package opengl

// #cgo LDFLAGS: -framework OpenGL
//
// #include <OpenGL/gl.h>
import "C"
import (
	"github.com/hajimehoshi/go-ebiten/graphics/texture"
	"image"
	"unsafe"
)

type RenderTarget struct {
	texture     *texture.Texture
	framebuffer C.GLuint
}

func (renderTarget *RenderTarget) SetAsViewport(setter interface{
	SetViewport(x, y, width, height int)
}) {
	renderTarget.texture.SetAsViewport(0, 0, setter)
}

func createNativeTexture(textureWidth, textureHeight int, pixels []uint8) C.GLuint {
	nativeTexture := C.GLuint(0)

	C.glGenTextures(1, (*C.GLuint)(&nativeTexture))
	if nativeTexture < 0 {
		panic("glGenTexture failed")
	}
	C.glPixelStorei(C.GL_UNPACK_ALIGNMENT, 4)
	C.glBindTexture(C.GL_TEXTURE_2D, C.GLuint(nativeTexture))

	ptr := unsafe.Pointer(nil)
	if pixels != nil {
		ptr = unsafe.Pointer(&pixels[0])
	}
	C.glTexImage2D(C.GL_TEXTURE_2D, 0, C.GL_RGBA,
		C.GLsizei(textureWidth), C.GLsizei(textureHeight),
		0, C.GL_RGBA, C.GL_UNSIGNED_BYTE, ptr)

	C.glTexParameteri(C.GL_TEXTURE_2D, C.GL_TEXTURE_MAG_FILTER, C.GL_LINEAR)
	C.glTexParameteri(C.GL_TEXTURE_2D, C.GL_TEXTURE_MIN_FILTER, C.GL_LINEAR)
	C.glBindTexture(C.GL_TEXTURE_2D, 0)

	return nativeTexture
}

type NativeTextureCreator struct{}

func (creator *NativeTextureCreator) Create(textureWidth, textureHeight int) (interface{}, error) {
	return createNativeTexture(textureWidth, textureHeight, nil), nil
}

func (creator *NativeTextureCreator) CreateFromImage(img *image.NRGBA) (interface{}, error) {
	size := img.Bounds().Size()
	return createNativeTexture(size.X, size.Y, img.Pix), nil
}

func newRenderTarget(width, height int) (*RenderTarget, error) {
	texture, err := texture.New(width, height, &NativeTextureCreator{})
	if err != nil {
		return nil, err
	}
	framebuffer := createFramebuffer(texture.Native().(C.GLuint))
	return &RenderTarget{
		texture:     texture,
		framebuffer: framebuffer,
	}, nil
}

func newRenderTargetWithFramebuffer(width, height int, framebuffer C.GLuint) (*RenderTarget, error) {
	texture, err := texture.New(width, height, &NativeTextureCreator{})
	if err != nil {
		return nil, err
	}
	return &RenderTarget{
		texture:     texture,
		framebuffer: framebuffer,
	}, nil
}

func createFramebuffer(nativeTexture C.GLuint) C.GLuint {
	framebuffer := C.GLuint(0)
	C.glGenFramebuffers(1, &framebuffer)

	origFramebuffer := C.GLint(0)
	C.glGetIntegerv(C.GL_FRAMEBUFFER_BINDING, &origFramebuffer)
	C.glBindFramebuffer(C.GL_FRAMEBUFFER, framebuffer)
	C.glFramebufferTexture2D(C.GL_FRAMEBUFFER, C.GL_COLOR_ATTACHMENT0,
		C.GL_TEXTURE_2D, nativeTexture, 0)
	C.glBindFramebuffer(C.GL_FRAMEBUFFER, C.GLuint(origFramebuffer))
	if C.glCheckFramebufferStatus(C.GL_FRAMEBUFFER) !=
		C.GL_FRAMEBUFFER_COMPLETE {
		panic("creating framebuffer failed")
	}

	return framebuffer
}