groceries/Groceries/Components/Table.razor

@using Microsoft.EntityFrameworkCore
@using Microsoft.EntityFrameworkCore.Query

@typeparam TItem
@attribute [CascadingTypeParameter(nameof(TItem))]

@inject NavigationManager Navigation

<table>
    <CascadingValue IsFixed="true" Value="this">@ChildContent</CascadingValue>
    <thead>
        <tr>
            @foreach (var column in columns)
            {
                <th scope="col"
                    class="@GetHeaderClass(column)"
                    style="@(column.Fill ? "width: 100%" : null)"
                    aria-sort="@GetAriaSortValue(column)"
                >
                    @if (column.Sortable)
                    {
                        <a href="@GetUriForColumnSort(column)">@column.HeaderContent</a>
                    }
                    else
                    {
                        @column.HeaderContent
                    }
                </th>
            }
        </tr>
    </thead>
    <tbody>
        @foreach (var item in currentPageItems)
        {
            <tr>
                @foreach (var column in columns)
                {
                    <td class="@GetCellClass(column)">
                        @column.CellContent(item)
                    </td>
                }
            </tr>
        }
    </tbody>
    @if (FooterContent != null)
    {
        <tfoot>@FooterContent</tfoot>
    }
</table>

@code {
    private readonly List<TableColumn<TItem>> columns = [];
    private TItem[] currentPageItems = [];
    private IQueryable<TItem>? lastAssignedItems;
    private int? lastLoadedPaginationStateHash;

    [Parameter, EditorRequired]
    public required IQueryable<TItem> Items { get; set; }

    [Parameter]
    public PaginationState? Pagination { get; set; }

    [Parameter]
    public string? HeaderClass { get; set; }

    [Parameter]
    public string? CellClass { get; set; }

    [Parameter]
    public RenderFragment? ChildContent { get; set; }

    [Parameter]
    public RenderFragment? FooterContent { get; set; }

    [SupplyParameterFromQuery(Name = "page")]
    private int CurrentPage { get; set; }

    [SupplyParameterFromQuery(Name = "sort")]
    private string? SortKey { get; set; }

    [SupplyParameterFromQuery(Name = "desc")]
    private bool SortDescending { get; set; }

    protected override async Task OnParametersSetAsync()
    {
        var dataSourceHasChanged = Items != lastAssignedItems;
        if (dataSourceHasChanged)
        {
            lastAssignedItems = Items;
        }

        if (Pagination != null)
        {
            Pagination.CurrentPage = CurrentPage;
        }

        if (dataSourceHasChanged || Pagination?.GetHashCode() != lastLoadedPaginationStateHash)
        {
            await LoadDataAsync();
        }
    }

    internal void AddColumn(TableColumn<TItem> column)
    {
        columns.Add(column);
        StateHasChanged();
    }

    private async Task LoadDataAsync()
    {
        await LoadDataCoreAsync();
        lastLoadedPaginationStateHash = Pagination?.GetHashCode();
    }

    private async Task LoadDataCoreAsync()
    {
        if (Pagination?.CurrentPage < 1)
        {
            Pagination.CurrentPage = 1;
            NavigateToCurrentPage();
            return;
        }

        var totalCount = Items.Provider is IAsyncQueryProvider
            ? await Items.CountAsync()
            : Items.Count();

        var itemsQuery = Items;
        if (SortKey != null &&
            columns
                .Select(column => column.SortBy)
                .SingleOrDefault(sortBy => sortBy?.Key == SortKey) is DataSort<TItem> sortBy)
        {
            itemsQuery = sortBy.Apply(itemsQuery, SortDescending);
        }

        if (Pagination != null)
        {
            Pagination.TotalItemCount = totalCount;

            if (Pagination.LastPage < Pagination.CurrentPage)
            {
                Pagination.CurrentPage = Pagination.LastPage;
                NavigateToCurrentPage();
                return;
            }

            itemsQuery = itemsQuery
                .Skip(Pagination.Offset)
                .Take(Pagination.PageSize);
        }

        currentPageItems = Items.Provider is IAsyncQueryProvider
            ? await itemsQuery.ToArrayAsync()
            : itemsQuery.ToArray();

        if (Pagination != null)
        {
            Pagination.ItemCount = currentPageItems.Length;
        }

        StateHasChanged();
    }

    private void NavigateToCurrentPage()
    {
        Navigation.NavigateTo(Navigation.GetUriWithQueryParameter("page", Pagination!.CurrentPage));
    }

    private string? GetAriaSortValue(TableColumn<TItem> column)
        => column.Sortable && SortKey == column.SortBy!.Key
            ? (SortDescending ? "descending" : "ascending")
            : null;

    private string GetHeaderClass(TableColumn<TItem> column)
    {
        string?[] classes = [
            "table__header",
            column.Sortable ? "table__header--sortable" : null,
            HeaderClass,
        ];
        return string.Join(' ', classes.Where(c => c != null));
    }

    private string GetCellClass(TableColumn<TItem> column)
    {
        string?[] classes = [
            "table__cell",
            column.Align switch
            {
                Align.Center => "table__cell--align-center",
                Align.End => "table__cell--align-end",
                _ => null,
            },
            CellClass,
        ];
        return string.Join(' ', classes.Where(c => c != null));
    }

    private string GetUriForColumnSort(TableColumn<TItem> column)
    => Navigation.GetUriWithQueryParameters(new Dictionary<string, object?>
        {
            { "page", 1 },
            { "sort", SortKey == column.SortBy!.Key && SortDescending ? null : column.SortBy.Key},
            { "desc", SortKey != column.SortBy!.Key || SortDescending ? null : "true" },
        });
}