(GH-70) Provide Chocolatey Language Server support

src/Chocolatey.Language.Server/Utility/Utility.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Net;
+
+namespace Chocolatey.Language.Server.Utility
+{
+
+    public class Utility
+    {
+
+        /// <summary>
+        ///   Tries to validate an URL
+        /// </summary>
+        /// <param name="url">Uri object</param>
+        public static bool url_is_valid(Uri url)
+        {
+            var request = (HttpWebRequest)WebRequest.Create(url);
+
+            request.Timeout = 15000;
+            //This would allow 301 and 302 to be valid as well
+            request.AllowAutoRedirect = true;
+            try
+            {
+                using (var response = (HttpWebResponse)request.GetResponse())
+                {
+                    return response.StatusCode == HttpStatusCode.OK;
+                }
+            }
+            catch (WebException)
+            {
+                return false;
+            }
+        }        
+    }
+}

src/Chocolatey.Language.Server/Validations/UrlValidValidation.cs

@@ -0,0 +1,54 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Chocolatey.Language.Server.Utility;
+using Microsoft.Language.Xml;
+using OmniSharp.Extensions.LanguageServer.Protocol.Models;
+using DiagnosticSeverity = OmniSharp.Extensions.LanguageServer.Protocol.Models.DiagnosticSeverity;
+
+namespace Chocolatey.Language.Server.Validations
+{
+    /// <summary>
+    ///   Handler to validate the length of description in the package metadata.
+    /// </summary>
+    /// TODO: Add <seealso> elements once PR is merged
+    public class UrlValidValidation : INuSpecRule
+    {
+
+        private static readonly IReadOnlyCollection<string> UrlElements = new []
+        {
+            "bugTrackerUrl",
+            "docsUrl",
+            "iconUrl",
+            "licenseUrl",
+            "mailingListUrl",
+            "packageSourceUrl",
+            "projectSourceUrl",
+            "projectUrl",
+            "wikiUrl",
+        };
+
+        public IEnumerable<Diagnostic> Validate(XmlDocumentSyntax syntaxTree, TextPositions textPositions)
+        {
+            foreach (var elementName in UrlElements) {
+                var element = syntaxTree.DescendantNodes().OfType<XmlElementSyntax>().FirstOrDefault(x => string.Equals(x.Name, elementName, StringComparison.OrdinalIgnoreCase));
+                if (element != null) {
+                    var uriString = element.GetContentValue().Trim();
+                    Uri uri;
+                    if(
+                        !Uri.IsWellFormedUriString(uriString, UriKind.Absolute) ||
+                        !Uri.TryCreate(uriString, UriKind.Absolute, out uri) || 
+                        !Utility.Utility.url_is_valid(uri)
+                    ) {
+                        var range = textPositions.GetRange(element.StartTag.End, element.EndTag.Start);
+                        yield return new Diagnostic {
+                            Message = "Url in " + elementName + " is invalid. See https://github.com/chocolatey/package-validator/wiki/InvalidUrlProvided",
+                            Severity = DiagnosticSeverity.Error,
+                            Range = range
+                        };
+                    }
+                }
+            }
+        }
+    }
+}