package gbuffer

import (
	"errors"

	"github.com/go-gl/gl/v4.6-core/gl"
)

type GBuffer struct {
	framebuffer      uint32
	depth            uint32
	colorAttachments [4]uint32 // albedo, normal, material, position
}

var attachments = [...]uint32{
	gl.COLOR_ATTACHMENT0,
	gl.COLOR_ATTACHMENT1,
	gl.COLOR_ATTACHMENT2,
	gl.COLOR_ATTACHMENT3,
}

func (b *GBuffer) Bind() {
	gl.BindFramebuffer(gl.FRAMEBUFFER, b.framebuffer)
	gl.DrawBuffers(int32(len(b.colorAttachments)), &attachments[0])
}

func (b *GBuffer) BindTextures() {
	// albedo
	gl.ActiveTexture(gl.TEXTURE0)
	gl.BindTexture(gl.TEXTURE_2D, b.colorAttachments[0])

	// depth
	gl.ActiveTexture(gl.TEXTURE1)
	gl.BindTexture(gl.TEXTURE_2D, b.depth)

	// normal
	gl.ActiveTexture(gl.TEXTURE2)
	gl.BindTexture(gl.TEXTURE_2D, b.colorAttachments[1])

	// material
	gl.ActiveTexture(gl.TEXTURE3)
	gl.BindTexture(gl.TEXTURE_2D, b.colorAttachments[2])

	// position
	gl.ActiveTexture(gl.TEXTURE4)
	gl.BindTexture(gl.TEXTURE_2D, b.colorAttachments[3])
}

func (b *GBuffer) Delete() {
	gl.DeleteFramebuffers(1, &b.framebuffer)
	for i, _ := range b.colorAttachments {
		gl.DeleteTextures(1, &b.colorAttachments[i])

	}
	gl.DeleteTextures(1, &b.depth)
}

func New(width int, height int) (buffer GBuffer, _ error) {
	gl.GenFramebuffers(1, &buffer.framebuffer)
	gl.BindFramebuffer(gl.FRAMEBUFFER, buffer.framebuffer)

	var i uint32 = 0

	// albedo
	gl.GenTextures(1, &buffer.colorAttachments[i])
	gl.BindTexture(gl.TEXTURE_2D, buffer.colorAttachments[i])
	gl.TexImage2D(gl.TEXTURE_2D, 0, gl.RGB, int32(width), int32(height), 0, gl.RGB, gl.FLOAT, nil)
	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR)
	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR)
	gl.BindTexture(gl.TEXTURE_2D, 0)
	gl.FramebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0+i, gl.TEXTURE_2D, buffer.colorAttachments[i], 0)
	i++

	// depth
	gl.GenTextures(1, &buffer.depth)
	gl.BindTexture(gl.TEXTURE_2D, buffer.depth)
	gl.TexImage2D(gl.TEXTURE_2D, 0, gl.DEPTH_COMPONENT, int32(width), int32(height), 0, gl.DEPTH_COMPONENT, gl.FLOAT, nil)
	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR)
	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR)
	gl.BindTexture(gl.TEXTURE_2D, 0)
	gl.FramebufferTexture2D(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.TEXTURE_2D, buffer.depth, 0)

	// normal
	gl.GenTextures(1, &buffer.colorAttachments[i])
	gl.BindTexture(gl.TEXTURE_2D, buffer.colorAttachments[i])
	gl.TexImage2D(gl.TEXTURE_2D, 0, gl.RGB, int32(width), int32(height), 0, gl.RGB, gl.FLOAT, nil)
	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR)
	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR)
	gl.BindTexture(gl.TEXTURE_2D, 0)
	gl.FramebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0+i, gl.TEXTURE_2D, buffer.colorAttachments[i], 0)
	i++

	// material
	gl.GenTextures(1, &buffer.colorAttachments[i])
	gl.BindTexture(gl.TEXTURE_2D, buffer.colorAttachments[i])
	gl.TexImage2D(gl.TEXTURE_2D, 0, gl.RGB, int32(width), int32(height), 0, gl.RGB, gl.FLOAT, nil)
	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR)
	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR)
	gl.BindTexture(gl.TEXTURE_2D, 0)
	gl.FramebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0+i, gl.TEXTURE_2D, buffer.colorAttachments[i], 0)
	i++

	// position
	gl.GenTextures(1, &buffer.colorAttachments[i])
	gl.BindTexture(gl.TEXTURE_2D, buffer.colorAttachments[i])
	gl.TexImage2D(gl.TEXTURE_2D, 0, gl.RGB, int32(width), int32(height), 0, gl.RGB, gl.FLOAT, nil)
	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR)
	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR)
	gl.BindTexture(gl.TEXTURE_2D, 0)
	gl.FramebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0+i, gl.TEXTURE_2D, buffer.colorAttachments[i], 0)
	i++

	if gl.CheckFramebufferStatus(gl.FRAMEBUFFER) != gl.FRAMEBUFFER_COMPLETE {
		return buffer, errors.New("failed to create framebuffer")
	}

	gl.BindFramebuffer(gl.FRAMEBUFFER, 0)

	return buffer, nil
}