using System;
using System.Collections.Generic;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;

namespace BadGame
{
    public struct PlayerData
    {
        public Vector2 Position;
        public Vector2 Velocity;
        public bool IsAlive;
        public bool Win;
        public bool CanJump;
    }

    public class Game1 : Microsoft.Xna.Framework.Game
    {
        GraphicsDeviceManager graphics;
        GraphicsDevice device;

        SpriteBatch spriteBatch;
        SpriteFont font;

        Texture2D backgroundTexture;
        Texture2D foregroundTexture;
        Texture2D playerTexture;
        Texture2D rect;

        int screenHeight;
        int screenWidth;

        public Game1()
        {
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";

            IsFixedTimeStep = false;
        }

        protected override void Initialize()
        {
            graphics.PreferredBackBufferWidth = 800;
            graphics.PreferredBackBufferHeight = 400;
            graphics.IsFullScreen = false;
            graphics.ApplyChanges();

            Window.Title = "Terrible Game";

            base.Initialize();
        }

        PlayerData Player = new PlayerData();
        void BuildPlayerData()
        {
            Player.Position = new Vector2(0, 250); // Start them in the air because it looks/feels cool when a player falls at the start
            Player.IsAlive = true;
            Player.Win = false;
            //Player.Velocity = new Vector2(0.3f, 0); // It defaults to Vector2.Zero (stationary)
            Player.CanJump = true;
        }


        List<Rectangle> Platform = new List<Rectangle>();
        void BuildPlatformData()
        {
            Platform.Add(new Rectangle(100, 210, 150, 30));
            Platform.Add(new Rectangle(150, 140, 100, 30));
            Platform.Add(new Rectangle(150, 310, 230, 30));
            Platform.Add(new Rectangle(230, 280, 150, 30));
            Platform.Add(new Rectangle(310, 250, 70, 30));
            Platform.Add(new Rectangle(350, 140, 100, 30));
            Platform.Add(new Rectangle(400, 230, 150, 30));
            Platform.Add(new Rectangle(400, 170, 30, 60));
            Platform.Add(new Rectangle(500, 170, 30, 30));
            Platform.Add(new Rectangle(600, 130, 30, 300));
            Platform.Add(new Rectangle(600, 130, 130, 30));
            Platform.Add(new Rectangle(600, 330, 200, 10));
            Platform.Add(new Rectangle(700, 250, 100, 30));
            Platform.Add(new Rectangle(770, 0, 30, 260));

            // Adding new platforms to keep the player confined within the level
            // These others are positioned right off the screen so you won't see them
            // The only downside would be that these are now DRAWN on the screen (just out of view)
            // However, if you ever expand on the project, you would likely check if an element is visible on the screen, and if not, don't draw it :)
            // You could do this by settings a rectangle that is the size/position of the screen.. and check if the platforms intersect this screen rect
            Platform.Add(new Rectangle(0, 340, 380, 61)); // Bottom boundry (THIS USED TO BE "LEVEL")
            Platform.Add(new Rectangle(0, -30, screenWidth, 30)); // Top boundry
            Platform.Add(new Rectangle(-30, 0, 30, screenHeight)); // Left boundry
            Platform.Add(new Rectangle(screenWidth, 0, 30, screenHeight)); // Right boundry
        }

        List<Rectangle> Hazard = new List<Rectangle>();
        void BuildHazardData()
        {
            Hazard.Add(new Rectangle(380, 340, 420, 61));
        }

        protected override void LoadContent()
        {
            device = graphics.GraphicsDevice;
            spriteBatch = new SpriteBatch(GraphicsDevice);

            backgroundTexture = Content.Load<Texture2D>("background");
            playerTexture = Content.Load<Texture2D>("player");
            foregroundTexture = Content.Load<Texture2D>("foreground");
            font = Content.Load<SpriteFont>("gameFont");

            rect = new Texture2D(GraphicsDevice, 1, 1);
            rect.SetData(new[] { Color.White });

            screenWidth = device.PresentationParameters.BackBufferWidth;
            screenHeight = device.PresentationParameters.BackBufferHeight;

            BuildPlayerData();
            BuildPlatformData();
            BuildHazardData();
        }

        protected override void UnloadContent()
        {

        }

        void CollisionDetection()
        {
            // I removed checking collision with LEVEL and added "LEVEL" as a platform.. there is nothing special about it
            // And it should really just be treated like any other platform

            // I've also removed the screen bounds checking... because if you ever add a camera and have your level "scroll"
            // Your code wouldn't be useful anymore. Just add platforms to the screen edges to prevent movement! Then all your code above works with it :)
            // Less, more generalized code is the way to do things!


            // Figure out the character's destination... collision code will be run based on this position... not the current position!
            Rectangle player = new Rectangle((int)Player.Position.X, (int)Player.Position.Y, 28, 28);
            Player.CanJump = false; // if they're moving they can't jump until they collide with the top of an object (platform/ground)


            // Check horizontal collision
            int finalH = (int)(player.X + Player.Velocity.X);
            while (true)
            {
                // We want to move from point A to point B slowly to check for collisions along the way
                player.X += Interpolate(player.X, finalH, player.Width);
                bool collided = false;
                foreach (Rectangle i in Platform)
                {
                    if (player.Intersects(i))
                    {
                        collided = true;
                        if (player.Center.X > i.Center.X)
                            player.X = i.Right; // Intersecting right
                        else
                            player.X = i.Left - player.Width; // intersecting left
                    }
                }
                // If we collided with an object or reached our destination with no collision, we're done here
                if (collided || player.X == finalH)
                    break;
            }

            // Check Vertical collision
            int finalV = (int)(player.Y + Player.Velocity.Y);
            while (true)
            {
                // We want to move from point A to point B slowly to check for collisions along the way
                player.Y += Interpolate(player.Y, finalV, player.Height);
                bool collided = false;
                foreach (Rectangle i in Platform)
                {
                    if (player.Intersects(i))
                    {
                        collided = true;
                        if (player.Center.Y > i.Center.Y)
                            player.Y = i.Bottom; // Intersecting bottom
                        else
                        {
                            player.Y = i.Top - player.Height; // Intersecting top
                            Player.CanJump = true;
                        }
                    }

                }

                foreach (Rectangle o in Hazard)
                {
                    if (player.Intersects(o))
                    {
                        Player.IsAlive = false;
                        collided = true;
                        if (player.Center.Y > o.Center.Y)
                            player.Y = o.Bottom; // Intersecting bottom
                        else
                        {
                            player.Y = o.Top ; // Intersecting top
                            Player.CanJump = true;
                        }
                    }

                }

                // If we collided with an object or reached our destination with no collision, we're done here
                if (collided || player.Y == finalV)
                    break;
            }

            // Now that the collisions have been figured out, let's update the player's location to where it should be!
            Player.Position = new Vector2(player.X, player.Y);
        }

        void CheckWin()
        {
            if (Player.Position.X >= screenWidth - 28) Player.Win = true;
        }

        int Interpolate(int start, int end, int step)
        {
            // This function just returns a value starting from START and moving towards END in STEP increments
            int difference = Math.Abs(end - start);
            int increment = Math.Min(difference, step);
            if (start > end)
                return -increment;
            else
                return increment;
        }

        // We can make this a const since we won't be changing it
        const float gravity = 1.25f;

        protected override void Update(GameTime gameTime)
        {
            float elapsedTime = (float)gameTime.ElapsedGameTime.TotalMilliseconds;
            float speed = elapsedTime * .3f;
            KeyboardState keyboard = Keyboard.GetState();

            if (Player.IsAlive && !Player.Win)
            {
                // Horizontal movement
                if (keyboard.IsKeyDown(Keys.A))
                    Player.Velocity.X += speed*-5;
                else if (keyboard.IsKeyDown(Keys.D))
                    Player.Velocity.X += speed*5;
                else
                    Player.Velocity.X = 0; // Cancel momentum... Stop moving when they let go
                // Limit their horizontal velocity
                const float maxVelocityH = 5f;
                Player.Velocity.X = MathHelper.Clamp(Player.Velocity.X, -maxVelocityH, maxVelocityH);

                // Vertical movement
                if (keyboard.IsKeyDown(Keys.W) && Player.CanJump)
                    Player.Velocity.Y += speed*-15;
                else if (keyboard.IsKeyDown(Keys.S))
                    Player.Velocity.Y += speed*1;
                // Limit their vertical velocity
                const float maxVelocityV = 15f;
                Player.Velocity.Y = MathHelper.Clamp(Player.Velocity.Y, -maxVelocityV, maxVelocityV / 2);

                // Apply Gravity (downwards force)
                Player.Velocity.Y += gravity;

                // Collision Detection
                CollisionDetection();

                CheckWin();
            }

            if (keyboard.IsKeyDown(Keys.R)) BuildPlayerData();

            base.Update(gameTime);
        }

        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(Color.CornflowerBlue);

            spriteBatch.Begin();

            DrawLevel();
            DrawText();
            if (!Player.IsAlive) PlayerDead();
            else if (Player.Win) PlayerWin();

            spriteBatch.End(); 

            base.Draw(gameTime);

        }

        private void PlayerDead()
        {
            //spriteBatch.Draw(rect, new Rectangle(screenWidth / 2, screenHeight / 2, 92, 22), Color.Red);
            spriteBatch.DrawString(font, "YOU DIED!\nPress R to restart.", new Vector2(screenWidth / 2, screenHeight / 2), Color.White);
        }

        private void PlayerWin()
        {
            spriteBatch.DrawString(font, "YOU WON!\nPress R to restart.", new Vector2(screenWidth / 2, screenHeight / 2), Color.White);
        }

        private void DrawText()
        {
            spriteBatch.DrawString(font, String.Format("Position: {0} Gravity: {1} Velocity: {2}", Player.Position, gravity, Player.Velocity), new Vector2(0, 0), Color.White);
        }

        private void DrawLevel()
        {
            Rectangle screenRectangle = new Rectangle(0, 0, screenWidth, screenHeight);

            spriteBatch.Draw(backgroundTexture, screenRectangle, Color.White);

            foreach (Rectangle i in Platform) spriteBatch.Draw(rect, i, Color.Green);
            foreach (Rectangle i in Hazard) spriteBatch.Draw(rect, i, Color.Red);

            DrawPlayer();

           spriteBatch.Draw(foregroundTexture, new Rectangle(0, 0, 380, screenHeight), Color.White);
        }

        private void DrawPlayer()
        {
            spriteBatch.Draw(playerTexture, Player.Position, Color.White);
        }
    }
}