docs(extensions): add comprehensive extension loader documentation

Covers architecture, API reference, lifecycle, database isolation,
RPC methods, HTTP routes, event handling, and complete examples.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
Patrick Mulligan 2026-02-13 13:58:56 -05:00
parent b2dbcd6a20
commit f048e71821

731
src/extensions/README.md Normal file
View file

@ -0,0 +1,731 @@
# Lightning.Pub Extension System
A modular extension system that allows third-party functionality to be added to Lightning.Pub without modifying core code.
## Table of Contents
- [Overview](#overview)
- [Architecture](#architecture)
- [Creating an Extension](#creating-an-extension)
- [Extension Lifecycle](#extension-lifecycle)
- [ExtensionContext API](#extensioncontext-api)
- [Database Isolation](#database-isolation)
- [RPC Methods](#rpc-methods)
- [HTTP Routes](#http-routes)
- [Event Handling](#event-handling)
- [Configuration](#configuration)
- [Examples](#examples)
---
## Overview
The extension system provides:
- **Modularity**: Extensions are self-contained modules with their own code and data
- **Isolation**: Each extension gets its own SQLite database
- **Integration**: Extensions can register RPC methods, handle events, and interact with Lightning.Pub's payment and Nostr systems
- **Lifecycle Management**: Automatic discovery, loading, and graceful shutdown
### Built-in Extensions
| Extension | Description |
|-----------|-------------|
| `marketplace` | NIP-15 Nostr marketplace for selling products via Lightning |
| `withdraw` | LNURL-withdraw (LUD-03) for vouchers, faucets, and gifts |
---
## Architecture
```
┌─────────────────────────────────────────────────────────────────┐
│ Lightning.Pub │
├─────────────────────────────────────────────────────────────────┤
│ Extension Loader │
│ ┌─────────────┐ ┌─────────────┐ ┌─────────────┐ │
│ │ Extension A │ │ Extension B │ │ Extension C │ ... │
│ │ ┌───────┐ │ │ ┌───────┐ │ │ ┌───────┐ │ │
│ │ │Context│ │ │ │Context│ │ │ │Context│ │ │
│ │ └───────┘ │ │ └───────┘ │ │ └───────┘ │ │
│ │ ┌───────┐ │ │ ┌───────┐ │ │ ┌───────┐ │ │
│ │ │ DB │ │ │ │ DB │ │ │ │ DB │ │ │
│ │ └───────┘ │ │ └───────┘ │ │ └───────┘ │ │
│ └─────────────┘ └─────────────┘ └─────────────┘ │
├─────────────────────────────────────────────────────────────────┤
│ Payment Manager │ Nostr Transport │ Application Manager │
└─────────────────────────────────────────────────────────────────┘
```
### Key Components
| Component | File | Description |
|-----------|------|-------------|
| `ExtensionLoader` | `loader.ts` | Discovers, loads, and manages extensions |
| `ExtensionContext` | `context.ts` | Bridge between extensions and Lightning.Pub |
| `ExtensionDatabase` | `database.ts` | Isolated SQLite database per extension |
---
## Creating an Extension
### Directory Structure
```
src/extensions/
└── my-extension/
├── index.ts # Main entry point (required)
├── types.ts # TypeScript interfaces
├── migrations.ts # Database migrations
└── managers/ # Business logic
└── myManager.ts
```
### Minimal Extension
```typescript
// src/extensions/my-extension/index.ts
import { Extension, ExtensionInfo, ExtensionContext, ExtensionDatabase } from '../types.js'
export default class MyExtension implements Extension {
readonly info: ExtensionInfo = {
id: 'my-extension', // Must match directory name
name: 'My Extension',
version: '1.0.0',
description: 'Does something useful',
author: 'Your Name',
minPubVersion: '1.0.0' // Minimum Lightning.Pub version
}
async initialize(ctx: ExtensionContext, db: ExtensionDatabase): Promise<void> {
// Run migrations
await db.execute(`
CREATE TABLE IF NOT EXISTS my_table (
id TEXT PRIMARY KEY,
data TEXT
)
`)
// Register RPC methods
ctx.registerMethod('my-extension.doSomething', async (req, appId) => {
return { result: 'done' }
})
ctx.log('info', 'Extension initialized')
}
async shutdown(): Promise<void> {
// Cleanup resources
}
}
```
### Extension Interface
```typescript
interface Extension {
// Required: Extension metadata
readonly info: ExtensionInfo
// Required: Called once when extension is loaded
initialize(ctx: ExtensionContext, db: ExtensionDatabase): Promise<void>
// Optional: Called when Lightning.Pub shuts down
shutdown?(): Promise<void>
// Optional: Health check for monitoring
healthCheck?(): Promise<boolean>
}
interface ExtensionInfo {
id: string // Unique identifier (lowercase, no spaces)
name: string // Display name
version: string // Semver version
description: string // Short description
author: string // Author name
minPubVersion?: string // Minimum Lightning.Pub version
dependencies?: string[] // Other extension IDs required
}
```
---
## Extension Lifecycle
```
┌──────────────┐
│ Discover │ Scan extensions directory for index.ts files
└──────┬───────┘
┌──────────────┐
│ Load │ Import module, instantiate class
└──────┬───────┘
┌──────────────┐
│ Initialize │ Create database, call initialize()
└──────┬───────┘
┌──────────────┐
│ Ready │ Extension is active, handling requests
└──────┬───────┘
▼ (on shutdown)
┌──────────────┐
│ Shutdown │ Call shutdown(), close database
└──────────────┘
```
### States
| State | Description |
|-------|-------------|
| `loading` | Extension is being loaded |
| `ready` | Extension is active and healthy |
| `error` | Initialization failed |
| `stopped` | Extension has been shut down |
---
## ExtensionContext API
The `ExtensionContext` is passed to your extension during initialization. It provides access to Lightning.Pub functionality.
### Application Management
```typescript
// Get information about an application
const app = await ctx.getApplication(applicationId)
// Returns: { id, name, nostr_public, balance_sats } | null
```
### Payment Operations
```typescript
// Create a Lightning invoice
const invoice = await ctx.createInvoice(amountSats, {
memo: 'Payment for service',
expiry: 3600, // seconds
metadata: { order_id: '123' } // Returned in payment callback
})
// Returns: { id, paymentRequest, paymentHash, expiry }
// Pay a Lightning invoice
const result = await ctx.payInvoice(applicationId, bolt11Invoice, maxFeeSats)
// Returns: { paymentHash, feeSats }
```
### Nostr Operations
```typescript
// Send encrypted DM (NIP-44)
const eventId = await ctx.sendEncryptedDM(applicationId, recipientPubkey, content)
// Publish a Nostr event (signed by application's key)
const eventId = await ctx.publishNostrEvent({
kind: 30017,
pubkey: appPubkey,
created_at: Math.floor(Date.now() / 1000),
tags: [['d', 'identifier']],
content: JSON.stringify(data)
})
```
### RPC Method Registration
```typescript
// Register a method that can be called via RPC
ctx.registerMethod('my-extension.methodName', async (request, applicationId, userPubkey?) => {
// request: The RPC request payload
// applicationId: The calling application's ID
// userPubkey: The user's Nostr pubkey (if authenticated)
return { result: 'success' }
})
```
### Event Subscriptions
```typescript
// Subscribe to payment received events
ctx.onPaymentReceived(async (payment) => {
// payment: { invoiceId, paymentHash, amountSats, metadata }
if (payment.metadata?.extension === 'my-extension') {
// Handle payment for this extension
}
})
// Subscribe to incoming Nostr events
ctx.onNostrEvent(async (event, applicationId) => {
// event: { id, pubkey, kind, tags, content, created_at }
// applicationId: The application this event is for
if (event.kind === 4) { // DM
// Handle incoming message
}
})
```
### Logging
```typescript
ctx.log('debug', 'Detailed debugging info')
ctx.log('info', 'Normal operation info')
ctx.log('warn', 'Warning message')
ctx.log('error', 'Error occurred', errorObject)
```
---
## Database Isolation
Each extension gets its own SQLite database file at:
```
{databaseDir}/{extension-id}.db
```
### Database Interface
```typescript
interface ExtensionDatabase {
// Execute write queries (INSERT, UPDATE, DELETE, CREATE)
execute(sql: string, params?: any[]): Promise<{ changes?: number; lastId?: number }>
// Execute read queries (SELECT)
query<T>(sql: string, params?: any[]): Promise<T[]>
// Run multiple statements in a transaction
transaction<T>(fn: () => Promise<T>): Promise<T>
}
```
### Migration Pattern
```typescript
// migrations.ts
export interface Migration {
version: number
name: string
up: (db: ExtensionDatabase) => Promise<void>
}
export const migrations: Migration[] = [
{
version: 1,
name: 'create_initial_tables',
up: async (db) => {
await db.execute(`
CREATE TABLE items (
id TEXT PRIMARY KEY,
name TEXT NOT NULL,
created_at INTEGER NOT NULL
)
`)
}
},
{
version: 2,
name: 'add_status_column',
up: async (db) => {
await db.execute(`ALTER TABLE items ADD COLUMN status TEXT DEFAULT 'active'`)
}
}
]
// Run migrations in initialize()
export async function runMigrations(db: ExtensionDatabase): Promise<void> {
const result = await db.query<{ value: string }>(
`SELECT value FROM _extension_meta WHERE key = 'migration_version'`
).catch(() => [])
const currentVersion = result.length > 0 ? parseInt(result[0].value, 10) : 0
for (const migration of migrations) {
if (migration.version > currentVersion) {
console.log(`Running migration ${migration.version}: ${migration.name}`)
await migration.up(db)
await db.execute(
`INSERT INTO _extension_meta (key, value) VALUES ('migration_version', ?)
ON CONFLICT(key) DO UPDATE SET value = excluded.value`,
[String(migration.version)]
)
}
}
}
```
---
## RPC Methods
Extensions register RPC methods that can be called by clients.
### Naming Convention
Methods should be namespaced with the extension ID:
```
{extension-id}.{methodName}
```
Examples:
- `marketplace.createStall`
- `withdraw.createLink`
### Method Handler Signature
```typescript
type RpcMethodHandler = (
request: any, // The request payload
applicationId: string, // The calling application
userPubkey?: string // The authenticated user (if any)
) => Promise<any>
```
### Example
```typescript
ctx.registerMethod('my-extension.createItem', async (req, appId, userPubkey) => {
// Validate request
if (!req.name) {
throw new Error('Name is required')
}
// Create item
const item = await this.manager.create(appId, req)
// Return response
return { item }
})
```
---
## HTTP Routes
Some extensions need HTTP endpoints (e.g., LNURL protocol). Extensions can define routes that the main application mounts.
### Defining Routes
```typescript
interface HttpRoute {
method: 'GET' | 'POST'
path: string
handler: (req: HttpRequest) => Promise<HttpResponse>
}
interface HttpRequest {
params: Record<string, string> // URL path params
query: Record<string, string> // Query string params
body?: any // POST body
headers: Record<string, string>
}
interface HttpResponse {
status: number
body: any
headers?: Record<string, string>
}
```
### Example
```typescript
class MyExtension implements Extension {
getHttpRoutes(): HttpRoute[] {
return [
{
method: 'GET',
path: '/api/v1/my-extension/:id',
handler: async (req) => {
const item = await this.getItem(req.params.id)
return {
status: 200,
body: item,
headers: { 'Content-Type': 'application/json' }
}
}
}
]
}
}
```
---
## Event Handling
### Payment Callbacks
When you create an invoice with metadata, you'll receive that metadata back in the payment callback:
```typescript
// Creating invoice with metadata
const invoice = await ctx.createInvoice(1000, {
metadata: {
extension: 'my-extension',
order_id: 'order-123'
}
})
// Handling payment
ctx.onPaymentReceived(async (payment) => {
if (payment.metadata?.extension === 'my-extension') {
const orderId = payment.metadata.order_id
await this.handlePayment(orderId, payment)
}
})
```
### Nostr Events
Subscribe to Nostr events for your application:
```typescript
ctx.onNostrEvent(async (event, applicationId) => {
// Filter by event kind
if (event.kind === 4) { // Encrypted DM
await this.handleDirectMessage(event, applicationId)
}
})
```
---
## Configuration
### Loader Configuration
```typescript
interface ExtensionLoaderConfig {
extensionsDir: string // Directory containing extensions
databaseDir: string // Directory for extension databases
enabledExtensions?: string[] // Whitelist (if set, only these load)
disabledExtensions?: string[] // Blacklist
}
```
### Usage
```typescript
import { createExtensionLoader } from './extensions'
const loader = createExtensionLoader({
extensionsDir: './src/extensions',
databaseDir: './data/extensions',
disabledExtensions: ['experimental-ext']
}, mainHandler)
await loader.loadAll()
// Call extension methods
const result = await loader.callMethod(
'marketplace.createStall',
{ name: 'My Shop', currency: 'sat', shipping_zones: [] },
applicationId,
userPubkey
)
// Dispatch events
loader.dispatchPaymentReceived(paymentData)
loader.dispatchNostrEvent(event, applicationId)
// Shutdown
await loader.shutdown()
```
---
## Examples
### Example: Simple Counter Extension
```typescript
// src/extensions/counter/index.ts
import { Extension, ExtensionInfo, ExtensionContext, ExtensionDatabase } from '../types.js'
export default class CounterExtension implements Extension {
readonly info: ExtensionInfo = {
id: 'counter',
name: 'Simple Counter',
version: '1.0.0',
description: 'A simple counter for each application',
author: 'Example'
}
private db!: ExtensionDatabase
async initialize(ctx: ExtensionContext, db: ExtensionDatabase): Promise<void> {
this.db = db
await db.execute(`
CREATE TABLE IF NOT EXISTS counters (
application_id TEXT PRIMARY KEY,
count INTEGER NOT NULL DEFAULT 0
)
`)
ctx.registerMethod('counter.increment', async (req, appId) => {
await db.execute(
`INSERT INTO counters (application_id, count) VALUES (?, 1)
ON CONFLICT(application_id) DO UPDATE SET count = count + 1`,
[appId]
)
const result = await db.query<{ count: number }>(
'SELECT count FROM counters WHERE application_id = ?',
[appId]
)
return { count: result[0]?.count || 0 }
})
ctx.registerMethod('counter.get', async (req, appId) => {
const result = await db.query<{ count: number }>(
'SELECT count FROM counters WHERE application_id = ?',
[appId]
)
return { count: result[0]?.count || 0 }
})
ctx.registerMethod('counter.reset', async (req, appId) => {
await db.execute(
'UPDATE counters SET count = 0 WHERE application_id = ?',
[appId]
)
return { count: 0 }
})
}
}
```
### Example: Payment-Triggered Extension
```typescript
// src/extensions/donations/index.ts
import { Extension, ExtensionContext, ExtensionDatabase } from '../types.js'
export default class DonationsExtension implements Extension {
readonly info = {
id: 'donations',
name: 'Donations',
version: '1.0.0',
description: 'Accept donations with thank-you messages',
author: 'Example'
}
private db!: ExtensionDatabase
private ctx!: ExtensionContext
async initialize(ctx: ExtensionContext, db: ExtensionDatabase): Promise<void> {
this.db = db
this.ctx = ctx
await db.execute(`
CREATE TABLE IF NOT EXISTS donations (
id TEXT PRIMARY KEY,
application_id TEXT NOT NULL,
amount_sats INTEGER NOT NULL,
donor_pubkey TEXT,
message TEXT,
created_at INTEGER NOT NULL
)
`)
// Create donation invoice
ctx.registerMethod('donations.createInvoice', async (req, appId) => {
const invoice = await ctx.createInvoice(req.amount_sats, {
memo: req.message || 'Donation',
metadata: {
extension: 'donations',
donor_pubkey: req.donor_pubkey,
message: req.message
}
})
return { invoice: invoice.paymentRequest }
})
// Handle successful payments
ctx.onPaymentReceived(async (payment) => {
if (payment.metadata?.extension !== 'donations') return
// Record donation
await db.execute(
`INSERT INTO donations (id, application_id, amount_sats, donor_pubkey, message, created_at)
VALUES (?, ?, ?, ?, ?, ?)`,
[
payment.paymentHash,
payment.metadata.application_id,
payment.amountSats,
payment.metadata.donor_pubkey,
payment.metadata.message,
Math.floor(Date.now() / 1000)
]
)
// Send thank-you DM if donor has pubkey
if (payment.metadata.donor_pubkey) {
await ctx.sendEncryptedDM(
payment.metadata.application_id,
payment.metadata.donor_pubkey,
`Thank you for your donation of ${payment.amountSats} sats!`
)
}
})
// List donations
ctx.registerMethod('donations.list', async (req, appId) => {
const donations = await db.query(
`SELECT * FROM donations WHERE application_id = ? ORDER BY created_at DESC LIMIT ?`,
[appId, req.limit || 50]
)
return { donations }
})
}
}
```
---
## Best Practices
1. **Namespace your methods**: Always prefix RPC methods with your extension ID
2. **Use migrations**: Never modify existing migration files; create new ones
3. **Handle errors gracefully**: Throw descriptive errors, don't return error objects
4. **Clean up in shutdown**: Close connections, cancel timers, etc.
5. **Log appropriately**: Use debug for verbose info, error for failures
6. **Validate inputs**: Check request parameters before processing
7. **Use transactions**: For multi-step database operations
8. **Document your API**: Include types and descriptions for RPC methods
---
## Troubleshooting
### Extension not loading
1. Check that directory name matches `info.id`
2. Verify `index.ts` has a default export
3. Check for TypeScript/import errors in logs
### Database errors
1. Check migration syntax
2. Verify column types match queries
3. Look for migration version conflicts
### RPC method not found
1. Verify method is registered in `initialize()`
2. Check method name includes extension prefix
3. Ensure extension status is `ready`
### Payment callbacks not firing
1. Verify `metadata.extension` matches your extension ID
2. Check that `onPaymentReceived` is registered in `initialize()`
3. Confirm invoice was created through the extension