Improve code structure

- Add separate API project
- Add notification system

HyperbolicDownloaderApi/FileProcessing/FilesManager.cs

@@ -0,0 +1,98 @@
+using HyperbolicDownloaderApi.Managment;
+
+using System.Text.Json;
+
+namespace HyperbolicDownloaderApi.FileProcessing;
+
+public class FilesManager
+{
+    private readonly List<PrivateHyperFileInfo> files = new List<PrivateHyperFileInfo>();
+
+    public bool TryAdd(string filePath, out PrivateHyperFileInfo? fileInfo, out string? errorMessage)
+    {
+        if (string.IsNullOrWhiteSpace(filePath))
+        {
+            fileInfo = null;
+            errorMessage = "Path is empty!";
+            return false;
+        }
+
+        string fullPath = Path.GetFullPath(filePath);
+
+        if (!File.Exists(fullPath))
+        {
+            fileInfo = null;
+            errorMessage = "Invalid file path!";
+            return false;
+        }
+
+        string hash = FileValidator.CalculateHash(filePath);
+
+        if (Contains(hash))
+        {
+            fileInfo = null;
+            errorMessage = "File already tracked!";
+            return false;
+        }
+
+        fileInfo = new PrivateHyperFileInfo(hash, fullPath);
+
+        files.Add(fileInfo);
+
+        SaveFiles();
+
+        errorMessage = null;
+        return true;
+    }
+
+    public void AddRange(IEnumerable<PrivateHyperFileInfo> fileInfos)
+    {
+        foreach (PrivateHyperFileInfo fileInfo in fileInfos)
+        {
+            if (File.Exists(fileInfo.FilePath) && !Contains(fileInfo.Hash))
+            {
+                files.Add(fileInfo);
+            }
+        }
+
+        SaveFiles();
+    }
+
+    public bool TryGet(string hash, out PrivateHyperFileInfo? fileInfo)
+    {
+        if (Contains(hash))
+        {
+            fileInfo = files.First(x => x.Hash == hash);
+            return true;
+        }
+        else
+        {
+            fileInfo = null;
+            return false;
+        }
+    }
+
+    public bool TryRemove(string hash)
+    {
+        int count = files.RemoveAll(f => f.Hash == hash);
+
+        SaveFiles();
+
+        return count > 0;
+    }
+
+    public bool Contains(string? hash)
+    {
+        return files.Any(f => f.Hash == hash);
+    }
+
+    public List<PrivateHyperFileInfo> ToList()
+    {
+        return files.ToList();
+    }
+
+    private void SaveFiles()
+    {
+        File.WriteAllText(ApiConfiguration.FilesInfoPath, JsonSerializer.Serialize(files));
+    }
+}