extends SceneTree

# Headless test: run with
#   godot --headless -s res://tests/test_surface_feature_depth.gd
# Forgejo #91: on a gas planet the gas source was drawn ON TOP of the player.
#
# SurfaceFeatures is added after Fleet in PlanetSurface.tscn, so anything
# down there that keeps the default z_index of 0 wins the tie against the
# ships purely by being the later sibling. The player then flies under their
# own scenery, which reads as a rendering fault rather than as depth.
#
# Checks the RULE rather than the one node that was wrong: every feature that
# actually draws, on every surface profile that has features, must end up
# behind the fleet. A feature added later is covered without editing this.
#
# Covers:
#   A. the gas giant's vent field draws behind the ships (the #91 report)
#   B. the same for every other drawing feature on every profile
#   C. the fleet's own ships are where the comparison says they are, so a
#      future change that pushed the ships back instead cannot make A and B
#      pass by moving the goalposts

const PROFILE_PLANETS: Array = ["gas_giant", "rocky", "research_lab"]

var game_state: Node
var surface: Node
var planets: Array = []
var checked: int = 0
var stage: int = 0
var elapsed: float = 0.0


func _initialize() -> void:
	# The autoload is reached by node, not by the bare `GameState` name: from
	# a SceneTree script that name resolves only far enough for constants,
	# and an instance member through it is a COMPILE error for the whole
	# file. Every other test here does the same.
	game_state = root.get_node("GameState")
	planets = PROFILE_PLANETS.duplicate()
	game_state.reset_progression()
	game_state.surviving_ship_count = 3
	_load_next()


func _load_next() -> void:
	if surface != null and is_instance_valid(surface):
		surface.queue_free()
		surface = null
	if planets.is_empty():
		return
	var definition_id: String = String(planets.pop_front())
	game_state.planet_definition_id = definition_id
	game_state.planet_name = "Depth Probe"
	game_state.planet_id = "depth-probe-%s" % definition_id
	surface = load("res://surface/PlanetSurface.tscn").instantiate()
	surface.get_node("SurfaceController").fade_duration = 0.0
	root.add_child(surface)


# z_index is RELATIVE to the parent by default, so a node's real depth is the
# running sum up the chain - reading z_index alone would call a +1 child of a
# -1 parent "behind", which it is not.
func _effective_z(node: CanvasItem) -> int:
	var total: int = 0
	var current: Node = node
	while current is CanvasItem:
		total += (current as CanvasItem).z_index
		if not (current as CanvasItem).z_as_relative:
			break
		current = current.get_parent()
	return total


func _drawing_descendants(node: Node, found: Array) -> Array:
	for child in node.get_children():
		# Enemies are spawned under SurfaceFeatures by the planet's setup
		# markers, but they are combatants, not scenery: they share the
		# fleet's plane on purpose, the same way they do in space. Only the
		# ground the fight happens on has to stay behind it.
		if child.is_in_group("enemies"):
			continue
		# has_method("_draw") is true only where a script defines one, which
		# is exactly "this node puts pixels on the surface". Plain Node2D
		# hosts that only spawn their children draw nothing themselves and
		# are free to sit at 0 - the rocky surface's RockField is one.
		if child is CanvasItem and child.has_method("_draw"):
			found.append(child)
		_drawing_descendants(child, found)
	return found


func _process(delta: float) -> bool:
	elapsed += delta
	if elapsed < 0.35:
		return false
	elapsed = 0.0

	var fleet: Node2D = surface.get_node("Fleet")
	if fleet.ships.is_empty():
		return _fail("no ships spawned, so there is nothing to be in front of")
	var ship_z: int = _effective_z(fleet.ships[0])
	if ship_z != 0:
		# C. The comparison below is "behind the ships", and the ships being
		# at 0 is what makes "negative" mean that.
		return _fail("ships are at z=%d, not 0 - this test's premise moved" % ship_z)

	var features: Array = _drawing_descendants(surface.get_node("SurfaceFeatures"), [])
	# A profile is allowed to have no scenery of its own - the research lab
	# had none but the capture rings, and #211 took those away. The rule is
	# about features that EXIST, so an empty profile is skipped rather than
	# failed; the run-wide check below is what stops this test quietly
	# checking nothing at all.
	if features.is_empty():
		print("%s: no drawing surface features of its own" \
			% game_state.planet_definition_id)
	for feature in features:
		var z: int = _effective_z(feature)
		if z >= ship_z:
			return _fail("%s on %s draws at z=%d, in front of the fleet at z=%d" % [
				feature.name, game_state.planet_definition_id, z, ship_z
			])
	print("%s: %d drawing features, all behind the fleet" % [
		game_state.planet_definition_id, features.size()
	])
	checked += features.size()

	if planets.is_empty():
		if checked == 0:
			return _fail("no profile had a single drawing feature - this test proved nothing")
		print("TEST_SURFACE_FEATURE_DEPTH: PASS (%d features checked)" % checked)
		quit(0)
		return true
	_load_next()
	return false


func _fail(message: String) -> bool:
	print("TEST_SURFACE_FEATURE_DEPTH: FAIL (%s)" % message)
	quit(1)
	return true