# Milestone 5: conditional optional unwrapping, guards, and multi-unwrap.

observe :: func(counter @mut i32, value ?i32) ?i32 {
	counter^ = counter^ + 1
	return value
}

main :: func() i32 {
	total i32 = 0

	# present optional scalar -> binds v to the unwrapped value
	a ?i32 = 40
	if a |v| {
		total = total + v          # 40
	} else {
		total = total + 99
	}

	# none -> else branch taken; the binding is not in scope there
	b ?i32 = none
	if b |v| {
		total = total + v
	} else {
		total = total + 2          # 42
	}

	# optional pointer present -> binds q to a non-null @i32; deref proves it
	n i32 = 0
	p ?@i32 = &n
	if p |q| {
		total = total + q^         # +0
	}

	# optional pointer none -> skipped
	z ?@i32 = none
	if z |q| {
		total = total + 1000
	}

	# guarded multi-unwrap exposes every capture to the guard and then-block
	age ?i32 = 2
	if a and age |value, years : value + years == 42| {
		total = total
	} else {
		total = total + 100
	}

	# parenthesized chains and three-value unwraps are equivalent
	bonus ?i32 = 0
	if (a and age and bonus) |value, years, extra : value + years + extra == 42| {
		total = total
	} else {
		total = total + 100
	}

	# false guards use the else branch, or simply fall through without one
	if a |value : value == 0| {
		total = total + 100
	} else {
		total = total
	}
	if a |value : value == 0| {
		total = total + 100
	}

	# a failed unwrap prevents later expressions from being evaluated
	calls i32 = 0
	if b and observe(&calls, age) |missing, observed| {
		total = total + missing + observed
	}
	if calls != 0 {
		total = total + 100
	}

	# short-circuiting also applies after an earlier successful unwrap
	if a and b and observe(&calls, age) |value, missing, observed| {
		total = total + value + missing + observed
	}
	if calls != 0 {
		total = total + 100
	}

	# optional pointers participate in multi-unwrap and guards
	if a and p |value, q : value == 40 and q^ == 0| {
		total = total
	} else {
		total = total + 100
	}

	return total                   # expect exit code 42
}