// Updating the list of Points that this LineRender should be rendering.
func (lr *LineRender) UpdatePoints(points []Point) {
	// Determining the buffer mode.
	var mode uint32
	if lr.static {
		mode = gl.STATIC_DRAW
	} else {
		mode = gl.DYNAMIC_DRAW
	}

	// Setting the number of points.
	lr.points = int32(len(points))

	// Generating the buffer data.
	vboData := generateVBOData(points)
	eboData := generateEBOData(len(points))

	// Filling the buffer data.
	gl.BindVertexArray(lr.vao)

	gl.BindBuffer(gl.ARRAY_BUFFER, lr.vbo)
	gl.BufferData(gl.ARRAY_BUFFER, len(vboData)*4, gl.Ptr(vboData), mode)

	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, lr.ebo)
	gl.BufferData(gl.ELEMENT_ARRAY_BUFFER, len(eboData)*4, gl.Ptr(eboData), mode)
}

// Creating a RenderObject with a given shaderProgram, texture, and set of
// vertices.
func CreateRenderObject(shaderProgram ShaderProgram, texture Texture, vertices []float32) *RenderObject {
	renderObject := new(RenderObject)

	// Creating the basic information.
	renderObject.shaderProgram = uint32(shaderProgram)
	renderObject.texture = uint32(texture)

	gl.GenVertexArrays(1, &renderObject.vao)
	gl.GenBuffers(1, &renderObject.vbo)
	gl.GenBuffers(1, &renderObject.ebo)

	// Filling the RenderObject with information.
	gl.BindVertexArray(renderObject.vao)
	gl.BindBuffer(gl.ARRAY_BUFFER, renderObject.vbo)
	gl.BufferData(gl.ARRAY_BUFFER, len(vertices)*4, gl.Ptr(vertices), gl.STATIC_DRAW)

	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, renderObject.ebo)
	vertOrder := []uint32{
		0, 1, 2,
		2, 3, 0,
	}
	gl.BufferData(gl.ELEMENT_ARRAY_BUFFER, len(vertOrder)*4, gl.Ptr(vertOrder), gl.STATIC_DRAW)

	// Loading up vertex attributes.
	vertAttrib := uint32(gl.GetAttribLocation(renderObject.shaderProgram, gl.Str("vert\x00")))
	gl.EnableVertexAttribArray(vertAttrib)
	gl.VertexAttribPointer(vertAttrib, 2, gl.FLOAT, false, 4*4, gl.PtrOffset(0))

	// Loading up texture attributes.
	texAttrib := uint32(gl.GetAttribLocation(renderObject.shaderProgram, gl.Str("vertTexCoord\x00")))
	gl.EnableVertexAttribArray(texAttrib)
	gl.VertexAttribPointer(texAttrib, 2, gl.FLOAT, false, 4*4, gl.PtrOffset(2*4))

	return renderObject
}

func createPlane(x0, y0, x1, y1 float32, verts [12]float32, indexes [6]uint32, uvs [8]float32, normals [12]float32) *Renderable {
	const floatSize = 4
	const uintSize = 4

	r := NewRenderable()
	gl.GenVertexArrays(1, &r.Vao)
	r.FaceCount = 2

	// create a VBO to hold the vertex data
	gl.GenBuffers(1, &r.VertVBO)
	gl.BindBuffer(gl.ARRAY_BUFFER, r.VertVBO)
	gl.BufferData(gl.ARRAY_BUFFER, floatSize*len(verts), gl.Ptr(&verts[0]), gl.STATIC_DRAW)

	// create a VBO to hold the uv data
	gl.GenBuffers(1, &r.UvVBO)
	gl.BindBuffer(gl.ARRAY_BUFFER, r.UvVBO)
	gl.BufferData(gl.ARRAY_BUFFER, floatSize*len(uvs), gl.Ptr(&uvs[0]), gl.STATIC_DRAW)

	// create a VBO to hold the normals data
	gl.GenBuffers(1, &r.NormsVBO)
	gl.BindBuffer(gl.ARRAY_BUFFER, r.NormsVBO)
	gl.BufferData(gl.ARRAY_BUFFER, floatSize*len(normals), gl.Ptr(&normals[0]), gl.STATIC_DRAW)

	// create a VBO to hold the face indexes
	gl.GenBuffers(1, &r.ElementsVBO)
	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, r.ElementsVBO)
	gl.BufferData(gl.ELEMENT_ARRAY_BUFFER, uintSize*len(indexes), gl.Ptr(&indexes[0]), gl.STATIC_DRAW)

	return r
}

func CreateSprite(t Texture) (s Sprite, err error) {

	s.texture = t
	s.shader, err = CreateShader(vertexShader, fragmentShader)
	if err != nil {
		return s, err
	}

	gl.GenBuffers(1, &s.ebo)
	gl.GenBuffers(1, &s.vbo)
	gl.GenVertexArrays(1, &s.vao)

	gl.BindVertexArray(s.vao)

	gl.BindBuffer(gl.ARRAY_BUFFER, s.vbo)
	gl.BufferData(gl.ARRAY_BUFFER, len(vertices)*4, gl.Ptr(vertices), gl.STATIC_DRAW)

	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, s.ebo)
	gl.BufferData(gl.ELEMENT_ARRAY_BUFFER, len(indices)*4, gl.Ptr(indices), gl.STATIC_DRAW)

	err = s.shader.SetAttrib("vert", 2, gl.FLOAT, 4*4, 0)
	err = s.shader.SetAttrib("vertTexCoord", 2, gl.FLOAT, 4*4, 2*4)

	gl.BindVertexArray(0)

	return s, err
}

func LoadText(f *Font) (t *Text) {
	t = new(Text)
	t.font = f

	// text hover values
	// "resting state" of a text object is the min scale
	t.ScaleMin = 1.0
	t.ScaleMax = 1.1
	t.SetScale(1)

	// size of glfloat
	glfloat_size := int32(4)

	// stride of the buffered data
	xy_count := int32(2)
	stride := xy_count + int32(2)

	gl.GenVertexArrays(1, &t.vao)
	gl.GenBuffers(1, &t.vbo)
	gl.GenBuffers(1, &t.ebo)

	// vao
	gl.BindVertexArray(t.vao)

	gl.ActiveTexture(gl.TEXTURE0)
	gl.BindTexture(gl.TEXTURE_2D, t.font.textureID)

	// vbo
	// specify the buffer for which the VertexAttribPointer calls apply
	gl.BindBuffer(gl.ARRAY_BUFFER, t.vbo)

	gl.EnableVertexAttribArray(t.font.centeredPosition)
	gl.VertexAttribPointer(
		t.font.centeredPosition,
		2,
		gl.FLOAT,
		false,
		glfloat_size*stride,
		gl.PtrOffset(0),
	)

	gl.EnableVertexAttribArray(t.font.uv)
	gl.VertexAttribPointer(
		t.font.uv,
		2,
		gl.FLOAT,
		false,
		glfloat_size*stride,
		gl.PtrOffset(int(glfloat_size*xy_count)),
	)

	// ebo
	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, t.ebo)

	// i am guessing that order is important here
	gl.BindVertexArray(0)
	gl.BindBuffer(gl.ARRAY_BUFFER, 0)
	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, 0)
	return t
}

func (r *GlowRenderer) Draw() (err error) {
	gl.UseProgram(r.shader)
	gl.Uniform1i(r.textureUnitLoc, 0)
	gl.BindBuffer(gl.ARRAY_BUFFER, r.coords)
	gl.EnableVertexAttribArray(r.positionLoc)
	gl.VertexAttribPointer(r.positionLoc, 3, gl.FLOAT, false, 5*4, gl.PtrOffset(0))
	gl.EnableVertexAttribArray(r.textureLoc)
	gl.VertexAttribPointer(r.textureLoc, 2, gl.FLOAT, false, 5*4, gl.PtrOffset(3*4))
	gl.Uniform1i(r.blurAmountLoc, int32(r.blur))
	gl.Uniform1f(r.blurScaleLoc, r.scale)
	gl.Uniform1f(r.blurStrengthLoc, r.strength)
	gl.Uniform2f(r.bufferDimensionsLoc, float32(r.width), float32(r.height))

	gl.BindFramebuffer(gl.FRAMEBUFFER, r.BlurFb)
	gl.Viewport(0, 0, int32(r.width), int32(r.height))
	gl.ActiveTexture(gl.TEXTURE0)
	gl.BindTexture(gl.TEXTURE_2D, r.GlowTex)
	gl.Uniform1i(r.orientationLoc, 0)
	gl.DrawArrays(gl.TRIANGLE_STRIP, 0, 4)
	gl.BindFramebuffer(gl.FRAMEBUFFER, 0)

	gl.Viewport(0, 0, int32(r.oldwidth), int32(r.oldheight))
	gl.BlendFunc(gl.ONE, gl.ONE)
	gl.BindTexture(gl.TEXTURE_2D, r.BlurTex)
	gl.Uniform1i(r.orientationLoc, 1)
	gl.DrawArrays(gl.TRIANGLE_STRIP, 0, 4)

	gl.BindBuffer(gl.ARRAY_BUFFER, 0)
	gl.BlendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA)
	return nil
}

// Rendering this LineRender.
func (lr *LineRender) Render() {
	// Binding the appropriate information.
	gl.BindVertexArray(lr.vao)
	gl.BindBuffer(gl.ARRAY_BUFFER, lr.vbo)
	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, lr.ebo)
	gl.UseProgram(lr.shaderProgram)

	// Loading up vertex attributes.
	vertAttrib := uint32(gl.GetAttribLocation(lr.shaderProgram, gl.Str("vert\x00")))
	gl.EnableVertexAttribArray(vertAttrib)
	gl.VertexAttribPointer(vertAttrib, 2, gl.FLOAT, false, 2*4, gl.PtrOffset(0))

	// Line thickness information.
	gl.Uniform1f(
		gl.GetUniformLocation(lr.shaderProgram, gl.Str("in_thickness\x00")),
		lr.weight)

	// Fragment shader color information.
	gl.Uniform4f(
		gl.GetUniformLocation(lr.shaderProgram, gl.Str("in_color\x00")),
		lr.color.Red,
		lr.color.Green,
		lr.color.Blue,
		lr.color.Alpha)

	gl.BindFragDataLocation(lr.shaderProgram, 0, gl.Str("out_color\x00"))

	// Performing the render.
	gl.DrawElements(gl.LINE_STRIP, lr.points, gl.UNSIGNED_INT, nil)
}

func (t *Text) SetString(fs string, argv ...interface{}) {
	var indices []rune
	if len(argv) == 0 {
		indices = []rune(fs)
	} else {
		indices = []rune(fmt.Sprintf(fs, argv...))
	}
	if len(indices) == 0 {
		return
	}
	if t.MaxRuneCount > 0 && len(indices) > t.MaxRuneCount+1 {
		indices = indices[0:t.MaxRuneCount]
	}
	t.String = string(indices)

	// ebo, vbo data
	glfloat_size := int32(4)

	t.vboIndexCount = len(indices) * 4 * 2 * 2 // 4 indexes per rune (containing 2 position + 2 texture)
	t.eboIndexCount = len(indices) * 6         // each rune requires 6 triangle indices for a quad
	t.RuneCount = len(indices)
	t.vboData = make([]float32, t.vboIndexCount, t.vboIndexCount)
	t.eboData = make([]int32, t.eboIndexCount, t.eboIndexCount)

	// generate the basic vbo data and bounding box
	t.X1 = Point{0, 0}
	t.X2 = Point{0, 0}
	t.makeBufferData(indices)

	// find the centered position of the bounding box
	lowerLeft := t.getLowerLeft()

	// reposition the vbo data so that it is centered at (0,0)
	// according to the orthographic projection being used
	t.setDataPosition(lowerLeft)

	if t.IsDebug {
		fmt.Printf("bounding box %v %v\n", t.X1, t.X2)
		fmt.Printf("lower left\n%v\n", lowerLeft)
		fmt.Printf("text vbo data\n%v\n", t.vboData)
		fmt.Printf("text ebo data\n%v\n", t.eboData)
	}
	gl.BindVertexArray(t.vao)
	gl.BindBuffer(gl.ARRAY_BUFFER, t.vbo)
	gl.BufferData(
		gl.ARRAY_BUFFER, int(glfloat_size)*t.vboIndexCount, gl.Ptr(t.vboData), gl.DYNAMIC_DRAW)
	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, t.ebo)
	gl.BufferData(
		gl.ELEMENT_ARRAY_BUFFER, int(glfloat_size)*t.eboIndexCount, gl.Ptr(t.eboData), gl.DYNAMIC_DRAW)
	gl.BindVertexArray(0)

	// not necesssary, but i just want to better understand using vertex arrays
	gl.BindBuffer(gl.ARRAY_BUFFER, 0)
	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, 0)

	// SetString can be called at anytime.  we want to make sure that if the user is updating the text,
	// the previous position will be maintained
	t.SetPosition(t.SetPositionX, t.SetPositionY)
}

func (lr *LinesRenderer) Unbind() (err error) {
	gl.BindBuffer(gl.ARRAY_BUFFER, 0)
	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, 0)
	if e := gl.GetError(); e != 0 {
		err = fmt.Errorf("ERROR: OpenGL error %X", e)
	}
	return
}

func createElementArrayBuffer(data []uint16) uint32 {
	var name uint32
	gl.GenBuffers(1, &name)
	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, name)
	gl.BufferData(gl.ELEMENT_ARRAY_BUFFER, len(data)*2 /* total bytes */, gl.Ptr(data), gl.STATIC_DRAW)
	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, 0)
	return name
}

func createArrayBuffer(data []float32) uint32 {
	var name uint32
	gl.GenBuffers(1, &name)
	gl.BindBuffer(gl.ARRAY_BUFFER, name)
	gl.BufferData(gl.ARRAY_BUFFER, len(data)*4 /* total bytes */, gl.Ptr(data), gl.STATIC_DRAW)
	gl.BindBuffer(gl.ARRAY_BUFFER, 0)
	return name
}

func (lr *LinesRenderer) Delete() (err error) {
	gl.BindBuffer(gl.ARRAY_BUFFER, 0)
	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, 0)
	gl.DeleteBuffers(1, &lr.buffer)
	gl.DeleteBuffers(1, &lr.indexBuffer)
	if e := gl.GetError(); e != 0 {
		err = fmt.Errorf("ERROR: OpenGL error %X", e)
	}
	return
}

func (s *Sprite) Draw() {
	s.shader.Use()
	s.texture.Bind()

	gl.BindVertexArray(s.vao)
	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, s.ebo)
	gl.BindBuffer(gl.ARRAY_BUFFER, s.vbo)
	//gl.DrawArrays(gl.TRIANGLES, 0, 3)
	gl.DrawElements(gl.TRIANGLES, 6, gl.UNSIGNED_INT, gl.PtrOffset(0))
	gl.BindVertexArray(0)
	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, 0)

}

func (renderObject *RenderObject) Render() {
	gl.BindVertexArray(renderObject.vao)
	gl.BindBuffer(gl.ARRAY_BUFFER, renderObject.vbo)
	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, renderObject.ebo)
	gl.UseProgram(renderObject.shaderProgram)

	// Binding the texture.
	gl.ActiveTexture(gl.TEXTURE0)
	gl.BindTexture(gl.TEXTURE_2D, renderObject.texture)
	gl.BindFragDataLocation(renderObject.shaderProgram, 0, gl.Str("outputColor\x00"))

	// Drawing the object.
	gl.DrawElements(gl.TRIANGLES, 6, gl.UNSIGNED_INT, nil)
}

func (r *BatchRenderer) Draw(batch *Batch, x, y, rot float32) error {
	batch.Texture.Bind()
	gl.BindBuffer(gl.ARRAY_BUFFER, batch.Buffer)
	gl.EnableVertexAttribArray(r.PositionLoc)
	gl.VertexAttribPointer(r.PositionLoc, 3, gl.FLOAT, false, 5*4, gl.PtrOffset(0))
	gl.EnableVertexAttribArray(r.TextureLoc)
	gl.VertexAttribPointer(r.TextureLoc, 2, gl.FLOAT, false, 5*4, gl.PtrOffset(3*4))
	m := mgl32.Translate3D(x, y, 0.0).Mul4(mgl32.HomogRotate3DZ(rot))
	gl.UniformMatrix4fv(r.ModelViewLoc, 1, false, &m[0])
	gl.Uniform2f(r.TexOffsetLoc, batch.textureOffset.X(), batch.textureOffset.Y())
	gl.DrawArrays(gl.TRIANGLES, 0, int32(batch.Count))
	gl.BindBuffer(gl.ARRAY_BUFFER, 0)
	return nil
}

func (tr *TextRenderer) Draw(tex *Texture, x, y, scale float32) (err error) {
	gl.ActiveTexture(gl.TEXTURE0)
	if e := gl.GetError(); e != 0 {
		return fmt.Errorf("ERROR: %X", e)
	}
	gl.BindTexture(gl.TEXTURE_2D, tex.Texture)
	if e := gl.GetError(); e != 0 {
		return fmt.Errorf("ERROR: %X", e)
	}
	gl.Uniform3f(tr.ScaleLoc, float32(tex.Width)*scale, float32(tex.Height)*scale, 1)
	if e := gl.GetError(); e != 0 {
		return fmt.Errorf("ERROR: %X", e)
	}
	gl.Uniform3f(tr.TransLoc, x, y, 0)
	if e := gl.GetError(); e != 0 {
		return fmt.Errorf("ERROR: %X", e)
	}
	gl.DrawArrays(gl.TRIANGLE_STRIP, 0, 4)
	if e := gl.GetError(); e != 0 {
		return fmt.Errorf("ERROR: %X", e)
	}
	gl.BindBuffer(gl.ARRAY_BUFFER, 0)
	if e := gl.GetError(); e != 0 {
		return fmt.Errorf("ERROR: %X", e)
	}
	return nil
}

func (tr *TextRenderer) Unbind() error {
	gl.BindBuffer(gl.ARRAY_BUFFER, 0)
	if e := gl.GetError(); e != 0 {
		return fmt.Errorf("ERROR: %X", e)
	}
	return nil
}

func (lr *LinesRenderer) Bind() (err error) {
	gl.UseProgram(lr.program)
	gl.BindBuffer(gl.ARRAY_BUFFER, lr.buffer)
	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, lr.indexBuffer)
	gl.EnableVertexAttribArray(lr.positionLoc)
	gl.EnableVertexAttribArray(lr.normalLoc)
	gl.EnableVertexAttribArray(lr.miterLoc)
	gl.VertexAttribPointer(lr.positionLoc, 2, gl.FLOAT, false, lr.stride, lr.offPosition)
	gl.VertexAttribPointer(lr.normalLoc, 2, gl.FLOAT, false, lr.stride, lr.offNormal)
	gl.VertexAttribPointer(lr.miterLoc, 1, gl.FLOAT, false, lr.stride, lr.offMiter)
	gl.UniformMatrix4fv(lr.projectionLoc, 1, false, &lr.Renderer.Camera.Projection[0])
	if e := gl.GetError(); e != 0 {
		err = fmt.Errorf("ERROR: OpenGL error %X", e)
	}
	return
}

func (tr *TextRenderer) Bind() error {
	gl.UseProgram(tr.Program)
	if e := gl.GetError(); e != 0 {
		return fmt.Errorf("ERROR: %X", e)
	}
	gl.Uniform1i(tr.TextureUnitLoc, 0)
	if e := gl.GetError(); e != 0 {
		return fmt.Errorf("ERROR: %X", e)
	}
	gl.BindBuffer(gl.ARRAY_BUFFER, tr.VBO)
	if e := gl.GetError(); e != 0 {
		return fmt.Errorf("ERROR: %X", e)
	}
	gl.EnableVertexAttribArray(tr.PositionLoc)
	gl.VertexAttribPointer(tr.PositionLoc, 3, gl.FLOAT, false, 5*4, gl.PtrOffset(0))
	if e := gl.GetError(); e != 0 {
		return fmt.Errorf("ERROR: %X", e)
	}
	gl.EnableVertexAttribArray(tr.TextureLoc)
	gl.VertexAttribPointer(tr.TextureLoc, 2, gl.FLOAT, false, 5*4, gl.PtrOffset(3*4))
	if e := gl.GetError(); e != 0 {
		return fmt.Errorf("ERROR: %X", e)
	}
	gl.UniformMatrix4fv(tr.ProjectionLoc, 1, false, &tr.Renderer.Camera.Projection[0])
	if e := gl.GetError(); e != 0 {
		return fmt.Errorf("ERROR: %X", e)
	}
	return nil
}

func customLandscapeBinder(renderer fizzle.Renderer, r *fizzle.Renderable, shader *fizzle.RenderShader) {
	shaderCombo1 := shader.GetAttribLocation("VERTEX_COLOR")
	if shaderCombo1 >= 0 {
		gl.BindBuffer(gl.ARRAY_BUFFER, r.Core.ComboVBO1)
		gl.EnableVertexAttribArray(uint32(shaderCombo1))
		gl.VertexAttribPointer(uint32(shaderCombo1), 3, gl.FLOAT, false, 0, gl.PtrOffset(0))
	}
}