// 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.Components;
using Microsoft.AspNetCore.Components.Endpoints;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using Microsoft.AspNetCore.Razor.TagHelpers;
using Microsoft.Extensions.DependencyInjection;
 
namespace Microsoft.AspNetCore.Mvc.TagHelpers;
 
/// <summary>
/// A <see cref="TagHelper"/> that saves the state of Razor components rendered on the page up to that point.
/// </summary>
[HtmlTargetElement(TagHelperName, TagStructure = TagStructure.WithoutEndTag)]
public class PersistComponentStateTagHelper : TagHelper
{
    private const string TagHelperName = "persist-component-state";
    private const string PersistenceModeName = "persist-mode";
    private PersistenceMode? _persistenceMode;
 
    /// <summary>
    /// Gets or sets the <see cref="Rendering.ViewContext"/> for the current request.
    /// </summary>
    [HtmlAttributeNotBound]
    [ViewContext]
    public ViewContext ViewContext { get; set; }
 
    /// <summary>
    /// Gets or sets the <see cref="PersistenceMode"/> for the state to persist.
    /// </summary>
    [HtmlAttributeName(PersistenceModeName)]
    public PersistenceMode? PersistenceMode
    {
        get => _persistenceMode;
        set => _persistenceMode = value;
    }
 
    /// <inheritdoc />
    public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
    {
        ArgumentNullException.ThrowIfNull(context);
        ArgumentNullException.ThrowIfNull(output);
 
        var componentPrerenderer = ViewContext.HttpContext.RequestServices.GetRequiredService<IComponentPrerenderer>();
        var serializationMode = PersistenceMode switch
        {
            null => PersistedStateSerializationMode.Infer,
            TagHelpers.PersistenceMode.Server => PersistedStateSerializationMode.Server,
            TagHelpers.PersistenceMode.WebAssembly => PersistedStateSerializationMode.WebAssembly,
            _ => throw new InvalidOperationException("Invalid persistence mode."),
        };
 
        var content = await componentPrerenderer.PrerenderPersistedStateAsync(ViewContext.HttpContext, serializationMode);
        output.TagName = null;
        output.Content.SetHtmlContent(content);
    }
}