/**
 * - is_valid_z_level
 *
 * Checks if source_loc and checking_loc is both on the station, or on the same z level.
 * This is because the station's several levels aren't considered the same z, so multi-z stations need this special case.
 *
 * Args:
 * source_loc - turf of the source we're comparing.
 * checking_loc - turf we are comparing to source_loc.
 *
 * returns TRUE if connection is valid, FALSE otherwise.
 */
/proc/is_valid_z_level(turf/source_loc, turf/checking_loc)
	// if we're both on "station", regardless of multi-z, we'll pass by.
	if(is_station_level(source_loc.z) && is_station_level(checking_loc.z))
		return TRUE
	if(source_loc.z == checking_loc.z)
		return TRUE
	return FALSE

/**
 * Checks if the passed non-area atom is on a "planet".
 *
 * A planet is defined as anything with planetary atmos that has gravity, with some hardcoded exceptions.
 *
 * * Nullspace counts as "not a planet", so you may want to check that separately.
 * * The mining z-level (Lavaland) is always considered a planet.
 * * The station z-level is considered a planet if the map config says so.
 * * Central Command is always not a planet.
 * * Syndicate recon outpost is always on a planet.
 *
 * Returns TRUE if we are on a planet.
 * Returns FALSE if we are not in a planet, or otherwise, "in space".
 */
/proc/is_on_a_planet(atom/what)
	ASSERT(!isarea(what))

	var/turf/open/what_turf = get_turf(what)
	if(isnull(what_turf))
		// Nullspace is, well, not a planet?
		return FALSE

	if(is_mining_level(what_turf.z))
		// Always assume Lavaland / mining level is a planet. (Asteroid mining crying right now)
		return TRUE

	if(is_station_level(what_turf.z))
		// Station levels rely on the map config, I.E. Icebox is planetary but Meta is not
		return SSmapping.is_planetary()

	if(is_centcom_level(what_turf.z))
		// Central Command is definitely in space
		return FALSE

	if(what.onSyndieBase() && !what.on_escaped_shuttle())
		// Syndicate recon outpost is on some moon or something
		return TRUE

	if(is_reserved_level(what_turf.z))
		// Reserved levels are primarily shuttles aside from syndie base
		return FALSE

	// Finally, more specific checks are ran for edge cases, such as lazily loaded map templates or away missions. Not perfect.
	return istype(what_turf) && what_turf.planetary_atmos && what_turf.has_gravity()

/**
 * Gets the angle between two linked z-levels.
 * Returns an angle (in degrees) if the z-levels are crosslinked/neighbors,
 * or null if they are not.
 *
 * Arguments:
 * * start: The starting Z level. Can either be a numeric z-level, or a [/datum/space_level].
 * * end: The destination Z level. Can either be a numeric z-level, or a [/datum/space_level].
 */
/proc/get_linked_z_angle(datum/space_level/start, datum/space_level/end)
	if(isnum(start))
		start = SSmapping.get_level(start)
	if(isnum(end))
		end = SSmapping.get_level(end)
	// Check the neighbors first, and return the appropiate angle if it is a neighbor.
	for(var/direction in start.neigbours)
		var/datum/space_level/neighbor = start.neigbours[direction]
		if(neighbor == end)
			var/angle = GLOB.cardinal_angles[direction]
			if(!isnull(angle))
				return angle
	// Otherwise, if they're both crosslinked, calculate the angle using their grid coordinates.
	if(start.linkage == CROSSLINKED && end.linkage == CROSSLINKED)
		var/dx = end.xi - start.xi
		var/dy = end.yi - start.yi
		return round(delta_to_angle(dy, dx))
	return null

/**
 * Gets all connected z-levels within a given manhattan distance of center.
 *
 * Arguments:
 * * center: The starting Z level. Can either be a numeric z-level, or a [/datun/space_level].
 * * dist: The maximum distance to search.
 */
/proc/get_linked_z_levels_in_range(datum/space_level/center, dist)
	if(isnum(center))
		center = SSmapping.get_level(center)
	var/list/to_check = list(center)
	var/list/checked = list()
	var/total_search_distance = 0
	while(to_check.len && total_search_distance <= dist)
		var/list/current_pass = to_check.Copy()
		to_check.Cut()
		for(var/datum/space_level/level as anything in current_pass)
			checked[level] = TRUE
			for(var/direction in level.neigbours)
				var/datum/space_level/neighbor = level.neigbours[direction]
				if(!checked[neighbor])
					to_check |= neighbor
		total_search_distance++
	return checked