2021-09-08 20:57:38 +02:00

89 lines
3.2 KiB
C#

// Kyoo - A portable and vast media library solution.
// Copyright (c) Kyoo.
//
// See AUTHORS.md and LICENSE file in the project root for full license information.
//
// Kyoo is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// any later version.
//
// Kyoo is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Kyoo. If not, see <https://www.gnu.org/licenses/>.
using System;
using System.Linq.Expressions;
using Kyoo.Utils;
namespace Kyoo.Abstractions.Controllers
{
/// <summary>
/// Information about how a query should be sorted. What factor should decide the sort and in which order.
/// </summary>
/// <typeparam name="T">For witch type this sort applies</typeparam>
public readonly struct Sort<T>
{
/// <summary>
/// The sort key. This member will be used to sort the results.
/// </summary>
public Expression<Func<T, object>> Key { get; }
/// <summary>
/// If this is set to true, items will be sorted in descend order else, they will be sorted in ascendant order.
/// </summary>
public bool Descendant { get; }
/// <summary>
/// Create a new <see cref="Sort{T}"/> instance.
/// </summary>
/// <param name="key">The sort key given. It is assigned to <see cref="Key"/>.</param>
/// <param name="descendant">Should this be in descendant order? The default is false.</param>
/// <exception cref="ArgumentException">If the given key is not a member.</exception>
public Sort(Expression<Func<T, object>> key, bool descendant = false)
{
Key = key;
Descendant = descendant;
if (!Utility.IsPropertyExpression(Key))
throw new ArgumentException("The given sort key is not valid.");
}
/// <summary>
/// Create a new <see cref="Sort{T}"/> instance from a key's name (case insensitive).
/// </summary>
/// <param name="sortBy">A key name with an optional order specifier. Format: "key:asc", "key:desc" or "key".</param>
/// <exception cref="ArgumentException">An invalid key or sort specifier as been given.</exception>
public Sort(string sortBy)
{
if (string.IsNullOrEmpty(sortBy))
{
Key = null;
Descendant = false;
return;
}
string key = sortBy.Contains(':') ? sortBy[..sortBy.IndexOf(':')] : sortBy;
string order = sortBy.Contains(':') ? sortBy[(sortBy.IndexOf(':') + 1)..] : null;
ParameterExpression param = Expression.Parameter(typeof(T), "x");
MemberExpression property = Expression.Property(param, key);
Key = property.Type.IsValueType
? Expression.Lambda<Func<T, object>>(Expression.Convert(property, typeof(object)), param)
: Expression.Lambda<Func<T, object>>(property, param);
Descendant = order switch
{
"desc" => true,
"asc" => false,
null => false,
_ => throw new ArgumentException($"The sort order, if set, should be :asc or :desc but it was :{order}.")
};
}
}
}