using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Content;

namespace CarFire
{
    /// <summary>
    /// A trigger is an invisible entity whose only purpose is
    /// to check a condition and run a script when the condition
    /// is right.
    /// </summary>
    public class Trigger : IEntity
    {
        #region Public Methods

        /// <summary>
        /// Construct a trigger entity.
        /// </summary>
        /// <param name="identifier">The entity identifier.</param>
        /// <param name="position">The position.</param>
        /// <param name="info">The key-value pairs.</param>
        /// <param name="game">The game reference.</param>
        public Trigger(char identifier, Point position, Dictionary<string, string> info, Game game)
        {
            mGame = game;
            mPrevCondition = false;
            mCoordinates = position;

            string condition;
            if (info.TryGetValue("condition", out condition))
            {
                mCondition = new Script(condition, game);
            }
            else throw new Exception("Triggers must define a condition script.");

            string eventt;
            if (info.TryGetValue("event", out eventt))
            {
                mEvent = new Script(eventt, game);
            }
            else throw new Exception("Triggers must define an event script.");
        }

        /// <summary>
        /// Check the trigger condition and execute the event if the
        /// condition evaluates to true.
        /// </summary>
        public void Call()
        {
            Player player = mGame.GetPlayerAtCoordinates(mCoordinates);
            if (player != null)
            {
                bool condition = mCondition.Run(player);
                if (condition && condition != mPrevCondition)
                {
                    mEvent.Run(player);
                }
                mPrevCondition = condition;
            }
            else
            {
                mPrevCondition = false;
            }
        }


        /// <summary>
        /// Calls the trigger.
        /// </summary>
        /// <param name="timeSpan">Unused.</param>
        public virtual void Update(TimeSpan timeSpan)
        {
            Call();
        }

        public virtual void LoadContent(ContentManager contentManager)
        {
            // No implementation needed.
        }

        public virtual void Draw(SpriteBatch spriteBatch)
        {
            // No implementation needed.
        }

        public bool IsCollidable
        {
            get { return false; }
        }

        public Vector2 Position
        {
            get { return Vector2.Zero; }
        }

        public Point Coordinates
        {
            get { return mCoordinates; }
        }

        #endregion


        #region Private Variables

        Script mCondition;
        Script mEvent;
        Game mGame;
        bool mPrevCondition;
        Point mCoordinates;

        #endregion
    }
}