# Shader attribute
#
# It will use either the `uniform` value or the data at `array_pointer` if
# and only if `array_enabled`.
class Attribute
	super ShaderVariable

	private var array_enabled_cache = false

	# Is the array attribute enabled?
	fun array_enabled: Bool do return array_enabled_cache

	# Set whether to use the data at `array_pointer` over `uniform`.
	fun array_enabled=(value: Bool)
	do
		if not is_active then return

		glUseProgram program

		self.array_enabled_cache = value
		if value then
			glEnableVertexAttribArray location
		else glDisableVertexAttribArray location
	end

	# Define the `array` of vertex data
	fun array(array: Array[Float], data_per_vertex: Int)
	do
		# TODO move this and native_float_array to a subclass specific to float

		if not is_active then return

		var native = native_float_array
		if native == null or array.length > native.length then
			if native != null then native.finalize
			native = new GLfloatArray.from(array)
			self.native_float_array = native
		else
			native.fill_from(array)
		end

		glVertexAttribPointer(location, data_per_vertex, gl_FLOAT, false, 0, native.native_array)
	end

	private var native_float_array: nullable GLfloatArray = null
end