Import march-2020-03-10 from private repo (scrubbed 2026-05-27)

Targets Rec Room 2020.03.10 client (also serves 2020.03.06). Re-import after adding: - DorkNet.ClientMod/dorknet-clientmod.json.template — config schema the launcher's manifest-driven patcher renders into UserData/. - tools/build-patcher-zip.ps1 — produces dorknet-clientpatch-{key}.zip for v1-march-* Release uploads. - .github/workflows/release.yml — on tag push publishes both dorknet-server-march_2020_03_10-win-x64.zip and dorknet-clientpatch-march_2020_03_10.zip as Release assets. Same scrub rules as december; tools/build-patcher-zip.ps1 added to the maintainer-side allow-list so it survives.
2026-10-26 15:38:45 -07:00 · 2026-05-27 01:06:12 +03:00
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+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+using DorkNet.Models.Notification;
+using DorkNet.Server.Auth;
+using DorkNet.Server.Data;
+using DorkNet.Server.Data.Entities;
+using DorkNet.Server.Services;
+using System.Text.Json;
+
+namespace DorkNet.Server.Controllers.Chat;
+
+/// <summary>
+/// chat.rec.net — DM / group-chat endpoints. Three entities back this:
+/// <list type="bullet">
+/// <item><see cref="ChatMessageEntity"/> — append-only message log
+///       keyed by thread.</item>
+/// <item><see cref="ChatThreadEntity"/> — optional per-thread metadata
+///       (custom name, creator) for group chats and renamed DMs.</item>
+/// <item><see cref="ChatThreadMemberEntity"/> — per-(thread, player)
+///       row carrying snooze timestamp and last-read message pointer.
+///       For unmodified 2-person DMs we create rows lazily on first
+///       mutation; the message table is the source of truth for
+///       participants.</item>
+/// </list>
+/// </summary>
+[ApiController]
+[Authorize]
+public class ChatController(
+    DorkNetDbContext db,
+    NotificationService notifications) : ControllerBase
+{
+    private const int ChatSuccess = 0;
+    private const int ChatInvalidArguments = 1;
+    private const int ChatMembershipNotFound = 3;
+    private const int ChatPlayerAlreadyOnThread = 4;
+
+    private long Me => this.RequireCurrentPlayerId();
+
+    /// <summary>List the caller's chat threads, most-recently-active
+    /// first. Each thread carries the most recent message preview so
+    /// the watch can render the inbox without per-thread fetches.</summary>
+    [HttpGet("/thread")]
+    public async Task<IActionResult> GetThreads([FromQuery] int? maxCount)
+    {
+        var take = Math.Clamp(maxCount ?? 50, 1, 100);
+
+        // Two sources of "threads I see in my inbox":
+        //   1. Explicit membership rows (group chats — leaving deletes
+        //      the row, so its presence means "still in").
+        //   2. DM threads where I sent or received at least one message.
+        // We union both, then filter out group keys I'm NOT a member
+        // of (in case I sent a message to a group then left).
+        var memberKeys = (await db.ChatThreadMembers
+            .Where(m => m.PlayerId == Me)
+            .Select(m => m.ThreadKey)
+            .ToListAsync()).ToHashSet();
+
+        var sentOrReceived = await db.ChatMessages
+            .Where(c => c.SenderPlayerId == Me ||
+                        c.ThreadKey.StartsWith($"dm:{Me}:") ||
+                        c.ThreadKey.EndsWith($":{Me}"))
+            .Select(c => c.ThreadKey)
+            .Distinct()
+            .ToListAsync();
+
+        var keys = sentOrReceived
+            .Concat(memberKeys)
+            .Distinct()
+            .Where(k => !k.StartsWith("group:") || memberKeys.Contains(k))
+            .ToList();
+        if (keys.Count == 0) return Ok(Array.Empty<object>());
+
+        var latest = await db.ChatMessages
+            .Where(c => keys.Contains(c.ThreadKey))
+            .GroupBy(c => c.ThreadKey)
+            .Select(g => g.OrderByDescending(c => c.SentAt).First())
+            .Take(take)
+            .ToListAsync();
+
+        var threadMeta = await EnsureThreadRowsAsync(keys);
+        var myMembership = await db.ChatThreadMembers
+            .Where(m => m.PlayerId == Me && keys.Contains(m.ThreadKey))
+            .ToDictionaryAsync(m => m.ThreadKey, m => m);
+        var participants = await LoadParticipantsAsync(keys);
+
+        return Ok(latest
+            .OrderByDescending(c => c.SentAt)
+            .Select(c =>
+            {
+                var meta = threadMeta[c.ThreadKey];
+                myMembership.TryGetValue(c.ThreadKey, out var member);
+                participants.TryGetValue(c.ThreadKey, out var playerIds);
+                return ToWireThread(
+                    meta,
+                    member,
+                    playerIds ?? new List<int>(),
+                    latestMessage: c);
+            })
+            .ToList());
+    }
+
+    /// <summary>Return the single thread by its key, with the most
+    /// recent N messages.</summary>
+    [HttpGet("/thread/{chatThreadId}")]
+    public async Task<IActionResult> GetThreadById(string chatThreadId,
+        [FromQuery] int maxCount = 50)
+    {
+        var take = Math.Clamp(maxCount, 1, 200);
+        var key = await ResolveThreadKeyAsync(chatThreadId);
+        var rows = await db.ChatMessages
+            .Where(c => c.ThreadKey == key)
+            .OrderByDescending(c => c.SentAt)
+            .Take(take)
+            .ToListAsync();
+        if (rows.Count == 0) return NotFound();
+        var meta = (await EnsureThreadRowsAsync(new[] { key }))[key];
+        var member = await db.ChatThreadMembers
+            .FirstOrDefaultAsync(m => m.ThreadKey == key && m.PlayerId == Me);
+        var participants = await LoadParticipantsAsync(new[] { key });
+        participants.TryGetValue(key, out var playerIds);
+        return Ok(ToWireThread(
+            meta,
+            member,
+            playerIds ?? new List<int>(),
+            messages: rows.OrderBy(c => c.SentAt).ToList()));
+    }
+
+    /// <summary>Recent messages for a thread, paginated by
+    /// <paramref name="beforeMessageId"/>.</summary>
+    [HttpGet("/thread/{chatThreadId}/message")]
+    public async Task<IActionResult> GetMessages(string chatThreadId,
+        [FromQuery] int maxCount = 50,
+        [FromQuery] int? messageCount = null,
+        [FromQuery] long? beforeMessageId = null,
+        [FromQuery] long? referenceMessageId = null)
+    {
+        var take = Math.Clamp(messageCount ?? maxCount, 1, 200);
+        var key = await ResolveThreadKeyAsync(chatThreadId);
+        var thread = await db.ChatThreads.FirstOrDefaultAsync(t => t.ThreadKey == key);
+        if (thread is null) return Ok(Array.Empty<object>());
+        var q = db.ChatMessages.Where(c => c.ThreadKey == key);
+        var before = beforeMessageId ?? referenceMessageId;
+        if (before is long b)
+            q = q.Where(c => c.Id < b);
+        var rows = await q
+            .OrderByDescending(c => c.SentAt)
+            .Take(take)
+            .ToListAsync();
+        return Ok(rows.OrderBy(c => c.SentAt).Select(c => ToWireMessage(c, thread.Id)).ToList());
+    }
+
+    /// <summary>Unread-thread count from per-thread last-read pointers.
+    /// A thread counts as unread when there's at least one message
+    /// after the caller's <c>LastReadMessageId</c> (or any message at
+    /// all when the caller has never read).</summary>
+    [HttpGet("/thread/unreadcount")]
+    public async Task<IActionResult> UnreadCount()
+    {
+        // Threads the caller participates in via membership row.
+        var memberKeys = await db.ChatThreadMembers
+            .Where(m => m.PlayerId == Me)
+            .ToListAsync();
+        var memberKeyToLastRead = memberKeys.ToDictionary(m => m.ThreadKey, m => m.LastReadMessageId);
+
+        // DM threads also count even without an explicit member row.
+        var dmKeys = await db.ChatMessages
+            .Where(c => c.ThreadKey.StartsWith($"dm:{Me}:") || c.ThreadKey.EndsWith($":{Me}"))
+            .Select(c => c.ThreadKey)
+            .Distinct()
+            .ToListAsync();
+
+        var keys = memberKeyToLastRead.Keys.Concat(dmKeys).Distinct().ToList();
+        if (keys.Count == 0) return Ok(0);
+
+        var perThreadMax = await db.ChatMessages
+            .Where(c => keys.Contains(c.ThreadKey) && c.SenderPlayerId != Me)
+            .GroupBy(c => c.ThreadKey)
+            .Select(g => new { Key = g.Key, MaxId = g.Max(c => c.Id) })
+            .ToListAsync();
+
+        var unread = perThreadMax.Count(t =>
+        {
+            memberKeyToLastRead.TryGetValue(t.Key, out var lastRead);
+            return lastRead is null || t.MaxId > lastRead.Value;
+        });
+        return Ok(unread);
+    }
+
+    public sealed record SendChatRequest(string? ChatThreadId, long? RecipientId, string Body);
+
+    /// <summary>Append a message to a thread. The thread is either
+    /// referenced by id (existing thread) or by RecipientId (new DM
+    /// to that player; we synthesise the canonical dm key). JSON shape
+    /// used by the admin SPA / API callers; the 2020 watch posts the
+    /// form-urlencoded variant in <see cref="SendForm"/> with multi-
+    /// valued <c>ids</c> + a <c>messageContents</c> JSON blob.</summary>
+    [HttpPost("/thread")]
+    [HttpPost("/thread/{chatThreadId}/message")]
+    [Consumes("application/json")]
+    public async Task<IActionResult> Send(string? chatThreadId,
+        [FromBody] SendChatRequest body)
+    {
+        if (string.IsNullOrWhiteSpace(body.Body)) return BadRequest("empty");
+        var trimmed = body.Body.Trim();
+        if (trimmed.Length > 2000) trimmed = trimmed[..2000];
+
+        var key = chatThreadId is null ? null : await ResolveThreadKeyAsync(chatThreadId);
+        key ??= body.ChatThreadId is null ? null : await ResolveThreadKeyAsync(body.ChatThreadId);
+        key ??= body.RecipientId is long otherId
+            ? ChatMessageEntity.DmKey(Me, otherId)
+            : null;
+        if (key is null) return BadRequest("missing_thread");
+        var thread = await EnsureThreadRowAsync(key);
+
+        var entry = new ChatMessageEntity
+        {
+            ThreadKey = key,
+            SenderPlayerId = Me,
+            Body = trimmed,
+        };
+        db.ChatMessages.Add(entry);
+        await db.SaveChangesAsync();
+
+        // Notify every participant — INCLUDING the sender. The 2020
+        // watch's chat send path doesn't update its local thread cache
+        // off the HTTP 200 response, so without a self-targeted push
+        // the sender's chat UI doesn't show its own outgoing message
+        // until the next thread refresh. DM keys encode the two
+        // participants directly; group chat threads fan out across the
+        // explicit membership table.
+        var recipients = new List<long>();
+        if (key.StartsWith("dm:") && TryParseDmKey(key, out var a, out var b))
+        {
+            var other = a == Me ? b : a;
+            recipients.Add(other);
+        }
+        else if (key.StartsWith("group:"))
+        {
+            recipients = await db.ChatThreadMembers
+                .Where(m => m.ThreadKey == key && m.PlayerId != Me)
+                .Select(m => m.PlayerId)
+                .ToListAsync();
+        }
+        recipients.Add(Me);
+        foreach (var rid in recipients)
+        {
+            await notifications.NotifyAsync(rid,
+                PushNotificationId.ChatMessageReceived,
+                ToWireMessage(entry, thread.Id));
+        }
+
+        return Ok(ToWireSendMessageResponse(entry, thread.Id));
+    }
+
+    /// <summary>Set the caller's last-read pointer on the thread to
+    /// the most recent message id. Drives the inbox's unread badge.</summary>
+    [HttpPut("/thread/{chatThreadId}/read")]
+    [HttpPost("/thread/{chatThreadId}/read")]
+    public async Task<IActionResult> MarkRead(string chatThreadId) =>
+        await UpdateLastRead(await ResolveThreadKeyAsync(chatThreadId), latestOnly: true, explicitMessageId: null);
+
+    /// <summary>PUT <c>/thread/{id}/message/{messageId}/read</c> — set
+    /// the caller's last-read pointer to a specific message (not just
+    /// "latest"). The 2020 watch uses this when the inbox view scrolls
+    /// to a particular message rather than the bottom. URL verified
+    /// at stringliteral.json: <c>"thread/{0}/message/{1}/read"</c>.</summary>
+    [HttpPut("/thread/{chatThreadId}/message/{messageId:long}/read")]
+    [HttpPost("/thread/{chatThreadId}/message/{messageId:long}/read")]
+    public async Task<IActionResult> MarkMessageRead(string chatThreadId, long messageId) =>
+        await UpdateLastRead(await ResolveThreadKeyAsync(chatThreadId), latestOnly: false, explicitMessageId: messageId);
+
+    private async Task<IActionResult> UpdateLastRead(string chatThreadId, bool latestOnly, long? explicitMessageId)
+    {
+        long? latestId = explicitMessageId;
+        if (latestId is null)
+        {
+            latestId = await db.ChatMessages
+                .Where(c => c.ThreadKey == chatThreadId)
+                .OrderByDescending(c => c.Id)
+                .Select(c => (long?)c.Id)
+                .FirstOrDefaultAsync();
+        }
+        if (latestId is null) return Ok(ChatSuccess);
+        _ = latestOnly;
+
+        var row = await db.ChatThreadMembers
+            .FirstOrDefaultAsync(m => m.ThreadKey == chatThreadId && m.PlayerId == Me);
+        if (row is null)
+        {
+            row = new ChatThreadMemberEntity
+            {
+                ThreadKey = chatThreadId,
+                PlayerId = Me,
+            };
+            db.ChatThreadMembers.Add(row);
+        }
+        row.LastReadMessageId = latestId;
+        await db.SaveChangesAsync();
+        return Ok(ChatSuccess);
+    }
+
+    public sealed record SnoozeRequest(DateTime? Until);
+
+    /// <summary>Mute notifications for the thread until
+    /// <c>Until</c> (UTC). Null/missing payload clears the snooze.</summary>
+    [HttpPost("/thread/{chatThreadId}/snooze")]
+    public async Task<IActionResult> Snooze(string chatThreadId, [FromBody] SnoozeRequest? body)
+    {
+        chatThreadId = await ResolveThreadKeyAsync(chatThreadId);
+        var row = await db.ChatThreadMembers
+            .FirstOrDefaultAsync(m => m.ThreadKey == chatThreadId && m.PlayerId == Me);
+        if (row is null)
+        {
+            row = new ChatThreadMemberEntity
+            {
+                ThreadKey = chatThreadId,
+                PlayerId = Me,
+            };
+            db.ChatThreadMembers.Add(row);
+        }
+        row.SnoozeUntil = body?.Until;
+        await db.SaveChangesAsync();
+        var thread = await EnsureThreadRowAsync(chatThreadId);
+        return Ok(new Dictionary<string, object?>
+        {
+            ["chatResult"] = ChatSuccess,
+            ["snoozedUntil"] = row.SnoozeUntil,
+        });
+    }
+
+    /// <summary>Remove the caller from the thread's membership. They
+    /// stop receiving new messages and the thread drops off their
+    /// inbox. DMs can't be left — there are only two participants and
+    /// removing one effectively ends the conversation; the watch
+    /// surfaces a "delete chat" option for DMs instead.</summary>
+    [HttpDelete("/thread/{chatThreadId}/leave")]
+    public async Task<IActionResult> Leave(string chatThreadId)
+    {
+        chatThreadId = await ResolveThreadKeyAsync(chatThreadId);
+        if (chatThreadId.StartsWith("dm:"))
+            return Ok(ChatInvalidArguments);
+        var removed = await db.ChatThreadMembers
+            .Where(m => m.ThreadKey == chatThreadId && m.PlayerId == Me)
+            .ExecuteDeleteAsync();
+        return Ok(removed > 0 ? ChatSuccess : ChatMembershipNotFound);
+    }
+
+    public sealed record RenameRequest(string Name);
+
+    /// <summary>Set the thread's display name. Permission: any member
+    /// of the thread can rename. For DMs the watch typically nudges
+    /// users to pick a nickname after first send; group-chat creators
+    /// usually set the name at creation time.</summary>
+    [HttpPut("/thread/{chatThreadId}/rename")]
+    public async Task<IActionResult> Rename(string chatThreadId, [FromBody] RenameRequest body)
+    {
+        chatThreadId = await ResolveThreadKeyAsync(chatThreadId);
+        var name = (body.Name ?? string.Empty).Trim();
+        if (name.Length > 128) name = name[..128];
+
+        var iAmMember = chatThreadId.StartsWith("dm:")
+            ? IsDmParticipant(chatThreadId, Me)
+            : await db.ChatThreadMembers
+                .AnyAsync(m => m.ThreadKey == chatThreadId && m.PlayerId == Me);
+        if (!iAmMember) return Ok(ChatMembershipNotFound);
+
+        var meta = await db.ChatThreads.FirstOrDefaultAsync(t => t.ThreadKey == chatThreadId);
+        if (meta is null)
+        {
+            meta = new ChatThreadEntity
+            {
+                ThreadKey = chatThreadId,
+                CreatorPlayerId = Me,
+            };
+            db.ChatThreads.Add(meta);
+        }
+        meta.Name = name;
+        meta.UpdatedAt = DateTime.UtcNow;
+        await db.SaveChangesAsync();
+        return Ok(ChatSuccess);
+    }
+
+    public sealed record CreateGroupChatRequest(List<long> MemberIds, string? Name);
+
+    /// <summary>Create a group chat. Generates a fresh
+    /// <c>group:&lt;guid&gt;</c> key, inserts membership rows for the
+    /// creator + each invited player, and returns the new thread id.
+    /// Empty or duplicate member lists are tolerated (the caller is
+    /// always added as a member regardless). JSON variant — the 2020
+    /// watch hits the form-urlencoded form in <see cref="WithMembersForm"/>.
+    /// </summary>
+    [HttpPost("/thread/withmembers")]
+    [Consumes("application/json")]
+    public async Task<IActionResult> CreateGroup([FromBody] CreateGroupChatRequest body)
+    {
+        var key = $"group:{Guid.NewGuid():N}";
+        var members = (body?.MemberIds ?? new())
+            .Where(id => id > 0 && id != Me)
+            .Distinct()
+            .ToList();
+        members.Add(Me);
+
+        db.ChatThreads.Add(new ChatThreadEntity
+        {
+            ThreadKey = key,
+            Name = (body?.Name ?? string.Empty).Trim(),
+            CreatorPlayerId = Me,
+        });
+        foreach (var pid in members)
+        {
+            db.ChatThreadMembers.Add(new ChatThreadMemberEntity
+            {
+                ThreadKey = key,
+                PlayerId = pid,
+            });
+        }
+        await db.SaveChangesAsync();
+
+        var thread = await db.ChatThreads.FirstAsync(t => t.ThreadKey == key);
+        var playerIds = members.Select(x => (int)x).ToList();
+        return Ok(new Dictionary<string, object?>
+        {
+            ["chatThread"] = ToWireThread(thread, null, playerIds),
+            ["chatResult"] = ChatSuccess,
+        });
+    }
+
+    /// <summary>Form-urlencoded variant of <see cref="CreateGroup"/>
+    /// used by the 2020 watch. Wire shape verified from the live
+    /// request: <c>ids=A&amp;ids=B&amp;messageCount=N</c>. The watch
+    /// calls this to "open a chat with these people" — semantics are
+    /// fetch-or-create-then-return-recent-messages, NOT just create.
+    /// We resolve <c>ids</c> to a canonical thread key (DM if two
+    /// participants total including the caller, otherwise group), pull
+    /// the latest <c>messageCount</c> messages, and return a shape the
+    /// watch's inbox can render directly.</summary>
+    [HttpPost("/thread/withmembers")]
+    [Consumes("application/x-www-form-urlencoded", "multipart/form-data")]
+    public async Task<IActionResult> WithMembersForm()
+    {
+        var (ids, _) = ParseIdsAndContents(Request.Form);
+        if (ids.Count == 0) return BadRequest(new { error = "missing_ids" });
+
+        var count = Math.Clamp(
+            int.TryParse(Request.Form["messageCount"], out var mc) ? mc : 50,
+            1, 200);
+        var key = await ResolveOrCreateThreadAsync(ids);
+        var rows = await db.ChatMessages
+            .Where(c => c.ThreadKey == key)
+            .OrderByDescending(c => c.SentAt)
+            .Take(count)
+            .ToListAsync();
+        var meta = await EnsureThreadRowAsync(key);
+        var participants = ids.Concat(new[] { Me }).Distinct().Select(x => (int)x).ToList();
+        return Ok(ToWireThread(meta, null, participants, messages: rows.OrderBy(c => c.SentAt).ToList()));
+    }
+
+    /// <summary>Form-urlencoded variant of <see cref="Send"/> used by
+    /// the 2020 watch. Wire shape: <c>ids=A&amp;ids=B&amp;
+    /// messageContents={JSON}</c> where <c>messageContents</c> is the
+    /// JSON-encoded <c>RecNet.ChatMessage.Contents</c> blob
+    /// (<c>{Type,Version,Data}</c>) — Data is the actual text. The
+    /// watch sends this to BOTH create-or-find-thread AND post-message
+    /// in one call.</summary>
+    [HttpPost("/thread")]
+    [Consumes("application/x-www-form-urlencoded", "multipart/form-data")]
+    public async Task<IActionResult> SendForm()
+    {
+        var (ids, contents) = ParseIdsAndContents(Request.Form);
+        if (ids.Count == 0) return BadRequest(new { error = "missing_ids" });
+
+        var text = ExtractChatDataField(contents);
+        if (string.IsNullOrWhiteSpace(text)) return BadRequest(new { error = "empty_body" });
+        if (text.Length > 2000) text = text[..2000];
+
+        var key = await ResolveOrCreateThreadAsync(ids);
+        var thread = await EnsureThreadRowAsync(key);
+        var entry = new ChatMessageEntity
+        {
+            ThreadKey = key,
+            SenderPlayerId = Me,
+            Body = text,
+        };
+        db.ChatMessages.Add(entry);
+        await db.SaveChangesAsync();
+
+        // Notify every participant, sender INCLUDED — see SendMessageJson
+        // above for the rationale; the 2020 watch's chat send path needs
+        // the self-push to refresh its own UI.
+        var recipients = new List<long>();
+        if (key.StartsWith("dm:") && TryParseDmKey(key, out var a, out var b))
+        {
+            var other = a == Me ? b : a;
+            if (other != Me) recipients.Add(other);
+        }
+        else if (key.StartsWith("group:"))
+        {
+            recipients = await db.ChatThreadMembers
+                .Where(m => m.ThreadKey == key && m.PlayerId != Me)
+                .Select(m => m.PlayerId)
+                .ToListAsync();
+        }
+        recipients.Add(Me);
+        foreach (var rid in recipients)
+        {
+            await notifications.NotifyAsync(rid,
+                PushNotificationId.ChatMessageReceived,
+                ToWireMessage(entry, thread.Id));
+        }
+        var participants = await LoadParticipantsAsync(new[] { key });
+        participants.TryGetValue(key, out var playerIds);
+        return Ok(new Dictionary<string, object?>
+        {
+            ["chatThread"] = ToWireThread(thread, null, playerIds ?? new List<int>(), latestMessage: entry),
+            ["chatResult"] = ChatSuccess,
+        });
+    }
+
+    /// <summary>Form-urlencoded send used by the 2020 watch:
+    /// <c>POST /thread/{chatId}</c> with <c>messageContents</c>.
+    /// The response is a SendMessageResponse wrapper, not a raw message.</summary>
+    [HttpPost("/thread/{chatThreadId}")]
+    [Consumes("application/x-www-form-urlencoded", "multipart/form-data")]
+    public async Task<IActionResult> SendMessageForm(string chatThreadId)
+    {
+        var key = await ResolveThreadKeyAsync(chatThreadId);
+        var text = ExtractChatDataField(Request.Form["messageContents"].ToString());
+        if (string.IsNullOrWhiteSpace(text)) return Ok(new Dictionary<string, object?>
+        {
+            ["chatResult"] = ChatInvalidArguments,
+        });
+        if (text.Length > 2000) text = text[..2000];
+
+        var thread = await EnsureThreadRowAsync(key);
+        var entry = new ChatMessageEntity
+        {
+            ThreadKey = key,
+            SenderPlayerId = Me,
+            Body = text,
+        };
+        db.ChatMessages.Add(entry);
+        await db.SaveChangesAsync();
+
+        var recipients = new List<long>();
+        if (key.StartsWith("dm:") && TryParseDmKey(key, out var a, out var b))
+        {
+            var other = a == Me ? b : a;
+            if (other != Me) recipients.Add(other);
+        }
+        else if (key.StartsWith("group:"))
+        {
+            recipients = await db.ChatThreadMembers
+                .Where(m => m.ThreadKey == key && m.PlayerId != Me)
+                .Select(m => m.PlayerId)
+                .ToListAsync();
+        }
+        // Include the sender so the form-POST send path also refreshes
+        // its own chat thread — same reason as the JSON send path above.
+        recipients.Add(Me);
+        foreach (var rid in recipients)
+        {
+            await notifications.NotifyAsync(rid,
+                PushNotificationId.ChatMessageReceived,
+                ToWireMessage(entry, thread.Id));
+        }
+
+        return Ok(ToWireSendMessageResponse(entry, thread.Id));
+    }
+
+    /// <summary>Pull <c>ids</c> (multi-valued) + <c>messageContents</c>
+    /// out of the watch's form post. <c>ids</c> excludes the caller
+    /// (the caller is implied by their JWT).</summary>
+    private (List<long> ids, string? contents) ParseIdsAndContents(
+        Microsoft.AspNetCore.Http.IFormCollection form)
+    {
+        var ids = new List<long>();
+        foreach (var v in form["ids"])
+        {
+            if (long.TryParse(v, out var id) && id > 0 && id != Me)
+                ids.Add(id);
+        }
+        ids = ids.Distinct().ToList();
+        var contents = form["messageContents"].ToString();
+        return (ids, string.IsNullOrEmpty(contents) ? null : contents);
+    }
+
+    /// <summary>Resolve <paramref name="otherIds"/> + caller to a
+    /// canonical thread key. 1 other → DM key. 2+ others → existing
+    /// group with the exact same membership, or a fresh
+    /// <c>group:&lt;guid&gt;</c> if none. Membership rows are created
+    /// lazily so the inbox listing path can find the thread.</summary>
+    private async Task<string> ResolveOrCreateThreadAsync(List<long> otherIds)
+    {
+        if (otherIds.Count == 1)
+        {
+            var key = ChatMessageEntity.DmKey(Me, otherIds[0]);
+            // Ensure a ChatThreadEntity row exists for DMs the watch
+            // is mutating, so /thread inbox listings carry consistent
+            // metadata. The membership rows aren't needed for DM
+            // routing (the key carries the pair) but the inbox queries
+            // are simpler when every active thread has a row.
+            if (!await db.ChatThreads.AnyAsync(t => t.ThreadKey == key))
+            {
+                db.ChatThreads.Add(new ChatThreadEntity
+                {
+                    ThreadKey = key,
+                    CreatorPlayerId = Me,
+                });
+                await db.SaveChangesAsync();
+            }
+            return key;
+        }
+
+        var full = otherIds.Concat(new[] { Me }).Distinct().OrderBy(x => x).ToList();
+        // Look for an existing group whose membership matches exactly.
+        // Counts the rows per thread that intersect `full`, then takes
+        // the threads where total membership == |full| AND intersection
+        // size == |full|.
+        var candidateGroups = await db.ChatThreadMembers
+            .Where(m => full.Contains(m.PlayerId) && m.ThreadKey.StartsWith("group:"))
+            .GroupBy(m => m.ThreadKey)
+            .Where(g => g.Count() == full.Count)
+            .Select(g => g.Key)
+            .ToListAsync();
+        foreach (var k in candidateGroups)
+        {
+            var rows = await db.ChatThreadMembers
+                .Where(m => m.ThreadKey == k)
+                .Select(m => m.PlayerId)
+                .ToListAsync();
+            if (rows.OrderBy(x => x).SequenceEqual(full)) return k;
+        }
+
+        // No matching group → create one.
+        var newKey = $"group:{Guid.NewGuid():N}";
+        db.ChatThreads.Add(new ChatThreadEntity
+        {
+            ThreadKey = newKey,
+            CreatorPlayerId = Me,
+        });
+        foreach (var pid in full)
+        {
+            db.ChatThreadMembers.Add(new ChatThreadMemberEntity
+            {
+                ThreadKey = newKey,
+                PlayerId = pid,
+            });
+        }
+        await db.SaveChangesAsync();
+        return newKey;
+    }
+
+    /// <summary>Pull the <c>Data</c> field out of the watch's
+    /// <c>messageContents</c> JSON: <c>{"Type":0,"Version":1,"Data":"hi"}</c>.
+    /// Returns null/empty when the body isn't well-formed.</summary>
+    private static string ExtractChatDataField(string? messageContents)
+    {
+        if (string.IsNullOrWhiteSpace(messageContents)) return string.Empty;
+        try
+        {
+            using var doc = System.Text.Json.JsonDocument.Parse(messageContents);
+            if (doc.RootElement.TryGetProperty("Data", out var data)
+                && data.ValueKind == System.Text.Json.JsonValueKind.String)
+                return data.GetString() ?? string.Empty;
+        }
+        catch { }
+        return string.Empty;
+    }
+
+    /// <summary>Add a player to an existing group chat. Idempotent —
+    /// re-adding an existing member is a no-op.</summary>
+    [HttpPost("/thread/{chatThreadId}/member/{playerId:long}")]
+    public async Task<IActionResult> AddMember(string chatThreadId, long playerId)
+    {
+        chatThreadId = await ResolveThreadKeyAsync(chatThreadId);
+        if (!chatThreadId.StartsWith("group:"))
+            return Ok(ChatInvalidArguments);
+        var iAmMember = await db.ChatThreadMembers
+            .AnyAsync(m => m.ThreadKey == chatThreadId && m.PlayerId == Me);
+        if (!iAmMember) return Ok(ChatMembershipNotFound);
+        var exists = await db.ChatThreadMembers
+            .AnyAsync(m => m.ThreadKey == chatThreadId && m.PlayerId == playerId);
+        if (exists) return Ok(ChatPlayerAlreadyOnThread);
+        if (!exists)
+        {
+            db.ChatThreadMembers.Add(new ChatThreadMemberEntity
+            {
+                ThreadKey = chatThreadId,
+                PlayerId = playerId,
+            });
+            await db.SaveChangesAsync();
+        }
+        return Ok(ChatSuccess);
+    }
+
+    private async Task<string> ResolveThreadKeyAsync(string idOrKey)
+    {
+        if (long.TryParse(idOrKey, out var id))
+        {
+            var key = await db.ChatThreads
+                .Where(t => t.Id == id)
+                .Select(t => t.ThreadKey)
+                .FirstOrDefaultAsync();
+            return key ?? idOrKey;
+        }
+        return idOrKey;
+    }
+
+    private async Task<Dictionary<string, ChatThreadEntity>> EnsureThreadRowsAsync(IEnumerable<string> keys)
+    {
+        var distinct = keys.Distinct().ToList();
+        var rows = await db.ChatThreads
+            .Where(t => distinct.Contains(t.ThreadKey))
+            .ToDictionaryAsync(t => t.ThreadKey, t => t);
+
+        foreach (var key in distinct.Where(k => !rows.ContainsKey(k)))
+        {
+            var row = new ChatThreadEntity
+            {
+                ThreadKey = key,
+                CreatorPlayerId = Me,
+            };
+            db.ChatThreads.Add(row);
+            rows[key] = row;
+        }
+
+        if (db.ChangeTracker.HasChanges())
+            await db.SaveChangesAsync();
+
+        return rows;
+    }
+
+    private async Task<ChatThreadEntity> EnsureThreadRowAsync(string key) =>
+        (await EnsureThreadRowsAsync(new[] { key }))[key];
+
+    private async Task<Dictionary<string, List<int>>> LoadParticipantsAsync(IEnumerable<string> keys)
+    {
+        var distinct = keys.Distinct().ToList();
+        var result = distinct.ToDictionary(k => k, _ => new List<int>());
+
+        foreach (var key in distinct)
+        {
+            if (TryParseDmKey(key, out var a, out var b))
+            {
+                result[key] = new List<int> { (int)a, (int)b };
+            }
+        }
+
+        var groupKeys = distinct.Where(k => k.StartsWith("group:")).ToList();
+        if (groupKeys.Count > 0)
+        {
+            var members = await db.ChatThreadMembers
+                .Where(m => groupKeys.Contains(m.ThreadKey))
+                .Select(m => new { m.ThreadKey, m.PlayerId })
+                .ToListAsync();
+            foreach (var group in members.GroupBy(m => m.ThreadKey))
+                result[group.Key] = group.Select(m => (int)m.PlayerId).Distinct().ToList();
+        }
+
+        return result;
+    }
+
+    private static Dictionary<string, object?> ToWireThread(
+        ChatThreadEntity thread,
+        ChatThreadMemberEntity? member,
+        List<int> playerIds,
+        ChatMessageEntity? latestMessage = null,
+        List<ChatMessageEntity>? messages = null)
+    {
+        var dto = new Dictionary<string, object?>
+        {
+            ["chatThreadId"] = thread.Id,
+            ["chatThreadName"] = thread.Name ?? string.Empty,
+            ["lastReadMessageId"] = member?.LastReadMessageId ?? 0,
+            ["snoozedUntil"] = member?.SnoozeUntil,
+            ["playerIds"] = playerIds,
+        };
+
+        if (messages is not null)
+        {
+            dto["messages"] = messages.Select(m => ToWireMessage(m, thread.Id)).ToList();
+        }
+        else if (latestMessage is not null)
+        {
+            dto["latestMessage"] = ToWireMessage(latestMessage, thread.Id);
+        }
+
+        return dto;
+    }
+
+    private static Dictionary<string, object?> ToWireMessage(ChatMessageEntity c, long chatThreadId) => new()
+    {
+        ["chatMessageId"] = c.Id,
+        ["chatThreadId"] = chatThreadId,
+        ["senderPlayerId"] = (int)c.SenderPlayerId,
+        ["timeSent"] = c.SentAt,
+        ["contents"] = JsonSerializer.Serialize(new
+        {
+            Type = 0,
+            Version = 1,
+            Data = c.Body,
+        }),
+    };
+
+    private static Dictionary<string, object?> ToWireSendMessageResponse(ChatMessageEntity c, long chatThreadId) => new()
+    {
+        ["chatMessage"] = ToWireMessage(c, chatThreadId),
+        ["chatResult"] = ChatSuccess,
+    };
+
+    private static bool TryParseDmKey(string key, out long a, out long b)
+    {
+        a = b = 0;
+        var parts = key.Split(':');
+        return parts.Length == 3 && parts[0] == "dm" &&
+               long.TryParse(parts[1], out a) &&
+               long.TryParse(parts[2], out b);
+    }
+
+    private static bool IsDmParticipant(string key, long playerId) =>
+        TryParseDmKey(key, out var a, out var b) && (a == playerId || b == playerId);
+}