@namespace ZB.MOM.WW.ScadaBridge.CentralUI.Components.Shared

@* Reusable offset-pagination bar.  Purely presentational: the host page
   owns page-number state, query execution, and the HasNextPage decision.
   Parameters: Page, PageChanged, HasNextPage, TotalCount, PageSize, Disabled,
   HideWhenSinglePage. *@

@if (!IsSinglePageAndHidden)
{
<div class="d-flex align-items-center gap-2">
    <button class="btn btn-outline-secondary btn-sm"
            data-test="pager-prev"
            disabled="@(!HasPrev || Disabled)"
            @onclick="OnPrevAsync">
        Previous
    </button>

    <span data-test="pager-summary">@SummaryText</span>

    <button class="btn btn-outline-secondary btn-sm"
            data-test="pager-next"
            disabled="@(!HasNextPage || Disabled)"
            @onclick="OnNextAsync">
        Next
    </button>
</div>
}

@code {
    [Parameter] public int Page { get; set; } = 1;
    [Parameter] public EventCallback<int> PageChanged { get; set; }
    [Parameter] public bool HasNextPage { get; set; }
    [Parameter] public int? TotalCount { get; set; }
    [Parameter] public int PageSize { get; set; }
    [Parameter] public bool Disabled { get; set; }

    /// <summary>
    /// When <c>true</c>, the whole bar is suppressed once the result set is
    /// provably a single page — the conventional behaviour for a pager whose only
    /// controls would be permanently disabled. Opt-in (default <c>false</c>)
    /// because the summary span doubles as the "N total" result-count readout on
    /// pages that have no other place to show it; a host that relies on that
    /// readout leaves this off.
    /// </summary>
    [Parameter] public bool HideWhenSinglePage { get; set; }

    private bool HasPrev => Page > 1;

    // Hide only when single-page-ness is POSITIVELY established: a known page
    // count of 0/1, sitting on page 1, with no next page. A null TotalCount
    // (host cannot count) or any disagreement between the signals renders the
    // bar, so the controls never vanish while a further page still exists.
    private bool IsSinglePageAndHidden =>
        HideWhenSinglePage && PageCount is <= 1 && Page <= 1 && !HasNextPage;

    private int? PageCount =>
        TotalCount is { } t && PageSize > 0
            ? (int)Math.Ceiling(t / (double)PageSize)
            : (int?)null;

    private string SummaryText
    {
        get
        {
            var text = $"Page {Page}";
            if (PageCount is { } pc) text += $" of {pc}";
            if (TotalCount is { } total) text += $" · {total} total";
            return text;
        }
    }

    private Task OnPrevAsync() => PageChanged.InvokeAsync(Page - 1);
    private Task OnNextAsync() => PageChanged.InvokeAsync(Page + 1);
}