Add IDutyState (#1275)

Dalamud/Plugin/Services/IDutyState.cs

@@ -0,0 +1,36 @@
+using System;
+
+namespace Dalamud.Plugin.Services;
+
+/// <summary>
+/// This class represents the state of the currently occupied duty.
+/// </summary>
+public interface IDutyState
+{
+    /// <summary>
+    /// Event that gets fired when the duty starts.
+    /// Triggers when the "Duty Start" message displays, and on the removal of the ring at duty's spawn.
+    /// Does not trigger when loading into a duty that was in progress, or from loading in after a disconnect.
+    /// </summary>
+    public event EventHandler<ushort> DutyStarted;
+    
+    /// <summary>
+    /// Event that gets fired when everyone in the party dies and the screen fades to black.
+    /// </summary>
+    public event EventHandler<ushort> DutyWiped;
+    
+    /// <summary>
+    /// Event that gets fired when the "Duty Recommence" message displays, and on the removal of the ring at duty's spawn.
+    /// </summary>
+    public event EventHandler<ushort> DutyRecommenced;
+    
+    /// <summary>
+    /// Event that gets fired when the duty is completed successfully.
+    /// </summary>
+    public event EventHandler<ushort> DutyCompleted;
+    
+    /// <summary>
+    /// Gets a value indicating whether the current duty has been started.
+    /// </summary>
+    public bool IsDutyStarted { get; }
+}