using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using System.Windows.Forms;

namespace PixelWarfare
{
    /// <summary>
    /// An abstract class that all game screens need to conform too.
    /// </summary>
    abstract class Screen
    {
        #region Fields

        private bool invalid;           // Whether the screen is invalid and needs to switch to nextScreen.
        private Screen nextScreen;      // The screen you switch too when invalid is true.

        #endregion

        #region Abstract Methods

        /// <summary>
        /// Draw the screen.
        /// </summary>
        /// <param name="g">Graphics to be drawn on.</param>
        public abstract void Draw(Graphics g);

        /// <summary>
        /// Update the state of the screen.
        /// </summary>
        public abstract void Update();

        /// <summary>
        /// Do any action associated with the mouse moving over the screen.
        /// </summary>
        /// <param name="x">X coordinate.</param>
        /// <param name="y">Y coordinate.</param>
        public abstract void MouseMove(int x, int y);

        /// <summary>
        /// Do any action associated with the mouse getting pressed.
        /// </summary>
        /// <param name="x">X coordinate.</param>
        /// <param name="y">Y coordinate.</param>
        public abstract void MousePress(int x, int y);

        /// <summary>
        /// Do any action associated with the mouse getting released.
        /// </summary>
        /// <param name="x">X coordinate.</param>
        /// <param name="y">Y coordinate.</param>
        public abstract void MouseRelease(int x, int y);

        /// <summary>
        /// Do any action associated with a key getting pressed.
        /// </summary>
        /// <param name="x">X coordinate.</param>
        /// <param name="y">Y coordinate.</param>
        public abstract void KeyPress(Keys key);

        /// <summary>
        /// Do any action associated with a key getting released.
        /// </summary>
        /// <param name="x">X coordinate.</param>
        /// <param name="y">Y coordinate.</param>
        public abstract void KeyRelease(Keys key);

        #endregion

        #region Public Methods

        /// <summary>
        /// Returns the next screen that needs to be switched too.
        /// Will return null until the screen has expired and
        /// Expired is set to true.
        /// </summary>
        /// <returns>The next screen to switch too.</returns>
        public Screen NextScreen() { return nextScreen; }

        /// <summary>
        /// Returns whether the screen is invalid and needs to be switched.
        /// </summary>
        /// <returns>Whether the screen is invalid.</returns>
        public bool IsInvalid()
        {
            return invalid;
        }

        /// <summary>
        /// Sets the screen to valid when you ever you need to reload it.
        /// </summary>
        public void ValidateScreen()
        {
            invalid = false;
        }

        #endregion

        #region Protected Methods

        /// <summary>
        /// Sets the screen to invalid, and sets the next screen
        /// to switch too.
        /// </summary>
        /// <param name="next">The next screen.</param>
        protected void InvalidateScreen(Screen next)
        {
            nextScreen = next;
            invalid = true;
        }

        #endregion
    }
}