using System.Globalization;

namespace BookStoreItem
{
    /// <summary>
    /// Represents the an item in a book store.
    /// </summary>
    public class BookStoreItem
    {
        private readonly string? authorName;
        private readonly string? isni;
        private readonly bool hasIsni;
        private decimal price;
        private string currency;
        private int amount;

        /// <summary>
        /// Initializes a new instance of the <see cref="BookStoreItem"/> class with the specified <paramref name="authorName"/>, <paramref name="title"/>, <paramref name="publisher"/> and <paramref name="isbn"/>.
        /// </summary>
        /// <param name="authorName">A book author's name.</param>
        /// <param name="title">A book title.</param>
        /// <param name="publisher">A book publisher.</param>
        /// <param name="isbn">A book ISBN.</param>
        public BookStoreItem(string authorName, string title, string publisher, string isbn)
            : this(authorName, string.Empty, title, publisher, isbn)
        {
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="BookStoreItem"/> class with the specified <paramref name="authorName"/>, <paramref name="isni"/>, <paramref name="title"/>, <paramref name="publisher"/> and <paramref name="isbn"/>.
        /// </summary>
        /// <param name="authorName">A book author's name.</param>
        /// <param name="isni">A book author's ISNI.</param>
        /// <param name="title">A book title.</param>
        /// <param name="publisher">A book publisher.</param>
        /// <param name="isbn">A book ISBN.</param>
        public BookStoreItem(string authorName, string? isni, string title, string publisher, string isbn)
            : this(authorName, isni, title, publisher, isbn, null, string.Empty, 0, "USD", 0)
        {
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="BookStoreItem"/> class with the specified <paramref name="authorName"/>, <paramref name="title"/>, <paramref name="publisher"/> and <paramref name="isbn"/>, <paramref name="published"/>, <paramref name="bookBinding"/>, <paramref name="price"/>, <paramref name="currency"/> and <paramref name="amount"/>.
        /// </summary>
        /// <param name="authorName">A book author's name.</param>
        /// <param name="title">A book title.</param>
        /// <param name="publisher">A book publisher.</param>
        /// <param name="isbn">A book ISBN.</param>
        /// <param name="published">A book publishing date.</param>
        /// <param name="bookBinding">A book binding type.</param>
        /// <param name="price">An amount of money that a book costs.</param>
        /// <param name="currency">A price currency.</param>
        /// <param name="amount">An amount of books in the store's stock.</param>
        public BookStoreItem(string authorName, string title, string publisher, string isbn, DateTime? published, string bookBinding, decimal price, string currency, int amount)
            : this(authorName, string.Empty, title, publisher, isbn, published, bookBinding, price, currency, amount)
        {
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="BookStoreItem"/> class with the specified <paramref name="authorName"/>, <paramref name="isni"/>, <paramref name="title"/>, <paramref name="publisher"/> and <paramref name="isbn"/>, <paramref name="published"/>, <paramref name="bookBinding"/>, <paramref name="price"/>, <paramref name="currency"/> and <paramref name="amount"/>.
        /// </summary>
        /// <param name="authorName">A book author's name.</param>
        /// <param name="isni">A book author's ISNI.</param>
        /// <param name="title">A book title.</param>
        /// <param name="publisher">A book publisher.</param>
        /// <param name="isbn">A book ISBN.</param>
        /// <param name="published">A book publishing date.</param>
        /// <param name="bookBinding">A book binding type.</param>
        /// <param name="price">An amount of money that a book costs.</param>
        /// <param name="currency">A price currency.</param>
        /// <param name="amount">An amount of books in the store's stock.</param>
        public BookStoreItem(string authorName, string? isni, string title, string publisher, string isbn, DateTime? published, string bookBinding, decimal price, string currency, int amount)
        {
            if (string.IsNullOrWhiteSpace(authorName))
            {
                throw new ArgumentException(" ", nameof(authorName));
            }

            if (!ValidateIsni(isni))
            {
                throw new ArgumentException(" ", nameof(isni));
            }

            if (string.IsNullOrWhiteSpace(title))
            {
                throw new ArgumentException(" ", nameof(title));
            }

            if (string.IsNullOrWhiteSpace(publisher))
            {
                throw new ArgumentException(" ", nameof(publisher));
            }

            if (!ValidateIsbn(isbn) && !ValidateIsbnChecksum(isbn))
            {
                throw new ArgumentException(" ", nameof(isbn));
            }

            this.authorName = authorName;
            this.isni = isni;
            this.currency = currency;
            this.amount = amount;
            this.Title = title;
            this.Publisher = publisher;
            this.Isbn = isbn;
            this.Published = published;
            this.BookBinding = bookBinding;
            this.Price = price;
            this.hasIsni = isni != null;
        }

        /// <summary>
        /// Gets a book author's name.
        /// </summary>
        public string? AuthorName => this.authorName;

        /// <summary>
        /// Gets an International Standard Name Identifier (ISNI) that uniquely identifies a book author.
        /// </summary>
        public string? Isni => this.isni;

        /// <summary>
        /// Gets a value indicating whether an author has an International Standard Name Identifier (ISNI).
        /// </summary>
        public bool HasIsni => this.hasIsni;

        /// <summary>
        /// Gets a book title.
        /// </summary>
        public string Title { get; private set; }

        /// <summary>
        /// Gets a book publisher.
        /// </summary>
        public string Publisher { get; private set; }

        /// <summary>
        /// Gets a book International Standard Book Number (ISBN).
        /// </summary>
        public string Isbn { get; private set; }

        /// <summary>
        /// Gets or sets a book publishing date.
        /// </summary>
        public DateTime? Published { get; set; }

        /// <summary>
        /// Gets or sets a book binding type.
        /// </summary>
        public string BookBinding { get; set; }

        /// <summary>
        /// Gets or sets an amount of money that a book costs.
        /// </summary>
        public decimal Price
        {
            get => this.price;

            set
            {
                if (this.price < 0)
                {
                    throw new ArgumentOutOfRangeException(nameof(this.Price), "Price is less then zero.");
                }

                this.price = value;
            }
        }

        /// <summary>
        /// Gets or sets a price currency.
        /// </summary>
        public string Currency
        {
            get => this.currency;

            set
            {
                ThrowExceptionIfCurrencyIsNotValid(this.currency);

                this.currency = value;
            }
        }

        /// <summary>
        /// Gets or sets an amount of books in the store's stock.
        /// </summary>
        public int Amount { get; set; }

        /// <summary>
        /// Gets a <see cref="Uri"/> to the contributor's page at the isni.org website.
        /// </summary>
        /// <returns>A <see cref="Uri"/> to the contributor's page at the isni.org website.</returns>
        public Uri GetIsniUri()
        {
            if (!this.HasIsni)
            {
                throw new InvalidOperationException();
            }

            return new Uri($"https://isni.org/isni/{this.isni}");
        }

        /// <summary>
        /// Gets an <see cref="Uri"/> to the publication page on the isbnsearch.org website.
        /// </summary>
        /// <returns>an <see cref="Uri"/> to the publication page on the isbnsearch.org website.</returns>
        public Uri GetIsbnSearchUri() => new Uri($"https://isbnsearch.org/isbn/{this.Isbn}");

        /// <summary>
        /// Returns the string that represents a current object.
        /// </summary>
        /// <returns>A string that represents the current object.</returns>
        public override string ToString()
        {
            string formatPriceAndCurrency = this.price.ToString("N", CultureInfo.InvariantCulture);
            formatPriceAndCurrency = formatPriceAndCurrency.Contains(',', StringComparison.InvariantCulture) ? $"\"{formatPriceAndCurrency} {this.currency}\"" : $"{formatPriceAndCurrency} {this.currency}";

            if (!this.HasIsni)
            {
                return $"{this.Title}, {this.authorName}, ISNI IS NOT SET, {formatPriceAndCurrency}, {this.Amount}";
            }

            return $"{this.Title}, {this.authorName}, {this.isni}, {formatPriceAndCurrency}, {this.Amount}";
        }

        private static bool ValidateIsni(string? isni)
        {
            if (isni == null || isni.Length != 16)
            {
                return false;
            }

            for (int i = 0; i < isni.Length; i++)
            {
                if (CharToInt(isni[i]) == -1)
                {
                    return false;
                }
            }

            return true;
        }

        private static bool ValidateIsbn(string? isbn)
        {
            if (isbn == null || isbn.Length != 16)
            {
                return false;
            }

            for (int i = 0; i < isbn.Length; i++)
            {
                if (CharToInt(isbn[i]) == -1)
                {
                    return false;
                }
            }

            return ValidateIsbnChecksum(isbn);
        }

        private static bool ValidateIsbnChecksum(string isbn)
        {
            int checkSum = 0;
            for (int i = 0; i < isbn.Length; i++)
            {
                checkSum += CharToInt(isbn[i]) * (10 - i);
            }

            return checkSum % 11 == 0;
        }

        private static void ThrowExceptionIfCurrencyIsNotValid(string currency)
        {
            if (currency.Length != 3)
            {
                throw new ArgumentException(" ", nameof(currency));
            }

            for (int i = 0; i < currency.Length; i++)
            {
                if (!char.IsLetter(currency[i]))
                {
                    throw new ArgumentException(" ", nameof(currency));
                }
            }
        }

        private static int CharToInt(char digit) =>
            digit switch
            {
                '0' => 0,
                '1' => 1,
                '2' => 2,
                '3' => 3,
                '4' => 4,
                '5' => 5,
                '6' => 6,
                '7' => 7,
                '8' => 8,
                '9' => 9,
                'X' => 10,
                _ => -1
            };
    }
}