using System;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Barotrauma.Lights;
using System.Diagnostics;

namespace Barotrauma
{
    class GameScreen : Screen
    {
        Camera cam;

        readonly RenderTarget2D renderTarget;
        readonly RenderTarget2D renderTargetWater;
        readonly RenderTarget2D renderTargetAir;

        readonly Sprite background, backgroundTop;
        readonly Texture2D dustParticles;

        Vector2 dustOffset;

        public BackgroundSpriteManager BackgroundSpriteManager;

        public Camera Cam
        {
            get { return cam; }
        }

        public GameScreen(GraphicsDevice graphics)
        {
            cam = new Camera();
            cam.Translate(new Vector2(-10.0f, 50.0f));
            
            renderTarget = new RenderTarget2D(graphics, GameMain.GraphicsWidth, GameMain.GraphicsHeight);
            renderTargetWater = new RenderTarget2D(graphics, GameMain.GraphicsWidth, GameMain.GraphicsHeight);
            renderTargetAir = new RenderTarget2D(graphics, GameMain.GraphicsWidth, GameMain.GraphicsHeight);

            background = new Sprite("Content/Map/background.png", Vector2.Zero);
            backgroundTop = new Sprite("Content/Map/background2.png", Vector2.Zero);
            dustParticles = Sprite.LoadTexture("Content/Map/dustparticles.png");
            
            BackgroundSpriteManager = new BackgroundSpriteManager("Content/BackgroundSprites/BackgroundSpritePrefabs.xml");
        }

        public override void Select()
        {
            base.Select();

            foreach (MapEntity entity in MapEntity.mapEntityList)
                entity.IsHighlighted = false;
        }

        public override void Deselect()
        {
            base.Deselect();

            Sounds.SoundManager.LowPassHFGain = 1.0f;
        }

        /// <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>
        public override void Update(double deltaTime)
        {
            //the accumulator code is based on this article:
            //http://gafferongames.com/game-physics/fix-your-timestep/
            Physics.accumulator += deltaTime;

#if DEBUG
            if (GameMain.GameSession != null && GameMain.GameSession.Level != null && GameMain.GameSession.Submarine != null)
            {
                Vector2 targetMovement = Vector2.Zero;
                if (PlayerInput.KeyDown(Keys.I)) targetMovement.Y += 1.0f;
                if (PlayerInput.KeyDown(Keys.K)) targetMovement.Y -= 1.0f;
                if (PlayerInput.KeyDown(Keys.J)) targetMovement.X -= 1.0f;
                if (PlayerInput.KeyDown(Keys.L)) targetMovement.X += 1.0f;

                GameMain.GameSession.Submarine.ApplyForce(targetMovement * 1000000.0f);
            }
#endif
            dustOffset -= Vector2.UnitY * 10.0f * (float)deltaTime;

            if (GameMain.GameSession!=null) GameMain.GameSession.Update((float)deltaTime);
            //EventManager.Update(gameTime);

            Character.UpdateAll(cam, (float)deltaTime);

            BackgroundSpriteManager.Update(cam, (float)deltaTime);

            GameMain.ParticleManager.Update((float)deltaTime);

            StatusEffect.UpdateAll((float)deltaTime);

            Physics.accumulator = Math.Min(Physics.accumulator, Physics.step * 4);
            //Physics.accumulator = Physics.step;
            while (Physics.accumulator >= Physics.step)
            {
                cam.MoveCamera((float)Physics.step);

                foreach (PhysicsBody pb in PhysicsBody.list)
                {
                    pb.SetPrevTransform(pb.SimPosition, pb.Rotation);
                }
                    
                MapEntity.UpdateAll(cam, (float)Physics.step);

                Character.UpdateAnimAll((float)Physics.step);

                Ragdoll.UpdateAll(cam, (float)Physics.step);

                if (GameMain.GameSession != null && GameMain.GameSession.Level != null && GameMain.GameSession.Submarine!=null)
                {
                    GameMain.GameSession.Submarine.Update((float)Physics.step);
                }

                GameMain.World.Step((float)Physics.step);

                Level.AfterWorldStep();

                Physics.accumulator -= Physics.step;
            }


            Physics.Alpha = Physics.accumulator / Physics.step;

        }

        public override void Draw(double deltaTime, GraphicsDevice graphics, SpriteBatch spriteBatch)
        {
            //if (!Physics.updated) return;

            cam.UpdateTransform();

            DrawMap(graphics, spriteBatch);

            spriteBatch.Begin();

            if (Character.Controlled != null && Character.Controlled.SelectedConstruction != null)
            {
                if (Character.Controlled.SelectedConstruction == Character.Controlled.ClosestItem)
                {
                    Character.Controlled.SelectedConstruction.DrawHUD(spriteBatch, Character.Controlled);
                }
                else
                {
                    Character.Controlled.SelectedConstruction = null;
                }
            }

            if (GameMain.GameSession != null) GameMain.GameSession.Draw(spriteBatch);

            GUI.Draw((float)deltaTime, spriteBatch, cam);
                        
            if (PlayerInput.GetMouseState.LeftButton != ButtonState.Pressed) Inventory.draggingItem = null;

            spriteBatch.End();
        }

        public void DrawMap(GraphicsDevice graphics, SpriteBatch spriteBatch)
        {
            GameMain.LightManager.ObstructVision = Character.Controlled != null && Character.Controlled.ObstructVision;

            GameMain.LightManager.UpdateLightMap(graphics, spriteBatch, cam);
            GameMain.LightManager.UpdateObstructVision(graphics, spriteBatch, cam, 
                Character.Controlled==null ? LightManager.ViewPos : Character.Controlled.CursorPosition);

            //----------------------------------------------------------------------------------------
            //1. draw the background, characters and the parts of the submarine that are behind them
            //----------------------------------------------------------------------------------------

            graphics.SetRenderTarget(renderTarget);
            graphics.Clear(new Color(11, 18, 26, 255));

            spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend, SamplerState.LinearWrap);

            Vector2 backgroundPos = cam.Position;
            if (Level.Loaded != null) backgroundPos -= Level.Loaded.Position;
            backgroundPos.Y = -backgroundPos.Y;
            backgroundPos /= 20.0f;

            if (backgroundPos.Y < 1024)
            {
                if (backgroundPos.Y > -1024)
                {
                    background.SourceRect = new Rectangle((int)backgroundPos.X, (int)Math.Max(backgroundPos.Y, 0), 1024, 1024);
                    background.DrawTiled(spriteBatch, 
                        (backgroundPos.Y < 0) ? new Vector2(0.0f, -backgroundPos.Y) : Vector2.Zero, 
                        new Vector2(GameMain.GraphicsWidth, 1024 - backgroundPos.Y),
                        Vector2.Zero, Color.White);
                }

                if (backgroundPos.Y < 0)
                {
                    backgroundTop.SourceRect = new Rectangle((int)backgroundPos.X, (int)backgroundPos.Y, 1024, (int)Math.Min(-backgroundPos.Y, 1024));
                    backgroundTop.DrawTiled(spriteBatch, Vector2.Zero, new Vector2(GameMain.GraphicsWidth, Math.Min(-backgroundPos.Y, GameMain.GraphicsHeight)),
                        Vector2.Zero, Color.White);
                }
            }

            spriteBatch.End();

            spriteBatch.Begin(SpriteSortMode.BackToFront,
                BlendState.AlphaBlend,
                SamplerState.LinearWrap, null, null, null,
                cam.Transform);

            BackgroundSpriteManager.Draw(spriteBatch);

            backgroundPos = new Vector2(cam.WorldView.X, cam.WorldView.Y) + dustOffset;
            if (Level.Loaded != null) backgroundPos -= Level.Loaded.Position;

            Rectangle viewRect = cam.WorldView;
            viewRect.Y = -viewRect.Y;

            float multiplier = 0.8f;
            for (int i = 1; i < 4; i++)
            {
                spriteBatch.Draw(dustParticles, viewRect,
                    new Rectangle((int)((backgroundPos.X * multiplier)), (int)((-backgroundPos.Y * multiplier)), cam.WorldView.Width, cam.WorldView.Height),
                    Color.White * multiplier, 0.0f, Vector2.Zero, SpriteEffects.None, 1.0f-multiplier);
                multiplier -= 0.15f;
            }
            
            spriteBatch.End();

            spriteBatch.Begin(SpriteSortMode.BackToFront,
                BlendState.AlphaBlend,
                null, null, null, null,
                cam.Transform);

            Submarine.DrawBack(spriteBatch);

            foreach (Character c in Character.CharacterList) c.Draw(spriteBatch);

            spriteBatch.End();


            GameMain.LightManager.DrawLightMap(spriteBatch, cam);

            //----------------------------------------------------------------------------------------
            //draw the rendertarget and particles that are only supposed to be drawn in water into renderTargetWater

            graphics.SetRenderTarget(renderTargetWater);

            spriteBatch.Begin(SpriteSortMode.Immediate,
                BlendState.AlphaBlend);
            spriteBatch.Draw(renderTarget, new Rectangle(0, 0, GameMain.GraphicsWidth, GameMain.GraphicsHeight), new Color(0.75f, 0.8f, 0.9f, 1.0f));
            spriteBatch.End();

            spriteBatch.Begin(SpriteSortMode.Immediate,
                BlendState.AlphaBlend,
                null, DepthStencilState.DepthRead, null, null,
                cam.Transform);
            GameMain.ParticleManager.Draw(spriteBatch, true);

            spriteBatch.End();

            //----------------------------------------------------------------------------------------
            //draw the rendertarget and particles that are only supposed to be drawn in air into renderTargetAir

            graphics.SetRenderTarget(renderTargetAir);
            spriteBatch.Begin(SpriteSortMode.Immediate,
                BlendState.AlphaBlend);
            spriteBatch.Draw(renderTarget, new Rectangle(0, 0, GameMain.GraphicsWidth, GameMain.GraphicsHeight), Color.White);
            spriteBatch.End();

            spriteBatch.Begin(SpriteSortMode.Immediate,
                BlendState.AlphaBlend,
                null, DepthStencilState.DepthRead, null, null,
                cam.Transform);

            GameMain.ParticleManager.Draw(spriteBatch, false);
            spriteBatch.End();

            graphics.SetRenderTarget(null);

            //----------------------------------------------------------------------------------------
            //2. pass the renderTarget to the water shader to do the water effect
            //----------------------------------------------------------------------------------------

            Hull.renderer.RenderBack(spriteBatch, renderTargetWater);

            Array.Clear(Hull.renderer.vertices, 0, Hull.renderer.vertices.Length);
            Hull.renderer.PositionInBuffer = 0;
            foreach (Hull hull in Hull.hullList)
            {
                hull.Render(graphics, cam);
            }

            Hull.renderer.Render(graphics, cam, renderTargetAir, Cam.ShaderTransform);
            
            if (GameMain.GameSession != null && GameMain.GameSession.Level != null)
            {
                GameMain.GameSession.Level.Render(graphics, cam);
                //GameMain.GameSession.Level.SetObserverPosition(cam.WorldViewCenter);
            }

            //----------------------------------------------------------------------------------------
            //3. draw the sections of the map that are on top of the water
            //----------------------------------------------------------------------------------------

            spriteBatch.Begin(SpriteSortMode.BackToFront,
                BlendState.AlphaBlend, SamplerState.LinearWrap,
                null, null, null,
                cam.Transform);

            foreach (Character c in Character.CharacterList) c.DrawFront(spriteBatch);

            Submarine.DrawFront(spriteBatch);
            
            if (Level.Loaded!=null) Level.Loaded.Draw(spriteBatch);            

            spriteBatch.End();

            GameMain.LightManager.DrawLOS(graphics, spriteBatch, cam, LightManager.ViewPos);
        }
    }
}