bitcoin-stub.js

export type BlockChainType = {|
    addBlock : (hashedBlock : string) => Promise<void>,
    createBlock : (publicKey : string, transactions : Array<string>) => Promise<?string>,
    getBalances : () => Promise<Counter>
|};

export function BlockChain() : BlockChainType {
    const createBlock = async (publicKey, transactions) : Promise<?string> => {

    };
    
    const addBlock = async (block : BlockType) => {

    };
    
    const getBalances = async () : Promise<Counter> => {

    };

    return {
        addBlock,
        createBlock,
        getBalances
    };
}