class_name KeyedRandom
extends RefCounted

const MASK_32 := 0xFFFFFFFF
const UINT32_RANGE := 4294967296.0


static func value_u32(
	world_seed: int, system_id: StringName, entity_id: StringName, occurrence: int
) -> int:
	var hash_value := int(world_seed) & MASK_32
	hash_value = _mix_u32(hash_value ^ 0x9E3779B9)
	for byte in String(system_id).to_utf8_buffer():
		hash_value = _mix_u32(hash_value ^ int(byte))
	hash_value = _mix_u32(hash_value ^ 0x85EBCA6B)
	for byte in String(entity_id).to_utf8_buffer():
		hash_value = _mix_u32(hash_value ^ int(byte))
	hash_value = _mix_u32(hash_value ^ (occurrence & MASK_32))
	return hash_value


static func value_float(
	world_seed: int, system_id: StringName, entity_id: StringName, occurrence: int
) -> float:
	return float(value_u32(world_seed, system_id, entity_id, occurrence)) / UINT32_RANGE


static func range_int(
	world_seed: int,
	system_id: StringName,
	entity_id: StringName,
	occurrence: int,
	minimum: int,
	maximum: int
) -> int:
	if maximum < minimum:
		return minimum
	var width := maximum - minimum + 1
	return minimum + value_u32(world_seed, system_id, entity_id, occurrence) % width


static func range_float(
	world_seed: int,
	system_id: StringName,
	entity_id: StringName,
	occurrence: int,
	minimum: float,
	maximum: float
) -> float:
	if maximum <= minimum:
		return minimum
	return lerpf(minimum, maximum, value_float(world_seed, system_id, entity_id, occurrence))


static func chance(
	world_seed: int,
	system_id: StringName,
	entity_id: StringName,
	occurrence: int,
	probability: float
) -> bool:
	return value_float(world_seed, system_id, entity_id, occurrence) < clampf(probability, 0.0, 1.0)


static func _mix_u32(value: int) -> int:
	var mixed := value & MASK_32
	mixed = ((mixed ^ (mixed >> 16)) * 0x7FEB352D) & MASK_32
	mixed = ((mixed ^ (mixed >> 15)) * 0x846CA68B) & MASK_32
	return (mixed ^ (mixed >> 16)) & MASK_32