parking/js advanced exam

class Parking {
    constructor(capacity) {
        this.capacity = capacity;
        this.vehicles = [];
    }

    addCar(carModel, carNumber) {
        if(this.capacity === 0) {
            throw new Error(`Not enough parking space.`);
        }

        this.vehicles.push({carModel, carNumber, payed: false});
        this.capacity--;

        return `The ${carModel}, with a registration number ${carNumber}, parked.`;
    }

    removeCar(carNumber) {
        const carIndex = this.vehicles.findIndex(car => car.carNumber === carNumber);

        if(carIndex < 0) {
            throw new Error(`The car, you're looking for, is not found.`);
        }

        if(!this.vehicles[carIndex].payed) {
            throw new Error(`${carNumber} needs to pay before leaving the parking lot.`)
        }

        this.vehicles.splice(carIndex, 1);
        this.capacity++;

        return `${carNumber} left the parking lot.`;
    }

    pay(carNumber) {
        let car = this.vehicles.find(car => car.carNumber === carNumber);

        if(!car) {
            throw new Error(`${carNumber} is not in the parking lot.`);
        }

        if(car.payed) {
            throw new Error(`${carNumber}'s driver has already payed his ticket.`);
        }

        car.payed = true;

        return `${carNumber}'s driver successfully payed for his stay.`;
    }

    getStatistics(carNumber) {
        if(!carNumber) {
            return [
                `The Parking Lot has ${this.capacity} empty spots left.`,
                this.vehicles
                .sort((a, b) => a.carModel.localeCompare(b.carModel))
                .map(car => `${car.carModel} == ${car.carNumber} - ${car.payed ? `Has payed` : `Not payed`}`)
                .join(`\n`)
            ].join(`\n`)
        }

        let car = this.vehicles.find(car => car.carNumber === carNumber);

        return `${car.carModel} == ${car.carNumber} - ${car.payed ? `Has payed` : `Not payed`}`;
    }
}