Rework file persistence

src/SharpIDE.Application/Features/FilePersistence/IdeFileManager.cs

@@ -0,0 +1,71 @@
+using System.Collections.Concurrent;
+using SharpIDE.Application.Features.Analysis;
+using SharpIDE.Application.Features.SolutionDiscovery;
+
+namespace SharpIDE.Application.Features.FilePersistence;
+#pragma warning disable VSTHRD011
+
+/// Holds the in memory copies of files, and manages saving/loading them to/from disk.
+public class IdeFileManager
+{
+	private ConcurrentDictionary<SharpIdeFile, Lazy<Task<string>>> _openFiles = new();
+
+	/// Implicitly 'opens' a file if not already open, and returns the text.
+	public async Task<string> GetFileTextAsync(SharpIdeFile file)
+	{
+		var textTaskLazy = _openFiles.GetOrAdd(file, f =>
+		{
+			var lazy = new Lazy<Task<string>>(Task<string> () => File.ReadAllTextAsync(f.Path));
+			return lazy;
+		});
+		var textTask = textTaskLazy.Value;
+		var text = await textTask;
+		return text;
+	}
+
+	// Calling this assumes that the file is already open - may need to be revisited for code fixes and refactorings. I think all files involved in a multi-file fix/refactor shall just be saved to disk immediately.
+	public void UpdateFileTextInMemory(SharpIdeFile file, string newText)
+	{
+		if (!_openFiles.ContainsKey(file)) throw new InvalidOperationException("File is not open in memory.");
+
+		var newLazyTask = new Lazy<Task<string>>(() => Task.FromResult(newText));
+		_openFiles[file] = newLazyTask;
+		// Potentially should be event based?
+		if (file.IsRoslynWorkspaceFile)
+		{
+			RoslynAnalysis.UpdateDocument(file, newText);
+		}
+	}
+
+	public async Task SaveFileAsync(SharpIdeFile file)
+	{
+		if (!_openFiles.ContainsKey(file)) throw new InvalidOperationException("File is not open in memory.");
+
+		var text = await GetFileTextAsync(file);
+		await File.WriteAllTextAsync(file.Path, text);
+		file.IsDirty.Value = false;
+	}
+
+	public async Task UpdateInMemoryIfOpenAndSaveAsync(SharpIdeFile file, string newText)
+	{
+		if (_openFiles.ContainsKey(file))
+		{
+			UpdateFileTextInMemory(file, newText);
+			await SaveFileAsync(file);
+		}
+		else
+		{
+			await File.WriteAllTextAsync(file.Path, newText);
+		}
+	}
+
+	public async Task SaveAllOpenFilesAsync()
+	{
+		foreach (var file in _openFiles.Keys)
+		{
+			await SaveFileAsync(file);
+		}
+	}
+}
+
+#pragma warning restore VSTHRD011