Dart Nostr Development Kit (NDK)

NDK (Nostr Development Kit) is a Dart library designed to enhance the Nostr development experience. It provides streamlined solutions for common use cases and abstracts away complex relay management, making it ideal for building constrained Nostr clients, particularly on mobile devices.
NDK implements the inbox/outbox (gossip) model by default, optimizing network usage and improving performance.

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Prerequisites

android SDK (also for desktop builds)
flutter SDK
rust ( + toolchain for target)

Rust toolchain android:

rustup target add \
    aarch64-linux-android \
    armv7-linux-androideabi \
    x86_64-linux-android \
    i686-linux-android

Rust toolchain ios:

# 64 bit targets (real device & simulator):
rustup target add aarch64-apple-ios x86_64-apple-ios
# New simulator target for Xcode 12 and later
rustup target add aarch64-apple-ios-sim
# 32 bit targets (you probably don't need these):
rustup target add armv7-apple-ios i386-apple-ios

Getting started

Install

flutter pub add ndk

Import

import 'package:ndk/ndk.dart';

Usage

usage examples

import 'package:ndk/ndk.dart';

// init
Ndk ndk = Ndk(
  NdkConfig(
    eventVerifier: RustEventVerifier(),
    cache: MemCacheManager(),
  ),
);

// query
NdkResponse response = ndk.requests.query(
  filters: [
    Filter(
      authors: ['hexPubkey']
      kinds: [Nip01Event.TEXT_NODE_KIND],
      limit: 10,
    ),
  ],
);

// result
await for (final event in response.stream) {
  print(event);
}

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Features / what does NDK do?

return nostr data based on filters (any kind).
automatically discover the best relays to satisfy the provided request (using gossip)
specify desired coverage on each request (e.g. x relays per pubkey)
publish nostr events to optimal relays or explicit relays
cache responses to save network bandwidth
stream directly from cache and network (if needed)
query and subscription, e.g., get data once; subscribe to data.
plugin cache interface, bring your own db or use included ones: inMemory
plug in verifier interface, bring your own event verifier, or use included ones: bip340, rust
plug in event signer interface, bring your own event signer, or use included ones: bip340, amber
contact list support, you can convert nostr_event to contact_list
nip51 list support, you can convert nostr_event to nip51_list

not Included

ready to use feeds, you have to build them on your own (🚫 not planned)
create && manage keypairs. You have to provide them (🚫 not planned)
file upload (🔜 planned)
nip05 caching (🔜 planned)
threading, you can do this on your own if you move ndk or only the event_verifier into its own thread (🔜 planned)
support for request overrides (you have to close and reopen requests) (🤔 unsure)

NIPs

x Event Builders / WebSocket Subscriptions (NIP-01)
x User Profiles (edit/follow/unfollow - NIP-02)
x Private Messages (NIP-04)
x Nostr Address (NIP-05)
x Event Deletion (NIP-09)
x Relay Info (NIP-11)
x Reactions (NIP-25)
x Lists (NIP-51)
x Relay List Metadata (NIP-65)
Bech Encoding support (NIP-19)
Wallet Connect API (NIP-47)
Zaps (private, public, anon, non-zap) (NIP-57)
Badges (NIP-58)

Performance

There are two main constrains that we aim for: battery/compute and network bandwidth.

network
Inbox/Outbox (gossip) is our main pillar to help avoid unnecessary nostr requests. We try to leverage the cache as much as possible.
Even splitting the users filters into smaller relay tailored filters if we know the relay has the information we need.

compute
Right now the most compute intensive operation is verifying signatures.
We use the cache to determine if we have already seen the event and only if it is unknown signature verification is done.
To make the operation as optimized as possible we strongly recommend using RustEventVerifier() because it uses a separate thread for verification.

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Gossip/outbox model of relay discovery and connectivity

The simplest characterization of the gossip model is just this: reading the posts of people you follow from the relays that they wrote them to.

more details on https://mikedilger.com/gossip-model/

common terminology

term	explanation	simmilar to
broadcastEvent	push event to nostr network/relays	postEvent, publishEvent
JIT	Just In Time, e.g. as it happens	-
query	get data once and close the request	get request
subscription	stream of events as they come in	stream of data
bootstrapRelays	default relays to connect when nothing else is specified	seed relays, initial relays

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Changelog 🔗

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Library development 🏗️

setup

Install prerequisites

If you work on rust code (rust_builder/rust) run flutter_rust_bridge_codegen generate --watch to generate the rust dart glue code.

Run build runner: (e.g for generating mocks)
dart run build_runner build

architecture

lib/
- config/
  - # contains configuration files
- shared/
  - nipX # folders for nip specific code
  - # only internal code, no external dependencies!
- data_layer/
  - data_sources/
    - # external apis, websocket impl etc.
  - models/
    - # type conversion e.g. json to entity
  - repositories/
    - # repository implementations (implementing domain_layer repos)
- domain_layer/
  - entities/
    - # our entities e.g. data types
  - repositories/
    - # contracts
  - usecases/
    - # our main code / business logic
- presentation_layer/
  - # contains our api design (makes usecases accessible to outside world)
- ndk.dart # entrypoint, points to presentation_layer

Dart Nostr Development Kit (NDK)

Prerequisites

Getting started

Install

Import

Usage

Features / what does NDK do?

not Included

NIPs

Performance

Gossip/outbox model of relay discovery and connectivity

common terminology

Changelog 🔗

Library development 🏗️

setup

architecture

Libraries

ndk package