extends RefCounted
## Decorative only: its own random stream keeps POI, loot and events unchanged.
const ATLAS_PATH := "res://assets/planets/nature/nature_atlas.png"
const TREE_CELLS := [[0, 1, 2], [1, 2], [1, 2], [0, 2, 3], [3], [0, 3]]
const DETAIL_CELLS := [[7, 8, 9, 10, 13, 14], [7, 8, 9, 10, 13, 14], [6, 8, 9, 14, 15], [4, 5, 7, 11], [4, 5, 7, 11], [4, 5, 6, 7, 11]]

static func generate(data: Dictionary) -> void:
	var rng := RandomNumberGenerator.new()
	rng.seed = int(data.seed) ^ 0x4e415455
	var biome := int(data.landscape.index)
	var trees: Array = TREE_CELLS[biome]
	for tree in data.trees:
		# Retain some of the original canopy alongside the new species.
		tree.variant = -1 if rng.randf() < 0.35 else int(trees[rng.randi_range(0, trees.size()-1)])
	for rock in data.rocks:
		rock.variant = rng.randi_range(4, 6)
	data.details = []
	var kinds: Array = DETAIL_CELLS[biome]
	# Local clusters read as vegetation patches, rather than a uniform scatter.
	for index in 150:
		var anchor := Vector2(rng.randf_range(-1760, 1760), rng.randf_range(-1760, 1760))
		var cell := int(kinds[rng.randi_range(0, kinds.size()-1)])
		for member in rng.randi_range(2, 5):
			var point := anchor + Vector2.from_angle(rng.randf()*TAU)*rng.randf_range(0, 65)
			var width := rng.randf_range(16, 32)
			if cell == 4 or cell == 5 or cell == 6:
				width = rng.randf_range(24, 43)
			elif cell == 8 or cell == 9 or cell == 15:
				width = rng.randf_range(26, 44)
			if not _clear_site(data, point, width*0.5):
				continue
			if cell == 15 and _height(data, point) > 0.39:
				continue
			data.details.append({"position":point,"size":width,"rotation":rng.randf_range(-PI, PI),"variant":cell,"shade":rng.randf_range(0.88, 1.08)})
	# At most one fallen tree, only on 8% of forested landing maps.
	if biome < 4 and rng.randf() < 0.08:
		for attempt in 80:
			if data.trees.is_empty():
				break
			var tree: Dictionary = data.trees[rng.randi_range(0, data.trees.size()-1)]
			var point: Vector2 = tree.position + Vector2.from_angle(rng.randf()*TAU)*rng.randf_range(70, 110)
			if _clear_site(data, point, 65):
				data.details.append({"position":point,"size":92.0,"rotation":rng.randf_range(-PI, PI),"variant":12,"shade":1.0})
				break

static func _height(data: Dictionary, point: Vector2) -> float:
	var x := clampi(int((point.x+1920)/40), 0, 95)
	var y := clampi(int((point.y+1920)/40), 0, 95)
	return float(data.heights[y*96+x])

static func _clear_site(data: Dictionary, point: Vector2, radius: float) -> bool:
	if point.length() < 210+radius or absf(point.x)+radius > 1860 or absf(point.y)+radius > 1860:
		return false
	# Sample the full footprint, keeping props away from water and steep peaks.
	for offset in [Vector2.ZERO, Vector2.LEFT, Vector2.RIGHT, Vector2.UP, Vector2.DOWN, Vector2(-0.7,-0.7), Vector2(0.7,-0.7), Vector2(-0.7,0.7), Vector2(0.7,0.7)]:
		var h := _height(data, point+offset*(radius+25))
		if h < 0.315 or h > 0.68:
			return false
	for poi in data.pois:
		if point.distance_to(poi.position) < 135+radius:
			return false
	for event in data.events:
		if point.distance_to(event.position) < 115+radius:
			return false
	for structure in data.structures:
		if point.distance_to(structure.position) < float(structure.size)*0.7+radius:
			return false
	for landmark in data.get("landmarks", []):
		if point.distance_to(landmark.position) < float(landmark.size)*0.58+radius+15:
			return false
	for mountain in data.mountains:
		if point.distance_to(mountain.position) < float(mountain.size)*0.48+radius:
			return false
	return true