# NATSBridge

A high-performance, bi-directional data bridge between **Julia**, **JavaScript**, and **Python/Micropython** applications using NATS (Core & JetStream), implementing the Claim-Check pattern for large payloads.

[![License: MIT](https://img.shields.io/badge/License-MIT-blue.svg)](https://opensource.org/licenses/MIT)
[![NATS](https://img.shields.io/badge/NATS-Enabled-green.svg)](https://nats.io)

---

## Table of Contents

- [Overview](#overview)
- [Features](#features)
- [Architecture](#architecture)
- [Installation](#installation)
- [Quick Start](#quick-start)
- [API Reference](#api-reference)
- [Payload Types](#payload-types)
- [Transport Strategies](#transport-strategies)
- [Examples](#examples)
- [Testing](#testing)
- [License](#license)

---

## Overview

NATSBridge enables seamless communication across Julia, JavaScript, and Python/Micropython applications through NATS, with intelligent transport selection based on payload size:

| Transport | Payload Size | Method |
|-----------|--------------|--------|
| **Direct** | < 1MB | Sent directly via NATS (Base64 encoded) |
| **Link** | >= 1MB | Uploaded to HTTP file server, URL sent via NATS |

### Use Cases

- **Chat Applications**: Text, images, audio, video in a single message
- **File Transfer**: Efficient transfer of large files using claim-check pattern
- **Streaming Data**: Sensor data, telemetry, and analytics pipelines
- **Cross-Platform Communication**: Julia ↔ JavaScript ↔ Python/Micropython
- **IoT Devices**: Micropython devices sending data to cloud services

---

## Features

- ✅ **Bi-directional messaging** between Julia, JavaScript, and Python/Micropython
- ✅ **Multi-payload support** - send multiple payloads with different types in one message
- ✅ **Automatic transport selection** - direct vs link based on payload size
- ✅ **Claim-Check pattern** for payloads > 1MB
- ✅ **Apache Arrow IPC** support for tabular data (zero-copy reading)
- ✅ **Exponential backoff** for reliable file server downloads
- ✅ **Correlation ID tracking** for message tracing
- ✅ **Reply-to support** for request-response patterns
- ✅ **JetStream support** for message replay and durability
- ✅ **Lightweight Micropython implementation** for microcontrollers

---

## Architecture

### System Components

```
┌─────────────────────────────────────────────────────────────────────┐
│                     NATSBridge Architecture                         │
├─────────────────────────────────────────────────────────────────────┤
│  ┌──────────────┐    ┌──────────────┐    ┌──────────────┐           │
│  │   Julia      │    │  JavaScript  │    │  Python/     │           │
│  │  (NATS.jl)   │◄──►│  (nats.js)   │◄──►│  Micropython │           │
│  └──────────────┘    └──────────────┘    └──────────────┘           │
│       │                    │                    │                   │
│       ▼                    ▼                    ▼                   │
│    ┌─────────────────────────────────────────────────────┐          │
│    │                    NATS                             │          │
│    │               (Message Broker)                      │          │
│    └─────────────────────────────────────────────────────┘          │
│                              │                                      │
│                              ▼                                      │
│                    ┌──────────────────────┐                         │
│                    │  File Server         │                         │
│                    │  (HTTP Upload/Get)   │                         │
│                    └──────────────────────┘                         │
└─────────────────────────────────────────────────────────────────────┘
```

### Message Flow

1. **Sender** creates a message envelope with payloads
2. **NATSBridge** serializes and encodes payloads based on type
3. **Transport Decision**: Small payloads go directly to NATS, large payloads are uploaded to file server
4. **NATS** routes messages to subscribers
5. **Receiver** fetches payloads (from NATS or file server)
6. **NATSBridge** deserializes and decodes payloads

---

## Installation

### Prerequisites

- **NATS Server** (v2.10+ recommended)
- **HTTP File Server** (optional, for payloads > 1MB)

### Julia

```julia
using Pkg
Pkg.add("NATS")
Pkg.add("Arrow")
Pkg.add("JSON3")
Pkg.add("HTTP")
Pkg.add("UUIDs")
Pkg.add("Dates")
```

Add to your `Project.toml`:
```toml
[NATSBridge]
deps = ["NATS", "Arrow", "JSON3", "HTTP", "UUIDs", "Dates"]
```

### JavaScript

```bash
npm install nats.js apache-arrow uuid base64-url
```

For Node.js:
```javascript
const { smartsend, smartreceive } = require('./src/NATSBridge');
```

For browser:
```html
<script src="./src/NATSBridge.js"></script>
<script>
  // NATSBridge is available as window.NATSBridge
</script>
```

### Python/Micropython

1. Copy [`src/nats_bridge.py`](src/nats_bridge.py) to your device
2. Install dependencies:

**For Python (desktop):**
```bash
pip install nats-py
```

**For Micropython:**
- `urequests` for HTTP requests (built-in for ESP32)
- `base64` for base64 encoding (built-in)
- `json` for JSON handling (built-in)

---

## Quick Start

### Step 1: Start NATS Server

```bash
docker run -p 4222:4222 nats:latest
```

### Step 2: Start HTTP File Server (Optional)

```bash
# Create a directory for file uploads
mkdir -p /tmp/fileserver

# Use Python's built-in server
python3 -m http.server 8080 --directory /tmp/fileserver
```

### Step 3: Send Your First Message

#### Python/Micropython

```python
from nats_bridge import smartsend

# Send a text message
data = [("message", "Hello World", "text")]
env = smartsend("/chat/room1", data, nats_url="nats://localhost:4222")
print("Message sent!")
```

#### JavaScript

```javascript
const { smartsend } = require('./src/NATSBridge');

// Send a text message
await smartsend("/chat/room1", [
    { dataname: "message", data: "Hello World", type: "text" }
], { natsUrl: "nats://localhost:4222" });

console.log("Message sent!");
```

#### Julia

```julia
using NATSBridge

# Send a text message
data = [("message", "Hello World", "text")]
env = smartsend("/chat/room1", data, nats_url="nats://localhost:4222")
println("Message sent!")
```

### Step 4: Receive Messages

#### Python/Micropython

```python
from nats_bridge import smartreceive

# Receive and process message
envelope = smartreceive(msg)
for dataname, data, type in envelope["payloads"]:
    print(f"Received {dataname}: {data}")
```

#### JavaScript

```javascript
const { smartreceive } = require('./src/NATSBridge');

// Receive and process message
const envelope = await smartreceive(msg);
for (const payload of envelope.payloads) {
    console.log(`Received ${payload.dataname}: ${payload.data}`);
}
```

#### Julia

```julia
using NATSBridge

# Receive and process message
envelope = smartreceive(msg, fileserverDownloadHandler)
for (dataname, data, type) in envelope["payloads"]
    println("Received $dataname: $data")
end
```

---

## API Reference

### smartsend

Sends data either directly via NATS or via a fileserver URL, depending on payload size.

#### Python/Micropython

```python
from nats_bridge import smartsend

env = smartsend(
    subject,                           # NATS subject to publish to
    data,                              # List of (dataname, data, type) tuples
    nats_url="nats://localhost:4222",  # NATS server URL
    fileserver_url="http://localhost:8080",  # File server URL
    fileserver_upload_handler=plik_oneshot_upload,  # Upload handler function
    size_threshold=1_000_000,          # Threshold in bytes (default: 1MB)
    correlation_id=None,               # Optional correlation ID for tracing
    msg_purpose="chat",                # Message purpose
    sender_name="NATSBridge",          # Sender name
    receiver_name="",                  # Receiver name (empty = broadcast)
    receiver_id="",                    # Receiver UUID (empty = broadcast)
    reply_to="",                       # Reply topic
    reply_to_msg_id=""                 # Reply message ID
)
```

#### JavaScript

```javascript
const { smartsend } = require('./src/NATSBridge');

const env = await smartsend(
    subject,                           // NATS subject
    data,                              // Array of {dataname, data, type}
    {
        natsUrl: "nats://localhost:4222",
        fileserverUrl: "http://localhost:8080",
        fileserverUploadHandler: customUploadHandler,
        sizeThreshold: 1_000_000,
        correlationId: "custom-id",
        msgPurpose: "chat",
        senderName: "NATSBridge",
        receiverName: "",
        receiverId: "",
        replyTo: "",
        replyToMsgId: ""
    }
);
```

#### Julia

```julia
using NATSBridge

env = smartsend(
    subject;                           # NATS subject
    data::AbstractArray{Tuple{String, Any, String}};  # List of (dataname, data, type)
    nats_url::String = "nats://localhost:4222",
    fileserver_url = "http://localhost:8080",
    fileserverUploadHandler::Function = plik_oneshot_upload,
    size_threshold::Int = 1_000_000,
    correlation_id::Union{String, Nothing} = nothing,
    msg_purpose::String = "chat",
    sender_name::String = "NATSBridge",
    receiver_name::String = "",
    receiver_id::String = "",
    reply_to::String = "",
    reply_to_msg_id::String = ""
)
```

### smartreceive

Receives and processes messages from NATS, handling both direct and link transport.

#### Python/Micropython

```python
from nats_bridge import smartreceive

envelope = smartreceive(
    msg,                               # NATS message
    fileserver_download_handler=_fetch_with_backoff,  # Download handler
    max_retries=5,                     # Max retry attempts
    base_delay=100,                    # Initial delay in ms
    max_delay=5000                     # Max delay in ms
)
# Returns: Dict with envelope metadata and 'payloads' field
```

#### JavaScript

```javascript
const { smartreceive } = require('./src/NATSBridge');

const envelope = await smartreceive(
    msg,                               // NATS message
    {
        fileserverDownloadHandler: customDownloadHandler,
        maxRetries: 5,
        baseDelay: 100,
        maxDelay: 5000
    }
);
// Returns: Object with envelope metadata and payloads array
```

#### Julia

```julia
using NATSBridge

envelope = smartreceive(
    msg::NATS.Msg;
    fileserverDownloadHandler::Function = _fetch_with_backoff,
    max_retries::Int = 5,
    base_delay::Int = 100,
    max_delay::Int = 5000
)
# Returns: Dict with envelope metadata and payloads array
```

---

## Payload Types

| Type | Description | Serialization |
|------|-------------|---------------|
| `text` | Plain text strings | UTF-8 bytes |
| `dictionary` | JSON-serializable dictionaries | JSON |
| `table` | Tabular data (DataFrames, arrays) | Apache Arrow IPC |
| `image` | Image data (PNG, JPG) | Raw bytes |
| `audio` | Audio data (WAV, MP3) | Raw bytes |
| `video` | Video data (MP4, AVI) | Raw bytes |
| `binary` | Generic binary data | Raw bytes |

---

## Transport Strategies

### Direct Transport (Payloads < 1MB)

Small payloads are sent directly via NATS with Base64 encoding.

#### Python/Micropython
```python
data = [("message", "Hello", "text")]
smartsend("/topic", data)
```

#### JavaScript
```javascript
await smartsend("/topic", [
    { dataname: "message", data: "Hello", type: "text" }
]);
```

#### Julia
```julia
data = [("message", "Hello", "text")]
smartsend("/topic", data)
```

### Link Transport (Payloads >= 1MB)

Large payloads are uploaded to an HTTP file server.

#### Python/Micropython
```python
data = [("file", large_data, "binary")]
smartsend("/topic", data, fileserver_url="http://localhost:8080")
```

#### JavaScript
```javascript
await smartsend("/topic", [
    { dataname: "file", data: largeData, type: "binary" }
], { fileserverUrl: "http://localhost:8080" });
```

#### Julia
```julia
data = [("file", large_data, "binary")]
smartsend("/topic", data, fileserver_url="http://localhost:8080")
```

---

## Examples

All examples include code for **Julia**, **JavaScript**, and **Python/Micropython** unless otherwise specified.

### Example 1: Chat with Mixed Content

Send text, small image, and large file in one message.

#### Python/Micropython
```python
from nats_bridge import smartsend

data = [
    ("message_text", "Hello!", "text"),
    ("user_avatar", image_data, "image"),
    ("large_document", large_file_data, "binary")
]

smartsend("/chat/room1", data, fileserver_url="http://localhost:8080")
```

#### JavaScript
```javascript
const { smartsend } = require('./src/NATSBridge');

await smartsend("/chat/room1", [
    { dataname: "message_text", data: "Hello!", type: "text" },
    { dataname: "user_avatar", data: image_data, type: "image" },
    { dataname: "large_document", data: large_file_data, type: "binary" }
], {
    fileserverUrl: "http://localhost:8080"
});
```

#### Julia
```julia
using NATSBridge

data = [
    ("message_text", "Hello!", "text"),
    ("user_avatar", image_data, "image"),
    ("large_document", large_file_data, "binary")
]

smartsend("/chat/room1", data, fileserver_url="http://localhost:8080")
```

### Example 2: Dictionary Exchange

Send configuration data between platforms.

#### Python/Micropython
```python
from nats_bridge import smartsend

config = {
    "wifi_ssid": "MyNetwork",
    "wifi_password": "password123",
    "update_interval": 60
}

data = [("config", config, "dictionary")]
smartsend("/device/config", data)
```

#### JavaScript
```javascript
const { smartsend } = require('./src/NATSBridge');

const config = {
    wifi_ssid: "MyNetwork",
    wifi_password: "password123",
    update_interval: 60
};

await smartsend("/device/config", [
    { dataname: "config", data: config, type: "dictionary" }
]);
```

#### Julia
```julia
using NATSBridge

config = Dict(
    "wifi_ssid" => "MyNetwork",
    "wifi_password" => "password123",
    "update_interval" => 60
)

data = [("config", config, "dictionary")]
smartsend("/device/config", data)
```

### Example 3: Table Data (Arrow IPC)

Send tabular data using Apache Arrow IPC format.

#### Python/Micropython
```python
import pandas as pd
from nats_bridge import smartsend

df = pd.DataFrame({
    "id": [1, 2, 3],
    "name": ["Alice", "Bob", "Charlie"],
    "score": [95, 88, 92]
})

data = [("students", df, "table")]
smartsend("/data/analysis", data)
```

#### JavaScript
```javascript
const { smartsend } = require('./src/NATSBridge');

const tableData = [
    { id: 1, name: "Alice", score: 95 },
    { id: 2, name: "Bob", score: 88 },
    { id: 3, name: "Charlie", score: 92 }
];

await smartsend("/data/analysis", [
    { dataname: "students", data: tableData, type: "table" }
]);
```

#### Julia
```julia
using NATSBridge
using DataFrames

df = DataFrame(
    id = [1, 2, 3],
    name = ["Alice", "Bob", "Charlie"],
    score = [95, 88, 92]
)

data = [("students", df, "table")]
smartsend("/data/analysis", data)
```

### Example 4: Request-Response Pattern

Bi-directional communication with reply-to support.

#### Python/Micropython (Requester)
```python
from nats_bridge import smartsend

env = smartsend(
    "/device/command",
    [("command", {"action": "read_sensor"}, "dictionary")],
    reply_to="/device/response"
)
```

#### Python/Micropython (Responder)
```python
from nats_bridge import smartreceive

envelope = smartreceive(msg)
for dataname, data, type in envelope["payloads"]:
    if data.get("action") == "read_sensor":
        response = {"sensor_id": "sensor-001", "value": 42.5}
        smartsend("/device/response", [("data", response, "dictionary")])
```

#### JavaScript (Requester)
```javascript
const { smartsend } = require('./src/NATSBridge');

await smartsend("/device/command", [
    { dataname: "command", data: { action: "read_sensor" }, type: "dictionary" }
], {
    replyTo: "/device/response"
});
```

#### JavaScript (Responder)
```javascript
const { smartreceive, smartsend } = require('./src/NATSBridge');

const envelope = await smartreceive(msg);
for (const payload of envelope.payloads) {
    if (payload.dataname === "command" && payload.data.action === "read_sensor") {
        const response = { sensor_id: "sensor-001", value: 42.5 };
        await smartsend("/device/response", [
            { dataname: "data", data: response, type: "dictionary" }
        ]);
    }
}
```

#### Julia (Requester)
```julia
using NATSBridge

env = smartsend(
    "/device/command",
    [("command", Dict("action" => "read_sensor"), "dictionary")],
    reply_to="/device/response"
)
```

#### Julia (Responder)
```julia
using NATSBridge

envelope = smartreceive(msg, fileserverDownloadHandler)
for (dataname, data, type) in envelope["payloads"]
    if dataname == "command" && data["action"] == "read_sensor"
        response = Dict("sensor_id" => "sensor-001", "value" => 42.5)
        smartsend("/device/response", [("data", response, "dictionary")])
    end
end
```

### Example 5: Micropython IoT Device

Lightweight Micropython device sending sensor data.

#### Micropython
```python
from nats_bridge import smartsend, smartreceive
import json

# Send sensor data
data = [("temperature", "25.5", "text"), ("humidity", 65, "dictionary")]
smartsend("/device/sensors", data, nats_url="nats://localhost:4222")

# Receive commands
envelope = smartreceive(msg)
for dataname, data, type in envelope["payloads"]:
    if type == "dictionary" and data.get("action") == "reboot":
        # Execute reboot
        pass
```

#### JavaScript (Receiver)
```javascript
const { smartreceive } = require('./src/NATSBridge');

const envelope = await smartreceive(msg);
for (const payload of envelope.payloads) {
    if (payload.dataname === "temperature") {
        console.log(`Temperature: ${payload.data}`);
    } else if (payload.dataname === "humidity") {
        console.log(`Humidity: ${payload.data}`);
    }
}
```

#### Julia (Receiver)
```julia
using NATSBridge

envelope = smartreceive(msg, fileserverDownloadHandler)
for (dataname, data, type) in envelope["payloads"]
    if dataname == "temperature"
        println("Temperature: $data")
    elseif dataname == "humidity"
        println("Humidity: $data")
    end
end
```

---

## Testing

Run the test scripts to verify functionality:

### Python/Micropython

```bash
# Basic functionality test
python test/test_micropython_basic.py

# Text message exchange
python test/test_micropython_text_sender.py
python test/test_micropython_text_receiver.py

# Dictionary exchange
python test/test_micropython_dict_sender.py
python test/test_micropython_dict_receiver.py

# File transfer
python test/test_micropython_file_sender.py
python test/test_micropython_file_receiver.py

# Mixed payload types
python test/test_micropython_mixed_sender.py
python test/test_micropython_mixed_receiver.py
```

### JavaScript

```bash
# Text message exchange
node test/test_js_text_sender.js
node test/test_js_text_receiver.js

# Dictionary exchange
node test/test_js_dict_sender.js
node test/test_js_dict_receiver.js

# File transfer
node test/test_js_file_sender.js
node test/test_js_file_receiver.js

# Mixed payload types
node test/test_js_mix_payload_sender.js
node test/test_js_mix_payloads_receiver.js

# Table exchange
node test/test_js_table_sender.js
node test/test_js_table_receiver.js
```

### Julia

```julia
# Text message exchange
julia test/test_julia_text_sender.jl
julia test/test_julia_text_receiver.jl

# Dictionary exchange
julia test/test_julia_dict_sender.jl
julia test/test_julia_dict_receiver.jl

# File transfer
julia test/test_julia_file_sender.jl
julia test/test_julia_file_receiver.jl

# Mixed payload types
julia test/test_julia_mix_payloads_sender.jl
julia test/test_julia_mix_payloads_receiver.jl

# Table exchange
julia test/test_julia_table_sender.jl
julia test/test_julia_table_receiver.jl
```

---

## License

MIT License

Copyright (c) 2026 NATSBridge Contributors

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.