extends Node
## Dev-only screenshot harness. Boots a target scene inside the real (GPU)
## renderer, lets it run a few frames, then reads the rendered frame back off
## the viewport and writes it to disk. Nothing in the shipped game touches this.
##
## Driven entirely by environment variables so it needs no CLI parsing:
##   AGP_SHOT_SCENE   res:// path of the scene to capture   (default: game.tscn)
##   AGP_SHOT_OUT     output PNG path (absolute)            (default: /tmp/agp_shot.png)
##   AGP_SHOT_FRAMES  frames to settle before the first shot (default: 45)
##   AGP_SHOT_SEQ     "count:gap" -> take <count> shots <gap> frames apart,
##                    suffixing the filename _01.._NN (default: single shot)
##
## Launch (hardware Vulkan on cloudbison's Radeon, via Xvfb):
##   Xvfb :99 -screen 0 1280x720x24 &
##   sg render -c "sg video -c 'DISPLAY=:99 AGP_SHOT_SCENE=res://scenes/game.tscn \
##     AGP_SHOT_OUT=/abs/shot.png ~/godot/godot --path . \
##     --rendering-driver vulkan --gpu-index 0 --resolution 1280x720 \
##     res://scenes/dev/screenshot_rig.tscn'"

func _ready() -> void:
	_run.call_deferred()


func _run() -> void:
	var target := OS.get_environment("AGP_SHOT_SCENE")
	if target.is_empty():
		target = "res://scenes/game.tscn"
	var out := OS.get_environment("AGP_SHOT_OUT")
	if out.is_empty():
		out = "/tmp/agp_shot.png"
	var settle := int(OS.get_environment("AGP_SHOT_FRAMES"))
	if settle <= 0:
		settle = 45

	var seq_count := 1
	var seq_gap := 0
	var seq_env := OS.get_environment("AGP_SHOT_SEQ")
	if seq_env.contains(":"):
		var parts := seq_env.split(":")
		seq_count = maxi(1, int(parts[0]))
		seq_gap = maxi(1, int(parts[1]))

	var packed: PackedScene = load(target)
	if packed == null:
		push_error("screenshot_rig: cannot load %s" % target)
		get_tree().quit(1)
		return
	var inst: Node = packed.instantiate()
	get_tree().root.add_child(inst)
	get_tree().current_scene = inst

	for i in settle:
		await get_tree().process_frame

	for shot in seq_count:
		# get_image() on the viewport texture is a GPU->CPU readback of the
		# frame that was just rendered -- no window presentation needed, which
		# is why this works over Xvfb (no DRI3).
		var img: Image = get_viewport().get_texture().get_image()
		var path := out
		if seq_count > 1:
			path = "%s_%02d.png" % [out.get_basename(), shot + 1]
		var err := img.save_png(path)
		if err != OK:
			push_error("screenshot_rig: save_png(%s) failed: %d" % [path, err])
		else:
			print("SHOT %s (%dx%d)" % [path, img.get_width(), img.get_height()])
		if shot < seq_count - 1:
			for j in seq_gap:
				await get_tree().process_frame

	get_tree().quit()