class_name WorldGen
extends RefCounted

const PLANET_DEFINITIONS = preload("res://planets/PlanetDefinitions.gd")

# Deterministic procedural world generation: the world is divided into
# square chunks, and each chunk's biome is derived from a seeded
# low-frequency noise field sampled at the chunk's own coordinates - so
# revisiting the same chunk always yields the same biome, and biomes form
# smooth multi-chunk regions instead of a per-chunk random checkerboard.

enum Biome { SPACE, ASTEROID_FIELD, OCTOPUS }

const CHUNK_SIZE: float = 1200.0
const NOISE_SEED: int = 1337
const ASTEROID_FIELD_THRESHOLD: float = 0.15
# Planets used to sit one per ~29 chunks - 35,000 world units of empty space
# between them, which is a long flight to find anything at all. Lowered to
# about one per 12 chunks (measured over 14,641 chunks, not estimated).
#
# The two thresholds moved by DIFFERENT amounts on purpose. Every planet in a
# SPACE biome is a gas giant, so lowering both equally would have shifted the
# mix as well as the density - dropping these to 0.20/0.40 more than tripled
# the gas-giant share, from 10% of planets to 34%. 0.18/0.50 leaves it at 11%,
# so this is a change in how OFTEN you find a planet and not in what you find.
const PLANET_THRESHOLD: float = 0.18
const GAS_GIANT_THRESHOLD: float = 0.50
# A flat per-planet-chunk probability rather than another noise field: gas
# giants already cover every SPACE-biome planet chunk (see GAS_GIANT_THRESHOLD
# above), so making black holes noticeably rarer just needs a small, uniform
# chance independent of biome - not a second smooth region to tune against
# the first.
const BLACK_HOLE_CHANCE: float = 0.05
# #63/#74: findable without excessive exploration - research points gate
# mid/late skill-tree nodes and vessel research, so a player needs to run
# into one of these reasonably often, not just as a rare curiosity. Raised
# from 0.08 after playtesting found that rate too scarce for how central
# research points had become to progression.
const RESEARCH_LAB_CHANCE: float = 0.16
# The hostile region is authored into procedural space as one finite,
# deterministic island. A probability per chunk can only say "rare"; over an
# infinite world it inevitably creates infinitely many boss worlds. One
# anchor and one shape make the actual rule representable: one multi-chunk
# octopus biome, with its boss at the centre.
const OCTOPUS_BIOME_CENTER: Vector2i = Vector2i(12, -9)

# Forgejo #234: a gas giant the opening is guaranteed to be able to reach.
#
# Gas is gated behind two independent noise fields - the SPACE biome and the
# planet roll - so whether any is in reach of the spawn was luck, and on this
# seed it lost: measured, there were ZERO gas planets within four chunks and
# the nearest sat five away, past five rocky ones. Gas is needed early (the
# burner, ammunition), so the opening cannot depend on the noise being kind.
#
# Authored like OCTOPUS_BIOME_CENTER above rather than found by searching
# outward: a fixed chunk is reproducible from anywhere without walking the
# map, which is the property everything in this file is built on.
const SPAWN_GAS_GIANT_CHUNK: Vector2i = Vector2i(2, -2)
const OCTOPUS_BIOME_OFFSETS: Array[Vector2i] = [
	Vector2i(0, 0), Vector2i(-1, 0), Vector2i(1, 0),
	Vector2i(0, -1), Vector2i(0, 1),
	Vector2i(-1, -1), Vector2i(1, -1),
	Vector2i(-1, 1), Vector2i(1, 1),
]

# DEV MODE ONLY: one of every planet type, parked in the chunks immediately
# around the spawn so all five can be reached in seconds.
#
# This replaces the guaranteed gas giant that used to sit in the origin
# chunk for every game. That was a play-testing convenience which had become
# part of the real world's shape - every player got the same landmark in the
# same place, and the surrounding space was generated as if it were normal.
# Play-testing wants ALL the planet types to hand, not just gas, and a
# normal game wants none of them handed over; those are different needs and
# they now have different mechanisms.
#
# The local positions keep each planet off the spawn point itself: a fresh
# fleet starts at world origin, which is the top-left corner of chunk (0,0).
const DEV_PLANET_CHUNKS: Dictionary = {
	Vector2i(0, 0): PLANET_DEFINITIONS.GAS_GIANT_ID,
	Vector2i(1, 0): PLANET_DEFINITIONS.ROCKY_ID,
	Vector2i(0, 1): PLANET_DEFINITIONS.RESEARCH_LAB_ID,
	Vector2i(1, 1): PLANET_DEFINITIONS.BLACK_HOLE_ID,
	Vector2i(-1, 0): PLANET_DEFINITIONS.BOSS_ID,
}
const DEV_PLANET_LOCAL_POS: Vector2 = Vector2(600.0, 600.0)


# Dev mode plants a fixed set of planets; a normal game must not see them.
#
# PUSHED here by GameState.dev_mode's setter rather than read back out of the
# autoload. World generation is deliberately dependency-free - it is static,
# seeded purely by chunk coordinates, and callable from anywhere - and an
# autoload cannot be named from here anyway: `GameState` is not resolvable as
# a global identifier this early, the same load-order hazard PlanetSetups.gd
# and PlanetSurfaceController.gd already work around. GameState.dev_mode
# stays the single source of truth; this is its mirror.
static var dev_planets_enabled: bool = false


static func _dev_planets_active() -> bool:
	return dev_planets_enabled

static var _noise: FastNoiseLite
static var _planet_noise: FastNoiseLite


static func _get_noise() -> FastNoiseLite:
	if _noise == null:
		_noise = FastNoiseLite.new()
		_noise.seed = NOISE_SEED
		_noise.frequency = 0.06
	return _noise


static func _get_planet_noise() -> FastNoiseLite:
	if _planet_noise == null:
		_planet_noise = FastNoiseLite.new()
		_planet_noise.seed = NOISE_SEED + 777
		# Higher frequency than the biome noise so it spikes on individual
		# chunks rather than forming its own smooth multi-chunk regions -
		# "once or twice per asteroid biome [region]" needs a sparse, mostly
		# independent chance per chunk, not another smooth blob.
		_planet_noise.frequency = 0.35
	return _planet_noise


static func chunk_coords(world_pos: Vector2) -> Vector2i:
	return Vector2i(int(floor(world_pos.x / CHUNK_SIZE)), int(floor(world_pos.y / CHUNK_SIZE)))


static func chunk_origin(chunk: Vector2i) -> Vector2:
	return Vector2(chunk.x * CHUNK_SIZE, chunk.y * CHUNK_SIZE)


static func biome_at_chunk(chunk: Vector2i) -> int:
	if is_octopus_chunk(chunk):
		return Biome.OCTOPUS
	var n: float = _get_noise().get_noise_2d(float(chunk.x), float(chunk.y))
	if n > ASTEROID_FIELD_THRESHOLD:
		return Biome.ASTEROID_FIELD
	return Biome.SPACE


static func has_planet_at_chunk(chunk: Vector2i) -> bool:
	if _dev_planets_active() and DEV_PLANET_CHUNKS.has(chunk):
		return true
	if chunk == OCTOPUS_BIOME_CENTER:
		return true
	if chunk == SPAWN_GAS_GIANT_CHUNK:
		return true
	if is_octopus_chunk(chunk):
		return false
	var n: float = _get_planet_noise().get_noise_2d(float(chunk.x), float(chunk.y))
	return (biome_at_chunk(chunk) == Biome.ASTEROID_FIELD and n > PLANET_THRESHOLD) or (biome_at_chunk(chunk) == Biome.SPACE and n > GAS_GIANT_THRESHOLD)


static func planet_data_at_chunk(chunk: Vector2i) -> Dictionary:
	# Single source of truth for a planet's identity within its chunk -
	# seeded purely from the chunk's own coordinates (same pattern as the
	# biome/planet noise fields above) so it's reproducible from anywhere,
	# without needing an actual spawned Planet node. Both PlanetField (to
	# actually spawn the planet) and the world map (to draw a marker for
	# an explored-but-not-currently-loaded chunk) call this, so the two
	# can never drift out of sync with each other.
	var rng: RandomNumberGenerator = RandomNumberGenerator.new()
	rng.seed = hash(chunk)
	var forced_definition_id: String = String(DEV_PLANET_CHUNKS.get(chunk, "")) \
		if _dev_planets_active() else ""
	var local_pos: Vector2 = DEV_PLANET_LOCAL_POS if not forced_definition_id.is_empty() \
		else Vector2(rng.randf() * CHUNK_SIZE, rng.randf() * CHUNK_SIZE)
	var shape_seed: int = rng.randi()
	# Drawn unconditionally, in the same fixed position every call,
	# regardless of biome or the gas-giant roll below - so adding this
	# roll doesn't shift which random values any LATER draw (planet_name,
	# below) consumes for chunks that would have existed before it.
	var black_hole_roll: float = rng.randf()
	# Same principle, its own independent roll (#63).
	var research_lab_roll: float = rng.randf()
	# A stable per-chunk roll makes gas giants persistent landmarks rather
	# than a different resource whenever the scene reloads.
	var gas_giant: bool = biome_at_chunk(chunk) == Biome.SPACE
	var definition_id: String = PLANET_DEFINITIONS.GAS_GIANT_ID if gas_giant else PLANET_DEFINITIONS.ROCKY_ID
	# Rare authored outcomes, seeded deterministically like everything else.
	if chunk == OCTOPUS_BIOME_CENTER:
		definition_id = PLANET_DEFINITIONS.BOSS_ID
	elif black_hole_roll < BLACK_HOLE_CHANCE:
		definition_id = PLANET_DEFINITIONS.BLACK_HOLE_ID
	elif research_lab_roll < RESEARCH_LAB_CHANCE:
		definition_id = PLANET_DEFINITIONS.RESEARCH_LAB_ID
	# #234, applied after the rolls for the same reason the dev planting is:
	# forcing this chunk must not shift which random values any OTHER chunk
	# consumes, or one guaranteed planet would reshuffle the whole map.
	if chunk == SPAWN_GAS_GIANT_CHUNK:
		definition_id = PLANET_DEFINITIONS.GAS_GIANT_ID
	# Dev mode's fixed planting wins over every roll above. Applied last, and
	# AFTER all the rng draws, so switching it on cannot shift which random
	# values any other chunk consumes - a dev world and a normal one differ
	# only in these five chunks.
	if not forced_definition_id.is_empty():
		definition_id = forced_definition_id
	var definition: Resource = PLANET_DEFINITIONS.get_definition(definition_id)
	var names: PackedStringArray = definition.names
	# Guarded for the same reason as the hangar grid: an empty names array
	# would be a modulo by zero, which traps on wasm and takes the whole
	# engine down rather than raising a script error.
	var planet_name: String = "Unnamed" if names.is_empty() \
		else names[rng.randi() % names.size()]
	var planet_id: String = "chunk:%d:%d" % [chunk.x, chunk.y]
	return {"planet_id": planet_id, "local_pos": local_pos, "name": planet_name, "shape_seed": shape_seed,
		"definition_id": definition_id}


static func biome_color(biome: int) -> Color:
	match biome:
		Biome.ASTEROID_FIELD:
			return Color(0.55, 0.36, 0.18, 1.0)
		Biome.OCTOPUS:
			return Color(0.34, 0.07, 0.24, 1.0)
		_:
			return Color(0.10, 0.13, 0.28, 1.0)


static func biome_background_color(biome: int) -> Color:
	match biome:
		Biome.OCTOPUS:
			return Color(0.075, 0.012, 0.065, 1.0)
		_:
			return Color(0.02, 0.02, 0.08, 1.0)


static func is_octopus_chunk(chunk: Vector2i) -> bool:
	return chunk - OCTOPUS_BIOME_CENTER in OCTOPUS_BIOME_OFFSETS


static func octopus_biome_chunks() -> Array[Vector2i]:
	var chunks: Array[Vector2i] = []
	for offset in OCTOPUS_BIOME_OFFSETS:
		chunks.append(OCTOPUS_BIOME_CENTER + offset)
	return chunks