App.razor

@using System.Text
@using KristofferStrube.Blazor.FileSystem
@inject IFileSystemAccessService FileSystemAccessService;
@inject IJSRuntime JSRuntime
@inject ILogger<App> Logger

<main>

    <div>
        <h1>
            Text file encoding converter
        </h1>
    </div>

    <div>
        <span class="caption">
            Source folder
        </span>
        <button @onclick="OpenFolderToRead">
            @if (_sourceFolderName is null)
            {
                <text>(Chose the source folder)</text>
            }
            else
            {
                <text>📂 @_sourceFolderName (Click here to chose another folder)</text>
            }
        </button>
    </div>

    <div>
        <span class="caption">
            Source encoding
        </span>

        <InputSelect @bind-Value="_sourceEncodingName">
            @foreach (var encoding in _encodings)
            {
                <option value="@encoding.Name">@encoding.DisplayName</option>
            }
        </InputSelect>
    </div>

    <div class="source-files">
        <span class="caption">
            Source files
        </span>

        <ul>
            @foreach (var file in _sourceFiles)
            {
                <li>🗒️@file.Name</li>
            }
        </ul>
    </div>

    <div>
        <span class="caption">
            Output folder
        </span>

        <button @onclick="OpenFolderToWrite">
            @if (_outputFolderName is null)
            {
                <text>(Chose the output folder)</text>
            }
            else
            {
                <text>📂 @_outputFolderName (Click here to chose another folder)</text>
            }
        </button>
    </div>

    <div>
        <span class="caption">
            Output encoding
        </span>

        <InputSelect @bind-Value="_outputEncodingName">
            @foreach (var encoding in _encodings)
            {
                <option value="@encoding.Name">@encoding.DisplayName</option>
            }
        </InputSelect>
    </div>

    <div>
        <button @onclick="ConvertIt" disabled="@(!IsReadyToConvert())">
            🚀 Convert
        </button>
    </div>

</main>

<footer>
    <a href="https://github.com/sample-by-jsakamoto/Blazor-TextFileEncodingConverter/blob/master/LICENSE" target="_blank">GNU General Public License v3.0</a>
    <span>|</span>
    <a href="https://github.com/sample-by-jsakamoto/Blazor-TextFileEncodingConverter" target="_blank">Source Code</a>
    <span>|</span>
    <span>Powered by <a href="https://github.com/KristofferStrube/Blazor.FileSystemAccess" target="_blank">KristofferStrube.Blazor.FileSystemAccess</a></span>
</footer>

@code
{
    private IEnumerable<EncodingInfo> _encodings = [];

    private string? _sourceEncodingName;

    private string? _sourceFolderName;

    private string? _outputEncodingName;

    private string? _outputFolderName;

    private FileSystemDirectoryHandle? _outputFolderHandle;

    private IEnumerable<File> _sourceFiles = [];

    public class File
    {
        public required string Name;
        public required FileSystemFileHandle Handle;
    }

    protected override void OnInitialized()
    {
        _encodings = Encoding.GetEncodings();
        _sourceEncodingName = _encodings.First().Name;
        _outputEncodingName = "utf-8";
    }

    private async Task OpenFolderToRead()
    {
        if (_sourceEncodingName is null) return;

        try
        {
            var directoryHandle = await this.FileSystemAccessService.ShowDirectoryPickerAsync();

            _sourceFolderName = await directoryHandle.GetNameAsync();
            var fileHandles = await directoryHandle.ValuesAsync();
            var fileNameGetterTasks = fileHandles.OfType<FileSystemFileHandle>().Select(async h =>
            {
                var name = await h.GetNameAsync();
                return new File { Name = name, Handle = h };
            }).ToArray();
            await Task.WhenAll(fileNameGetterTasks);
            _sourceFiles = fileNameGetterTasks.Select(t => t.Result);
        }
        catch (Exception ex)
        {
            Logger.LogError(ex, ex.Message);
            _sourceFolderName = null;
            _sourceFiles = [];
        }
    }

    private async Task OpenFolderToWrite()
    {
        try
        {
            _outputFolderHandle = await this.FileSystemAccessService.ShowDirectoryPickerAsync();
            await _outputFolderHandle.RequestPermissionAsync(new() { Mode = FileSystemPermissionMode.ReadWrite });
            _outputFolderName = await _outputFolderHandle.GetNameAsync();
        }
        catch (Exception ex)
        {
            Logger.LogError(ex, ex.Message);
            _outputFolderHandle = null;
            _outputFolderName = null;
        }
    }

    private bool IsReadyToConvert()
    {
        return
            _sourceFolderName is not null &&
            _sourceEncodingName is not null &&
            _outputFolderName is not null &&
            _outputEncodingName is not null;
    }

    private async Task ConvertIt(MouseEventArgs args)
    {
        if (_outputFolderHandle is null) return;
        var sourceEncoding = Encoding.GetEncoding(_sourceEncodingName ?? "utf-8");
        var outputEncoding = Encoding.GetEncoding(_outputEncodingName ?? "utf-8");

        var convertingTasks = _sourceFiles.Select(async sourceFile =>
        {
            await using var file = await sourceFile.Handle.GetFileAsync();
            var sourceBytes = await file.ArrayBufferAsync();
            var sourceText = sourceEncoding.GetString(sourceBytes);

            var outputFileName = sourceFile.Name;
            await using var outputFileHandle = await _outputFolderHandle.GetFileHandleAsync(outputFileName, new FileSystemGetFileOptions { Create = true });
            await using var outputFileStream = await outputFileHandle.CreateWritableAsync();
            var outputBytes = outputEncoding.GetBytes(sourceText);
            await outputFileStream.WriteAsync(outputBytes);
        }).ToArray();

        await Task.WhenAll(convertingTasks);

        await JSRuntime.InvokeVoidAsync("alert", "Conversion done.");
    }
}