class_name SimulationClock
extends RefCounted

var tick_interval: float
var accumulator := 0.0
var elapsed_ticks := 0
var cycle_duration_seconds := 240.0


func _init(interval: float = 1.0) -> void:
	tick_interval = maxf(interval, 0.0001)


func advance(delta: float, max_ticks: int = 0) -> int:
	accumulator += maxf(delta, 0.0)
	var ticks_due := 0
	while accumulator >= tick_interval and (max_ticks <= 0 or ticks_due < max_ticks):
		accumulator -= tick_interval
		elapsed_ticks += 1
		ticks_due += 1
	return ticks_due


func reset() -> void:
	accumulator = 0.0
	elapsed_ticks = 0


func time_of_day() -> float:
	# A capped frame can leave several whole ticks in the accumulator. Those ticks
	# are backlog, not simulated time yet; only retain the sub-tick fraction for
	# smooth presentation until the manager consumes the remaining work.
	var fractional_progress := fmod(accumulator, tick_interval)
	var total_seconds := elapsed_ticks * tick_interval + fractional_progress
	return fmod(total_seconds / maxf(cycle_duration_seconds, 1.0), 1.0)