libraryCollection

class LibraryCollection {
    constructor(capacity) {
        this.capacity = capacity;
        this.books = [];
    }
    addBook(bookName, bookAuthor) {
        if (this.books.length === this.capacity) {
            throw new Error('Not enough space in the collection.');
        }
        this.books.push({ bookName, bookAuthor, payed: false });
        return `The ${bookName}, with an author ${bookAuthor}, collect.`;
    }
    payBook(bookName) {
        let searchedBook = this.books.find((b) => b.bookName === bookName);
        if (!searchedBook) {
            throw new Error(`${bookName} is not in the collection.`);
        }
        if (searchedBook.payed) {
            throw new Error(`${bookName} has already been paid.`);
        }
        searchedBook.payed = true;
        return `${bookName} has been successfully paid.`;
    }
    removeBook(bookName) {
        let bookIdx = this.books.findIndex((b) => b.bookName === bookName);
        if (bookIdx === -1) {
            throw new Error("The book, you're looking for, is not found.");
        }
        if (!this.books[bookIdx].payed) {
            throw new Error(
                `${bookName} need to be paid before removing from the collection.`
            );
        }
        this.books.splice(bookIdx, 1);
        return `${bookName} remove from the collection.`;
    }
    getStatistics(bookAuthor) {
        let result = [];
        if (bookAuthor === undefined) {
            result.push(
                `The book collection has ${
                    this.capacity - this.books.length
                } empty spots left.`
            );
            this.books
                .sort((a, b) => a.bookName.localeCompare(b.bookName))
                .forEach((b) =>
                    result.push(
                        `${b.bookName} == ${b.bookAuthor} - ${
                            b.payed ? 'Has Paid' : 'Not Paid'
                        }.`
                    )
                );
            return result.join('\n');
        }
        let searchedBook = this.books.find((b) => b.bookAuthor === bookAuthor);
        if (!searchedBook) {
            throw new Error(`${bookAuthor} is not in the collection.`);
        }
        return `${searchedBook.bookName} == ${searchedBook.bookAuthor} - ${
            searchedBook.payed ? 'Has Paid' : 'Not Paid'
        }.`;
    }
}