# NDK Quick Reference

Fast lookup guide for common NDK tasks.

## Quick Start

```typescript
import NDK from '@nostr-dev-kit/ndk'

const ndk = new NDK({ explicitRelayUrls: ['wss://relay.damus.io'] })
await ndk.connect()
```

## Authentication

### Browser Extension (NIP-07)
```typescript
import { NDKNip07Signer } from '@nostr-dev-kit/ndk'
const signer = new NDKNip07Signer()
await signer.blockUntilReady()
ndk.signer = signer
```

### Private Key
```typescript
import { NDKPrivateKeySigner } from '@nostr-dev-kit/ndk'
const signer = new NDKPrivateKeySigner(privateKeyHex)
await signer.blockUntilReady()
ndk.signer = signer
```

### Remote Signer (NIP-46)
```typescript
import { NDKNip46Signer, NDKPrivateKeySigner } from '@nostr-dev-kit/ndk'
const localSigner = new NDKPrivateKeySigner()
const remoteSigner = new NDKNip46Signer(ndk, bunkerUrl, localSigner)
await remoteSigner.blockUntilReady()
ndk.signer = remoteSigner
```

## Publish Event

```typescript
import { NDKEvent } from '@nostr-dev-kit/ndk'

const event = new NDKEvent(ndk)
event.kind = 1
event.content = "Hello Nostr!"
event.tags = [['t', 'nostr']]

await event.sign()
await event.publish()
```

## Query Events (One-time)

```typescript
const events = await ndk.fetchEvents({
  kinds: [1],
  authors: [pubkey],
  limit: 50
})

// Convert Set to Array
const eventArray = Array.from(events)
```

## Subscribe (Real-time)

```typescript
const sub = ndk.subscribe(
  { kinds: [1], authors: [pubkey] },
  { closeOnEose: false }
)

sub.on('event', (event) => {
  console.log('New event:', event.content)
})

// Cleanup
sub.stop()
```

## Get User Profile

```typescript
// By npub
const user = ndk.getUser({ npub })
const profile = await user.fetchProfile()

// By hex pubkey
const user = ndk.getUser({ hexpubkey: pubkey })
const profile = await user.fetchProfile()

// By NIP-05
const user = await ndk.getUserFromNip05('user@domain.com')
const profile = await user?.fetchProfile()
```

## Common Filters

```typescript
// By author
{ kinds: [1], authors: [pubkey] }

// By tag
{ kinds: [1], '#p': [pubkey] }
{ kinds: [30402], '#d': [productSlug] }

// By time
{ 
  kinds: [1], 
  since: Math.floor(Date.now() / 1000) - 86400,  // Last 24h
  until: Math.floor(Date.now() / 1000)
}

// By event ID
{ ids: [eventId] }

// Multiple conditions
{
  kinds: [16, 17],
  '#order': [orderId],
  since: timestamp,
  limit: 100
}
```

## Tag Helpers

```typescript
// Get first tag value
const orderId = event.tagValue('order')

// Find specific tag
const tag = event.tags.find(t => t[0] === 'payment')
const value = tag?.[1]

// Get all of one type
const pTags = event.tags.filter(t => t[0] === 'p')

// Common tag formats
['p', pubkey]                          // Mention
['e', eventId]                         // Event reference
['t', 'nostr']                         // Hashtag
['d', identifier]                      // Replaceable ID
['a', '30402:pubkey:d-tag']           // Addressable reference
```

## Error Handling Pattern

```typescript
const ndk = ndkActions.getNDK()
if (!ndk) throw new Error('NDK not initialized')

const signer = ndk.signer
if (!signer) throw new Error('No active signer')

try {
  await event.publish()
} catch (error) {
  console.error('Publish failed:', error)
  throw error
}
```

## React Integration

```typescript
// Query function
export const fetchProducts = async (pubkey: string) => {
  const ndk = ndkActions.getNDK()
  if (!ndk) throw new Error('NDK not initialized')
  
  const events = await ndk.fetchEvents({
    kinds: [30402],
    authors: [pubkey]
  })
  
  return Array.from(events)
}

// React Query hook
export const useProducts = (pubkey: string) => {
  return useQuery({
    queryKey: ['products', pubkey],
    queryFn: () => fetchProducts(pubkey),
    enabled: !!pubkey,
  })
}

// Subscription in useEffect
useEffect(() => {
  if (!ndk || !orderId) return
  
  const sub = ndk.subscribe(
    { kinds: [16], '#order': [orderId] },
    { closeOnEose: false }
  )
  
  sub.on('event', () => {
    queryClient.invalidateQueries(['order', orderId])
  })
  
  return () => sub.stop()
}, [ndk, orderId, queryClient])
```

## Common Event Kinds

```typescript
0     // Metadata (profile)
1     // Text note
4     // Encrypted DM (NIP-04)
7     // Reaction
9735  // Zap receipt
10000 // Mute list
10002 // Relay list
30402 // Product listing (Marketplace)
31990 // App handler (NIP-89)
```

## Relay Management

```typescript
// Check connection
const connected = ndk.pool?.connectedRelays().length > 0

// Get connected relays
const relays = Array.from(ndk.pool?.relays.values() || [])
  .filter(r => r.status === 1)

// Add relay
ndk.addExplicitRelay('wss://relay.example.com')
```

## Connection with Timeout

```typescript
const connectWithTimeout = async (timeoutMs = 10000) => {
  const connectPromise = ndk.connect()
  const timeoutPromise = new Promise((_, reject) =>
    setTimeout(() => reject(new Error('Timeout')), timeoutMs)
  )
  
  await Promise.race([connectPromise, timeoutPromise])
}
```

## Current User

```typescript
// Active user
const user = ndk.activeUser

// From signer
const user = await ndk.signer?.user()

// User info
const pubkey = user.pubkey  // hex
const npub = user.npub      // NIP-19
```

## Parameterized Replaceable Events

```typescript
// Create
const event = new NDKEvent(ndk)
event.kind = 30402
event.content = JSON.stringify(data)
event.tags = [
  ['d', uniqueIdentifier],  // Required for replaceable
  ['title', 'Product Name'],
]

await event.sign()
await event.publish()

// Query (returns latest only)
const events = await ndk.fetchEvents({
  kinds: [30402],
  authors: [pubkey],
  '#d': [identifier]
})
```

## Validation Checks

```typescript
// Event age check
const now = Math.floor(Date.now() / 1000)
const age = now - (event.created_at || 0)
if (age > 86400) console.log('Event older than 24h')

// Required fields
if (!event.pubkey || !event.created_at || !event.sig) {
  throw new Error('Invalid event')
}

// Tag existence
const orderId = event.tagValue('order')
if (!orderId) throw new Error('Missing order tag')
```

## Performance Tips

```typescript
// Batch queries
const [products, orders] = await Promise.all([
  ndk.fetchEvents(productFilter),
  ndk.fetchEvents(orderFilter)
])

// Limit results
const filter = {
  kinds: [1],
  limit: 50,
  since: recentTimestamp
}

// Cache with React Query
const { data } = useQuery({
  queryKey: ['profile', npub],
  queryFn: () => fetchProfile(npub),
  staleTime: 5 * 60 * 1000,  // 5 min
})
```

## Debugging

```typescript
// Check NDK state
console.log('Connected:', ndk.pool?.connectedRelays())
console.log('Signer:', ndk.signer)
console.log('Active user:', ndk.activeUser)

// Event inspection
console.log('Event ID:', event.id)
console.log('Tags:', event.tags)
console.log('Content:', event.content)
console.log('Author:', event.pubkey)

// Subscription events
sub.on('event', e => console.log('Event:', e))
sub.on('eose', () => console.log('End of stored events'))
```

---

For detailed explanations and advanced patterns, see `ndk-skill.md`.

