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.

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.