// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System;
using CommunityToolkit.Mvvm.Input;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace CommunityToolkit.Mvvm.UnitTests;

[TestClass]
public class Test_RelayCommandOfT
{
    [TestMethod]
    public void Test_RelayCommandOfT_AlwaysEnabled()
    {
        string? text = string.Empty;

        RelayCommand<string>? command = new(s => text = s);

        Assert.IsTrue(command.CanExecute("Text"));
        Assert.IsTrue(command.CanExecute(null));

        _ = Assert.ThrowsException<InvalidCastException>(() => command.CanExecute(new object()));

        (object?, EventArgs?) args = default;

        command.CanExecuteChanged += (s, e) => args = (s, e);

        command.NotifyCanExecuteChanged();

        Assert.AreSame(args.Item1, command);
        Assert.AreSame(args.Item2, EventArgs.Empty);

        command.Execute((object)"Hello");

        Assert.AreEqual(text, "Hello");

        command.Execute(null);

        Assert.AreEqual(text, null);
    }

    [TestMethod]
    public void Test_RelayCommand_WithCanExecuteFunction()
    {
        string? text = string.Empty;

        RelayCommand<string>? command = new(s => text = s, s => s != null);

        Assert.IsTrue(command.CanExecute("Text"));
        Assert.IsFalse(command.CanExecute(null));

        _ = Assert.ThrowsException<InvalidCastException>(() => command.CanExecute(new object()));

        command.Execute((object)"Hello");

        Assert.AreEqual(text, "Hello");

        command.Execute(null);

        // Logic is unconditionally invoked, the caller should check CanExecute first
        Assert.IsNull(text);
    }

    [TestMethod]
    public void Test_RelayCommand_NullWithValueType()
    {
        int n = 0;

        RelayCommand<int>? command = new(i => n = i);

        Assert.IsFalse(command.CanExecute(null));
        _ = Assert.ThrowsException<NullReferenceException>(() => command.Execute(null));

        command = new RelayCommand<int>(i => n = i, i => i > 0);

        Assert.IsFalse(command.CanExecute(null));
        _ = Assert.ThrowsException<NullReferenceException>(() => command.Execute(null));
    }
}