// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using Microsoft.AspNetCore.Mvc.ModelBinding;
 
namespace Microsoft.AspNetCore.Mvc.ViewFeatures;
 
public class ModelExplorerTest
{
    [Fact]
    public void ModelType_UsesRuntimeType()
    {
        // Arrange
        var provider = new EmptyModelMetadataProvider();
        var modelExplorer = provider.GetModelExplorerForType(typeof(BaseClass), new DerivedClass());
 
        // Act
        var modelType = modelExplorer.ModelType;
 
        // Assert
        Assert.Equal(typeof(DerivedClass), modelType);
    }
 
    [Fact]
    public void ModelType_UsesDeclaredType_WhenModelIsNull()
    {
        // Arrange
        var provider = new EmptyModelMetadataProvider();
        var modelExplorer = provider.GetModelExplorerForType(typeof(BaseClass), model: null);
 
        // Act
        var modelType = modelExplorer.ModelType;
 
        // Assert
        Assert.Equal(typeof(BaseClass), modelType);
    }
 
    [Fact]
    public void Properties_UsesRuntimeType()
    {
        // Arrange
        var provider = new EmptyModelMetadataProvider();
        var modelExplorer = provider.GetModelExplorerForType(typeof(BaseClass), new DerivedClass());
 
        // Act
        var properties = modelExplorer.Properties.ToArray();
 
        // Assert
        Assert.Equal(2, properties.Length);
 
        var baseProperty = Assert.Single(properties, p => p.Metadata.PropertyName == "Base1");
        Assert.Equal(typeof(int), baseProperty.Metadata.ModelType);
        Assert.Equal(typeof(DerivedClass), baseProperty.Metadata.ContainerType);
        Assert.Same(modelExplorer, baseProperty.Container);
 
        var derivedProperty = Assert.Single(properties, p => p.Metadata.PropertyName == "Derived1");
        Assert.Equal(typeof(string), derivedProperty.Metadata.ModelType);
        Assert.Equal(typeof(DerivedClass), derivedProperty.Metadata.ContainerType);
        Assert.Same(modelExplorer, derivedProperty.Container);
    }
 
    [Fact]
    public void Properties_UsesDeclaredType_WhenModelIsNull()
    {
        // Arrange
        var provider = new EmptyModelMetadataProvider();
        var modelExplorer = provider.GetModelExplorerForType(typeof(BaseClass), model: null);
 
        // Act
        var properties = modelExplorer.Properties.ToArray();
 
        // Assert
        Assert.Single(properties);
 
        var baseProperty = Assert.Single(properties, p => p.Metadata.PropertyName == "Base1");
        Assert.Equal(typeof(int), baseProperty.Metadata.ModelType);
        Assert.Equal(typeof(BaseClass), baseProperty.Metadata.ContainerType);
        Assert.Same(modelExplorer, baseProperty.Container);
    }
 
    [Fact]
    public void GetPropertyExplorer_DeferredModelAccess()
    {
        // Arrange
        var model = new DerivedClass()
        {
            Base1 = 5,
        };
 
        var provider = new EmptyModelMetadataProvider();
        var modelExplorer = provider.GetModelExplorerForType(typeof(BaseClass), model);
 
        // Change the model value after creating the explorer
        var propertyExplorer = modelExplorer.GetExplorerForProperty("Base1");
        model.Base1 = 17;
 
        // Act
        var propertyValue = propertyExplorer.Model;
 
        // Assert
        Assert.Equal(17, propertyValue);
    }
 
    [Fact]
    public void GetPropertyExplorer_DeferredModelAccess_ContainerModelIsNull()
    {
        // Arrange
        var provider = new EmptyModelMetadataProvider();
        var modelExplorer = provider.GetModelExplorerForType(typeof(BaseClass), model: null);
 
        var propertyExplorer = modelExplorer.GetExplorerForProperty("Base1");
 
        // Act
        var propertyValue = propertyExplorer.Model;
 
        // Assert
        Assert.Null(propertyValue);
    }
 
    [Fact]
    public void GetPropertyExplorer_ReturnsNull_ForPropertyNotFound()
    {
        // Arrange
        var model = new DerivedClass()
        {
            Base1 = 5,
        };
 
        var provider = new EmptyModelMetadataProvider();
        var modelExplorer = provider.GetModelExplorerForType(typeof(BaseClass), model);
 
        // Act
        var propertyExplorer = modelExplorer.GetExplorerForProperty("BadName");
 
        // Assert
        Assert.Null(propertyExplorer);
    }
 
    private class BaseClass
    {
        public int Base1 { get; set; }
    }
 
    private class DerivedClass : BaseClass
    {
        public string Derived1 { get; set; }
    }
}