using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace LibrarySystem
{
    public abstract class Item
    {
        // Instance variables.
        private string title;
        protected DateTime? dateBorrowed = null;
        private Member borrower = null;

        // Constructor.
        public Item(string title)
        {
            this.title = title;
        }

        // Business methods / properties.
        public bool Borrowed
        {
            get { return borrower != null; }
        }

        public virtual bool CanBeBorrowedBy(Member member)
        {
            return true;
        }

        public bool BorrowItemBy(Member member)
        {
            // Has the item not been borrowed yet, and is the specified member allowed to borrow it?
            if (!Borrowed && CanBeBorrowedBy(member))
            {
                // Record the fact that this item is now borrowed by the member.
                borrower = member;
                dateBorrowed = DateTime.Today;
                borrower.BorrowedItem();
                return true;
            }
            else
            {
                return false;
            }
        }

        public virtual void ReturnItem()
        {
            // Record the fact that this item is no longer borrowed by the member.
            borrower.ReturnedItem();
            borrower = null;
            dateBorrowed = null;
        }

        public abstract DateTime? DateDueBack { get; }

        // string representation.
        public override string ToString()
        {
            if (borrower != null)
            {
                return string.Format("{0} is on loan to {1} [borrowed at {2}].", title, borrower.Name, dateBorrowed.Value.ToShortDateString());
            }
            else
            {
                return string.Format("{0} is not on loan.", title);
            }
        }
    }
}