mashafrancis/butternut-user

import { forwardRef, Inject, OnModuleInit } from '@nestjs/common';
import { AccessEnum } from './access.enum';
import { VoterRegistry } from './voter-registry';
import { VoterInterface } from './voter.interface';

export abstract class Voter implements VoterInterface, OnModuleInit {
    @Inject(forwardRef(() => VoterRegistry))
    private readonly voterRegistry: VoterRegistry;

    public onModuleInit() {
        this.voterRegistry.register(this);
    }

    public async vote(
        token: any,
        subject: any,
        attributes: any[],
    ): Promise<AccessEnum> {
        let vote = AccessEnum.ACCESS_ABSTAIN;

        for (const attribute of attributes) {
            if (!this.supports(attribute, subject)) {
                continue;
            }
            // as soon as at least one attribute is supported, default is to deny access
            vote = AccessEnum.ACCESS_DENIED;
            if (await this.voteOnAttribute(attribute, subject, token)) {
                // grant access as soon as at least one attribute returns a positive response
                return AccessEnum.ACCESS_GRANTED;
            }
        }

        return vote;
    }

    protected abstract supports(attribute, subject): boolean;

    protected abstract async voteOnAttribute(
        attribute,
        subject,
        token,
    ): Promise<boolean>;
}