package ox

import "surdeus.su/core/gg"
import "surdeus.su/core/gg/mx"


// Default camera implementation.
var _ = gg.Camera(&Camera{})
type Camera struct {
	ObjectImpl
	// The Transform to interact with
	// to change camera position, rotation etc.
	Transform

	// The shaders that will be applied to everything
	// that the camera shows.
	Shaderity

	// The bufferization implementation
	// to keep everything fast.
	absMatrice, realMatrice mx.Matrice
}

// Returns the new camera
// with default settings.
func NewCamera() Camera {
	ret := Camera{}
	ret.Transform = *T()
	return ret
}

// Returns the matrix satysfying camera
// position, scale and rotation to apply
// it to the objects to get the real
// transform to display on the screen.
func (c *Camera) GetRealMatrice(ctx gg.Context) mx.Matrice {
	// Bufferization
	// so we do not need to recalculate
	// Transform again.
	if !c.Transform.IsDirty() {
		return c.realMatrice
	}

	var g mx.Matrice
	position := c.GetPosition().Neg()
	around := c.GetAround()
	scale  := c.GetScale()
	rotation := c.GetRotation()

	g.Translate(-position.X, -position.Y)
	g.Rotate(rotation)

	size := ctx.Engine().GetAbsWinSize()
	g.Translate(around.X * size.X, around.Y * size.Y)

	g.Scale(scale.X, scale.Y)

	c.realMatrice = g
	return g
}

// The matrix to convert things into the 
// inside engine representation, 
// get the position of cursor inside the world
// basing on its window position.
func (camera *Camera) GetAbsMatrice(ctx gg.Context) mx.Matrice {
	if !camera.Transform.IsDirty() {
		return camera.absMatrice
	}
	m := camera.GetRealMatrice(ctx)
	m.Invert()

	camera.absMatrice = m
	return m
}

func (camera *Camera) GetAbsWinSize(
	ctx gg.Context,
) mx.Vector {
	return ctx.Engine().GetRealWinSize().
		Div(camera.GetScale())
}