# Note: The code might not be as pretty it could be, since it's written
# in a way that maximizes performance. Methods are inlined and loops are avoided.
class_name UUID

const BYTE_MASK: int = 0b11111111

static func uuidbin():
	# 16 random bytes with the bytes on index 6 and 8 modified
	return [
		randi() & BYTE_MASK, randi() & BYTE_MASK, randi() & BYTE_MASK, randi() & BYTE_MASK,
		randi() & BYTE_MASK, randi() & BYTE_MASK, ((randi() & BYTE_MASK) & 0x0f) | 0x40, randi() & BYTE_MASK,
		((randi() & BYTE_MASK) & 0x3f) | 0x80, randi() & BYTE_MASK, randi() & BYTE_MASK, randi() & BYTE_MASK,
		randi() & BYTE_MASK, randi() & BYTE_MASK, randi() & BYTE_MASK, randi() & BYTE_MASK,
		]

static func uuidbinrng(rng: RandomNumberGenerator):
	return [
		rng.randi() & BYTE_MASK, rng.randi() & BYTE_MASK, rng.randi() & BYTE_MASK, rng.randi() & BYTE_MASK,
		rng.randi() & BYTE_MASK, rng.randi() & BYTE_MASK, ((rng.randi() & BYTE_MASK) & 0x0f) | 0x40, rng.randi() & BYTE_MASK,
		((rng.randi() & BYTE_MASK) & 0x3f) | 0x80, rng.randi() & BYTE_MASK, rng.randi() & BYTE_MASK, rng.randi() & BYTE_MASK,
		rng.randi() & BYTE_MASK, rng.randi() & BYTE_MASK, rng.randi() & BYTE_MASK, rng.randi() & BYTE_MASK,
		]

static func v4():
	# 16 random bytes with the bytes on index 6 and 8 modified
	var b = uuidbin()
	return '%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x' % [
	# low
	b[0], b[1], b[2], b[3],

	# mid
	b[4], b[5],

	# hi
	b[6], b[7],

	# clock
	b[8], b[9],

	# clock
	b[10], b[11], b[12], b[13], b[14], b[15]
  ]
  
static func v4_rng(rng: RandomNumberGenerator):
	# 16 random bytes with the bytes on index 6 and 8 modified
	var b = uuidbinrng(rng)
	
	return '%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x' % [
	# low
	b[0], b[1], b[2], b[3],

	# mid
	b[4], b[5],

	# hi
	b[6], b[7],

	# clock
	b[8], b[9],

	# clock
	b[10], b[11], b[12], b[13], b[14], b[15]
  ]
  
var _uuid: Array

func _init(rng := RandomNumberGenerator.new()):
	_uuid = uuidbinrng(rng)

func as_array():
	return _uuid.duplicate()

func as_dict(big_endian := true):
	if big_endian:
		return {
			"low"  : (_uuid[0]  << 24) + (_uuid[1]  << 16) + (_uuid[2]  << 8 ) +  _uuid[3],
			"mid"  : (_uuid[4]  << 8 ) +  _uuid[5],
			"hi"   : (_uuid[6]  << 8 ) +  _uuid[7],
			"clock": (_uuid[8]  << 8 ) +  _uuid[9],
			"node" : (_uuid[10] << 40) + (_uuid[11] << 32) + (_uuid[12] << 24) + (_uuid[13] << 16) + (_uuid[14] << 8 ) +  _uuid[15]
		}
	else:
		return {
			"low"  : _uuid[0]          + (_uuid[1]  << 8 ) + (_uuid[2]  << 16) + (_uuid[3]  << 24),
			"mid"  : _uuid[4]          + (_uuid[5]  << 8 ),
			"hi"   : _uuid[6]          + (_uuid[7]  << 8 ),
			"clock": _uuid[8]          + (_uuid[9]  << 8 ),
			"node" : _uuid[10]         + (_uuid[11] << 8 ) + (_uuid[12] << 16) + (_uuid[13] << 24) + (_uuid[14] << 32) + (_uuid[15] << 40)
		}
	
func as_string():
	return '%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x' % [
		# low
		_uuid[0], _uuid[1], _uuid[2], _uuid[3],
		
		# mid
		_uuid[4], _uuid[5],
		
		# hi
		_uuid[6], _uuid[7],
		
		# clock
		_uuid[8], _uuid[9],
		
		# node
		_uuid[10], _uuid[11], _uuid[12], _uuid[13], _uuid[14], _uuid[15]
	]
  
func is_equal(other):
	# Godot Engine compares Array recursively
	# There's no need for custom comparison here.
	return _uuid == other._uuid
