using AlienAttack.MonoGame.Things;
using AlienAttack.MonoGame.Things.Enemies;
using AlienAttack.MonoGame.Things.Stars;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using System;
using System.Collections.Generic;
using System.Linq;

namespace AlienAttack.MonoGame.GameLoops;

internal class GameLoop : GameLoopBase
{
    private readonly List<Sprite> _spritesToAdd = [];
    private readonly Random _random = new();

    private int _spawnNewEnemyThreshold = 100;
    private float _backgroundYOffset = 0;

    private Starfield _starfield;
    private Texture2D _pixel;

    protected readonly List<Sprite> Sprites = [];

    public GameLoop(AlienAttackGame game) : base(game)
    {
        InitializeStarField(game);
        Sprites.Add(new Player(game.ViewTransform.ScreenWidth / 2 - 32, game.ViewTransform.ScreenHeight - 64));
    }

    private void InitializeStarField(AlienAttackGame game)
    {
        _starfield = new Starfield(seed: 42);

        //// Far layer: many tiny, slow, faint
        //_starfield.AddLayer(count: 450, speedPxPerSec: 20f, minSize: 1f, maxSize: 1.5f, minAlpha: 0.15f, maxAlpha: 0.35f);

        //// Mid layer
        //_starfield.AddLayer(count: 220, speedPxPerSec: 45f, minSize: 1.5f, maxSize: 2.2f, minAlpha: 0.25f, maxAlpha: 0.60f);

        //// Near layer: fewer, bigger, faster, brighter
        //_starfield.AddLayer(count: 90, speedPxPerSec: 85f, minSize: 2.0f, maxSize: 3.2f, minAlpha: 0.40f, maxAlpha: 0.90f);

        _starfield.AddLayer(count: 450, velocityPxPerSec: new Vector2(+4f, 20f), minSize: 1f, maxSize: 1.5f, minAlpha: 0.15f, maxAlpha: 0.35f);
        _starfield.AddLayer(count: 220, velocityPxPerSec: new Vector2(-10f, 45f), minSize: 1.5f, maxSize: 2.2f, minAlpha: 0.25f, maxAlpha: 0.60f);
        _starfield.AddLayer(count: 90, velocityPxPerSec: new Vector2(+20f, 85f), minSize: 2.0f, maxSize: 3.2f, minAlpha: 0.40f, maxAlpha: 0.90f);


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

        _starfield.Initialize(ViewTransform.ScreenWidth, ViewTransform.ScreenHeight);
    }

    public override void OnDraw()
    {
        _starfield.Draw(SpriteBatch, _pixel);
        //DrawBackground();
        DrawSprites();
    }

    private void DrawBackground()
    {
        Texture2D backgroundTexture = Content.Load<Texture2D>($@"Background\PixelBackgroundSeamlessVertically");
        int blockCountY = (int)Math.Ceiling((decimal)ViewTransform.ScreenHeight / (decimal)backgroundTexture.Height);
        int blockCountX = (int)Math.Ceiling((decimal)ViewTransform.ScreenWidth / (decimal)backgroundTexture.Width);

        for (int y = 0; y < blockCountY; y++)
        {
            float startY = (y * backgroundTexture.Height) + _backgroundYOffset;
            _backgroundYOffset = _backgroundYOffset + 0.25f;

            if (_backgroundYOffset > ViewTransform.ScreenHeight)
            {
                _backgroundYOffset = 0;
            }

            for (int x = 0; x < blockCountX; x++)
            {
                int width = backgroundTexture.Width;

                if (x * backgroundTexture.Width + backgroundTexture.Width > ViewTransform.ScreenWidth)
                {
                    width = ViewTransform.ScreenWidth - (x * backgroundTexture.Width);
                }

                Vector2 position = new(x * backgroundTexture.Width, startY);
                SpriteBatch.Draw(backgroundTexture, position, new Rectangle(new Point(x, y), new Point(width, backgroundTexture.Height)), Color.White);
            }
        }
    }

    private void DrawSprites()
    {
        SpriteDrawArgs args = new(Game);

        foreach (Sprite sprite in Sprites)
        {
            sprite.Draw(args);
        }
    }

    public override void OnUpdate(GameTime gameTime)
    {
        _starfield.Update(gameTime);
        UpdateSprites(gameTime);
        CheckSpriteCollisions();
        ClearDeadSprites();
        AddEnemySprites();
        AddNewSprites();
    }

    private void UpdateSprites(GameTime gameTime)
    {
        SpriteUpdateContext args = new(Game)
        {
            Random = _random,
            GameTime = gameTime,
            SpawnSprite = _spritesToAdd.Add
        };

        foreach (Sprite sprite in Sprites)
        {
            sprite.Update(args);
        }
    }

    private void CheckSpriteCollisions()
    {
        var collisionSprites = Sprites.Where(x => x.CanCollide).ToList();

        foreach (var sprite in collisionSprites)
        {
            foreach (var otherSprite in collisionSprites.Where(x => x != sprite))
            {
                SpriteCollisionContext context = new(Game)
                {
                    Sprite = otherSprite,
                    SpawnSprite = _spritesToAdd.Add
                };

                // TODO: If perfomed once; do not perform again
                if (sprite.Intersects(otherSprite))
                {
                    sprite.OnCollision(context);
                }
            }
        }
    }

    private void ClearDeadSprites()
    {
        var deadSprites = Sprites.Where(x => x.IsDead).ToList();

        foreach (var sprite in deadSprites)
        {
            Sprites.Remove(sprite);
        }
    }

    private void AddNewSprites()
    {
        foreach (Sprite sprite in _spritesToAdd)
        {
            Sprites.Add(sprite);
        }

        _spritesToAdd.Clear();
    }

    private void AddEnemySprites()
    {
        if (_spawnNewEnemyThreshold > 0)
        {
            _spawnNewEnemyThreshold--;
        }

        if (_spawnNewEnemyThreshold == 0)
        {
            int randomNumber = _random.Next(0, 100);

            if (randomNumber == 0)
            {
                GreenEnemy enemy = new(_random.Next(0, ViewTransform.ScreenWidth - 64), -64);
                Sprites.Add(enemy);
                _spawnNewEnemyThreshold = 100 + _random.Next(0, 100);
            }
            else if (randomNumber == 1)
            {
                RedEnemy enemy = new(_random.Next(0, ViewTransform.ScreenWidth - 64), -64);
                Sprites.Add(enemy);
                _spawnNewEnemyThreshold = 100 + _random.Next(0, 100);
            }
            else if (randomNumber == 2)
            {
                TealEnemy enemy = new(_random.Next(0, ViewTransform.ScreenWidth - 64), -64);
                Sprites.Add(enemy);
                _spawnNewEnemyThreshold = 100 + _random.Next(0, 100);
            }
        }
    }
}