extends Control

const INPUT_TEX_WIDTH := 2048
const INPUT_FORMAT := Image.FORMAT_RGBA8  # Image.FORMAT_LA8
const INPUT_BYTES_PER_TEXEL := 4         # 2
const OUTPUT_BYTES_PER_TEXEL := 4
const OUTPUT_FRAMEBUFFER_SIZE := Vector2(4096, 4096)
const OUTPUT_WIDTH := int(OUTPUT_FRAMEBUFFER_SIZE.x)
const OUTPUT_HEIGHT := int(OUTPUT_FRAMEBUFFER_SIZE.y)
const QUAD_COLOR := PoolColorArray([Color.white, Color.white, Color.white, Color.white])
var viewport: Viewport
var render_queue: Array  # of Images
var result_queue: Array  # of [String, PoolByteArray]
var current_textures: Array  # of ImageTextures - Needed to prevent GC before draw
var waiting_for_viewport: Array
var done_first_draw: bool

func _ready() -> void:
	self.viewport = get_parent()
	self.render_queue = []
	self.result_queue = []
	self.waiting_for_viewport = []
	self.done_first_draw = false
	self.current_textures = []
	self.get_parent().size = OUTPUT_FRAMEBUFFER_SIZE
	self.material.set_shader_param('OUTPUT_FRAMEBUFFER_SIZE', OUTPUT_FRAMEBUFFER_SIZE)
	self.material.set_shader_param('INT_OUTPUT_WIDTH', OUTPUT_WIDTH)

func push_image(img: Image, target_samples: int = -1, desc: String = '') -> void:
	var target_rows = ceil(target_samples/float(OUTPUT_WIDTH))
	if target_samples <= 0:
		target_rows = int(img.get_size().y)
	self.render_queue.append([img, target_rows, desc])

func push_bytes(data: PoolByteArray, target_samples: int = -1, desc: String = '') -> void:
	var rows = int(pow(2, ceil(log((len(data)/INPUT_BYTES_PER_TEXEL) / INPUT_TEX_WIDTH)/log(2))))
	var target_length = rows * INPUT_BYTES_PER_TEXEL * INPUT_FORMAT
	while len(data) < target_length:  # This is inefficient, but this function should be called with pre-padded data anyway
		data.append(0)
	var image := Image.new()
	image.create_from_data(INPUT_TEX_WIDTH, rows, false, INPUT_FORMAT, data)
	var target_rows = ceil(target_samples/float(OUTPUT_WIDTH))
	if target_samples <= 0:
		target_rows = rows
	self.render_queue.append([image, target_rows, desc])

func _process(_delta) -> void:
	update()

func _draw() -> void:
	# Seems like the first one always fails
	if not self.done_first_draw:
		self.done_first_draw = true
		return

	if self.waiting_for_viewport:
		# Another node later in the draw sequence can call this within the same frame,
		# otherwise, this picks it up the following frame
		get_result()

	if not self.render_queue:
		return

	self.waiting_for_viewport = []
	var rows_drawn := 0
	while self.render_queue:
		var draw_rows: int = self.render_queue[0][1]
		rows_drawn += draw_rows
		if rows_drawn > OUTPUT_HEIGHT:
			break

		# Draw the next ImageTexture
		var image_and_uv_rows_and_desc = self.render_queue.pop_front()
		var i := len(self.waiting_for_viewport)
		if len(self.current_textures) < i+1:
			self.current_textures.append(ImageTexture.new())
		var tex: ImageTexture = self.current_textures[i]
		tex.create_from_image(image_and_uv_rows_and_desc[0], 0)
		self.material.set_shader_param('midi_events_size', tex.get_size())
		var y_top: int = OUTPUT_HEIGHT - rows_drawn
		var y_bot: int = y_top + draw_rows
		var uv_inv_v: float = 1 - (draw_rows / OUTPUT_FRAMEBUFFER_SIZE.y)
		var uvs := PoolVector2Array([Vector2(0, uv_inv_v), Vector2(1, uv_inv_v), Vector2(1, 1), Vector2(0, 1)])
		var points := PoolVector2Array([Vector2(0, y_top), Vector2(OUTPUT_WIDTH, y_top), Vector2(OUTPUT_WIDTH, y_bot), Vector2(0, y_bot)])
		draw_primitive(points, QUAD_COLOR, uvs, tex)
		self.waiting_for_viewport.append([draw_rows, image_and_uv_rows_and_desc[2]])  # Grab the result next draw


func get_result() -> void:
	var result_texture := self.viewport.get_texture()
	var result_image := result_texture.get_data()
	var result_bytes := result_image.get_data()

	var retrieved_rows := 0
	for rows_and_desc in self.waiting_for_viewport:
		var entry_rows: int = rows_and_desc[0]
		var entry_desc: String = rows_and_desc[1]
		var bytes_start := retrieved_rows * OUTPUT_WIDTH * OUTPUT_BYTES_PER_TEXEL
		var bytes_end := (retrieved_rows + entry_rows) * OUTPUT_WIDTH * OUTPUT_BYTES_PER_TEXEL
		var entry_bytes := result_bytes.subarray(bytes_start, bytes_end-1)
		self.result_queue.append([entry_desc, entry_bytes])
		retrieved_rows += entry_rows
	# result_bytes.resize(result_byte_count)
	self.waiting_for_viewport = []

	# # Debugging: compare a sequence of all the possible 16bit integers
	# print_debug('result_image format is %d and has size'%result_image.get_format(), result_image.get_size(), result_bytes.subarray(0, 11))
	# test_readback(result_bytes)

func test_readback(result_bytes: PoolByteArray):
	# Debugging: compare a sequence of all the possible 16bit integers
	var buff := StreamPeerBuffer.new()
	buff.set_data_array(result_bytes)
	var tex_readback = 0
	var uv_readback = 0
	for i in 0x1000:
		tex_readback = buff.get_u16()
		uv_readback = buff.get_u16()
		if tex_readback != i:
			print('tex readback %d (0x%04x) was instead %d (0x%04x)'%[i, i, tex_readback, tex_readback])
		if uv_readback != i:
			print('uv readback %d (0x%04x) was instead %d (0x%04x)'%[i, i, uv_readback, uv_readback])