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

namespace PingPong.GameEngine.Components
{
    public class Score
    {	
		#region Members
		
        /// <summary>
        /// The score history.
        /// </summary>
        private Stack<int> history;
		
        /// <summary>
        /// The score value.
        /// </summary>
        private Lazy<int> value;
		
		#endregion
		
		#region Properties
		
        /// <summary>
        /// Gets the score value.
        /// </summary>
        /// <value>
        /// The value.
        /// </value>
        public int Value
        {
            get
            {
                return this.value.Value;
            }
            private set
            {
                history.Push(this.Value);
                this.value = new Lazy<int>(() => value);
            }
        }
		
        /// <summary>
        /// Gets the increment expression.
        /// </summary>
        /// <value>
        /// The increment expression.
        /// </value>
        public string IncrementExpression { get; private set; }
		
        /// <summary>
        /// Gets the decrement expression.
        /// </summary>
        /// <value>
        /// The decrement expression.
        /// </value>
        public string DecrementExpression { get; private set; }
			
		#endregion
		
		#region Constructors
		
		/// <summary>
		/// Initializes a new instance of the <see cref="PingPong.GameEngine.Score"/> class.
		/// </summary>
        public Score()
		{
			this.history = new Stack<int>();
			this.value = new Lazy<int>(() => default(int));
        }
		
		#endregion
		
		#region Methods
		
		/// <summary>
		/// Sets the increment expression.
		/// </summary>
		/// <returns>
		/// The increment expression.
		/// </returns>
		/// <param name='expression'>
		/// Expression.
		/// </param>
        public Score SetIncrementExpression(string expression)
		{
			if (string.IsNullOrWhiteSpace(expression))
			{
				throw new ArgumentNullException("expression");
			}
			
            this.IncrementExpression = expression;
            return this;
        }
		
        /// <summary>
        /// Sets the decrement expression.
        /// </summary>
        /// <returns>
        /// The decrement expression.
        /// </returns>
        /// <param name='expression'>
        /// Expression.
        /// </param>
        public Score SetDecrementExpression(string expression)
        {
            this.DecrementExpression = expression;
            return this;
        }
		
		/// <summary>
		/// Sets the score.
		/// </summary>
		/// <returns>
		/// The score.
		/// </returns>
		/// <param name='expression'>
		/// Expression.
		/// </param>
		public Score SetScore(string expression)
		{
			if (string.IsNullOrWhiteSpace(expression))
			{
				throw new ArgumentNullException("expression");
			}
			
			Engine.ExpressionParser.Interpret(expression);
			this.Value = Engine.ExpressionParser.Int;
			return this;
		}

        /// <summary>
        /// Sets the score.
        /// </summary>
        /// <returns>
        /// The score.
        /// </returns>
        /// <param name='score'>
        /// Score.
        /// </param>
        public Score SetScore(int score)
        {
            this.Value = score;
            return this;
        }
		
        /// <summary>
        /// Increment this instance.
        /// </summary>
        public int Increment()
		{
			if (string.IsNullOrWhiteSpace(this.IncrementExpression))
			{
				throw new NotImplementedException("No increment expression set.");
			}
			
			Engine.ExpressionParser.Interpret(this.IncrementExpression);
			this.Value += Engine.ExpressionParser.Int;
			return this.Value;
        }
		
        /// <summary>
        /// Decrement this instance.
        /// </summary>
        public int Decrement()
		{
			if (string.IsNullOrWhiteSpace(this.DecrementExpression))
			{
				Reverse();
			}
			else
			{
				throw new NotImplementedException("No decrement expression set.");
			}
			
			Engine.ExpressionParser.Interpret(this.DecrementExpression);
			this.Value += Engine.ExpressionParser.Int;
			return this.Value;
        }
		
        /// <summary>
        /// Reverse the last action.
        /// </summary>
        public int Reverse()
        {
            if (!this.history.Any())
            {
                throw new ArgumentOutOfRangeException("No history found.");
            }
			
            this.value = new Lazy<int>(() => this.history.Pop());
            return this.Value;
        }
		
		#endregion

        #region Operators

        /// <param name='score'>
        /// Score.
        /// </param>
        public static implicit operator int(Score score)
        {
            return score.Value;
        }
    
        #endregion
    }
}