scadalink-design/src/ScadaLink.CentralUI/Components/Shared/ConfirmDialog.razor

@* Reusable confirmation dialog using Bootstrap modal.
   z-index ladder: Toast container 1090 > this modal 1055 > this backdrop 1040. *@
@inject IJSRuntime JS
@implements IAsyncDisposable

@if (_visible)
{
    <div class="modal-backdrop fade show"></div>
    <div @ref="_modalRef"
         class="modal fade show d-block"
         tabindex="-1"
         role="dialog"
         @onkeydown="OnKeyDownAsync">
        <div class="modal-dialog modal-dialog-centered" role="document">
            <div class="modal-content">
                <div class="modal-header">
                    <h5 class="modal-title">@Title</h5>
                    <button type="button" class="btn-close" @onclick="Cancel"></button>
                </div>
                <div class="modal-body">
                    <p>@Message</p>
                </div>
                <div class="modal-footer">
                    <button type="button" class="btn btn-outline-secondary btn-sm" @onclick="Cancel">Cancel</button>
                    <button type="button" class="btn @ConfirmButtonClass btn-sm" @onclick="Confirm">@ConfirmText</button>
                </div>
            </div>
        </div>
    </div>
}

@code {
    private bool _visible;
    private bool _bodyLocked;
    private TaskCompletionSource<bool>? _tcs;
    private ElementReference _modalRef;

    [Parameter] public string Title { get; set; } = "Confirm";
    [Parameter] public string Message { get; set; } = "Are you sure?";
    [Parameter] public string ConfirmText { get; set; } = "Confirm";
    [Parameter] public string ConfirmButtonClass { get; set; } = "btn-primary";

    public Task<bool> ShowAsync(string? message = null, string? title = null)
    {
        if (message != null) Message = message;
        if (title != null) Title = title;
        _visible = true;
        _tcs = new TaskCompletionSource<bool>();
        StateHasChanged();
        return _tcs.Task;
    }

    protected override async Task OnAfterRenderAsync(bool firstRender)
    {
        if (_visible && !_bodyLocked)
        {
            _bodyLocked = true;
            await TryLockBodyAsync();
            // Focus the modal so the @onkeydown handler receives Escape.
            try { await _modalRef.FocusAsync(); }
            catch { /* prerender or detached: ignore */ }
        }
    }

    private async Task OnKeyDownAsync(KeyboardEventArgs e)
    {
        if (e.Key == "Escape")
        {
            await CancelAsync();
        }
    }

    private void Confirm()
    {
        Close(true);
    }

    private void Cancel()
    {
        Close(false);
    }

    private Task CancelAsync()
    {
        Close(false);
        return Task.CompletedTask;
    }

    private void Close(bool result)
    {
        _visible = false;
        _ = TryUnlockBodyAsync();
        _tcs?.TrySetResult(result);
    }

    private async Task TryLockBodyAsync()
    {
        try
        {
            await JS.InvokeVoidAsync("document.body.classList.add", "modal-open");
        }
        catch
        {
            // Prerendering has no JS runtime; log only.
            try { await JS.InvokeVoidAsync("console.debug", "ConfirmDialog: JS interop unavailable for body lock."); }
            catch { /* swallow */ }
        }
    }

    private async Task TryUnlockBodyAsync()
    {
        _bodyLocked = false;
        try
        {
            await JS.InvokeVoidAsync("document.body.classList.remove", "modal-open");
        }
        catch
        {
            try { await JS.InvokeVoidAsync("console.debug", "ConfirmDialog: JS interop unavailable for body unlock."); }
            catch { /* swallow */ }
        }
    }

    public async ValueTask DisposeAsync()
    {
        if (_bodyLocked)
        {
            await TryUnlockBodyAsync();
        }
    }
}