Magic the magic happen

Dalamud/Plugin/Internal/LocalDevPlugin.cs

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+using System;
+using System.IO;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+
+using Dalamud.Configuration.Internal;
+using Dalamud.Plugin.Internal.Types;
+
+namespace Dalamud.Plugin.Internal
+{
+    /// <summary>
+    /// This class represents a dev plugin and all facets of its lifecycle.
+    /// The DLL on disk, dependencies, loaded assembly, etc.
+    /// </summary>
+    internal class LocalDevPlugin : LocalPlugin, IDisposable
+    {
+        private static readonly ModuleLog Log = new("PLUGIN");
+
+        // Ref to Dalamud.Configuration.DevPluginSettings
+        private readonly DevPluginSettings devSettings;
+
+        private FileSystemWatcher fileWatcher;
+        private CancellationTokenSource fileWatcherTokenSource;
+        private int reloadCounter;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="LocalDevPlugin"/> class.
+        /// </summary>
+        /// <param name="dalamud">Dalamud instance.</param>
+        /// <param name="dllFile">Path to the DLL file.</param>
+        /// <param name="manifest">The plugin manifest.</param>
+        public LocalDevPlugin(Dalamud dalamud, FileInfo dllFile, LocalPluginManifest manifest)
+            : base(dalamud, dllFile, manifest)
+        {
+            // base is called first, ensuring that this is a valid plugin assembly
+            var devSettings = dalamud.Configuration.DevPluginSettings.FirstOrDefault(cfg => cfg.DllFile == dllFile.FullName);
+
+            if (devSettings == default)
+            {
+                devSettings = new DevPluginSettings(dllFile.FullName);
+                dalamud.Configuration.DevPluginSettings.Add(devSettings);
+                dalamud.Configuration.Save();
+            }
+
+            this.devSettings = devSettings;
+
+            if (this.AutomaticReload)
+            {
+                this.EnableReloading();
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets a value indicating whether this dev plugin should start on boot.
+        /// </summary>
+        public bool StartOnBoot
+        {
+            get => this.devSettings.StartOnBoot;
+            set => this.devSettings.StartOnBoot = value;
+        }
+
+        /// <summary>
+        /// Gets or sets a value indicating whether this dev plugin should reload on change.
+        /// </summary>
+        public bool AutomaticReload
+        {
+            get => this.devSettings.AutomaticReloading;
+            set
+            {
+                this.devSettings.AutomaticReloading = value;
+
+                if (this.devSettings.AutomaticReloading)
+                {
+                    this.EnableReloading();
+                }
+                else
+                {
+                    this.DisableReloading();
+                }
+            }
+        }
+
+        /// <inheritdoc/>
+        public new void Dispose()
+        {
+            if (this.fileWatcher != null)
+            {
+                this.fileWatcher.Changed -= this.OnFileChanged;
+                this.fileWatcherTokenSource.Cancel();
+                this.fileWatcher.Dispose();
+            }
+
+            base.Dispose();
+        }
+
+        /// <summary>
+        /// Configure this plugin for automatic reloading and enable it.
+        /// </summary>
+        public void EnableReloading()
+        {
+            if (this.fileWatcher == null)
+            {
+                this.fileWatcherTokenSource = new();
+                this.fileWatcher = new FileSystemWatcher(this.DllFile.DirectoryName);
+                this.fileWatcher.Changed += this.OnFileChanged;
+                this.fileWatcher.Filter = this.DllFile.Name;
+                this.fileWatcher.NotifyFilter = NotifyFilters.LastWrite;
+                this.fileWatcher.EnableRaisingEvents = true;
+            }
+        }
+
+        /// <summary>
+        /// Disable automatic reloading for this plugin.
+        /// </summary>
+        public void DisableReloading()
+        {
+            if (this.fileWatcher != null)
+            {
+                this.fileWatcherTokenSource.Cancel();
+                this.fileWatcher.Changed -= this.OnFileChanged;
+                this.fileWatcher.Dispose();
+                this.fileWatcher = null;
+            }
+        }
+
+        private void OnFileChanged(object sender, FileSystemEventArgs args)
+        {
+            var current = Interlocked.Increment(ref this.reloadCounter);
+
+            Task.Delay(500).ContinueWith(
+                task =>
+                {
+                    if (this.fileWatcherTokenSource.IsCancellationRequested)
+                    {
+                        Log.Debug($"Skipping reload of {this.Name}, file watcher was cancelled.");
+                        return;
+                    }
+
+                    if (current != this.reloadCounter)
+                    {
+                        Log.Debug($"Skipping reload of {this.Name}, file has changed again.");
+                        return;
+                    }
+
+                    if (this.State != PluginState.Loaded)
+                    {
+                        Log.Debug($"Skipping reload of {this.Name}, state ({this.State}) is not {PluginState.Loaded}.");
+                        return;
+                    }
+
+                    this.Reload();
+                },
+                this.fileWatcherTokenSource.Token);
+        }
+    }
+}