Add IPartyList (#1271)

Dalamud/Plugin/Services/IPartyList.cs

@@ -0,0 +1,81 @@
+using System.Collections.Generic;
+
+using Dalamud.Game.ClientState.Party;
+
+namespace Dalamud.Plugin.Services;
+
+/// <summary>
+/// This collection represents the actors present in your party or alliance.
+/// </summary>
+public interface IPartyList : IReadOnlyCollection<PartyMember>
+{
+    /// <summary>
+    /// Gets the amount of party members the local player has.
+    /// </summary>
+    public int Length { get; }
+    
+    /// <summary>
+    /// Gets the index of the party leader.
+    /// </summary>
+    public uint PartyLeaderIndex { get; }
+    
+    /// <summary>
+    /// Gets a value indicating whether this group is an alliance.
+    /// </summary>
+    public bool IsAlliance { get; }
+    
+    /// <summary>
+    /// Gets the address of the Group Manager.
+    /// </summary>
+    public nint GroupManagerAddress { get; }
+    
+    /// <summary>
+    /// Gets the address of the party list within the group manager.
+    /// </summary>
+    public nint GroupListAddress { get; }
+    
+    /// <summary>
+    /// Gets the address of the alliance member list within the group manager.
+    /// </summary>
+    public nint AllianceListAddress { get; }
+    
+    /// <summary>
+    /// Gets the ID of the party.
+    /// </summary>
+    public long PartyId { get; }
+    
+    /// <summary>
+    /// Get a party member at the specified spawn index.
+    /// </summary>
+    /// <param name="index">Spawn index.</param>
+    /// <returns>A <see cref="PartyMember"/> at the specified spawn index.</returns>
+    public PartyMember? this[int index] { get; }
+
+    /// <summary>
+    /// Gets the address of the party member at the specified index of the party list.
+    /// </summary>
+    /// <param name="index">The index of the party member.</param>
+    /// <returns>The memory address of the party member.</returns>
+    public nint GetPartyMemberAddress(int index);
+
+    /// <summary>
+    /// Create a reference to an FFXIV party member.
+    /// </summary>
+    /// <param name="address">The address of the party member in memory.</param>
+    /// <returns>The party member object containing the requested data.</returns>
+    public PartyMember? CreatePartyMemberReference(nint address);
+    
+    /// <summary>
+    /// Gets the address of the alliance member at the specified index of the alliance list.
+    /// </summary>
+    /// <param name="index">The index of the alliance member.</param>
+    /// <returns>The memory address of the alliance member.</returns>
+    public nint GetAllianceMemberAddress(int index);
+
+    /// <summary>
+    /// Create a reference to an FFXIV alliance member.
+    /// </summary>
+    /// <param name="address">The address of the alliance member in memory.</param>
+    /// <returns>The party member object containing the requested data.</returns>
+    public PartyMember? CreateAllianceMemberReference(nint address);
+}