1 files changed, 245 insertions, 0 deletions
diff --git a/src/daemon/server.ts b/src/daemon/server.ts
new file mode 100644
index 0000000..fea9bb7
--- /dev/null
+++ b/src/daemon/server.ts
@@ -0,0 +1,245 @@
+/**
+ * IpcServer — Unix socket server for daemon ↔ pi client communication.
+ *
+ * Accepts multiple concurrent pi client connections over a Unix domain
+ * stream socket. Uses newline-delimited JSON framing (one WireMessage per
+ * line). Clients are anonymous until they send a control.register message.
+ *
+ * References:
+ *   - net.createServer: https://nodejs.org/docs/latest-v22.x/api/net.html#netcreateserveroptions-connectionlistener
+ *   - server.listen(path): https://nodejs.org/docs/latest-v22.x/api/net.html#serverlistenpath-backlog-callback
+ *   - readline.createInterface: https://nodejs.org/docs/latest-v22.x/api/readline.html#readlinecreateinterfaceoptions
+ */
+
+import { createServer, type Server, type Socket } from "node:net";
+import { createInterface, type Interface } from "node:readline";
+import { unlinkSync } from "node:fs";
+import {
+  type WireMessage,
+  type WireControl,
+  isWireMessage,
+  DAEMON_SOCKET_PATH,
+  DAEMON_MAX_CLIENTS,
+  DAEMON_STALE_SOCKET_CLEANUP,
+} from "./protocol";
+
+// ── Types ──────────────────────────────────────────────────────────────────────
+
+/** A connected pi client with its socket and readline interface. */
+export type ClientSocket = {
+  /** Client namespace (set after registration). */
+  id: string;
+  readonly socket: Socket;
+  readonly rl: Interface;
+  /** True once a valid control.register message has been received. */
+  registered: boolean;
+};
+
+/** Handler called for every valid WireMessage from any client. */
+export type MessageHandler = (msg: WireMessage, client: ClientSocket) => void;
+
+/** Handler called when a client connects or disconnects. */
+export type ConnectionHandler = (client: ClientSocket) => void;
+
+export type IpcServer = {
+  /** Start listening on the Unix socket. Resolves when the server is ready. */
+  start(): Promise<void>;
+  /** Close the server and all client connections. Resolves when cleaned up. */
+  stop(): Promise<void>;
+  /** Register a handler for incoming WireMessages from any client. */
+  onMessage(handler: MessageHandler): void;
+  /** Register a handler for client connect events. */
+  onConnect(handler: ConnectionHandler): void;
+  /** Register a handler for client disconnect events. */
+  onDisconnect(handler: ConnectionHandler): void;
+  /** Send a WireMessage to a specific client by clientId. No-op if client not found. */
+  send(clientId: string, msg: WireMessage): void;
+  /** Send a WireMessage to all connected (registered) clients. */
+  broadcast(msg: WireMessage): void;
+  /** Force-disconnect a client by clientId. */
+  disconnectClient(clientId: string): void;
+  /** All currently connected clients (by clientId). */
+  clients(): ReadonlyMap<string, ClientSocket>;
+  /** Number of connected clients. */
+  clientCount(): number;
+};
+
+// ── Implementation ─────────────────────────────────────────────────────────────
+
+export const createIpcServer = (): IpcServer => {
+  let server: Server | null = null;
+  // Anonymous temp-id → ClientSocket. Temp ids are assigned before registration.
+  const sockets = new Map<string, ClientSocket>();
+  // clientId → ClientSocket (only registered clients).
+  const clients = new Map<string, ClientSocket>();
+  let messageHandler: MessageHandler | null = null;
+  let connectHandler: ConnectionHandler | null = null;
+  let disconnectHandler: ConnectionHandler | null = null;
+  let nextTempId = 1;
+
+  const start = (): Promise<void> =>
+    new Promise((resolve, reject) => {
+      // Clean up stale socket file from a previous crashed daemon.
+      if (DAEMON_STALE_SOCKET_CLEANUP) {
+        try {
+          unlinkSync(DAEMON_SOCKET_PATH);
+        } catch {
+          // ENOENT is expected — no stale socket to clean.
+        }
+      }
+
+      server = createServer({ pauseOnConnect: false }, (socket: Socket) => {
+        // Reject if at capacity (check registered clients only).
+        if (clients.size >= DAEMON_MAX_CLIENTS) {
+          socket.destroy();
+          return;
+        }
+
+        const tempId = `anon-${nextTempId++}`;
+        const rl = createInterface({ input: socket, crlfDelay: Infinity });
+        let currentClient: ClientSocket = { id: tempId, socket, rl, registered: false };
+
+        sockets.set(tempId, currentClient);
+
+        // Buffer for partial lines. readline handles line splitting, but
+        // we store a reference in case we need it for diagnostics.
+        let lineCount = 0;
+
+        rl.on("line", (line: string) => {
+          lineCount++;
+          let msg: WireMessage | null;
+          try {
+            const parsed: unknown = JSON.parse(line);
+            if (!isWireMessage(parsed)) return;
+            msg = parsed;
+          } catch {
+            // Malformed JSON — ignore silently, don't crash the daemon.
+            return;
+          }
+
+          // Handle registration before forwarding to the general handler.
+          if (msg.type === "control" && msg.action === "register" && !currentClient.registered) {
+            const clientId = msg.clientId;
+            if (!clientId) return;
+
+            // If a client with this id is already connected, reject.
+            if (clients.has(clientId)) {
+              const reply: WireControl = {
+                type: "control",
+                action: "shutdown",
+                reason: `clientId ${clientId} is already connected`,
+              };
+              socket.write(JSON.stringify(reply) + "\n");
+              socket.destroy();
+              return;
+            }
+
+            // Promote from anonymous to registered — mutate in place so the
+            // closure captures the updated client reference.
+            sockets.delete(tempId);
+            currentClient.id = clientId;
+            currentClient.registered = true;
+            clients.set(clientId, currentClient);
+
+            // Acknowledge registration.
+            const ack: WireControl = { type: "control", action: "registered", clientId };
+            socket.write(JSON.stringify(ack) + "\n");
+
+            connectHandler?.(currentClient);
+            return;
+          }
+
+          // Require registration for non-control messages.
+          if (!currentClient.registered) return;
+
+          // Forward to the general handler.
+          messageHandler?.(msg, currentClient);
+        });
+
+        socket.on("error", () => {
+          // Socket errors (ECONNRESET, etc.) are handled by the 'close' event.
+        });
+
+        socket.on("close", () => {
+          // Clean up whichever map the client is in.
+          const found = clients.get(currentClient.id) ?? sockets.get(tempId);
+          if (found) {
+            clients.delete(found.id);
+            sockets.delete(tempId);
+            // Notify if this was a registered client.
+            if (found.registered) {
+              disconnectHandler?.(found);
+            }
+          }
+          // Clean up readline to prevent memory leaks.
+          rl.close();
+        });
+      });
+
+      server.on("error", (err: NodeJS.ErrnoException) => {
+        reject(err);
+      });
+
+      server.listen(DAEMON_SOCKET_PATH, () => {
+        resolve();
+      });
+    });
+
+  const stop = (): Promise<void> =>
+    new Promise((resolve) => {
+      // Close all client sockets.
+      for (const [, client] of clients) {
+        try { client.socket.destroy(); } catch { /* best-effort */ }
+      }
+      for (const [, client] of sockets) {
+        try { client.socket.destroy(); } catch { /* best-effort */ }
+      }
+      clients.clear();
+      sockets.clear();
+
+      if (server) {
+        server.close(() => {
+          // Clean up the socket file.
+          try { unlinkSync(DAEMON_SOCKET_PATH); } catch { /* ENOENT ok */ }
+          resolve();
+        });
+      } else {
+        resolve();
+      }
+    });
+
+  return {
+    start,
+    stop,
+    onMessage(handler) {
+      messageHandler = handler;
+    },
+    onConnect(handler) {
+      connectHandler = handler;
+    },
+    onDisconnect(handler) {
+      disconnectHandler = handler;
+    },
+    send(clientId, msg) {
+      const client = clients.get(clientId);
+      if (!client) return;
+      try {
+        client.socket.write(JSON.stringify(msg) + "\n");
+      } catch {
+        // Socket write error — the close handler will clean up.
+      }
+    },
+    broadcast(msg) {
+      for (const [clientId] of clients) {
+        this.send(clientId, msg);
+      }
+    },
+    disconnectClient(clientId) {
+      const client = clients.get(clientId);
+      if (!client) return;
+      client.socket.destroy();
+    },
+    clients: (): ReadonlyMap<string, ClientSocket> => clients,
+    clientCount: (): number => clients.size,
+  };
+};