using System;
using System.Linq;
using Chernobyl.Collections.Generic.Event;
using Chernobyl.Config;
using Chernobyl.Dependency;
using Chernobyl.Graphics;
using Chernobyl.Plugin;
using Chernobyl.StateMachine;
using Chernobyl.Update;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;

namespace Chernobyl.Xna
{
    /// <summary>
    /// The plug-in that allows XNA to be used within Chernobyl. 
    /// </summary>
    public class XnaPlugin : Game, IPlugin
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="XnaPlugin"/> class.
        /// </summary>
        /// <param name="services">The instance that gives out services for use 
        /// by this type and takes services from this type for use by other systems.</param>
        public XnaPlugin(IEventCollection<object> services)
        {
            Graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "../../Content";
            Services = services;

            Core core = Services.OfType<Core>().First();
            if (core == null)
                throw new Exception("Failed to create the Chernobyl XNA plug-in. " +
                    "The Chernobyl core must be created before this plug-in can be created.");
            core.Runner = Run;

            // Note: IEventCollection<object>.Inject(this) is invoked in XnaPlugin.Initialize().
        }

        /// <summary>
        /// The services provided by this plug-in or null if no services are
        /// provided.
        /// </summary>
        public new IEventCollection<object> Services { get; set; }

        /// <summary>
        /// The device that is used to create and manager graphics level services 
        /// such as rendering and creating graphics objects like shaders.
        /// </summary>
        [Provide]
        public new GraphicsDevice GraphicsDevice
        {
            get { return base.GraphicsDevice; }
        }

        /// <summary>
        /// The <see cref="ContentManager"/> instance used by XNA to manage 
        /// content produced by the content pipeline.
        /// </summary>
        [Provide]
        public new ContentManager Content
        {
            get { return base.Content; } 
            set { base.Content = value; }
        }

        /// <summary>
        /// A <see cref="SpriteBatch"/> instance which can be used to draw a 
        /// group of XNA sprites with the same settings.
        /// </summary>
        [Provide]
        public SpriteBatch SpriteBatch { get; private set; }

        /// <summary>
        /// Gets the underlying operating system window for XNA.
        /// </summary>
        [Provide]
        public new GameWindow Window
        {
            get { return base.Window; }
        }

        /// <summary>
        /// The <see cref="IState"/> that manages the state of the entire 
        /// application.
        /// </summary>
        [Inject]
        public IState ApplicationState { get; set; }

        /// <summary>
        /// An <see cref="ILoadingState"/> used as the default value for 
        /// the <see cref="LoadingState"/>.
        /// </summary>
        [Inject]
        public ILoadingState LoadingState { get; set; }

        /// <summary>
        /// The <see cref="IState"/> that represents the started running state 
        /// after the configuration state (<see cref="IConfigurationState"/>).
        /// </summary>
        [Inject]
        public IRunningState RunningState { get; set; }

        /// <summary>
        /// The <see cref="Chernobyl.Update.IUpdateable"/> that is responible 
        /// for updating Chernobyl.
        /// </summary>
        [Inject(Type = typeof(IRootUpdateable))]
        public Update.IUpdateable RootUpdateable { get; set; }

        /// <summary>
        /// The primary <see cref="Scene"/> that needs to be drawn.
        /// </summary>
        [Inject]
        public Scene MainScene { get; set; }

        /// <summary>
        /// The <see cref="GraphicsDeviceManager"/> that manages the configuration 
        /// and management of the graphics device for XNA.
        /// </summary>
        GraphicsDeviceManager Graphics { get; set; }

        /// <summary>
        /// Allows the game to perform any initialization it needs to before starting to run.
        /// This is where it can query for any required services and load any non-graphic
        /// related content.  Calling base.Initialize will enumerate through any components
        /// and initialize them as well.
        /// </summary>
        protected override void Initialize()
        {
            SpriteBatch = new SpriteBatch(GraphicsDevice);
            Services.Inject(this);

            base.Initialize();
        }

        /// <summary>
        /// LoadContent will be called once per game and is the place to load
        /// all of your content.
        /// </summary>
        protected override void LoadContent()
        {
            ApplicationState.ChildState = LoadingState;



            ApplicationState.ChildState = RunningState;
        }

        /// <summary>
        /// UnloadContent will be called once per game and is the place to unload
        /// all content.
        /// </summary>
        protected override void UnloadContent()
        {
            
        }

        /// <summary>
        /// Allows the game to run logic such as updating the world,
        /// checking for collisions, gathering input, and playing audio.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Update(GameTime gameTime)
        {
            // Allows the game to exit
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed || Keyboard.GetState().IsKeyDown(Keys.Escape))
                this.Exit();

            RootUpdateable.Update(gameTime.ElapsedGameTime);

            base.Update(gameTime);
        }

        /// <summary>
        /// This is called when the game should draw itself.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(ClearOptions.Target | ClearOptions.DepthBuffer, Microsoft.Xna.Framework.Graphics.Color.CornflowerBlue, 1, 0);

            // This code ensures alpha blending works properly.
            // TODO: remove this code and place it in an IDrawable that can be
            // used where necessary.
            GraphicsDevice.RenderState.AlphaBlendEnable = true;
            GraphicsDevice.RenderState.SourceBlend = Blend.SourceAlpha;
            GraphicsDevice.RenderState.DestinationBlend = Blend.InverseSourceAlpha;

            MainScene.Draw();

            base.Draw(gameTime);
        }
    }
}