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

namespace ZuneModCore.Mods
{
    public class VideoSyncMod : Mod
    {
        private const int ZUNEENCENG_WMVCORA_OFFSET = 0x161E;

        public override string Title => "Fix Video Sync";

        public override string Description =>
            "Resolves \"Error C00D11CD\" when attempting to sync video to a Zune device using Windows 10 1607 (Anniversary Update) or newer";

        public override string Author => "sylvathemoth";

        public override string Id => nameof(VideoSyncMod);

        public override async Task<string?> Apply()
        {
            // Verify that ZuneEncEng.dll exists
            FileInfo zeeDllInfo = new(Path.Combine(ZuneInstallDir, "ZuneEncEng.dll"));
            if (!zeeDllInfo.Exists)
                return $"The file '{zeeDllInfo.FullName}' does not exist.";

            // Make a backup if it doesn't already exist
            FileInfo zeeDllBackupInfo = new(Path.Combine(StorageDirectory, "ZuneEncEng.original.dll"));
            if (!zeeDllBackupInfo.Exists)
                File.Copy(zeeDllInfo.FullName, zeeDllBackupInfo.FullName, true);

            try
            {
                // Verify that the DLL is from v4.8 (other versions not tested)
                var zeeDllVersion = FileVersionInfo.GetVersionInfo(zeeDllInfo.FullName);
                if (zeeDllVersion is null || zeeDllVersion.FileMajorPart != 4 || zeeDllVersion.FileMinorPart != 8)
                    return "This mod has not been tested on versions earlier than 4.8.";

                // Open the file
                using (FileStream zeeDll = zeeDllInfo.Open(FileMode.Open))
                using (BinaryWriter zeeDllWriter = new(zeeDll))
                {
                    // Patch ZuneEncEng.dll to point to the local WMVCORE.DLL
                    zeeDllWriter.Seek(ZUNEENCENG_WMVCORA_OFFSET, SeekOrigin.Begin);
                    zeeDllWriter.Write((byte)'a');

                    zeeDllWriter.Flush();
                }

                // Get the working WMVCORE.dll
                byte[] wmvDllAniv = ModResources.WMVCORE;

                // Copy the WMVCore files to the Zune directory.
                // Only ZuneEncEng.dll searches in System32 first; all other dependent
                // DLLs will search the Zune folder.
                await File.WriteAllBytesAsync(Path.Combine(ZuneInstallDir, "wmvcora.dll"), wmvDllAniv);
                await File.WriteAllBytesAsync(Path.Combine(ZuneInstallDir, "wmvcore.dll"), wmvDllAniv);

                return null;
            }
            catch (IOException)
            {
                return $"Unable to replace '{zeeDllInfo.FullName}'. Verify that the Zune software is not running and try again.";
            }
            catch (Exception ex)
            {
                return ex.Message;
            }
        }

        public override Task<string?> Reset()
        {
            var zeeDllPath = Path.Combine(ZuneInstallDir, "ZuneEncEng.dll");
            try
            {
                // Copy backup to application folder
                File.Copy(Path.Combine(StorageDirectory, "ZuneEncEng.original.dll"), zeeDllPath, true);

                // Delete WMVCore files
                File.Delete(Path.Combine(ZuneInstallDir, "wmvcora.dll"));
                File.Delete(Path.Combine(ZuneInstallDir, "wmvcore.dll"));

                return Task.FromResult<string?>(null);
            }
            catch (Exception ex)
            {
                return Task.FromResult(ex.Message)!;
            }
        }

        public override IReadOnlyList<Type>? DependentMods => null;
    }
}