heura

README

Heura

Ethereum DSL to interact with smart contracts, call and listen for events.

Install

go get github.com/umbracle/heura/heura

Usage

Start the REPL:

go run main.go

Run a specific file:

go run main.go source.hra

By default, Heura uses the Infura mainnet nodes to make calls to contracts (https) and listen for events (websockets). Those values can be modified by setting the next flags:

go run main.go --endpoint <endpoint> --wsendpoint <websocket endpoint> <file.hra>

Syntax

Heura is an interpreted language. It is still a work in progress and the syntax is expected to change.

Artifacts

Load artifacts from folder or files

artifact (
    "./abis",
    "./artifacts/0x.json"
)

or use the builtin ones:

artifacts (
    "ERC20"
)

Calls

Once the artifact is loaded, you can instantiate contracts at specific addresses:

let token = ERC20(0x...)

or use ENS:

let token = ERC20("sometoken.eth")

After this, the call functions specified in the ABI are available:

token.decimals();

Transactions are not supported.

Events

Listen for ethereum events:

on ERC20.Transfer (from, to, value) {
    print (from)
}

or filter for an specific address (with either the address or an ENS name):

on ERC20("somename.eth").Transfer (from, to, value)

Inside the scope of the event callback there is a special 'this' variable with information about the transaction that executed the event: blocknumber, blockhash, transaction hash and an instance of the contract that emit the event.

on ERC20.Transfer (from, to, value) {
    print (this.blocknumber)
    print (this.obj.symbol())
} 

It is possible to filter by specific topic values in the event:

let FROM=0xB9536d30A25466a909563EE4f35fE3c158fc2964

on ERC20.Transfer(from=FROM, to, value) {

Note that is only possible with parameters that are indexed on the event.

Functions

Functions are declared with the keyword 'fn' and can return multiple values.

fn some_function() {
    return 1, 2
}

let x, y := some_function()

Libraries

Etherscan

Query a specific contract on Etherscan:

import "etherscan"

print(ens.Contract("0x..."))

Fetch ABIs from Etherscan:

import "etherscan"

let Contract = ens.Contract("0x")

on Contract.Transfer(from, to, value) {

}

Ens

Resolve an ENS address:

import "ens"

print(ens.Resolve("address.eth"))