ViewCountService.cs

using Microsoft.Extensions.Logging;
using OrchardCore.ContentManagement;
using OrchardCore.Modules;
using OrchardCoreContrib.Infrastructure;
using OrchardCoreContrib.ViewCount.Handlers;
using OrchardCoreContrib.ViewCount.Models;

namespace OrchardCoreContrib.ViewCount.Services;

/// <summary>
/// Provides functionality for tracking and updating view counts on content items.
/// </summary>
/// <remarks>The <see cref="ViewCountService"/> enables retrieval and incrementing of view counts for content
/// items. It coordinates with registered <see cref="IViewCountContentHandler"/> instances to allow custom logic to be
/// executed before and after a view is recorded. This service is typically used to monitor content popularity or
/// engagement.
/// </remarks>
public class ViewCountService(
    IContentManager contentManager,
    IEnumerable<IViewCountContentHandler> handlers,
    ILogger<ViewCountService> logger) : IViewCountService
{
    private static readonly SemaphoreSlim _semaphore = new(initialCount: 1, maxCount: 1);

    /// <inheritdoc/>
    public int GetViewsCount(ContentItem contentItem)
    {
        Guard.ArgumentNotNull(contentItem, nameof(contentItem));

        var viewCountPart = contentItem.As<ViewCountPart>();
        
        return viewCountPart?.Count ?? 0;
    }

    /// <inheritdoc/>
    public async Task ViewAsync(ContentItem contentItem)
    {
        Guard.ArgumentNotNull(contentItem, nameof(contentItem));

        await _semaphore.WaitAsync();

        var viewCountPart = contentItem.As<ViewCountPart>()
            ?? throw new InvalidOperationException($"The content item doesn't have a `{nameof(ViewCountPart)}`.");
        var count = viewCountPart.Count;
        var context = new ViewCountContentContext(contentItem, count);

        await handlers.InvokeAsync((handler, context) => handler.ViewingAsync(context), context, logger);

        viewCountPart.Count = ++count;

        contentItem.Content.ViewCountPart.Count = count;

        await contentManager.UpdateAsync(contentItem);

        context = new ViewCountContentContext(contentItem, count);

        await handlers.InvokeAsync((handler, context) => handler.ViewedAsync(context), context, logger);

        _semaphore.Release();
    }
}