ExampleApi.ts

type SubscriptionKey = string;

interface Connector {
    trackAccount(account:string);
};

interface EventEmitter {
    emit(key, payload);
    subscribe():SubscriptionKey
    unsubscribe(subscriptionKey):boolean;
};

interface Signer {
    getAddress():string;
};

export class API implements EventEmitter {
    // Assume connector contains the provider for this exercise.
    _connector: Connector | null;
    _signer: Signer | null;

    // This would be used for initialization and reinitialization (switching accounts)
    initialize(signer, connector?: Connector) {
        if (connector) {
            this._connector = connector;
        }

        this.switchAccount(signer);
    };

    async switchAccount(signer: Signer) {
        this._connector.trackAccount(signer.getAddress());
        const prev = this._signer;;
        this._signer= signer;
        this.emit('LoggedOut', prev);
        this.emit('LoggedIn', signer);
    }

    getAccount() {
        // return account class with account specific apis.
    }

    // The rest of the api goes here....
    getOrders(maketId: number) {
        // make calls to lower level stuff to make it happen. Note the consumer of this class doesn't need to know contract addresses.
    }


    emit(key, payload) {}

    subscribe(): {}

    unsubscribe(subscriptionKey): boolean {
        return true;
    }


}

export const api = new API();