using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class DrawWithMouse : MonoBehaviour {

    public bool erase = false;
    public float radius = 50f;

    public SpriteRenderer sr;


    void Update () {

        if(Input.GetMouseButton(0))
        {
            Vector2 mousePos;
            if(GetSpritePixelColorUnderMousePointer(sr, out mousePos))
            {
                Circle(sr.sprite.texture, Mathf.RoundToInt(mousePos.x), Mathf.RoundToInt(mousePos.y), Mathf.RoundToInt(radius), erase ? new Color(0, 0, 0, 0) : Color.black);
            }
        }
    }


    void Circle(Texture2D tex, int cx, int cy, int r, Color col)
    {
        int x, y, px, nx, py, ny, d;
        Color32[] tempArray = tex.GetPixels32();

        for (x = 0; x <= r; x++)
        {
            d = (int)Mathf.Ceil(Mathf.Sqrt(r * r - x * x));
            for (y = 0; y <= d; y++)
            {
                if (x < tex.width && y < tex.height)
                {
                    px = cx + x;
                    nx = cx - x;
                    py = cy + y;
                    ny = cy - y;

                    tempArray[py * tex.width + px] = col;
                    tempArray[py * tex.width + nx] = col;
                    tempArray[ny * tex.width + px] = col;
                    tempArray[ny * tex.width + nx] = col;
                }
            }
        }
        tex.SetPixels32(tempArray);
        tex.Apply();
    }

    Vector2 MousePosToSpriteCoords()
    {
        var pixelWidth = sr.sprite.rect.width;
        var pixelHeight = sr.sprite.rect.height;
        var unitsToPixels = pixelWidth / sr.bounds.size.x * transform.localScale.x;

        var pos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
        pos.z = transform.position.z;
        pos = transform.InverseTransformPoint(pos);

        int xPixel = Mathf.RoundToInt(pos.x * unitsToPixels);
        int yPixel = Mathf.RoundToInt(pos.y * unitsToPixels);

        Color32 color32 = sr.sprite.texture.GetPixel(xPixel, yPixel);
        //Debug.Log("(" + xPixel + ", " + yPixel + ")  " + color32);

        return new Vector2((xPixel), (xPixel));
    }

    public bool GetSpritePixelColorUnderMousePointer(SpriteRenderer spriteRenderer, out Vector2 vec)
    {
        vec = Vector2.zero;

        Camera cam = Camera.main;
        Vector2 mousePos = Input.mousePosition;
        Vector2 viewportPos = cam.ScreenToViewportPoint(mousePos);
        if (viewportPos.x < 0.0f || viewportPos.x > 1.0f || viewportPos.y < 0.0f || viewportPos.y > 1.0f) return false; // out of viewport bounds
                                                                                                                        // Cast a ray from viewport point into world
        Ray ray = cam.ViewportPointToRay(viewportPos);

        // Check for intersection with sprite and get the color
        return getTextPos(spriteRenderer, ray, out vec);
    }
    private bool IntersectsSprite(SpriteRenderer spriteRenderer, Ray ray, out Color color)
    {
        color = new Color();
        if (spriteRenderer == null) return false;
        Sprite sprite = spriteRenderer.sprite;
        if (sprite == null) return false;
        Texture2D texture = sprite.texture;
        if (texture == null) return false;
        // Check atlas packing mode
        if (sprite.packed && sprite.packingMode == SpritePackingMode.Tight)
        {
            // Cannot use textureRect on tightly packed sprites
            Debug.LogError("SpritePackingMode.Tight atlas packing is not supported!");
            // TODO: support tightly packed sprites
            return false;
        }
        // Craete a plane so it has the same orientation as the sprite transform
        Plane plane = new Plane(transform.forward, transform.position);
        // Intersect the ray and the plane
        float rayIntersectDist; // the distance from the ray origin to the intersection point
        if (!plane.Raycast(ray, out rayIntersectDist)) return false; // no intersection
                                                                     // Convert world position to sprite position
                                                                     // worldToLocalMatrix.MultiplyPoint3x4 returns a value from based on the texture dimensions (+/- half texDimension / pixelsPerUnit) )
                                                                     // 0, 0 corresponds to the center of the TEXTURE ITSELF, not the center of the trimmed sprite textureRect
        Vector3 spritePos = spriteRenderer.worldToLocalMatrix.MultiplyPoint3x4(ray.origin + (ray.direction * rayIntersectDist));
        Rect textureRect = sprite.textureRect;
        float pixelsPerUnit = sprite.pixelsPerUnit;
        float halfRealTexWidth = texture.width * 0.5f; // use the real texture width here because center is based on this -- probably won't work right for atlases
        float halfRealTexHeight = texture.height * 0.5f;
        // Convert to pixel position, offsetting so 0,0 is in lower left instead of center
        int texPosX = (int)(spritePos.x * pixelsPerUnit + halfRealTexWidth);
        int texPosY = (int)(spritePos.y * pixelsPerUnit + halfRealTexHeight);
        // Check if pixel is within texture
        if (texPosX < 0 || texPosX < textureRect.x || texPosX >= Mathf.FloorToInt(textureRect.xMax)) return false; // out of bounds
        if (texPosY < 0 || texPosY < textureRect.y || texPosY >= Mathf.FloorToInt(textureRect.yMax)) return false; // out of bounds
                                                                                                                   // Get pixel color
        color = texture.GetPixel(texPosX, texPosY);
        return true;
    }

    bool getTextPos(SpriteRenderer spriteRenderer, Ray ray, out Vector2 vec)
    {
        vec = Vector2.zero;

        if (spriteRenderer == null) return false;
        Sprite sprite = spriteRenderer.sprite;
        if (sprite == null) return false;
        Texture2D texture = sprite.texture;
        if (texture == null) return false;
        // Check atlas packing mode
        if (sprite.packed && sprite.packingMode == SpritePackingMode.Tight)
        {
            // Cannot use textureRect on tightly packed sprites
            Debug.LogError("SpritePackingMode.Tight atlas packing is not supported!");
            // TODO: support tightly packed sprites
            return false;
        }
        // Craete a plane so it has the same orientation as the sprite transform
        Plane plane = new Plane(transform.forward, transform.position);
        // Intersect the ray and the plane
        float rayIntersectDist; // the distance from the ray origin to the intersection point
        if (!plane.Raycast(ray, out rayIntersectDist)) return false; // no intersection
                                                                     // Convert world position to sprite position
                                                                     // worldToLocalMatrix.MultiplyPoint3x4 returns a value from based on the texture dimensions (+/- half texDimension / pixelsPerUnit) )
                                                                     // 0, 0 corresponds to the center of the TEXTURE ITSELF, not the center of the trimmed sprite textureRect
        Vector3 spritePos = spriteRenderer.worldToLocalMatrix.MultiplyPoint3x4(ray.origin + (ray.direction * rayIntersectDist));
        Rect textureRect = sprite.textureRect;
        float pixelsPerUnit = sprite.pixelsPerUnit;
        float halfRealTexWidth = texture.width * 0.5f; // use the real texture width here because center is based on this -- probably won't work right for atlases
        float halfRealTexHeight = texture.height * 0.5f;
        // Convert to pixel position, offsetting so 0,0 is in lower left instead of center
        int texPosX = (int)(spritePos.x * pixelsPerUnit + halfRealTexWidth);
        int texPosY = (int)(spritePos.y * pixelsPerUnit + halfRealTexHeight);

        // Check if pixel is within texture
        if (texPosX < 0 || texPosX < textureRect.x || texPosX >= Mathf.FloorToInt(textureRect.xMax)) return false; // out of bounds
        if (texPosY < 0 || texPosY < textureRect.y || texPosY >= Mathf.FloorToInt(textureRect.yMax)) return false; // out of bounds

        vec = new Vector2(texPosX, texPosY);

        return true;
    }
}