zerobyte/app/server/modules/agents/controller/session.ts

import { Deferred, Effect, Queue, Ref, type Scope } from "effect";
import type { AgentKind } from "../../../db/schema";
import {
	createControllerMessage,
	parseAgentMessage,
	type AgentMessage,
	type BackupCancelPayload,
	type BackupRunPayload,
	type ControllerWireMessage,
	type VolumeCommand,
	type VolumeCommandResponsePayload,
} from "@zerobyte/contracts/agent-protocol";
import { logger } from "@zerobyte/core/node";
import { toMessage } from "@zerobyte/core/utils";

export type AgentConnectionData = {
	id: string;
	agentId: string;
	organizationId: string | null;
	agentName: string;
	agentKind: AgentKind;
};

type AgentSocket = Bun.ServerWebSocket<AgentConnectionData>;

type SessionState = {
	isReady: boolean;
	lastSeenAt: number | null;
	lastPongAt: number | null;
};

type PendingCommand = {
	deferred: Deferred.Deferred<VolumeCommandResponsePayload, Error>;
	description: string;
};

export type ControllerAgentSessionEvent =
	| Exclude<AgentMessage, { type: "volume.commandResult" }>
	| {
			type: "agent.disconnected";
	  };

export type ControllerAgentSession = {
	readonly connectionId: string;
	handleMessage: (data: string) => Effect.Effect<void>;
	sendBackup: (payload: BackupRunPayload) => Effect.Effect<boolean>;
	sendBackupCancel: (payload: BackupCancelPayload) => Effect.Effect<boolean>;
	runVolumeCommand: (command: VolumeCommand) => Effect.Effect<VolumeCommandResponsePayload, Error>;
	isReady: () => Effect.Effect<boolean>;
	run: Effect.Effect<void, never, Scope.Scope>;
};

export const createControllerAgentSession = (
	socket: AgentSocket,
	onEvent: (event: ControllerAgentSessionEvent) => Effect.Effect<void>,
): Effect.Effect<ControllerAgentSession, never, Scope.Scope> =>
	Effect.gen(function* () {
		let isClosed = false;
		const outboundQueue = yield* Queue.bounded<ControllerWireMessage>(64);
		const pendingCommands = yield* Ref.make(new Map<string, PendingCommand>());
		const state = yield* Ref.make<SessionState>({
			isReady: false,
			lastSeenAt: null,
			lastPongAt: null,
		});

		const offerOutbound = (message: ControllerWireMessage) =>
			Queue.offer(outboundQueue, message).pipe(
				Effect.catchAllCause((cause) =>
					Effect.sync(() => {
						logger.error(`Failed to queue outbound message for agent ${socket.data.agentId}: ${toMessage(cause)}`);
						return false;
					}),
				),
			);

		const updateState = (update: (current: SessionState) => SessionState) => Ref.update(state, update);

		const setPendingCommand = (commandId: string, pending: PendingCommand) =>
			Ref.update(pendingCommands, (current) => new Map(current).set(commandId, pending));

		const removePendingCommand = (commandId: string) =>
			Ref.modify(pendingCommands, (current) => {
				const pending = current.get(commandId) ?? null;
				const next = new Map(current);
				next.delete(commandId);
				return [pending, next];
			});

		const rejectPendingCommands = Effect.gen(function* () {
			const pendingCommandEntries = yield* Ref.get(pendingCommands);
			yield* Ref.set(pendingCommands, new Map());

			for (const pending of pendingCommandEntries.values()) {
				yield* Deferred.fail(
					pending.deferred,
					new Error(`Agent session closed before ${pending.description} completed`),
				);
			}
		});

		const releaseSession = Effect.gen(function* () {
			const disconnectedAt = Date.now();
			yield* updateState((current) => ({ ...current, isReady: false, lastSeenAt: disconnectedAt }));
			yield* rejectPendingCommands;
			yield* onEvent({ type: "agent.disconnected" });

			yield* Queue.shutdown(outboundQueue);
		});

		const closeSession = () =>
			Effect.suspend(() => {
				if (isClosed) {
					return Effect.sync(() => undefined);
				}

				isClosed = true;
				return releaseSession;
			});

		yield* Effect.addFinalizer(() => closeSession());

		const handleSendFailure = (reason: string) => {
			return Effect.gen(function* () {
				logger.error(
					`Closing session for agent ${socket.data.agentId} on ${socket.data.id} after an outbound websocket send failed: ${reason}`,
				);

				yield* Effect.sync(() => socket.close());
				yield* closeSession();
			});
		};

		const run = Effect.gen(function* () {
			yield* Effect.forkScoped(
				Effect.forever(
					Effect.gen(function* () {
						const message = yield* Queue.take(outboundQueue);

						const sendResult = yield* Effect.try({
							try: () => socket.send(message),
							catch: (error) => toMessage(error),
						});

						if (sendResult === 0) {
							yield* handleSendFailure("connection issue");
						}
					}).pipe(Effect.catchAll((reason) => handleSendFailure(reason))),
				),
			);

			yield* Effect.forkScoped(
				Effect.forever(
					Effect.gen(function* () {
						yield* Effect.sleep("15 seconds");
						yield* Queue.offer(
							outboundQueue,
							createControllerMessage("heartbeat.ping", {
								sentAt: Date.now(),
							}),
						);
					}),
				),
			);

			return yield* Effect.never;
		});

		const handleVolumeCommandResult = (payload: VolumeCommandResponsePayload) =>
			Effect.gen(function* () {
				const pending = yield* removePendingCommand(payload.commandId);
				if (!pending) {
					yield* logger.effect.warn(`Received response for unknown volume command ${payload.commandId}`);
					return;
				}

				yield* Deferred.succeed(pending.deferred, payload);
			});

		const handleAgentMessage = (message: AgentMessage) =>
			Effect.gen(function* () {
				switch (message.type) {
					case "agent.ready": {
						const readyAt = Date.now();
						yield* updateState((current) => ({ ...current, isReady: true, lastSeenAt: readyAt }));
						yield* logger.effect.info(`Agent "${socket.data.agentName}" (${socket.data.agentId}) is ready`);
						yield* onEvent(message);
						break;
					}
					case "heartbeat.pong": {
						const seenAt = Date.now();
						yield* updateState((current) => ({ ...current, lastSeenAt: seenAt, lastPongAt: message.payload.sentAt }));
						yield* onEvent(message);
						break;
					}
					case "volume.commandResult": {
						yield* handleVolumeCommandResult(message.payload);
						break;
					}
					default: {
						yield* onEvent(message);
						break;
					}
				}
			});

		return {
			connectionId: socket.data.id,
			handleMessage: (data: string) => {
				return Effect.gen(function* () {
					const parsed = parseAgentMessage(data);

					if (parsed === null) {
						yield* logger.effect.warn(`Invalid JSON from agent ${socket.data.agentId}`);
						return;
					}

					if (!parsed.success) {
						yield* logger.effect.warn(`Invalid agent message from ${socket.data.agentId}: ${parsed.error.message}`);
						return;
					}

					yield* handleAgentMessage(parsed.data);
				});
			},
			sendBackup: (payload) => offerOutbound(createControllerMessage("backup.run", payload)),
			sendBackupCancel: (payload) => offerOutbound(createControllerMessage("backup.cancel", payload)),
			runVolumeCommand: (command) =>
				Effect.gen(function* () {
					const commandId = Bun.randomUUIDv7();
					const description = `volume command ${command.name}`;
					const deferred = yield* Deferred.make<VolumeCommandResponsePayload, Error>();
					yield* setPendingCommand(commandId, { deferred, description });

					const queued = yield* offerOutbound(createControllerMessage("volume.command", { commandId, command }));
					if (!queued) {
						yield* removePendingCommand(commandId);
						return yield* Effect.fail(new Error(`Failed to queue volume command ${command.name}`));
					}

					return yield* Deferred.await(deferred).pipe(
						Effect.timeoutFail({
							duration: "60 seconds",
							onTimeout: () => new Error(`Volume command ${command.name} timed out`),
						}),
						Effect.ensuring(removePendingCommand(commandId)),
					);
				}),
			isReady: () => Ref.get(state).pipe(Effect.map((current) => current.isReady)),
			run,
		};
	});