Library

class Library {
    libraryName;
    subscribers;
    subscriptionTypes;

    constructor(libraryName) {
        this.libraryName = libraryName;
        this.subscribers = [];
        this.subscriptionTypes = {
            'normal': this.libraryName.length,
            'special': this.libraryName.length * 2,
            'vip': Number.MAX_SAFE_INTEGER
        };
        // this.subscriptionTypes = {
        //     normal: this.libraryName.length,
        //     special: this.libraryName.length * 2,
        //     vip: Number.MAX_SAFE_INTEGER
        // };
    }

    subscribe(name, type) {
        if (this.subscriptionTypes[type] === undefined) {
            throw new Error(`The type ${type} is invalid`);
        }
        let sub = this.subscribers.find(s => s.name === name);
        if (sub === undefined) {
            let newSub = {name, type, books: []};
            this.subscribers.push(newSub);
            return newSub;
        } else {
            sub.type = type;
            return sub;
        }
    }

    unsubscribe(name) {
        let sub = this.subscribers.find(s => s.name === name);
        if (sub === undefined) {
            throw new Error(`There is no such subscriber as ${name}`);
        }
        this.subscribers.splice(this.subscribers.indexOf(sub), 1);
        return this.subscribers;
    }

    receiveBook(name, title, author) {
        let sub = this.subscribers.find(s => s.name === name);
        if (sub === undefined) {
            throw new Error(`There is no such subscriber as ${name}`);
        }
        let max = this.subscriptionTypes[sub.type];
        if (sub.books.length < max) {
            sub.books.push({title, author});
        } else {
            throw new Error(`You have reached your subscription limit ${max}!`);
        }
        return sub;
    }

    showInfo() {
        if (this.subscribers.length > 0) {
            let str = '';
            this.subscribers.map(s => {
                let books = s.books.map(b => `${b.title} by ${b.author.trim()}`).join(', ');
                str += `Subscriber: ${s.name}, Type: ${s.type}\nReceived books: ${books.trim()}\n`;
            });
            return str;

        } else {
            return `${this.libraryName} has no information about any subscribers`;
        }
    }
}