implemented everything

Dalamud/Game/Text/SeStringHandling/Payload.cs

@@ -168,6 +168,12 @@ public abstract partial class Payload
                             payload = new DalamudLinkPayload();
                             break;
 
+                        case EmbeddedInfoType.PartyFinderNotificationLink:
+                        // this is handled by PartyFinderPayload, so let this fall through
+                        case EmbeddedInfoType.PartyFinderLink:
+                            payload = new PartyFinderPayload();
+                            break;
+
                         case EmbeddedInfoType.LinkTerminator:
                         // this has no custom handling and so needs to fallthrough to ensure it is captured
                         default:
@@ -267,11 +273,21 @@ public abstract partial class Payload
         /// </summary>
         QuestLink = 0x05,
 
+        /// <summary>
+        /// The link to the party finder search conditions.
+        /// </summary>
+        PartyFinderNotificationLink = 0x08,
+
         /// <summary>
         /// A status effect.
         /// </summary>
         Status = 0x09,
 
+        /// <summary>
+        /// The link to a party finder listing.
+        /// </summary>
+        PartyFinderLink = 0x0A,
+
         /// <summary>
         /// A custom Dalamud link.
         /// </summary>

Dalamud/Game/Text/SeStringHandling/PayloadType.cs

@@ -79,4 +79,9 @@ public enum PayloadType
     /// An SeString payload representing a doublewide SE hypen.
     /// </summary>
     SeHyphen,
+
+    /// <summary>
+    /// An SeString payload representing a party finder link.
+    /// </summary>
+    PartyFinder,
 }

Dalamud/Game/Text/SeStringHandling/Payloads/PartyFinderPayload.cs

@@ -0,0 +1,146 @@
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.IO;
+
+using Lumina.Extensions;
+using Newtonsoft.Json;
+
+namespace Dalamud.Game.Text.SeStringHandling.Payloads
+{
+    /// <summary>
+    /// An SeString Payload representing an interactable party finder link.
+    /// </summary>
+    public class PartyFinderPayload : Payload
+    {
+        /// <summary>
+        /// Delimiting byte for party finder payload flags.
+        /// </summary>
+        // at least that's what i think it is... in any case, this works.
+        [SuppressMessage("StyleCop.CSharp.NamingRules", "SA1310:Field names should not contain underscore", Justification = "This is preferred.")]
+        protected const byte FLAG_DELIMITER = 0x01;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="PartyFinderPayload"/> class.
+        /// Creates a payload representing an interactable party finder link for the specified party finder listing.
+        /// </summary>
+        /// <param name="listingId">The listing ID of the party finder listing.</param>
+        /// <param name="type">The party finder link type that should be encoded with this link.</param>
+        public PartyFinderPayload(uint listingId, PartyFinderLinkType type)
+        {
+            this.ListingId = listingId;
+            this.LinkType = type;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="PartyFinderPayload"/> class.
+        /// Creates a payload representing an interactable party finder notification link.
+        /// </summary>
+        public PartyFinderPayload()
+        {
+        }
+
+        /// <summary>
+        /// Represents the flags in a party finder link.
+        /// </summary>
+        public enum PartyFinderLinkType
+        {
+            /// <summary>
+            /// Indicates that the party finder link is for a party that is limited to the host's home world.
+            /// </summary>
+            LimitedToHomeWorld = 0xF3,
+
+            /// <summary>
+            /// Indicates that the party finder link is for the "Display advanced search results in log." option.
+            /// </summary>
+            PartyFinderNotification = 0xFF,
+
+            /// <summary>
+            /// Indicates that the party finder link type was unspecified. Only for internal use. Not used by SE and omitted from encoding.
+            /// </summary>
+            NotSpecified = 0x00,
+        }
+
+        /// <summary>
+        /// Gets the party finder listing ID.
+        /// </summary>
+        [JsonProperty]
+        public uint ListingId { get; private set; }
+
+        /// <summary>
+        /// Gets the link type.
+        /// </summary>
+        [JsonProperty]
+        public PartyFinderLinkType LinkType { get; private set; } = PartyFinderLinkType.PartyFinderNotification;
+
+        /// <inheritdoc/>
+        public override PayloadType Type => PayloadType.PartyFinder;
+
+        /// <inheritdoc/>
+        protected override void DecodeImpl(BinaryReader reader, long endOfStream)
+        {
+            // 0x01 here indicates a party finder notification, which needs to be handled uniquely
+            if (reader.PeekByte() == 0x01)
+            {
+                this.LinkType = PartyFinderLinkType.PartyFinderNotification;
+                return;
+            }
+
+            this.ListingId = GetInteger(reader);
+
+            // throw away always 0x01
+            reader.ReadByte();
+
+            // if the next byte is 0xF3 then this listing is limited to home world
+            byte nextByte = reader.ReadByte();
+            switch (nextByte)
+            {
+                case (byte)PartyFinderLinkType.LimitedToHomeWorld:
+                    this.LinkType = PartyFinderLinkType.LimitedToHomeWorld;
+                    break;
+
+                // if this byte is just the flag delimiter, then nothing was specified.
+                case FLAG_DELIMITER:
+                    this.LinkType = PartyFinderLinkType.NotSpecified;
+                    break;
+
+                default:
+                    Serilog.Log.Information($"Unrecognized PartyFinderLinkType code {nextByte} (Hex - {nextByte:X2})");
+                    break;
+            }
+        }
+
+        /// <inheritdoc/>
+        protected override byte[] EncodeImpl()
+        {
+            // if the link type is notification, just use premade payload data since it's always the same.
+            // i have no idea why it is formatted like this, but it is how it is.
+            // note it is identical to the link terminator payload except the embedded info type is 0x08
+            if (this.LinkType == PartyFinderLinkType.PartyFinderNotification) return new byte[] { 0x02, 0x27, 0x07, 0x08, 0x01, 0x01, 0x01, 0xFF, 0x01, 0x03, };
+
+            // back to our regularly scheduled programming...
+            var listingIDBytes = MakeInteger(this.ListingId);
+            bool isFlagSpecified = this.LinkType != PartyFinderLinkType.NotSpecified;
+
+            var chunkLen = listingIDBytes.Length + 4;
+            // 1 more byte for the type flag if it is specified
+            if (isFlagSpecified) chunkLen++;
+
+            var bytes = new List<byte>()
+            {
+                START_BYTE, (byte)SeStringChunkType.Interactable, (byte)chunkLen, (byte)EmbeddedInfoType.PartyFinderLink,
+            };
+
+            bytes.AddRange(listingIDBytes);
+
+            bytes.Add(FLAG_DELIMITER);
+
+            if (isFlagSpecified) bytes.Add((byte)this.LinkType);
+
+            bytes.Add(FLAG_DELIMITER);
+
+            bytes.Add(END_BYTE);
+
+            return bytes.ToArray();
+        }
+    }
+}

Dalamud/Game/Text/SeStringHandling/SeString.cs

@@ -314,6 +314,51 @@ public class SeString
         return null;
     }
 
+    /// <summary>
+    /// Creates an SeString representing an entire payload chain that can be used to link party finder listings in the chat log.
+    /// </summary>
+    /// <param name="listingId">The listing ID of the party finder entry.</param>
+    /// <param name="recruiterName">The name of the recruiter.</param>
+    /// <param name="isCrossWorld">Whether the listing is limited to the current world or not.</param>
+    /// <returns>An SeString containing all the payloads necessary to display a party finder link in the chat log.</returns>
+    public static SeString CreatePartyFinderLink(uint listingId, string recruiterName, bool isCrossWorld = false)
+    {
+        var payloads = new List<Payload>()
+        {
+            new PartyFinderPayload(listingId, isCrossWorld ? PartyFinderPayload.PartyFinderLinkType.NotSpecified : PartyFinderPayload.PartyFinderLinkType.LimitedToHomeWorld),
+            // ->
+            new TextPayload($"Looking for Party ({recruiterName})"),
+        };
+
+        payloads.InsertRange(1, TextArrowPayloads);
+
+        if (isCrossWorld)
+            payloads.Add(new IconPayload(BitmapFontIcon.CrossWorld));
+
+        payloads.Add(RawPayload.LinkTerminator);
+
+        return new SeString(payloads);
+    }
+
+    /// <summary>
+    /// Creates an SeString representing an entire payload chain that can be used to link the party finder search conditions.
+    /// </summary>
+    /// <param name="message">The text that should be displayed for the link.</param>
+    /// <returns>An SeString containing all the payloads necessary to display a link to the party finder search conditions.</returns>
+    public static SeString CreatePartyFinderSearchConditionsLink(string message)
+    {
+        var payloads = new List<Payload>()
+        {
+            new PartyFinderPayload(),
+            // ->
+            new TextPayload(message),
+        };
+        payloads.InsertRange(1, TextArrowPayloads);
+        payloads.Add(RawPayload.LinkTerminator);
+
+        return new SeString(payloads);
+    }
+
     /// <summary>
     /// Creates a SeString from a json. (For testing - not recommended for production use.)
     /// </summary>