using System;

/// <summary>
/// Represents a phone number for a contact. Contains methods to determine if two phone numbers are the same.
/// </summary>
namespace Contacts
{
    public class Phone : IEquatable<Phone>
    {
        public string number { get; }
        public PhoneType? Type { get; }

        /// <summary>
        /// Accepts an input string in the format "1234567890" to create a new Phone object for a Contacts.
        /// </summary>
        /// <param name="number"></param>
        /// <param name="type">If null, defaults to "Other"</param>
        /// <exception cref="ArgumentException">Thrown if input has an invalid format.</exception>
        public Phone(string number, PhoneType? type)
        {
            if (number.Length != 10)
                throw new ArgumentException("Input phone number should be in the format 1234567890.");

            this.number = number;
            this.Type = type;
        }

        /// <summary>
        /// Determines if two phone numbers are equal, to avoid potential duplication.
        /// </summary>
        /// <param name="numberToCompare">Phone number to compare to. If null, returns false.</param>
        /// <returns>Whether or not the two phone numbers are the same.</returns>
        public bool Equals(Phone? numberToCompare)
        {
            if (numberToCompare == null)
                return false;

            return this.ToString().Equals(numberToCompare.ToString());
        }


        /// <summary>
        /// Returns the phone number without any formatting, for use in saving contacts to a file.
        /// </summary>
        /// <returns>Unformatted phone number</returns>
        public string DisplayString()
        {
            return number;
        }

        /// <summary>
        /// Formats the phone number to "(123) 456 - 7890"
        /// </summary>
        /// <returns>Formatted phone number</returns>
        public override string ToString()
        {
            return "(" + number.Substring(0, 3) + ") " + number.Substring(3, 3) + " - " + number.Substring(6);
        }
    }
}