using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.IO.Compression;
using System.Linq;
using System.Runtime.InteropServices;
using System.Threading;
using NitroxModel.Platforms.OS.MacOS;
using NitroxModel.Platforms.OS.Unix;
using NitroxModel.Platforms.OS.Windows;

namespace NitroxModel.Platforms.OS.Shared;

public abstract class FileSystem
{
    private static readonly Lazy<FileSystem> instance = new(() =>
                                                            {
                                                                if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
                                                                {
                                                                    return new WinFileSystem();
                                                                }
                                                                if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
                                                                {
                                                                    return new UnixFileSystem();
                                                                }
                                                                if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
                                                                {
                                                                    return new MacFileSystem();
                                                                }
                                                                throw new NotSupportedException("Current OS is not supported");
                                                            },
                                                            LazyThreadSafetyMode.ExecutionAndPublication);

    public virtual IEnumerable<string> ExecutableFileExtensions => throw new NotSupportedException();
    public static FileSystem Instance => instance.Value;
    public virtual string TextEditor => throw new NotSupportedException();

    public virtual IEnumerable<string> GetDefaultPrograms(string file) => throw new NotSupportedException();

    /// <summary>
    ///     Opens the file with the default associated program or the default editor of the OS.
    ///     The returned <see cref="Process" /> should be disposed.
    /// </summary>
    /// <param name="file">File or program to open or execute.</param>
    /// <returns>Instance of a running process. Should be disposed.</returns>
    public virtual Process OpenOrExecuteFile(string file)
    {
        if (string.IsNullOrWhiteSpace(file))
        {
            throw new ArgumentException("File path must not be null or empty.", nameof(file));
        }

        string editorProgram = GetDefaultPrograms(file).FirstOrDefault() ?? TextEditor;
        // Handle special arguments for popular editors.
        string arguments = Path.GetFileName(editorProgram)?.ToLowerInvariant() switch
        {
            "code.cmd" => "--wait", // Allow to wait on VS code
            _ => ""
        };

        return Process.Start(new ProcessStartInfo
        {
            FileName = editorProgram,
            Arguments = $@"{(arguments.Length > 0 ? $"{arguments} " : "")}""{file}""",
            UseShellExecute = false,
            RedirectStandardOutput = true,
            RedirectStandardError = true,
        });
    }

    /// <summary>
    ///     Gets the full path to a file or program. Searches the PATH environment variables if file could not be found
    ///     relatively. Returns null if not found.
    /// </summary>
    /// <param name="fileName">File or program name to get the full path from.</param>
    /// <returns></returns>
    public string GetFullPath(string fileName)
    {
        if (File.Exists(fileName))
        {
            return Path.GetFullPath(fileName);
        }
        string values = Environment.GetEnvironmentVariable("PATH");
        if (values == null)
        {
            return null;
        }

        fileName = Path.GetFileName(fileName);
        // Always test filename in system lib root first, then other paths. On UNIX systems the path is case-sensitive.
        IEnumerable<string> pathsToTools = new[] { Environment.SystemDirectory }.Concat(values.Split(Path.PathSeparator)).Distinct();
        foreach (string path in pathsToTools)
        {
            string fullPath = Path.Combine(path, fileName);
            if (File.Exists(fullPath))
            {
                return fullPath;
            }
        }
        return null;
    }

    public string MakeRelativePath(string fromPath, string toPath)
    {
        if (string.IsNullOrEmpty(fromPath))
        {
            throw new ArgumentNullException(nameof(fromPath));
        }
        if (string.IsNullOrEmpty(toPath))
        {
            throw new ArgumentNullException(nameof(toPath));
        }
        // Ensure postfix so that result becomes relative to entire "from" path.
        fromPath = fromPath[fromPath.Length - 1] == Path.DirectorySeparatorChar ? fromPath : fromPath + Path.DirectorySeparatorChar;
        Uri fromUri = new(fromPath);
        Uri toUri = new(toPath);
        // Can path be made relative?
        if (fromUri.Scheme != toUri.Scheme)
        {
            return toPath;
        }

        Uri relativeUri = fromUri.MakeRelativeUri(toUri);
        string relativePath = Uri.UnescapeDataString(relativeUri.ToString());
        if (toUri.Scheme.Equals("file", StringComparison.InvariantCultureIgnoreCase))
        {
            relativePath = relativePath.Replace(Path.AltDirectorySeparatorChar, Path.DirectorySeparatorChar);
        }
        return relativePath;
    }

    /// <summary>
    ///     Zips the files found in the given directory.
    /// </summary>
    /// <param name="dir">Directory to search for files to zip.</param>
    /// <param name="outputPath">
    ///     Name of output zip, optionally including full path. If null, uses the directory name given by
    ///     <see cref="dir" />.
    /// </param>
    /// <param name="fileSearchPattern">Search pattern used to filter against files to zip.</param>
    /// <param name="replaceFile">If true, overwrites the file matching the output path.</param>
    /// <returns>Full path to the newly created zip or null if no files are found to zip.</returns>
    /// <exception cref="IOException">If zip file already exists.</exception>
    public string ZipFilesInDirectory(string dir, string outputPath = null, string fileSearchPattern = "*", bool replaceFile = false)
    {
        if (string.IsNullOrWhiteSpace(dir))
        {
            throw new ArgumentException("Directory must not be null or empty", nameof(dir));
        }
        dir = Path.GetFullPath(dir);
        if (!Directory.Exists(dir))
        {
            throw new ArgumentException("Path is not a directory", nameof(dir));
        }
        // Figure out relative path of output OR use <basename>.zip of directory.
        outputPath = Path.GetFullPath(outputPath ?? dir);
        string outZipName = Path.GetFileName(outputPath);
        if (string.IsNullOrEmpty(Path.GetExtension(outZipName)))
        {
            outZipName = Path.ChangeExtension(outZipName, ".zip");
        }
        string outZipDir = Path.GetDirectoryName(outputPath) ?? dir;
        string outZipFullName = Path.Combine(outZipDir, outZipName);
        if (!replaceFile && File.Exists(outZipFullName))
        {
            throw new IOException($"The file '{outZipFullName}' already exists");
        }
        string[] files = Directory.GetFiles(dir, fileSearchPattern, SearchOption.AllDirectories);
        if (files.Length < 1)
        {
            return null;
        }

        // Create the zip.
        Directory.CreateDirectory(outZipDir);
        using ZipArchive zip = new(File.Create(outZipFullName), ZipArchiveMode.Create);
        foreach (string file in files)
        {
            ZipArchiveEntry entry = zip.CreateEntry(MakeRelativePath(dir, file));
            using Stream sourceStream = new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.Read);
            using Stream targetStream = entry.Open();
            sourceStream.CopyTo(targetStream);
        }

        return outZipFullName;
    }

    /// <summary>
    ///     Replaces target file with source file. If target file does not exist then it moves the file.
    ///     This falls back to a copy if the target is on a different drive.
    ///     The source file will always be deleted.
    /// </summary>
    /// <param name="source">Source file to replace with.</param>
    /// <param name="target">Target file to replace.</param>
    /// <returns>True if file was moved or replaced successfully.</returns>
    public bool ReplaceFile(string source, string target)
    {
        if (!File.Exists(source))
        {
            return false;
        }
        source = Path.GetFullPath(source);

        if (!File.Exists(target))
        {
            File.Move(source, target);
            return true;
        }
        try
        {
            File.Replace(source, target, null, false);
        }
        catch (IOException ex)
        {
            // TODO: Need to test on Linux because the ex.HResult will likely not work or be different number cross-platform.
            switch ((uint)ex.HResult)
            {
                case 0x80070498:
                    // Tried to replace file between drives. This does not work, need to do so in steps.
                    try
                    {
                        string originalExtension = Path.GetExtension(target);
                        originalExtension = string.IsNullOrWhiteSpace(originalExtension) ? "" : $".{originalExtension}";
                        string backupFileName = $"{Path.GetFileNameWithoutExtension(target)}_{Path.GetFileNameWithoutExtension(Path.GetTempFileName())}{originalExtension}.bak";
                        Log.Debug($"Renaming file '{target}' to '{backupFileName}' as backup plan if file replace fails");
                        File.Move(target, backupFileName);
                        File.Copy(source, target);

                        // Cleanup redundant files, ignoring errors.
                        try
                        {
                            File.Delete(source);
                            File.Delete(backupFileName);
                        }
                        catch (Exception)
                        {
                            // ignored
                        }
                    }
                    catch (Exception ex2)
                    {
                        Log.Error(ex2, $"Failed to replace file '{source}' with '{target}' which is on another drive");
                        return false;
                    }
                    break;
                default:
                    // No special handling implemented for error, abort.
                    Log.Warn($"Unhandled file replace of '{source}' with '{target}' with HRESULT: 0x{ex.HResult:X}");
                    return false;
            }
        }
        return true;
    }


    public bool IsWritable(string directory)
    {
        if (!Directory.Exists(directory))
        {
            return false;
        }
        string randFileName = Path.GetRandomFileName();
        try
        {
            File.Create(Path.Combine(directory, randFileName)).Close();
            File.Delete(Path.Combine(directory, randFileName));
            return true;
        }
        catch
        {
            return false;
        }
    }

    public abstract bool SetFullAccessToCurrentUser(string directory);

    public virtual bool IsTrustedFile(string file) => true;
}