Add files part of new refactor

DuplicatePathChecker.cs

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+using System;
+
+namespace PathCleaner
+{
+    class DuplicatePathChecker : IPathChecker
+    {
+        public string Reason
+        {
+            get { return "Duplicate"; }
+        }
+
+        public bool Identify(string folder, string previousFolder)
+        {
+            return previousFolder != null 
+                && String.Compare(folder, previousFolder, StringComparison.InvariantCultureIgnoreCase) == 0;
+        }
+    }
+}

EmptyPathChecker.cs

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+using System.IO;
+using System.Linq;
+
+namespace PathCleaner
+{
+    class EmptyPathChecker : IPathChecker
+    {
+        public string Reason
+        {
+            get { return "Empty"; }
+        }
+
+        public bool Identify(string folder, string previousFolder)
+        {
+            return !Directory.EnumerateFiles(folder).Any();
+        }
+    }
+
+}

IPathChecker.cs

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+namespace PathCleaner
+{
+    interface IPathChecker
+    {
+        string Reason { get; }
+        bool Identify(string folder, string previousFolder);
+    }
+
+}

MissingPathChecker.cs

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+using System.IO;
+
+namespace PathCleaner
+{
+    class MissingPathChecker : IPathChecker
+    {
+        public string Reason
+        {
+            get { return "Missing"; }
+        }
+
+        public bool Identify(string folder, string previousFolder)
+        {
+            return !Directory.Exists(folder);
+        }
+    }
+
+}

NoExecutablesPathChecker.cs

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+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+
+namespace PathCleaner
+{
+    class NoExecutablesPathChecker : IPathChecker
+    {
+        private static HashSet<string> executableExtensions = new HashSet<string>() 
+        { 
+            ".exe", ".com", ".bat", ".cmd", ".ps1", ".dll"
+        };
+
+        public string Reason
+        {
+            get { return "No executables"; }
+        }
+
+        public bool Identify(string folder, string previousFolder)
+        {
+            return !Directory.EnumerateFiles(folder)
+                .Where(s => executableExtensions.Contains(Path.GetExtension(s)))
+                .Any();
+        }
+    }
+
+}

ProblemIdentifier.cs

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+using System.Collections.Generic;
+using System.Linq;
+
+namespace PathCleaner
+{
+    class ProblemIdentifier
+    {
+        public IEnumerable<IPathChecker> Checkers { get; private set; }
+        public PathString PathString { get; private set; }
+
+        public ProblemIdentifier(PathString pathString, IEnumerable<IPathChecker> checkers)
+        {
+            this.PathString = pathString;
+            this.Checkers = checkers;
+        }
+
+        public IEnumerable<PathProblem> Problems
+        {
+            get
+            {
+                var sortedFolders = new List<string>(PathString.Folders.OrderBy(s => s));
+                string previousFolder = null;
+                foreach(string folder in sortedFolders)
+                {
+                    var problem = Checkers.Where(c => c.Identify(folder, previousFolder))
+                        .Select(c => new PathProblem
+                        {
+                            Path = folder,
+                            Reason = c.Reason,
+                        })
+                        .FirstOrDefault();
+                    if (problem != null)
+                    {
+                        yield return problem;
+                    }
+                    previousFolder = folder;
+                }
+            }
+        }
+
+    }
+}