debugger.
        /// Pass parameter forceUpdate==true to force an update regardless of what exe is running.
        /// </summary>
        public TranslocateHandler(Action<string> writeDebug, Action onSuccess, Action onFail) {
            _ShowMessage = writeDebug;
            _OnSuccess = onSuccess;
            _OnFail = onFail;
        }

        public void Initialize() {
            ShowMessage($"ModeLoading initializing.");
            ShowMessage($"    Platform is: {PlatformType}");
            ShowMessage($"    Running in:  {Platform_PathCurrentRunningDirectory}");
            ShowMessage($"    PathExeDir:  {Platform_PathExeDirectory}");
            ShowMessage($"    FilenameExe: {Platform_FilenameExecutable}");
            Task.Factory.StartNew(() => {
                if (!RunUpdateFunctions()) {
                    _OnFail?.Invoke();
                }
                else {
                    _OnSuccess?.Invoke();
                }
            });
        }

        private void ShowMessage(string msg, int waitMS = 0) {
            _ShowMessage?.Invoke(msg);
            if (waitMS > 0) {
                Thread.Sleep(waitMS);
            }
        }

        // === Patch / Update routines live here  =====================================================================
        // ============================================================================================================

        private bool RunUpdateFunctions() {
            if (!VerifyRunningInClientAppFolder()) {
                // don't continue with update, allow called method to end program.
                return false;
            }
            return true;
        }

        private bool VerifyRunningInClientAppFolder() {
            string currentDirectory = Platform_PathCurrentRunningDirectory;
            if (!currentDirectory.Contains(Platform_PathClientApp)) {
                ShowMessage("Application must be restarted in correct location.", 2000);
                if (!VerifyDirectoryContents(currentDirectory, Platform_PathClientApp)) {
                    // delete client.app folder, copy in all files in this folder
                    ShowMessage($"Copying application to {Platform_PathClientApp}");
                    CopyAndReplace(currentDirectory, Platform_PathClientApp);
                }
                if (Platform_IsRunningInDebugger) {
                    ShowMessage("Debugger: will not restart.");
                }
                else {
                    string pathToExe = Path.Combine(Platform_PathExeDirectory, Platform_FilenameExecutable);
                    Process.Start(pathToExe);
                    return false;
                }
            }
            return true;
        }

        private bool VerifyDirectoryContents(string pathSource, string pathDestination, string specificFilenameToCheck = null) {
            string filePattern = specificFilenameToCheck ?? "*.exe";
            ShowMessage($"    Verifying files with pattern '{filePattern}':");
            ShowMessage($"    {pathSource} vs");
            ShowMessage($"    {pathDestination}");
            foreach (string filePath in Directory.GetFiles(pathSource, filePattern, SearchOption.AllDirectories)) {
                string fileLocalPath = filePath.Remove(0, pathSource.Length);
                if (fileLocalPath.Length > 0 && fileLocalPath[0] == Path.DirectorySeparatorChar) {
                    fileLocalPath = fileLocalPath.Remove(0, 1);
                }
                if (IgnoreLogsAndPbds(fileLocalPath)) {
                    continue;
                }
                string fileWeWant = Path.Combine(pathDestination, fileLocalPath);
                if (File.Exists(fileWeWant)) {
                    ShowMessage($"    Path exists: {Platform_RemoveUserPath(fileWeWant)}");
                    // We should replace files that are older than the current version...
                    // but I haven't written that code yet.
                }
                else {
                    ShowMessage($"    Path missing: {fileLocalPath}");
                    return false;
                }
            }
            return true;
        }

        private bool IgnoreLogsAndPbds(string filename) {
            if (Path.GetFileName(filename).StartsWith("log") && Path.GetFileName(filename).EndsWith(".txt"))
                return true;
            if (Path.GetExtension(filename) == ".pdb") {
                return true;
            }
            return false;
        }

        private void CopyAndReplace(string pathSource, string pathDestination) {
            if (Directory.Exists(pathDestination)) {
                Directory.Delete(pathDestination, true);
            }
            if (!pathDestination.EndsWith(Path.DirectorySeparatorChar.ToString())) {
                pathDestination += Path.DirectorySeparatorChar;
            }
            //Now Create all of the directories
            foreach (string dirPath in Directory.GetDirectories(pathSource, "*", SearchOption.AllDirectories)) {
                Directory.CreateDirectory(dirPath.Replace(pathSource, pathDestination));
            }
            //Copy all the files & Replaces any files with the same name
            foreach (string newPath in Directory.GetFiles(pathSource, "*.*", SearchOption.AllDirectories)) {
                if (IgnoreLogsAndPbds(newPath)) {
                    continue;
                }
                File.Copy(newPath, newPath.Replace(pathSource, pathDestination), true);
            }
        }

        // === Platform code lives here ===============================================================================
        // ============================================================================================================

        private const int NOT_SET = 0;
        public const int WINDOWS = 1;
        public const int MACOS = 2;
        public const int LINUX = 3;

        private int _PlatformType = NOT_SET;

        /// <summary>
        /// Returns an integer corresponding to the platform type we are running on.
        /// Possible values are Platform.WINDOWS, Platform.MACOS, and Platform.LINUX.
        /// Will throw a critical error if it cannot determine the platform.
        /// </summary>
        public int PlatformType {
            get {
                if (_PlatformType == NOT_SET) {
#if SDL
                    string platform = SDL.SDL_GetPlatform();
                    if (platform.Equals("Windows")) {
                        _PlatformType = WINDOWS;
                    }
                    else if (platform.Equals("Mac OS X")) {
                        _PlatformType = MACOS;
                    }
                    else if (platform.Equals("Linux")) {
                        _PlatformType = LINUX;
                    }
                    else {
                        Tracer.Critical($"Could not determine platform type (unknown type '{platform}').");
                    }
#else
                    _PlatformType = WINDOWS;
#endif
                }
                return _PlatformType;
            }
        }

        /// <summary>
        /// Path to the client application folder in the local storage.
        /// This is not necessarily the path to the folder containing the exectuable file and resources.
        /// Use PathExeDirectory for that.
        /// </summary>
        public string Platform_PathClientApp => Platform_GetPlatformSubDirectory($"{APPLICATION_NAME}.app");


        /// <summary>
        /// This will be true if we are running in the Visual Studio debugger.
        /// </summary>
        public bool Platform_IsRunningInDebugger => Debugger.IsAttached;

        /// <summary>
        /// This is the filename that is used to start the game.
        /// On Windows, it will be the name of the client executable.
        /// On mac, it will be the kickstart binary.
        /// </summary>
        public string Platform_FilenameExecutable {
            get {
                switch (PlatformType) {
                    case WINDOWS:
                        return AppDomain.CurrentDomain.FriendlyName;
                    case MACOS:
                        return "CommunityClient"; // this is the kickstart script
                    default:
                        return "NoExeFile";
                }
            }
        }

        /// <summary>
        /// This is the directory the application is currently running in. It is not necessarily local storage.
        /// If it is not local storage, then the application should be copied to local storage and run from there.
        /// </summary>
        public string Platform_PathCurrentRunningDirectory {
            get {
                switch (PlatformType) {
                    case WINDOWS:
                        return AppDomain.CurrentDomain.BaseDirectory;
                    case MACOS:
                        DirectoryInfo basePath = Directory.GetParent(AppDomain.CurrentDomain.BaseDirectory).Parent.Parent;
                        return basePath.ToString();
                    default:
                        return "NoPathBaseDirectory";
                }
            }
        }

        /// <summary>
        /// Path to the folder in local storage containing the executable file.
        /// This is where all the resource/dll/etc. files will be found.
        /// </summary>
        public string Platform_PathExeDirectory {
            get {
#if SERVER
                return PathCurrentRunningDirectory;
#else
                switch (PlatformType) {
                    case WINDOWS:
                        return Platform_PathClientApp;
                    case MACOS:
                        return $"{Platform_PathClientApp}/Contents/MacOS";
                    default:
                        return "NoPathExeDirectory";
                }
#endif
            }
        }

        private string Platform_GetPlatformSubDirectory(string subDirectory) {
            return Path.Combine(Platform_GetPlatformDirectory(), subDirectory);
        }

        private string Platform_GetPlatformDirectory() {
            switch (PlatformType) {
                case WINDOWS:
                    return Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "Games", APPLICATION_NAME);
                case MACOS: {
                        string osConfigDir = Environment.GetEnvironmentVariable("HOME");
                        if (string.IsNullOrEmpty(osConfigDir)) {
                            return "."; // Oh well.
                        }
                        return Path.Combine(osConfigDir, "Library", "Application Support", APPLICATION_NAME);
                    }
                case LINUX: {
                        string osConfigDir = Environment.GetEnvironmentVariable("XDG_DATA_HOME");
                        if (string.IsNullOrEmpty(osConfigDir)) {
                            osConfigDir = Environment.GetEnvironmentVariable("HOME");
                            if (string.IsNullOrEmpty(osConfigDir)) {
                                return "."; // Oh well.
                            }
                            osConfigDir += "/.local/share";
                        }
                        return Path.Combine(osConfigDir, APPLICATION_NAME);
                    }
                default:
                    return "NoPlatformDirectory";
            }
        }

        /// <summary>
        /// This is the user path.
        /// </summary>
        private readonly string Platform_PathUser = Environment.GetFolderPath(Environment.SpecialFolder.UserProfile);

        private string Platform_RemoveUserPath(string path) => path.Replace(Platform_PathUser, ".");
    }
}