Nois standard library

Use this library to integrate your app with the nois proxy.

Storing the proxy address

#[entry_point]
pub fn instantiate(
    deps: DepsMut,
    _env: Env,
    _info: MessageInfo,
    msg: InstantiateMsg,
) -> Result<Response, ContractError> {
    let nois_proxy_addr = deps
        .api
        .addr_validate(&msg.nois_proxy)
        .map_err(|_| ContractError::InvalidProxyAddress)?;
    NOIS_PROXY.save(deps.storage, &nois_proxy_addr)?;
    Ok(Response::new()
        .add_attribute("action", "instantiate")
        .add_attribute("nois_proxy", msg.nois_proxy))
}

Sending a request

use nois::ProxyExecuteMsg;

pub fn execute_estimate_pi(
    deps: DepsMut,
    _env: Env,
    _info: MessageInfo,
    job_id: String,
) -> Result<Response, ContractError> {
    let nois_proxy = NOIS_PROXY.load(deps.storage)?; // Nois proxy address stored in init

    let res = Response::new().add_message(WasmMsg::Execute {
        contract_addr: nois_proxy.into(),
        msg: to_binary(&ProxyExecuteMsg::GetNextRandomness { job_id })?,
        funds: vec![],
    });
    Ok(res)
}

Processing the callback

Create a ExecuteMsg enum case called Receive

use cosmwasm_schema::{cw_serde, QueryResponses};

use nois::NoisCallback;

#[cw_serde]
pub enum ExecuteMsg {
    // ...

    NoisReceive {
        callback: NoisCallback,
    },
}

and use it:

#[entry_point]
pub fn execute(
    deps: DepsMut,
    env: Env,
    info: MessageInfo,
    msg: ExecuteMsg,
) -> Result<Response, ContractError> {
    match msg {
        // ...

        ExecuteMsg::NoisReceive { callback } => execute_nois_receive(deps, env, info, callback),
    }
}

// ...

pub fn execute_nois_receive(
    deps: DepsMut,
    _env: Env,
    _info: MessageInfo,
    callback: NoisCallback,
) -> Result<Response, ContractError> {
    let proxy = NOIS_PROXY.load(deps.storage)?;
    ensure_eq!(info.sender, proxy, ContractError::UnauthorizedReceive);

    let NoisCallback { job_id, randomness, .. } = callback;
    let randomness: [u8; 32] = randomness
        .to_array()
        .map_err(|_| ContractError::InvalidRandomness)?;

    // use randomness 🎉
}

Build for JavaScript

The Nois Toolbox can be compiled to JavaScript via WebAssembly. This way you can simulate the outputs for every randomness value. The results match exactly those of CosmWasm contracts using the same tools.

In order to keep the JS/Wasm interface simple, there is a wrapper in the module lib/js which takes randomness inputs in hex format and uses types and error handling that plays well with JS. JS/Wasm bindings are created using wasm-bindgen.

The JS does not match 100% the contract implementation. The differences are documented here.

Contract function	JS function	Status	Note
nois::coinflip	coinflip	✅ Ready	Returns string instead of enum
nois::roll_dice	roll_dice	✅ Ready
nois::int_in_range	int_in_range	✅ Ready	Only supports safe integer range
nois::ints_in_range	ints_in_range	✅ Ready	Only supports safe integer range
nois::pick	pick	✅ Ready
nois::select_from_weighted	select_from_weighted	✅ Ready
nois::random_decimal	random_decimal	✅ Ready	Encodes result Decimal as string
nois::sub_randomness	sub_randomness	✅ Ready	Takes a count argument and returns an Array instead of an iterator
nois::shuffle	shuffle	✅ Ready

Installation

We need this:

$ cargo install wasm-pack -f
$ wasm-pack --version
wasm-pack 0.10.3

For Node.js

This creates a CommonJS module that is loaded synchonously.

$ wasm-pack build --target nodejs -- --features js
$ node
> const { coinflip, roll_dice, random_decimal, sub_randomness, int_in_range, ints_in_range, pick, select_from_weighted, shuffle } = require('./pkg/nois');

// Round 2497992

> coinflip("c59f098f3c12b8c36ed81f5c17660c72414a1ed63467888a374af529a205c584")
'tails'

// Round 2497994

> coinflip("2267ba7356c01a58e405d4194a31bddc3fd3eb1f0a86758f7a609ba8a47420ba")
'heads'
> roll_dice("2267ba7356c01a58e405d4194a31bddc3fd3eb1f0a86758f7a609ba8a47420ba")
6
> random_decimal("2267ba7356c01a58e405d4194a31bddc3fd3eb1f0a86758f7a609ba8a47420ba")
'0.126047856387596389'
> sub_randomness("2267ba7356c01a58e405d4194a31bddc3fd3eb1f0a86758f7a609ba8a47420ba", 3)
[
  'ac7b151d67cd4263520b16e450e6d1fc01750dab80b5d8b7cdc4075c99daf80a',
  '33622b0865f1ab35142e3e63a91c25cf89311b04b9540ca15e49413a4a114ce1',
  'f08927af18d4995c28f15f07e4038407f32d966087771314b9e64b6a33a9101c'
]
> int_in_range("2267ba7356c01a58e405d4194a31bddc3fd3eb1f0a86758f7a609ba8a47420ba", 5, 9)
9
> ints_in_range("2267ba7356c01a58e405d4194a31bddc3fd3eb1f0a86758f7a609ba8a47420ba", 20, 0, 1)
[
  1, 1, 1, 0, 0, 1, 1,
  0, 0, 1, 1, 1, 1, 1,
  0, 0, 0, 0, 0, 1
]
> shuffle("2267ba7356c01a58e405d4194a31bddc3fd3eb1f0a86758f7a609ba8a47420ba", [1, 2, 3, "a", "b", true])
[ 2, 'a', 1, 'b', 3, true ]
> pick("2267ba7356c01a58e405d4194a31bddc3fd3eb1f0a86758f7a609ba8a47420ba", 4, [1, 2, 3, "a", "b", true])
[ 'a', 'b', 3, true ]
> select_from_weighted("2267ba7356c01a58e405d4194a31bddc3fd3eb1f0a86758f7a609ba8a47420ba", [["red", 20], ["blue", 70]])
'blue'

For browsers and other JS environments

You need to change the target in order to get a suiteable package. E.g.

$ wasm-pack build --target web -- --features js
$ ls ./pkg

for browsers. Please refer to the wasm-bindgen handbook to learn more about targets.