CatherineLynwood/CatherineLynwood/TagHelpers/MetaTagHelper.cs

using Microsoft.AspNetCore.Razor.TagHelpers;

namespace CatherineLynwood.TagHelpers
{
    [HtmlTargetElement("MetaTag")]
    public class MetaTagHelper : TagHelper
    {
        #region Public Properties

        public DateTime? ArticleModifiedTime { get; set; }

        public DateTime? ArticlePublishedTime { get; set; }

        public string MetaAuthor { get; set; }

        public string MetaDescription { get; set; }

        public string MetaImage { get; set; }

        public string MetaImageAlt { get; set; }

        public string MetaImagePNG { get; set; }

        public string MetaKeywords { get; set; }

        public string MetaTitle { get; set; }

        public string MetaUrl { get; set; }

        public string OgSiteName { get; set; }

        public string OgType { get; set; } = "article";

        public string TwitterCardType { get; set; } = "summary_large_image";

        public string TwitterCreatorHandle { get; set; }

        public int? TwitterPlayerHeight { get; set; }

        public int? TwitterPlayerWidth { get; set; }

        public string TwitterSiteHandle { get; set; }

        public string TwitterVideoUrl { get; set; }

        #endregion Public Properties

        #region Public Methods

        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            output.TagName = null; // Remove wrapper tag
            var metaTags = new System.Text.StringBuilder();

            // General meta tags
            if (!string.IsNullOrWhiteSpace(MetaDescription))
                metaTags.AppendLine($"<meta name=\"description\" content=\"{MetaDescription}\">");

            if (!string.IsNullOrWhiteSpace(MetaKeywords))
                metaTags.AppendLine($"<meta name=\"keywords\" content=\"{MetaKeywords}\">");

            if (!string.IsNullOrWhiteSpace(MetaAuthor))
                metaTags.AppendLine($"<meta name=\"author\" content=\"{MetaAuthor}\">");

            // Open Graph meta tags
            if (!string.IsNullOrWhiteSpace(MetaTitle))
                metaTags.AppendLine($"<meta property=\"og:title\" content=\"{MetaTitle}\">");

            if (!string.IsNullOrWhiteSpace(MetaDescription))
                metaTags.AppendLine($"<meta property=\"og:description\" content=\"{MetaDescription}\">");

            if (!string.IsNullOrWhiteSpace(OgType))
                metaTags.AppendLine($"<meta property=\"og:type\" content=\"{OgType}\">");

            if (!string.IsNullOrWhiteSpace(MetaUrl))
                metaTags.AppendLine($"<meta property=\"og:url\" content=\"{MetaUrl}\">");

            if (!string.IsNullOrWhiteSpace(MetaImage))
                metaTags.AppendLine($"<meta property=\"og:image\" content=\"{MetaImage}\">");

            if (!string.IsNullOrWhiteSpace(MetaImagePNG))
                metaTags.AppendLine($"<meta property=\"og:image\" content=\"{MetaImagePNG}\">");

            if (!string.IsNullOrWhiteSpace(MetaImageAlt))
                metaTags.AppendLine($"<meta property=\"og:image:alt\" content=\"{MetaImageAlt}\">");

            if (!string.IsNullOrWhiteSpace(OgSiteName))
                metaTags.AppendLine($"<meta property=\"og:site_name\" content=\"{OgSiteName}\">");

            if (ArticlePublishedTime.HasValue)
                metaTags.AppendLine($"<meta property=\"article:published_time\" content=\"{ArticlePublishedTime.Value:yyyy-MM-ddTHH:mm:ssZ}\">");

            if (ArticleModifiedTime.HasValue)
                metaTags.AppendLine($"<meta property=\"article:modified_time\" content=\"{ArticleModifiedTime.Value:yyyy-MM-ddTHH:mm:ssZ}\">");

            // Twitter meta tags
            if (!string.IsNullOrWhiteSpace(TwitterVideoUrl))
            {
                // Ensure absolute URL for player
                var playerUrl = TwitterVideoUrl.StartsWith("http", StringComparison.OrdinalIgnoreCase)
                    ? TwitterVideoUrl
                    : $"https://www.catherinelynwood.com/{TwitterVideoUrl.TrimStart('/')}";

                metaTags.AppendLine("<meta name=\"twitter:card\" content=\"player\">");
                metaTags.AppendLine($"<meta name=\"twitter:player\" content=\"{playerUrl}\">");

                if (TwitterPlayerWidth.HasValue)
                    metaTags.AppendLine($"<meta name=\"twitter:player:width\" content=\"{TwitterPlayerWidth}\">");

                if (TwitterPlayerHeight.HasValue)
                    metaTags.AppendLine($"<meta name=\"twitter:player:height\" content=\"{TwitterPlayerHeight}\">");

                if (!string.IsNullOrWhiteSpace(MetaImage))
                    metaTags.AppendLine($"<meta name=\"twitter:image\" content=\"{MetaImage}\">");

                if (!string.IsNullOrWhiteSpace(MetaImageAlt))
                    metaTags.AppendLine($"<meta name=\"twitter:image:alt\" content=\"{MetaImageAlt}\">");
            }
            else
            {
                metaTags.AppendLine($"<meta name=\"twitter:card\" content=\"{TwitterCardType}\">");

                if (!string.IsNullOrWhiteSpace(MetaTitle))
                    metaTags.AppendLine($"<meta name=\"twitter:title\" content=\"{MetaTitle}\">");

                if (!string.IsNullOrWhiteSpace(MetaDescription))
                    metaTags.AppendLine($"<meta name=\"twitter:description\" content=\"{MetaDescription}\">");

                if (!string.IsNullOrWhiteSpace(MetaImage))
                    metaTags.AppendLine($"<meta name=\"twitter:image\" content=\"{MetaImage}\">");

                if (!string.IsNullOrWhiteSpace(MetaImageAlt))
                    metaTags.AppendLine($"<meta name=\"twitter:image:alt\" content=\"{MetaImageAlt}\">");
            }

            if (!string.IsNullOrWhiteSpace(TwitterSiteHandle))
                metaTags.AppendLine($"<meta name=\"twitter:site\" content=\"{TwitterSiteHandle}\">");

            if (!string.IsNullOrWhiteSpace(TwitterCreatorHandle))
                metaTags.AppendLine($"<meta name=\"twitter:creator\" content=\"{TwitterCreatorHandle}\">");

            output.Content.SetHtmlContent(metaTags.ToString());
        }

        #endregion Public Methods
    }
}