feat: convert tmux monitoring into a plugin (B10)

plugins/tmux-monitor/src/backend/service.ts

@@ -0,0 +1,54 @@
+import type { Client, ClientChannel } from "ssh2";
+import type { PluginContext } from "@termix/plugin-sdk/backend";
+import {
+  attachOrCreateTmuxSession,
+  detectTmux,
+  waitForTmuxSession,
+} from "./tmux-commands.js";
+
+export interface TmuxDetection {
+  available: boolean;
+  sessions: string[];
+}
+
+/**
+ * What the terminal (ssh-terminal's optional "tmux.sessions" consumer) asks
+ * of this plugin. Clients and streams cross the service boundary as
+ * `unknown`, since the SDK types services without an ssh2 dependency.
+ */
+export interface TmuxSessionsV1 {
+  detect: (client: unknown) => Promise<TmuxDetection>;
+  attachOrCreate: (
+    stream: unknown,
+    name?: string,
+    newName?: string,
+  ) => Promise<void>;
+  waitForSession: (client: unknown, name: string) => Promise<string>;
+}
+
+export function createTmuxSessionsService(ctx: PluginContext): TmuxSessionsV1 {
+  return {
+    async detect(client) {
+      const result = await detectTmux(client as Client);
+      return {
+        available: result.available,
+        sessions: result.sessions.map((s) => s.name),
+      };
+    },
+
+    async attachOrCreate(stream, name, newName) {
+      attachOrCreateTmuxSession(stream as ClientChannel, name, newName);
+    },
+
+    async waitForSession(client, name) {
+      const confirmed = await waitForTmuxSession(client as Client, name);
+      if (!confirmed) {
+        ctx.log.warn(
+          `Timed out waiting for a new tmux session to appear: ${name}`,
+        );
+        return name;
+      }
+      return confirmed;
+    },
+  };
+}