using System;

namespace DesignPatterns.Factory {
	public class Money : IMoney {
		public Money( double amount ) : this( amount, Currency.Canadian ) {}

		public Money( double amount, ICurrency currency ) {
			if ( amount < 0 ) {
				throw new NegativeMoneyException( );
			}
			_amount = amount;
			_currency = currency;
		}

		public double Amount {
			get { return _amount; }
		}

		public ICurrency TypeOfCurrency {
			get { return _currency; }
		}

		public IMoney Add( IMoney other ) {
			if ( other != null ) {
				if ( other.TypeOfCurrency.Equals( TypeOfCurrency ) ) {
					return new Money( other.Amount + Amount );
				}
				throw new CannotAddMoniesException( "Cannot add monies of different currency" );
			}
			return this;
		}

		public IMoney Subtract( IMoney money ) {
			return ( money != null ) ? new Money( Amount - money.Amount ) : null;
		}

		public override bool Equals( object obj ) {
			IMoney other = obj as Money;
			if ( other != null ) {
				return other.Amount == Amount;
			}
			return false;
		}

		public override int GetHashCode( ) {
			return base.GetHashCode( ) + new Random( ( int )DateTime.Now.Ticks ).Next( );
		}

		public override string ToString( ) {
			return _amount.ToString( "F" );
		}

		private readonly double _amount;
		private readonly ICurrency _currency;
	}
}