npm package: @push.rocks/smartrust
Description: a bridge between JS engines and rust
Author: Task Venture Capital GmbH
Latest version: 1.3.2

# @push.rocks/smartrust

A type-safe, production-ready bridge between TypeScript and Rust binaries — with support for **stdio** (child process) and **socket** (Unix socket / Windows named pipe) transports, request/response, streaming, and event patterns.

## Issue Reporting and Security

For reporting bugs, issues, or security vulnerabilities, please visit [community.foss.global/](https://community.foss.global/). This is the central community hub for all issue reporting. Developers who sign and comply with our contribution agreement and go through identification can also get a [code.foss.global/](https://code.foss.global/) account to submit Pull Requests directly.

## Install 📦

```bash
npm install @push.rocks/smartrust
# or
pnpm install @push.rocks/smartrust
```

## Overview 🔭

`@push.rocks/smartrust` provides a complete bridge for TypeScript applications that need to communicate with Rust binaries. It handles the entire lifecycle — binary discovery, process spawning **or socket connection**, request/response correlation, **streaming responses**, event pub/sub, and graceful shutdown — so you can focus on your command definitions instead of IPC plumbing.

### Two Transport Modes 🔌

| Mode | Method | Use Case |
|------|--------|----------|
| **Stdio** | `bridge.spawn()` | Spawn the Rust binary as a child process. Communicate via stdin/stdout. |
| **Socket** | `bridge.connect(path)` | Connect to an **already-running** Rust daemon via Unix socket or Windows named pipe. |

The JSON protocol is identical in both modes — only the transport layer changes. Socket mode enables use cases where the Rust binary runs as a **privileged system service** (e.g., a VPN daemon needing root for TUN devices, a network proxy binding to privileged ports) while the TypeScript app connects to it unprivileged.

### Why? 🤔

If you're integrating Rust into a Node.js project, you'll inevitably need:
- A way to **find** the compiled Rust binary across different environments (dev, CI, production, platform packages)
- A way to **spawn it** or **connect to it** and establish reliable two-way communication
- **Type-safe** request/response patterns with proper error handling
- **Streaming responses** for progressive data processing, log tailing, or chunked transfers
- **Event streaming** from Rust to TypeScript
- **Graceful lifecycle management** (ready detection, clean shutdown, auto-reconnection)

`smartrust` wraps all of this into a clean API: `RustBridge`, `RustBinaryLocator`, `StreamingResponse`, and pluggable transports.

## Usage 🚀

### The IPC Protocol

`smartrust` uses a simple, newline-delimited JSON protocol:

| Direction | Format | Description |
|-----------|--------|-------------|
| **TS → Rust** (Request) | `{"id": "req_1", "method": "start", "params": {...}}` | Command with unique ID |
| **Rust → TS** (Response) | `{"id": "req_1", "success": true, "result": {...}}` | Final response correlated by ID |
| **Rust → TS** (Error) | `{"id": "req_1", "success": false, "error": "msg"}` | Error correlated by ID |
| **Rust → TS** (Stream Chunk) | `{"id": "req_1", "stream": true, "data": {...}}` | Intermediate chunk (zero or more) |
| **Rust → TS** (Event) | `{"event": "ready", "data": {...}}` | Unsolicited event (no ID) |

This protocol works identically over stdio and socket transports. Your Rust binary reads JSON lines from one end and writes JSON lines to the other. That's it.

### Defining Your Commands

Start by defining a type map of commands your Rust binary supports:

```typescript
import { RustBridge } from '@push.rocks/smartrust';

// Define your command types
type TMyCommands = {
  start:      { params: { port: number; host: string }; result: { pid: number } };
  stop:       { params: {};                             result: void };
  getMetrics: { params: {};                             result: { connections: number; uptime: number } };
  reload:     { params: { configPath: string };         result: void };
};
```

### Stdio Mode — Spawn a Child Process

This is the classic mode. The bridge spawns the Rust binary and communicates via stdin/stdout:

```typescript
const bridge = new RustBridge<TMyCommands>({
  binaryName: 'my-rust-server',
  envVarName: 'MY_SERVER_BINARY',             // optional: env var override
  platformPackagePrefix: '@myorg/my-server',  // optional: platform npm packages
});

// Spawn the binary and wait for it to signal readiness
const ok = await bridge.spawn();
if (!ok) {
  console.error('Failed to start Rust binary');
  process.exit(1);
}

// Send type-safe commands — params and return types are inferred!
const { pid } = await bridge.sendCommand('start', { port: 8080, host: '0.0.0.0' });
console.log(`Server started with PID ${pid}`);

const metrics = await bridge.sendCommand('getMetrics', {});
console.log(`Active connections: ${metrics.connections}`);

// Listen for events from Rust
bridge.on('management:configChanged', (data) => {
  console.log('Config was changed:', data);
});

// Clean shutdown (SIGTERM → SIGKILL after 5s)
bridge.kill();
```

### Socket Mode — Connect to a Running Daemon 🔗

When the Rust binary runs as a system service (e.g., via `systemd`, `launchd`, or a Windows Service), use `connect()` to talk to it over a Unix socket or named pipe:

```typescript
const bridge = new RustBridge<TMyCommands>({
  binaryName: 'my-daemon',  // used for logging / error messages
});

// Connect to the daemon's management socket
const ok = await bridge.connect('/var/run/my-daemon.sock');
if (!ok) {
  console.error('Failed to connect to daemon');
  process.exit(1);
}

// Same API as stdio mode — completely transparent!
const { pid } = await bridge.sendCommand('start', { port: 8080, host: '0.0.0.0' });
const metrics = await bridge.sendCommand('getMetrics', {});

// kill() closes the socket — it does NOT kill the daemon
bridge.kill();
```

#### Auto-Reconnect

For long-running applications, enable automatic reconnection with exponential backoff:

```typescript
const ok = await bridge.connect('/var/run/my-daemon.sock', {
  autoReconnect: true,          // reconnect on unexpected disconnect
  reconnectBaseDelayMs: 100,    // initial retry delay (doubles each attempt)
  reconnectMaxDelayMs: 30000,   // max retry delay cap
  maxReconnectAttempts: 10,     // give up after 10 attempts
});

// Listen for reconnection events
bridge.on('reconnected', () => {
  console.log('Reconnected to daemon!');
});
```

#### Platform Notes

| Platform | Socket Path Format | Example |
|----------|-------------------|---------|
| **Linux** | `/var/run/<name>.sock` or `$XDG_RUNTIME_DIR/<name>.sock` | `/var/run/my-daemon.sock` |
| **macOS** | `/var/run/<name>.sock` | `/var/run/my-daemon.sock` |
| **Windows** | `\\.\pipe\<name>` | `\\.\pipe\my-daemon` |

Node.js `net.connect()` handles all formats transparently — no platform-specific code needed.

### Streaming Commands 🌊

For commands where the Rust binary sends a series of chunks before a final result, use `sendCommandStreaming`. This is perfect for progressive data processing, log tailing, search results, or any scenario where you want incremental output.

#### Defining Streaming Commands

Add a `chunk` field to your command type definition to mark it as streamable:

```typescript
type TMyCommands = {
  // Regular command (request → response)
  ping:        { params: {}; result: { pong: boolean } };

  // Streaming command (request → chunks... → final result)
  processData: { params: { count: number }; chunk: { index: number; progress: number }; result: { totalProcessed: number } };
  tailLogs:    { params: { lines: number }; chunk: string; result: { linesRead: number } };
};
```

#### Consuming Streams

```typescript
// Returns a StreamingResponse immediately (does NOT block)
const stream = bridge.sendCommandStreaming('processData', { count: 1000 });

// Consume chunks with for-await-of
for await (const chunk of stream) {
  console.log(`Processing item ${chunk.index}, progress: ${chunk.progress}%`);
}

// Get the final result after all chunks are consumed
const result = await stream.result;
console.log(`Done! Processed ${result.totalProcessed} items`);
```

#### Error Handling in Streams

Errors propagate to both the iterator and the `.result` promise:

```typescript
const stream = bridge.sendCommandStreaming('processData', { count: 100 });

try {
  for await (const chunk of stream) {
    console.log(chunk);
  }
} catch (err) {
  console.error('Stream failed:', err.message);
}

// .result also rejects on error
try {
  await stream.result;
} catch (err) {
  console.error('Same error here:', err.message);
}
```

#### Stream Timeout

By default, streaming commands use the same timeout as regular commands (`requestTimeoutMs`). The timeout **resets on each chunk received**, so it acts as an inactivity timeout rather than an absolute timeout. You can configure it separately:

```typescript
const bridge = new RustBridge<TMyCommands>({
  binaryName: 'my-server',
  requestTimeoutMs: 30000,   // regular command timeout: 30s
  streamTimeoutMs: 60000,    // streaming inactivity timeout: 60s
});
```

#### Implementing Streaming on the Rust Side

Your Rust binary sends stream chunks by writing lines with `"stream": true` before the final response:

```rust
// For each chunk:
println!(r#"{{"id":"{}","stream":true,"data":{{"index":{},"progress":{}}}}}"#, req.id, i, pct);
io::stdout().flush().unwrap();

// When done, send the final response (same as non-streaming):
println!(r#"{{"id":"{}","success":true,"result":{{"totalProcessed":{}}}}}"#, req.id, total);
io::stdout().flush().unwrap();
```

### Binary Locator 🔍

The `RustBinaryLocator` searches for your binary using a priority-ordered strategy:

| Priority | Source | Description |
|----------|--------|-------------|
| 1 | `binaryPath` option | Explicit path — skips all other search |
| 2 | Environment variable | e.g. `MY_SERVER_BINARY=/usr/local/bin/server` |
| 3 | Platform npm package | e.g. `@myorg/my-server-linux-x64/my-rust-server` |
| 4 | Local dev paths | `./rust/target/release/<name>` and `./rust/target/debug/<name>` |
| 5 | System PATH | Standard `$PATH` lookup |

You can also use the locator standalone:

```typescript
import { RustBinaryLocator } from '@push.rocks/smartrust';

const locator = new RustBinaryLocator({
  binaryName: 'my-rust-server',
  envVarName: 'MY_SERVER_BINARY',
  localPaths: ['/opt/myapp/bin/server'],  // custom search paths
});

const binaryPath = await locator.findBinary();
// Result is cached — call clearCache() to force re-search
```

### Configuration Reference ⚙️

The `RustBridge` constructor accepts an `IRustBridgeOptions` object:

```typescript
const bridge = new RustBridge<TMyCommands>({
  // --- Binary Locator Options ---
  binaryName: 'my-server',                    // required: name of the binary
  binaryPath: '/explicit/path/to/binary',     // optional: skip search entirely
  envVarName: 'MY_SERVER_BINARY',             // optional: env var for path override
  platformPackagePrefix: '@myorg/my-server',  // optional: platform npm package prefix
  localPaths: ['./build/server'],             // optional: custom local search paths
  searchSystemPath: true,                     // optional: search $PATH (default: true)

  // --- Bridge Options ---
  cliArgs: ['--management'],                  // optional: args passed to binary (default: ['--management'])
  requestTimeoutMs: 30000,                    // optional: per-request timeout (default: 30000)
  streamTimeoutMs: 30000,                     // optional: streaming inactivity timeout (default: requestTimeoutMs)
  readyTimeoutMs: 10000,                      // optional: ready event timeout (default: 10000)
  maxPayloadSize: 50 * 1024 * 1024,           // optional: max message size in bytes (default: 50MB)
  env: { RUST_LOG: 'debug' },                 // optional: extra env vars for the child process
  readyEventName: 'ready',                    // optional: name of the ready event (default: 'ready')
  logger: myLogger,                           // optional: logger implementing IRustBridgeLogger
});
```

Socket connection options (passed to `bridge.connect()`):

```typescript
interface ISocketConnectOptions {
  autoReconnect?: boolean;         // default: false
  reconnectBaseDelayMs?: number;   // default: 100
  reconnectMaxDelayMs?: number;    // default: 30000
  maxReconnectAttempts?: number;   // default: 10
}
```

### Events 📡

`RustBridge` extends `EventEmitter` and emits the following events:

| Event | Payload | Description |
|-------|---------|-------------|
| `ready` | — | Bridge connected and binary reported ready |
| `exit` | `(code, signal)` | Transport closed (process exited or socket disconnected) |
| `stderr` | `string` | A line from the binary's stderr (stdio mode only) |
| `reconnected` | — | Socket transport reconnected after unexpected disconnect |
| `management:<name>` | `any` | Custom event from Rust (e.g. `management:configChanged`) |

### Custom Logger 📝

Plug in your own logger by implementing the `IRustBridgeLogger` interface:

```typescript
import type { IRustBridgeLogger } from '@push.rocks/smartrust';

const logger: IRustBridgeLogger = {
  log(level: string, message: string, data?: Record<string, any>) {
    console.log(`[${level}] ${message}`, data || '');
  },
};

const bridge = new RustBridge<TMyCommands>({
  binaryName: 'my-server',
  logger,
});
```

### Writing the Rust Side 🦀

Your Rust binary needs to implement a simple protocol. The transport (stdio or socket) doesn't change the message format — only how connections are established.

#### Stdio Mode (Child Process)

1. **On startup**, write a ready event to stdout:
   ```
   {"event":"ready","data":{"version":"1.0.0"}}\n
   ```

2. **Read JSON lines from stdin**, parse each as `{"id": "...", "method": "...", "params": {...}}`

3. **Write JSON responses to stdout**, each as `{"id": "...", "success": true, "result": {...}}\n`

4. **For streaming commands**, write zero or more `{"id": "...", "stream": true, "data": {...}}\n` chunks before the final response

5. **Emit events** anytime by writing `{"event": "name", "data": {...}}\n` to stdout

6. **Use stderr** for logging — it won't interfere with the IPC protocol

#### Socket Mode (Daemon)

1. **Listen** on a Unix socket (e.g., `/var/run/my-daemon.sock`) or Windows named pipe
2. **On each new client connection**, send the `{"event":"ready","data":{...}}\n` event
3. Read/write JSON lines on the socket (same protocol as stdio)
4. Support multiple concurrent clients — each connection is independent

Here's a minimal Rust skeleton (stdio mode):

```rust
use serde::{Deserialize, Serialize};
use std::io::{self, BufRead, Write};

#[derive(Deserialize)]
struct Request {
    id: String,
    method: String,
    params: serde_json::Value,
}

#[derive(Serialize)]
struct Response {
    id: String,
    success: bool,
    #[serde(skip_serializing_if = "Option::is_none")]
    result: Option<serde_json::Value>,
    #[serde(skip_serializing_if = "Option::is_none")]
    error: Option<String>,
}

#[derive(Serialize)]
struct StreamChunk {
    id: String,
    stream: bool,
    data: serde_json::Value,
}

fn main() {
    // Signal ready
    println!(r#"{{"event":"ready","data":{{"version":"1.0.0"}}}}"#);
    io::stdout().flush().unwrap();

    let stdin = io::stdin();
    for line in stdin.lock().lines() {
        let line = line.unwrap();
        let req: Request = serde_json::from_str(&line).unwrap();

        match req.method.as_str() {
            "ping" => {
                let resp = Response {
                    id: req.id,
                    success: true,
                    result: Some(serde_json::json!({"pong": true})),
                    error: None,
                };
                println!("{}", serde_json::to_string(&resp).unwrap());
                io::stdout().flush().unwrap();
            }
            "processData" => {
                let count = req.params["count"].as_u64().unwrap_or(0);
                // Send stream chunks
                for i in 0..count {
                    let chunk = StreamChunk {
                        id: req.id.clone(),
                        stream: true,
                        data: serde_json::json!({"index": i, "progress": ((i+1) * 100 / count)}),
                    };
                    println!("{}", serde_json::to_string(&chunk).unwrap());
                    io::stdout().flush().unwrap();
                }
                // Send final response
                let resp = Response {
                    id: req.id,
                    success: true,
                    result: Some(serde_json::json!({"totalProcessed": count})),
                    error: None,
                };
                println!("{}", serde_json::to_string(&resp).unwrap());
                io::stdout().flush().unwrap();
            }
            _ => {
                let resp = Response {
                    id: req.id,
                    success: false,
                    result: None,
                    error: Some(format!("Unknown method: {}", req.method)),
                };
                println!("{}", serde_json::to_string(&resp).unwrap());
                io::stdout().flush().unwrap();
            }
        }
    }
}
```

## Architecture 🏗️

```
┌──────────────────────────────────────────────────────┐
│                    RustBridge<T>                      │
│  (protocol layer: handleLine, sendCommand, events)   │
├──────────────┬───────────────────────────────────────┤
│ StdioTransport │         SocketTransport             │
│  spawn() +     │   net.connect() + auto-reconnect    │
│  stdin/stdout  │   Unix socket / named pipe          │
├──────────────┴───────────────────────────────────────┤
│               IRustTransport interface               │
│         connect() / write() / disconnect()           │
├──────────────────────────────────────────────────────┤
│       LineScanner (shared newline scanner)            │
├──────────────────────────────────────────────────────┤
│              RustBinaryLocator                        │
│  (binary search — stdio mode only)                   │
└──────────────────────────────────────────────────────┘
```

- **`RustBridge`** — The main class. Protocol-level logic (JSON parsing, request correlation, streaming, events) is transport-agnostic.
- **`StdioTransport`** — Spawns a child process, manages stdin/stdout/stderr, handles SIGTERM/SIGKILL.
- **`SocketTransport`** — Connects to an existing Unix socket or named pipe, with optional auto-reconnect and exponential backoff.
- **`LineScanner`** — Shared buffer-based newline scanner used by both transports for efficient message framing.
- **`RustBinaryLocator`** — Priority-ordered binary search (used by stdio mode only).

## API Reference 📖

### `RustBridge<TCommands>`

| Method / Property | Signature | Description |
|---|---|---|
| `constructor` | `new RustBridge<T>(options: IRustBridgeOptions)` | Create a new bridge instance |
| `spawn()` | `Promise<boolean>` | **Stdio mode**: Spawn the binary and wait for ready; returns `false` on failure |
| `connect(socketPath, options?)` | `Promise<boolean>` | **Socket mode**: Connect to a running daemon; returns `false` on failure |
| `sendCommand(method, params)` | `Promise<TCommands[K]['result']>` | Send a typed command and await the response |
| `sendCommandStreaming(method, params)` | `StreamingResponse<TChunk, TResult>` | Send a streaming command; returns immediately |
| `kill()` | `void` | Stdio: SIGTERM the process, SIGKILL after 5s. Socket: close the connection (daemon stays alive) |
| `running` | `boolean` | Whether the bridge is currently connected and ready |

### `StreamingResponse<TChunk, TResult>`

| Method / Property | Type | Description |
|---|---|---|
| `[Symbol.asyncIterator]()` | `AsyncIterator<TChunk>` | Enables `for await...of` consumption of chunks |
| `result` | `Promise<TResult>` | Resolves with the final result after stream ends |

### `RustBinaryLocator`

| Method / Property | Signature | Description |
|---|---|---|
| `constructor` | `new RustBinaryLocator(options: IBinaryLocatorOptions, logger?)` | Create a locator instance |
| `findBinary()` | `Promise<string \| null>` | Find the binary using the priority search; result is cached |
| `clearCache()` | `void` | Clear the cached path to force a fresh search |

### `StdioTransport`

| Method / Property | Signature | Description |
|---|---|---|
| `constructor` | `new StdioTransport(options: IStdioTransportOptions)` | Create a stdio transport |
| `connect()` | `Promise<void>` | Spawn the child process |
| `write(data)` | `Promise<void>` | Write to stdin with backpressure handling |
| `disconnect()` | `void` | Kill the process (SIGTERM → SIGKILL after 5s) |
| `connected` | `boolean` | Whether the process is running |

### `SocketTransport`

| Method / Property | Signature | Description |
|---|---|---|
| `constructor` | `new SocketTransport(options: ISocketTransportOptions)` | Create a socket transport |
| `connect()` | `Promise<void>` | Connect to the Unix socket / named pipe |
| `write(data)` | `Promise<void>` | Write to socket with backpressure handling |
| `disconnect()` | `void` | Close the socket (does not kill the daemon) |
| `connected` | `boolean` | Whether the socket is connected |

### `LineScanner`

| Method / Property | Signature | Description |
|---|---|---|
| `constructor` | `new LineScanner(maxPayloadSize, logger)` | Create a line scanner |
| `push(chunk, onLine)` | `void` | Feed a `Buffer` chunk; calls `onLine` for each complete line |
| `clear()` | `void` | Reset the internal buffer |

### Exported Interfaces & Types

| Interface / Type | Description |
|---|---|
| `IRustBridgeOptions` | Full configuration for `RustBridge` |
| `IBinaryLocatorOptions` | Configuration for `RustBinaryLocator` |
| `ISocketConnectOptions` | Socket connection options (reconnect settings) |
| `IRustBridgeLogger` | Logger interface: `{ log(level, message, data?) }` |
| `IRustTransport` | Transport interface (extends `EventEmitter`) |
| `IManagementRequest` | IPC request shape: `{ id, method, params }` |
| `IManagementResponse` | IPC response shape: `{ id, success, result?, error? }` |
| `IManagementEvent` | IPC event shape: `{ event, data }` |
| `IManagementStreamChunk` | IPC stream chunk shape: `{ id, stream: true, data }` |
| `ICommandDefinition` | Single command definition: `{ params, result }` |
| `TCommandMap` | `Record<string, ICommandDefinition>` |
| `TStreamingCommandKeys<T>` | Extracts keys from a command map that have a `chunk` field |
| `TExtractChunk<T>` | Extracts the chunk type from a streaming command definition |

## License and Legal Information

This repository contains open-source code licensed under the MIT License. A copy of the license can be found in the [LICENSE](./LICENSE) file.

**Please note:** The MIT License does not grant permission to use the trade names, trademarks, service marks, or product names of the project, except as required for reasonable and customary use in describing the origin of the work and reproducing the content of the NOTICE file.

### Trademarks

This project is owned and maintained by Task Venture Capital GmbH. The names and logos associated with Task Venture Capital GmbH and any related products or services are trademarks of Task Venture Capital GmbH or third parties, and are not included within the scope of the MIT license granted herein.

Use of these trademarks must comply with Task Venture Capital GmbH's Trademark Guidelines or the guidelines of the respective third-party owners, and any usage must be approved in writing. Third-party trademarks used herein are the property of their respective owners and used only in a descriptive manner, e.g. for an implementation of an API or similar.

### Company Information

Task Venture Capital GmbH
Registered at District Court Bremen HRB 35230 HB, Germany

For any legal inquiries or further information, please contact us via email at hello@task.vc.

By using this repository, you acknowledge that you have read this section, agree to comply with its terms, and understand that the licensing of the code does not imply endorsement by Task Venture Capital GmbH of any derivative works.