Initial check-in

FileManager/UNTESTED/FilePathCache.cs

@@ -0,0 +1,94 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using Newtonsoft.Json;
+
+namespace FileManager
+{
+    public static class FilePathCache
+    {
+        internal class CacheEntry
+        {
+            public string Id { get; set; }
+            public FileType FileType { get; set; }
+            public string Path { get; set; }
+        }
+
+        static List<CacheEntry> inMemoryCache = new List<CacheEntry>();
+
+        public static string JsonFile => Path.Combine(Configuration.Instance.LibationFiles, "FilePaths.json");
+
+        static FilePathCache()
+        {
+            // load json into memory. if file doesn't exist, nothing to do. save() will create if needed
+            if (FileUtility.FileExists(JsonFile))
+                inMemoryCache = JsonConvert.DeserializeObject<List<CacheEntry>>(File.ReadAllText(JsonFile));
+        }
+
+        public static bool Exists(string id, FileType type) => GetPath(id, type) != null;
+
+        public static string GetPath(string id, FileType type)
+        {
+            var entry = inMemoryCache.SingleOrDefault(i => i.Id == id && i.FileType == type);
+
+            if (entry == null)
+                return null;
+
+            if (!FileUtility.FileExists(entry.Path))
+            {
+                remove(entry);
+                return null;
+            }
+
+            return entry.Path;
+        }
+
+        private static object locker { get; } = new object();
+
+        private static void remove(CacheEntry entry)
+        {
+            lock (locker)
+            {
+                inMemoryCache.Remove(entry);
+                save();
+            }
+        }
+
+        public static void Upsert(string id, FileType type, string path)
+        {
+            if (!FileUtility.FileExists(path))
+                throw new FileNotFoundException("Cannot add path to cache. File not found");
+
+            lock (locker)
+            {
+                var entry = inMemoryCache.SingleOrDefault(i => i.Id == id && i.FileType == type);
+                if (entry != null)
+                    entry.Path = path;
+                else
+                {
+                    entry = new CacheEntry { Id = id, FileType = type, Path = path };
+                    inMemoryCache.Add(entry);
+                }
+                save();
+            }
+        }
+
+        // ONLY call this within lock()
+        private static void save()
+        {
+            // create json if not exists
+            void resave() => File.WriteAllText(JsonFile, JsonConvert.SerializeObject(inMemoryCache, Formatting.Indented));
+            try { resave(); }
+            catch (IOException)
+            {
+                try { resave(); }
+                catch (IOException)
+                {
+                    Console.WriteLine("...that's not good");
+                    throw;
+                }
+            }
+        }
+    }
+}