[match] add developer tachyon override

apps/match/src/match.app.ts

@@ -229,6 +229,40 @@ function tachyonServerFor(env: Env, roomInstanceId: number): TachyonServer {
 	return pool[roomInstanceId % pool.length] ?? NO_TACHYON_SERVER
 }
 
+/**
+ * The Tachyon port a DEVELOPER is handed, in place of the port on the pool entry their
+ * instance resolved to. Developers connect to a separate Tachyon build running beside the
+ * live one on the same box, so only the PORT moves: the HOST stays whichever one
+ * {@link tachyonServerFor} picked, rather than scattering developers off the pool.
+ */
+const DEVELOPER_TACHYON_PORT = '7778'
+
+/**
+ * The id displayed for that dev server. Not `tachyon-N` — the generated ids are positional
+ * names for entries in the pool ({@link tachyonPool}), and the dev build is not one of
+ * them: it is a different server that happens to share a host. The id is cosmetic (the
+ * client displays it and never sends it anywhere), so it only has to say which server the
+ * player is on, and "dev" is that.
+ */
+const DEVELOPER_TACHYON_SERVER_ID = 'dev'
+
+/**
+ * `server` with its port replaced by {@link DEVELOPER_TACHYON_PORT} and its id by
+ * {@link DEVELOPER_TACHYON_SERVER_ID}. An empty address is left alone — the pool is unset or
+ * the caller is in no instance, so there is no server to point at another port, and writing
+ * a bare `:7778` would hand the client an address that answers nothing (and name a server
+ * that isn't there). Splits on the LAST colon so a bracketed IPv6 host survives.
+ */
+function developerTachyonServer(server: TachyonServer): TachyonServer {
+	if (server.hostPort === '') return server
+	const colon = server.hostPort.lastIndexOf(':')
+	const host = colon === -1 ? server.hostPort : server.hostPort.slice(0, colon)
+	return {
+		hostPort: `${host}:${DEVELOPER_TACHYON_PORT}`,
+		serverId: DEVELOPER_TACHYON_SERVER_ID,
+	}
+}
+
 /**
  * Networking feature flags the client reads off its connection info. Verbatim from
  * the reference server — the client changes how it replicates based on these, so they
@@ -2872,7 +2906,9 @@ const app = new Hono<App>()
 				'fields name the Tachyon server that instance was assigned — one entry out of the',
 				'`TACHYON_HOST_PORT` pool, chosen by instance id so every player in a session is',
 				'handed the same one, with a generated `voiceServerId` (`tachyon-1`, `tachyon-2`,',
-				'…). Both are empty when the pool is unset or the caller is in no instance.',
+				'…). Both are empty when the pool is unset or the caller is in no instance. A',
+				'caller holding the DEVELOPER role gets that same host on port 7778, the dev',
+				'Tachyon build, with a `voiceServerId` of `dev`.',
 				'`experiments` carries the client’s networking flags.',
 			].join(' '),
 			security: AUTHED,
@@ -2911,8 +2947,13 @@ const app = new Hono<App>()
 					photonRoomId = instance?.photonRoomId ?? ''
 				}
 			}
-			// The instance's server, the same one every other player in it is handed.
-			const tachyon = tachyonServerFor(c.env, roomInstanceId)
+			const account = await getAccount(c.env.DB, id)
+			// The instance's server, the same one every other player in it is handed — except
+			// for a DEVELOPER, who is sent to the same host on the dev port, under the id
+			// `dev` rather than the pool entry's positional name.
+			const assigned = tachyonServerFor(c.env, roomInstanceId)
+			const tachyon =
+				account?.isDeveloper === true ? developerTachyonServer(assigned) : assigned
 
 			// Identifies the player to Photon. Signed with the shared JWT secret; the token's
 			// `aud` is the realtime app it's for. Nothing verifies it while Photon is
@@ -2920,7 +2961,7 @@ const app = new Hono<App>()
 			const photonAuthToken = await generatePhotonAuthToken(
 				id,
 				{
-					platformId: (await getAccount(c.env.DB, id))?.platformId ?? '',
+					platformId: account?.platformId ?? '',
 					platform: presence?.platform ?? 0,
 					deviceClass: presence?.deviceClass ?? 0,
 					audience: apps.photonRealtimeAppId,
@@ -2936,7 +2977,8 @@ const app = new Hono<App>()
 					photonRoomId,
 					// The Tachyon server this instance runs on, picked out of the operator's
 					// pool by {@link tachyonServerFor} — empty strings when the pool is empty
-					// or the caller is in no instance. Empty rather than null: the client's
+					// or the caller is in no instance, and on the dev port (id `dev`) for a
+					// developer. Empty rather than null: the client's
 					// decoder is likelier to accept a missing-value string than a null on a
 					// string field. The presence payload's NULL_CONNECTION_INFO keeps its
 					// nulls — that one never carries credentials.