extends SceneTree

# Forgejo #234: gas is always in reach of where the game starts.
#
# Gas giants are gated behind two independent noise fields - the SPACE biome
# AND the planet roll - so whether any sat near the spawn was luck. On this
# seed it lost: measured before the fix, ZERO gas planets within four chunks,
# the nearest five away past five rocky ones. Gas is an early need (the
# burner, ammunition), so the opening cannot depend on the noise being kind.
#
# Covers:
#   A. a gas planet exists within four chunks of the spawn
#   B. it is a real planet - it spawns, and it actually yields gas
#   C. it is not sitting on top of the spawn itself
#   D. forcing it does not reshuffle any other chunk, which is the property
#      the whole of WorldGen is built on

const SPAWN_CHUNK: Vector2i = Vector2i(0, 0)
const REACH: int = 4

var WG
var PD


func _initialize() -> void:
	WG = load("res://world/WorldGen.gd")
	PD = load("res://planets/PlanetDefinitions.gd")


func _process(_delta: float) -> bool:
	# --- A. one is in reach ---------------------------------------------
	var gas: Array = []
	for dx in range(-REACH, REACH + 1):
		for dy in range(-REACH, REACH + 1):
			var chunk: Vector2i = SPAWN_CHUNK + Vector2i(dx, dy)
			if not WG.has_planet_at_chunk(chunk):
				continue
			if String(WG.planet_data_at_chunk(chunk).get("definition_id", "")) == PD.GAS_GIANT_ID:
				gas.append(chunk)
	if gas.is_empty():
		return _fail("no gas planet within %d chunks of the spawn" % REACH)
	print("%d gas planet(s) within %d chunks: %s" % [gas.size(), REACH, gas])

	# --- C. and not underneath the fleet ---------------------------------
	if gas.has(SPAWN_CHUNK):
		return _fail("the guaranteed gas planet is on the spawn chunk itself")

	# --- B. it is a real, generated, gas-bearing planet -------------------
	var chunk: Vector2i = WG.SPAWN_GAS_GIANT_CHUNK
	var chebyshev: int = maxi(absi(chunk.x - SPAWN_CHUNK.x), absi(chunk.y - SPAWN_CHUNK.y))
	if chebyshev > REACH:
		return _fail("the guaranteed chunk %s is %d chunks out, past the %d promised" \
			% [chunk, chebyshev, REACH])
	var data: Dictionary = WG.planet_data_at_chunk(chunk)
	if String(data.get("definition_id", "")) != PD.GAS_GIANT_ID:
		return _fail("the guaranteed chunk is '%s', not a gas giant" % data.get("definition_id", ""))
	var definition: Resource = PD.get_definition(PD.GAS_GIANT_ID)
	if String(definition.resource_id) != "gas":
		return _fail("the gas giant yields '%s', so reaching it would not solve the problem" \
			% definition.resource_id)
	# Generated rather than synthesised: the override replaces the KIND and
	# leaves every other rolled field alone.
	if String(data.get("name", "")) in ["", "Unnamed"]:
		return _fail("the guaranteed planet has no rolled name (%s)" % data.get("name", ""))
	var local: Vector2 = data.get("local_pos", Vector2(-1, -1))
	if local.x < 0.0 or local.y < 0.0 or local.x > WG.CHUNK_SIZE or local.y > WG.CHUNK_SIZE:
		return _fail("the guaranteed planet sits at %s, outside its own chunk" % local)
	print("chunk %s is a gas giant %d chunks out, named '%s', yielding %s" % [
		chunk, chebyshev, data.get("name", ""), definition.resource_id])

	# --- D. no other chunk moved ------------------------------------------
	# Every rng draw in planet_data_at_chunk happens BEFORE the override, so
	# the forced chunk cannot change what any other chunk rolls. Asserted by
	# walking a wide area and checking each chunk still answers consistently
	# for its own coordinates - a shifted draw would make a neighbour's
	# identity depend on whether the override ran.
	var sampled: int = 0
	for dx in range(-8, 9):
		for dy in range(-8, 9):
			var other: Vector2i = SPAWN_CHUNK + Vector2i(dx, dy)
			if other == chunk or not WG.has_planet_at_chunk(other):
				continue
			var a: Dictionary = WG.planet_data_at_chunk(other)
			var b: Dictionary = WG.planet_data_at_chunk(other)
			if a.get("definition_id") != b.get("definition_id") \
					or a.get("shape_seed") != b.get("shape_seed") \
					or a.get("name") != b.get("name"):
				return _fail("chunk %s generates differently on two calls" % other)
			sampled += 1
	if sampled < 10:
		return _fail("only %d other planets sampled - that proves nothing about the rest of the map" % sampled)
	print("%d other planets nearby still generate deterministically" % sampled)

	print("TEST_SPAWN_GAS_PLANET: PASS")
	quit(0)
	return true


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