// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Linq;
 
namespace Microsoft.AspNetCore.Components.QuickGrid;
 
/// <summary>
/// Parameters for data to be supplied by a <see cref="QuickGrid{TGridItem}"/>'s <see cref="QuickGrid{TGridItem}.ItemsProvider"/>.
/// </summary>
/// <typeparam name="TGridItem">The type of data represented by each row in the grid.</typeparam>
public readonly struct GridItemsProviderRequest<TGridItem>
{
    /// <summary>
    /// The zero-based index of the first item to be supplied.
    /// </summary>
    public int StartIndex { get; init; }
 
    /// <summary>
    /// If set, the maximum number of items to be supplied. If not set, the maximum number is unlimited.
    /// </summary>
    public int? Count { get; init; }
 
    /// <summary>
    /// Specifies which column represents the sort order.
    ///
    /// Rather than inferring the sort rules manually, you should normally call either <see cref="ApplySorting(IQueryable{TGridItem})"/>
    /// or <see cref="GetSortByProperties"/>, since they also account for <see cref="SortByColumn" /> and <see cref="SortByAscending" /> automatically.
    /// </summary>
    public ColumnBase<TGridItem>? SortByColumn { get; init; }
 
    /// <summary>
    /// Specifies the current sort direction.
    ///
    /// Rather than inferring the sort rules manually, you should normally call either <see cref="ApplySorting(IQueryable{TGridItem})"/>
    /// or <see cref="GetSortByProperties"/>, since they also account for <see cref="SortByColumn" /> and <see cref="SortByAscending" /> automatically.
    /// </summary>
    public bool SortByAscending { get; init; }
 
    /// <summary>
    /// A token that indicates if the request should be cancelled.
    /// </summary>
    public CancellationToken CancellationToken { get; init; }
 
    internal GridItemsProviderRequest(
        int startIndex, int? count, ColumnBase<TGridItem>? sortByColumn, bool sortByAscending,
        CancellationToken cancellationToken)
    {
        StartIndex = startIndex;
        Count = count;
        SortByColumn = sortByColumn;
        SortByAscending = sortByAscending;
        CancellationToken = cancellationToken;
    }
 
    /// <summary>
    /// Applies the request's sorting rules to the supplied <see cref="IQueryable{TGridItem}"/>.
    /// </summary>
    /// <param name="source">An <see cref="IQueryable{TGridItem}"/>.</param>
    /// <returns>A new <see cref="IQueryable{TGridItem}"/> representing the <paramref name="source"/> with sorting rules applied.</returns>
    public IQueryable<TGridItem> ApplySorting(IQueryable<TGridItem> source) =>
        SortByColumn?.SortBy?.Apply(source, SortByAscending) ?? source;
 
    /// <summary>
    /// Produces a collection of (property name, direction) pairs representing the sorting rules.
    /// </summary>
    /// <returns>A collection of (property name, direction) pairs representing the sorting rules</returns>
    public IReadOnlyCollection<SortedProperty> GetSortByProperties() =>
        SortByColumn?.SortBy?.ToPropertyList(SortByAscending) ?? Array.Empty<SortedProperty>();
}