extends RefCounted

const MAX_LEVEL := 1000
const COUNT_POINTS := [Vector2(1, 5), Vector2(10, 10), Vector2(50, 18), Vector2(100, 23), Vector2(250, 29), Vector2(500, 34), Vector2(1000, 40)]
# x = level, y = elite fraction. Each level has exactly one boss.
const TIER_POINTS := [Vector2(10, 0), Vector2(50, 0.15), Vector2(100, 0.25), Vector2(500, 0.45), Vector2(1000, 0.55)]

static func enemy_count(level: int) -> int:
	var clamped_level := clampi(level, 1, MAX_LEVEL)
	for index in range(1, COUNT_POINTS.size()):
		var before: Vector2 = COUNT_POINTS[index - 1]
		var after: Vector2 = COUNT_POINTS[index]
		if clamped_level <= after.x:
			return roundi(lerpf(before.y, after.y, inverse_lerp(before.x, after.x, clamped_level)))
	return 40

static func enemy_tiers(level: int) -> Array[int]:
	var count := enemy_count(level)
	var elite_fraction := 0.0
	for index in range(1, TIER_POINTS.size()):
		var before: Vector2 = TIER_POINTS[index - 1]
		var after: Vector2 = TIER_POINTS[index]
		if level <= after.x:
			var progress := clampf(inverse_lerp(before.x, after.x, level), 0.0, 1.0)
			elite_fraction = lerpf(before.y, after.y, progress)
			break
	if level >= MAX_LEVEL:
		elite_fraction = 0.55
	# One boss on every level, included in the total enemy count.
	var bosses := 1
	var elites := mini(count - bosses, roundi(count * elite_fraction))
	var tiers: Array[int] = [2]
	for elite in elites:
		tiers.append(1)
	for normal in count - bosses - elites:
		tiers.append(0)
	return tiers

static func power_scale(level: int) -> float:
	return 1.0 + 0.05 * (clampi(level, 1, MAX_LEVEL) - 1)