oh-my-pi/packages/coding-agent/src/modes/rpc/rpc-client.ts

/**
 * RPC Client for programmatic access to the coding agent.
 *
 * Spawns the agent in RPC mode and provides a typed API for all operations.
 */

import type { ImageContent } from "@mariozechner/pi-ai";
import type { AgentEvent, AgentMessage, ThinkingLevel } from "@oh-my-pi/pi-agent-core";
import type { Subprocess } from "bun";
import type { SessionStats } from "../../core/agent-session";
import type { BashResult } from "../../core/bash-executor";
import type { CompactionResult } from "../../core/compaction/index";
import type { RpcCommand, RpcResponse, RpcSessionState } from "./rpc-types";

// ============================================================================
// Types
// ============================================================================

/** Distributive Omit that works with union types */
type DistributiveOmit<T, K extends keyof T> = T extends unknown ? Omit<T, K> : never;

/** RpcCommand without the id field (for internal send) */
type RpcCommandBody = DistributiveOmit<RpcCommand, "id">;

export interface RpcClientOptions {
	/** Path to the CLI entry point (default: searches for dist/cli.js) */
	cliPath?: string;
	/** Working directory for the agent */
	cwd?: string;
	/** Environment variables */
	env?: Record<string, string>;
	/** Provider to use */
	provider?: string;
	/** Model ID to use */
	model?: string;
	/** Additional CLI arguments */
	args?: string[];
}

export interface ModelInfo {
	provider: string;
	id: string;
	contextWindow: number;
	reasoning: boolean;
}

export type RpcEventListener = (event: AgentEvent) => void;

// ============================================================================
// RPC Client
// ============================================================================

export class RpcClient {
	private process: Subprocess | null = null;
	private lineReader: ReadableStreamDefaultReader<string> | null = null;
	private eventListeners: RpcEventListener[] = [];
	private pendingRequests: Map<string, { resolve: (response: RpcResponse) => void; reject: (error: Error) => void }> =
		new Map();
	private requestId = 0;
	private stderr = "";

	constructor(private options: RpcClientOptions = {}) {}

	/**
	 * Start the RPC agent process.
	 */
	async start(): Promise<void> {
		if (this.process) {
			throw new Error("Client already started");
		}

		const cliPath = this.options.cliPath ?? "dist/cli.js";
		const args = ["--mode", "rpc"];

		if (this.options.provider) {
			args.push("--provider", this.options.provider);
		}
		if (this.options.model) {
			args.push("--model", this.options.model);
		}
		if (this.options.args) {
			args.push(...this.options.args);
		}

		this.process = Bun.spawn(["bun", cliPath, ...args], {
			cwd: this.options.cwd,
			env: { ...process.env, ...this.options.env },
			stdin: "pipe",
			stdout: "pipe",
			stderr: "pipe",
		});

		// Collect stderr for debugging
		(async () => {
			const reader = (this.process!.stderr as ReadableStream<Uint8Array>).getReader();
			const decoder = new TextDecoder();
			while (true) {
				const { done, value } = await reader.read();
				if (done) break;
				this.stderr += decoder.decode(value);
			}
		})();

		// Set up line reader for stdout
		const textStream = (this.process.stdout as ReadableStream<Uint8Array>).pipeThrough(new TextDecoderStream());
		this.lineReader = textStream
			.pipeThrough(
				new TransformStream<string, string>({
					transform(chunk, controller) {
						const lines = chunk.split("\n");
						for (const line of lines) {
							if (line.trim()) {
								controller.enqueue(line);
							}
						}
					},
				}),
			)
			.getReader() as ReadableStreamDefaultReader<string>;

		// Process lines in background
		(async () => {
			try {
				while (true) {
					const { done, value } = await this.lineReader!.read();
					if (done) break;
					this.handleLine(value);
				}
			} catch {
				// Stream closed
			}
		})();

		// Wait a moment for process to initialize
		await new Promise((resolve) => setTimeout(resolve, 100));

		try {
			const exitCode = await Promise.race([
				this.process.exited,
				new Promise<null>((resolve) => setTimeout(() => resolve(null), 50)),
			]);
			if (exitCode !== null) {
				throw new Error(`Agent process exited immediately with code ${exitCode}. Stderr: ${this.stderr}`);
			}
		} catch {
			// Process still running, which is what we want
		}
	}

	/**
	 * Stop the RPC agent process.
	 */
	async stop(): Promise<void> {
		if (!this.process) return;

		this.lineReader?.cancel();
		this.process.kill();

		// Wait for process to exit
		await Promise.race([
			this.process.exited,
			new Promise<void>((resolve) => {
				setTimeout(() => {
					try {
						this.process?.kill(9);
					} catch {
						// Already dead
					}
					resolve();
				}, 1000);
			}),
		]);

		this.process = null;
		this.lineReader = null;
		this.pendingRequests.clear();
	}

	/**
	 * Subscribe to agent events.
	 */
	onEvent(listener: RpcEventListener): () => void {
		this.eventListeners.push(listener);
		return () => {
			const index = this.eventListeners.indexOf(listener);
			if (index !== -1) {
				this.eventListeners.splice(index, 1);
			}
		};
	}

	/**
	 * Get collected stderr output (useful for debugging).
	 */
	getStderr(): string {
		return this.stderr;
	}

	// =========================================================================
	// Command Methods
	// =========================================================================

	/**
	 * Send a prompt to the agent.
	 * Returns immediately after sending; use onEvent() to receive streaming events.
	 * Use waitForIdle() to wait for completion.
	 */
	async prompt(message: string, images?: ImageContent[]): Promise<void> {
		await this.send({ type: "prompt", message, images });
	}

	/**
	 * Queue a steering message to interrupt the agent mid-run.
	 */
	async steer(message: string): Promise<void> {
		await this.send({ type: "steer", message });
	}

	/**
	 * Queue a follow-up message to be processed after the agent finishes.
	 */
	async followUp(message: string): Promise<void> {
		await this.send({ type: "follow_up", message });
	}

	/**
	 * Abort current operation.
	 */
	async abort(): Promise<void> {
		await this.send({ type: "abort" });
	}

	/**
	 * Start a new session, optionally with parent tracking.
	 * @param parentSession - Optional parent session path for lineage tracking
	 * @returns Object with `cancelled: true` if an extension cancelled the new session
	 */
	async newSession(parentSession?: string): Promise<{ cancelled: boolean }> {
		const response = await this.send({ type: "new_session", parentSession });
		return this.getData(response);
	}

	/**
	 * Get current session state.
	 */
	async getState(): Promise<RpcSessionState> {
		const response = await this.send({ type: "get_state" });
		return this.getData(response);
	}

	/**
	 * Set model by provider and ID.
	 */
	async setModel(provider: string, modelId: string): Promise<{ provider: string; id: string }> {
		const response = await this.send({ type: "set_model", provider, modelId });
		return this.getData(response);
	}

	/**
	 * Cycle to next model.
	 */
	async cycleModel(): Promise<{
		model: { provider: string; id: string };
		thinkingLevel: ThinkingLevel;
		isScoped: boolean;
	} | null> {
		const response = await this.send({ type: "cycle_model" });
		return this.getData(response);
	}

	/**
	 * Get list of available models.
	 */
	async getAvailableModels(): Promise<ModelInfo[]> {
		const response = await this.send({ type: "get_available_models" });
		return this.getData<{ models: ModelInfo[] }>(response).models;
	}

	/**
	 * Set thinking level.
	 */
	async setThinkingLevel(level: ThinkingLevel): Promise<void> {
		await this.send({ type: "set_thinking_level", level });
	}

	/**
	 * Cycle thinking level.
	 */
	async cycleThinkingLevel(): Promise<{ level: ThinkingLevel } | null> {
		const response = await this.send({ type: "cycle_thinking_level" });
		return this.getData(response);
	}

	/**
	 * Set steering mode.
	 */
	async setSteeringMode(mode: "all" | "one-at-a-time"): Promise<void> {
		await this.send({ type: "set_steering_mode", mode });
	}

	/**
	 * Set follow-up mode.
	 */
	async setFollowUpMode(mode: "all" | "one-at-a-time"): Promise<void> {
		await this.send({ type: "set_follow_up_mode", mode });
	}

	/**
	 * Compact session context.
	 */
	async compact(customInstructions?: string): Promise<CompactionResult> {
		const response = await this.send({ type: "compact", customInstructions });
		return this.getData(response);
	}

	/**
	 * Set auto-compaction enabled/disabled.
	 */
	async setAutoCompaction(enabled: boolean): Promise<void> {
		await this.send({ type: "set_auto_compaction", enabled });
	}

	/**
	 * Set auto-retry enabled/disabled.
	 */
	async setAutoRetry(enabled: boolean): Promise<void> {
		await this.send({ type: "set_auto_retry", enabled });
	}

	/**
	 * Abort in-progress retry.
	 */
	async abortRetry(): Promise<void> {
		await this.send({ type: "abort_retry" });
	}

	/**
	 * Execute a bash command.
	 */
	async bash(command: string): Promise<BashResult> {
		const response = await this.send({ type: "bash", command });
		return this.getData(response);
	}

	/**
	 * Abort running bash command.
	 */
	async abortBash(): Promise<void> {
		await this.send({ type: "abort_bash" });
	}

	/**
	 * Get session statistics.
	 */
	async getSessionStats(): Promise<SessionStats> {
		const response = await this.send({ type: "get_session_stats" });
		return this.getData(response);
	}

	/**
	 * Export session to HTML.
	 */
	async exportHtml(outputPath?: string): Promise<{ path: string }> {
		const response = await this.send({ type: "export_html", outputPath });
		return this.getData(response);
	}

	/**
	 * Switch to a different session file.
	 * @returns Object with `cancelled: true` if an extension cancelled the switch
	 */
	async switchSession(sessionPath: string): Promise<{ cancelled: boolean }> {
		const response = await this.send({ type: "switch_session", sessionPath });
		return this.getData(response);
	}

	/**
	 * Branch from a specific message.
	 * @returns Object with `text` (the message text) and `cancelled` (if extension cancelled)
	 */
	async branch(entryId: string): Promise<{ text: string; cancelled: boolean }> {
		const response = await this.send({ type: "branch", entryId });
		return this.getData(response);
	}

	/**
	 * Get messages available for branching.
	 */
	async getBranchMessages(): Promise<Array<{ entryId: string; text: string }>> {
		const response = await this.send({ type: "get_branch_messages" });
		return this.getData<{ messages: Array<{ entryId: string; text: string }> }>(response).messages;
	}

	/**
	 * Get text of last assistant message.
	 */
	async getLastAssistantText(): Promise<string | null> {
		const response = await this.send({ type: "get_last_assistant_text" });
		return this.getData<{ text: string | null }>(response).text;
	}

	/**
	 * Get all messages in the session.
	 */
	async getMessages(): Promise<AgentMessage[]> {
		const response = await this.send({ type: "get_messages" });
		return this.getData<{ messages: AgentMessage[] }>(response).messages;
	}

	// =========================================================================
	// Helpers
	// =========================================================================

	/**
	 * Wait for agent to become idle (no streaming).
	 * Resolves when agent_end event is received.
	 */
	waitForIdle(timeout = 60000): Promise<void> {
		return new Promise((resolve, reject) => {
			const timer = setTimeout(() => {
				unsubscribe();
				reject(new Error(`Timeout waiting for agent to become idle. Stderr: ${this.stderr}`));
			}, timeout);

			const unsubscribe = this.onEvent((event) => {
				if (event.type === "agent_end") {
					clearTimeout(timer);
					unsubscribe();
					resolve();
				}
			});
		});
	}

	/**
	 * Collect events until agent becomes idle.
	 */
	collectEvents(timeout = 60000): Promise<AgentEvent[]> {
		return new Promise((resolve, reject) => {
			const events: AgentEvent[] = [];
			const timer = setTimeout(() => {
				unsubscribe();
				reject(new Error(`Timeout collecting events. Stderr: ${this.stderr}`));
			}, timeout);

			const unsubscribe = this.onEvent((event) => {
				events.push(event);
				if (event.type === "agent_end") {
					clearTimeout(timer);
					unsubscribe();
					resolve(events);
				}
			});
		});
	}

	/**
	 * Send prompt and wait for completion, returning all events.
	 */
	async promptAndWait(message: string, images?: ImageContent[], timeout = 60000): Promise<AgentEvent[]> {
		const eventsPromise = this.collectEvents(timeout);
		await this.prompt(message, images);
		return eventsPromise;
	}

	// =========================================================================
	// Internal
	// =========================================================================

	private handleLine(line: string): void {
		try {
			const data = JSON.parse(line);

			// Check if it's a response to a pending request
			if (data.type === "response" && data.id && this.pendingRequests.has(data.id)) {
				const pending = this.pendingRequests.get(data.id)!;
				this.pendingRequests.delete(data.id);
				pending.resolve(data as RpcResponse);
				return;
			}

			// Otherwise it's an event
			for (const listener of this.eventListeners) {
				listener(data as AgentEvent);
			}
		} catch {
			// Ignore non-JSON lines
		}
	}

	private send(command: RpcCommandBody): Promise<RpcResponse> {
		if (!this.process?.stdin) {
			throw new Error("Client not started");
		}

		const id = `req_${++this.requestId}`;
		const fullCommand = { ...command, id } as RpcCommand;

		return new Promise((resolve, reject) => {
			const timeout = setTimeout(() => {
				this.pendingRequests.delete(id);
				reject(new Error(`Timeout waiting for response to ${command.type}. Stderr: ${this.stderr}`));
			}, 30000);

			this.pendingRequests.set(id, {
				resolve: (response) => {
					clearTimeout(timeout);
					resolve(response);
				},
				reject: (error) => {
					clearTimeout(timeout);
					reject(error);
				},
			});

			// Write to stdin after registering the handler
			const stdin = this.process!.stdin as import("bun").FileSink;
			stdin.write(new TextEncoder().encode(`${JSON.stringify(fullCommand)}\n`));
			// flush() returns number | Promise<number> - handle both cases
			const flushResult = stdin.flush();
			if (flushResult instanceof Promise) {
				flushResult.catch((err: Error) => {
					this.pendingRequests.delete(id);
					clearTimeout(timeout);
					reject(err);
				});
			}
		});
	}

	private getData<T>(response: RpcResponse): T {
		if (!response.success) {
			const errorResponse = response as Extract<RpcResponse, { success: false }>;
			throw new Error(errorResponse.error);
		}
		// Type assertion: we trust response.data matches T based on the command sent.
		// This is safe because each public method specifies the correct T for its command.
		const successResponse = response as Extract<RpcResponse, { success: true; data: unknown }>;
		return successResponse.data as T;
	}
}