/*
 * Process Hacker - 
 *   file-related utility functions
 *
 * Copyright (C) 2009 wj32
 * 
 * This file is part of Process Hacker.
 * 
 * Process Hacker is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Process Hacker is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Process Hacker.  If not, see <http://www.gnu.org/licenses/>.
 */

using System;
using System.Collections.Generic;
using System.Drawing;
using ProcessHacker.Native.Api;
using ProcessHacker.Native.Objects;
using ProcessHacker.Native.Security;

namespace ProcessHacker.Native
{
    /// <summary>
    /// Provides utility methods for managing files.
    /// </summary>
    public static class FileUtils
    {
        static FileUtils()
        {
            RefreshFileNamePrefixes();
        }

        /// <summary>
        /// Used to resolve device prefixes (\Device\Harddisk1) into DOS drive names.
        /// </summary>
        private static Dictionary<string, string> _fileNamePrefixes;

        public static string FindFile(string basePath, string fileName)
        {
            if (!string.IsNullOrEmpty(basePath))
            {
                // Search the base path first.
                if (System.IO.File.Exists(basePath + "\\" + fileName))
                    return System.IO.Path.Combine(basePath, fileName);
            }

            string path = Environment.GetEnvironmentVariable("Path");

            string[] directories = path.Split(';');

            foreach (var directory in directories)
            {
                if (System.IO.File.Exists(directory + "\\" + fileName))
                    return System.IO.Path.Combine(directory, fileName);
            }

            return null;
        }

        public static string FindFileWin32(string fileName)
        {
            using (MemoryAlloc data = new MemoryAlloc(0x400))
            {
                IntPtr filePart;

                int retLength = Win32.SearchPath(null, fileName, null, data.Size / 2, data, out filePart);

                if (retLength * 2 > data.Size)
                {
                    data.ResizeNew(retLength * 2);
                    retLength = Win32.SearchPath(null, fileName, null, data.Size / 2, data, out filePart);
                }

                if (retLength == 0)
                    return null;

                return data.ReadUnicodeString(0, retLength);
            }
        }

        public static Icon GetFileIcon(string fileName)
        {
            return GetFileIcon(fileName, false);
        }

        public static Icon GetFileIcon(string fileName, bool large)
        {
            if (string.IsNullOrEmpty(fileName))
                throw new Exception("File name cannot be empty.");

            try
            {
                ShFileInfo shinfo;

                if (Win32.SHGetFileInfo(
                    fileName, 
                    0, 
                    out shinfo,
                    (uint)ShFileInfo.SizeOf,
                    Win32.ShgFiIcon |
                    (large ? Win32.ShgFiLargeIcon : Win32.ShgFiSmallIcon)
                    ) == 0)
                {
                    return null;
                }

                return Icon.FromHandle(shinfo.hIcon);
            }
            catch
            {
                return null;
            }
        }

        public static unsafe string GetVistaFileName(int pid)
        {
            using (MemoryAlloc buffer = new MemoryAlloc(0x100))
            {
                SystemProcessImageNameInformation info;

                info.ProcessId = pid;
                info.ImageName.Length = 0;
                info.ImageName.MaximumLength = 0x100;
                info.ImageName.Buffer = buffer;

                NtStatus status = Win32.NtQuerySystemInformation(
                    SystemInformationClass.SystemProcessImageName,
                    &info,
                    SystemProcessImageNameInformation.SizeOf,
                    null
                    );

                if (status == NtStatus.InfoLengthMismatch)
                {
                    // Our buffer was too small. The required buffer length is stored in MaximumLength.
                    buffer.ResizeNew(info.ImageName.MaximumLength);

                    status = Win32.NtQuerySystemInformation(
                        SystemInformationClass.SystemProcessImageName,
                        &info,
                        SystemProcessImageNameInformation.SizeOf,
                        null
                        );
                }

                status.ThrowIf();

                return GetFileName(info.ImageName.Text);
            }
        }

        public static string GetFileName(string fileName)
        {
            return GetFileName(fileName, false);
        }

        public static string GetFileName(string fileName, bool canonicalize)
        {
            bool alreadyCanonicalized = false;

            // If the path starts with "\SystemRoot", we can replace it with C:\ (or whatever it is).
            if (fileName.StartsWith("\\systemroot", StringComparison.OrdinalIgnoreCase))
            {
                fileName = System.IO.Path.GetFullPath(Environment.SystemDirectory + "\\.." + fileName.Substring(11));
                alreadyCanonicalized = true;
            }
            // If the path starts with "\WINDOWS", we can replace it with C:\WINDOWS.
            else if (fileName.StartsWith("\\windows", StringComparison.OrdinalIgnoreCase))
            {
                fileName = System.IO.Path.GetFullPath(Environment.SystemDirectory + "\\.." + fileName.Substring(8));
                alreadyCanonicalized = true;
            }
            // If the path starts with "\??\", we can remove it and we will have the path.
            else if (fileName.StartsWith("\\??\\", StringComparison.OrdinalIgnoreCase))
            {
                fileName = fileName.Substring(4);
            }

            // If the path still starts with a backslash, we probably need to 
            // resolve any native object name to a DOS drive letter.
            if (fileName.StartsWith("\\", StringComparison.OrdinalIgnoreCase))
            {
                foreach (KeyValuePair<string, string> pair in _fileNamePrefixes)
                {
                    if (fileName.StartsWith(pair.Key + "\\", StringComparison.OrdinalIgnoreCase))
                    {
                        fileName = pair.Value + "\\" + fileName.Substring(pair.Key.Length + 1);
                        break;
                    }
                    if (fileName == pair.Key)
                    {
                        fileName = pair.Value;
                        break;
                    }
                }
            }

            if (canonicalize && !alreadyCanonicalized)
                fileName = System.IO.Path.GetFullPath(fileName);

            return fileName;
        }

        public static string GetPathForDosDrive(char driveLetter)
        {
            driveLetter = char.ToUpperInvariant(driveLetter);

            if (driveLetter < 'A' || driveLetter > 'Z')
                throw new ArgumentException("The drive letter must be between A to Z (inclusive).");

            using (SymbolicLinkHandle shandle = new SymbolicLinkHandle(@"\??\" + driveLetter + ":", SymbolicLinkAccess.Query))
            {
                return shandle.Target;
            }
        }

        public static void RefreshFileNamePrefixes()
        {
            if (_fileNamePrefixes == null)
            {
                // Just create a new dictionary to avoid having to lock the existing one.
                _fileNamePrefixes = new Dictionary<string, string>();

                for (char c = 'A'; c <= 'Z'; c++)
                {
                    using (MemoryAlloc data = new MemoryAlloc(1024))
                    {
                        int length;

                        if ((length = Win32.QueryDosDevice(c.ToString() + ":", data, data.Size/2)) > 2)
                        {
                            _fileNamePrefixes.Add(data.ReadUnicodeString(0, length - 2), c.ToString() + ":");
                        }
                    }
                }
            }
        }

        public static void ShowProperties(string fileName)
        {
            ShellExecuteInfo info = new ShellExecuteInfo
            {
                cbSize = ShellExecuteInfo.SizeOf, 
                lpFile = fileName, 
                nShow = ShowWindowType.Show, 
                fMask = Win32.SeeMaskInvokeIdList, 
                lpVerb = "properties"
            };

            Win32.ShellExecuteEx(ref info);
        }
    }
}