bookmark-manager-r4/Classes/WebParser.cs

using bzit.bomg.Models;
using HtmlAgilityPack;
using RyzStudio.Net;
using System;
using System.Net;

namespace BookmarkManager
{
    public class WebParser
    {
        protected HttpWeb webClient = null;


        public BookmarkResult RetrieveDetails(string url)
        {
            string sourceCode = retrieveSourceCode(url);
            if (string.IsNullOrWhiteSpace(sourceCode))
            {
                return null;
            }

            BookmarkResult rs = new BookmarkResult();
            rs.Item = new BookmarkItem();

            HtmlDocument document = new HtmlDocument();
            document.LoadHtml(sourceCode);

            rs.Item.SiteName = parseSiteTitle(document);
            rs.Item.SiteAddress = url;
            rs.Item.SiteDescription = parseSiteDescription(document);
            rs.IconURL = parseSiteIcon(document);

            // resolve relative URL
            if (!string.IsNullOrWhiteSpace(rs.IconURL))
            {
                Uri iconAddressURI;
                bool rv = Uri.TryCreate(new Uri(url), rs.IconURL, out iconAddressURI);
                if (rv)
                {
                    rs.IconURL = iconAddressURI.ToString();
                }
            }

            return rs;
        }


        protected string retrieveSourceCode(string url)
        {
            if (webClient == null) webClient = new HttpWeb();

            string sourceCode;

            try
            {
                int statusCode = webClient.GetResponse(out sourceCode, url);
                if ((statusCode == 200) || (statusCode == 301) || (statusCode == 302))
                {
                    return sourceCode;
                }
            }
            catch (Exception)
            {
                return null;
            }

            return null;
        }

        protected string parseSiteDescription(HtmlDocument doc)
        {
            string rs = null;

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//meta[@name='description']", "content", string.Empty);
            }

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//meta[@property='og:description']", "content", string.Empty);
            }

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//meta[@name='twitter:description']", "content", string.Empty);
            }

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//meta[@property='og:description']", "content", string.Empty);
            }

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//meta[@itemprop='description']", "content", string.Empty);
            }

            return rs;
        }

        protected string parseSiteIcon(HtmlDocument doc)
        {
            string rs = null;

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//link[translate(@rel, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz') = 'shortcut icon']", "href", string.Empty);
            }

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//link[translate(@rel, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz') = 'icon']", "href", string.Empty);
            }

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//link[translate(@rel, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz') = 'apple-touch-icon']", "href", string.Empty);
            }

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//link[translate(@rel, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz') = 'apple-touch-icon-precomposed']", "href", string.Empty);
            }

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//meta[translate(@property, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz') = 'og:image']", "content", string.Empty);
            }

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//meta[translate(@name, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz') = 'twitter:image']", "content", string.Empty);
            }

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//meta[translate(@property, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz') = 'og:image']", "content", string.Empty);
            }

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//meta[translate(@itemprop, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz') = 'image']", "content", string.Empty);
            }

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = "/favicon.ico";
            }

            return rs;
        }

        protected string parseSiteTitle(HtmlDocument doc)
        {
            string rs = null;

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue(doc, "//title", string.Empty);
            }

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//meta[@property='og:title']", "content", string.Empty);
            }

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//meta[@name='twitter:title']", "content", string.Empty);
            }

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//meta[@property='og:site_name']", "content", string.Empty);
            }

            if (string.IsNullOrWhiteSpace(rs))
            {
                rs = parseTagValue_Attr(doc, "//meta[@itemprop='name']", "content", string.Empty);
            }

            return rs?.Trim() ?? string.Empty;
        }

        protected string parseTagValue(HtmlDocument doc, string xpath, string defaultValue = "")
        {
            HtmlNodeCollection hnc = doc.DocumentNode.SelectNodes(xpath);
            if (hnc == null)
            {
                return defaultValue;
            }

            if (hnc.Count <= 0)
            {
                return defaultValue;
            }

            foreach (HtmlNode hn in hnc)
            {
                if (string.IsNullOrWhiteSpace(hn.InnerHtml))
                {
                    continue;
                }

                string rs = WebUtility.HtmlDecode(hn.InnerHtml)?.Replace("\r", "")?.Replace("\n", " ")?.Trim();
                if (string.IsNullOrWhiteSpace(rs))
                {
                    continue;
                }

                return rs;
            }

            return defaultValue;
        }

        protected string parseTagValue_Attr(HtmlDocument doc, string xpath, string attr, string defaultValue = "")
        {
            HtmlNodeCollection hnc = doc.DocumentNode.SelectNodes(xpath);
            if (hnc == null)
            {
                return defaultValue;
            }

            if (hnc.Count <= 0)
            {
                return defaultValue;
            }

            foreach (HtmlNode hn in hnc)
            {
                if (hn.Attributes[attr] == null)
                {
                    continue;
                }

                if (string.IsNullOrWhiteSpace(hn.Attributes[attr].Value))
                {
                    continue;
                }

                return System.Web.HttpUtility.HtmlDecode(hn.Attributes[attr].Value?.Trim());
            }

            return defaultValue;
        }

    }
}