fulpstation/code/modules/lighting/lighting_turf.dm

/turf
	var/dynamic_lighting = TRUE
	luminosity           = 1

	var/tmp/lighting_corners_initialised = FALSE

	var/tmp/list/datum/light_source/affecting_lights       // List of light sources affecting this turf.
	var/tmp/atom/movable/lighting_object/lighting_object // Our lighting object.
	var/tmp/list/datum/lighting_corner/corners
	var/tmp/has_opaque_atom = FALSE // Not to be confused with opacity, this will be TRUE if there's any opaque atom on the tile.

// Causes any affecting light sources to be queued for a visibility update, for example a door got opened.
/turf/proc/reconsider_lights()
	var/datum/light_source/L
	var/thing
	for (thing in affecting_lights)
		L = thing
		L.vis_update()

/turf/proc/lighting_clear_overlay()
	if (lighting_object)
		qdel(lighting_object, TRUE)

	var/datum/lighting_corner/C
	var/thing
	for (thing in corners)
		C = thing
		C.update_active()

// Builds a lighting object for us, but only if our area is dynamic.
/turf/proc/lighting_build_overlay()
	if (lighting_object)
		return

	var/area/A = loc
	if (!IS_DYNAMIC_LIGHTING(A))
		return

	if (!lighting_corners_initialised)
		generate_missing_corners()

	new/atom/movable/lighting_object(src)

	var/thing
	var/datum/lighting_corner/C
	var/datum/light_source/S
	for (thing in corners)
		C = thing
		if (!C.active) // We would activate the corner, calculate the lighting for it.
			for (thing in C.affecting)
				S = thing
				S.recalc_corner(C)
			C.active = TRUE

// Used to get a scaled lumcount.
/turf/proc/get_lumcount(var/minlum = 0, var/maxlum = 1)
	if (!lighting_object)
		return 1

	var/totallums = 0
	var/thing
	var/datum/lighting_corner/L
	for (thing in corners)
		L = thing
		totallums += L.lum_r + L.lum_b + L.lum_g

	totallums /= 12 // 4 corners, each with 3 channels, get the average.

	totallums = (totallums - minlum) / (maxlum - minlum)

	return CLAMP01(totallums)

// Returns a boolean whether the turf is on soft lighting.
// Soft lighting being the threshold at which point the overlay considers
// itself as too dark to allow sight and see_in_dark becomes useful.
// So basically if this returns true the tile is unlit black.
/turf/proc/is_softly_lit()
	if (!lighting_object)
		return FALSE

	return !lighting_object.luminosity

// Can't think of a good name, this proc will recalculate the has_opaque_atom variable.
/turf/proc/recalc_atom_opacity()
	has_opaque_atom = opacity
	if (!has_opaque_atom)
		for (var/atom/A in src.contents) // Loop through every movable atom on our tile PLUS ourselves (we matter too...)
			if (A.opacity)
				has_opaque_atom = TRUE
				break

// If an opaque movable atom moves around we need to potentially update visibility.
/turf/Entered(var/atom/movable/Obj, var/atom/OldLoc)
	. = ..()

	if (Obj && Obj.opacity)
		has_opaque_atom = TRUE // Make sure to do this before reconsider_lights(), incase we're on instant updates. Guaranteed to be on in this case.
		reconsider_lights()

/turf/Exited(var/atom/movable/Obj, var/atom/newloc)
	. = ..()

	if (Obj && Obj.opacity)
		recalc_atom_opacity() // Make sure to do this before reconsider_lights(), incase we're on instant updates.
		reconsider_lights()

/turf/proc/change_area(var/area/old_area, var/area/new_area)
	if (new_area.dynamic_lighting != old_area.dynamic_lighting)
		if (new_area.dynamic_lighting)
			lighting_build_overlay()

		else
			lighting_clear_overlay()

/turf/proc/get_corners()
	if (has_opaque_atom)
		return null // Since this proc gets used in a for loop, null won't be looped though.

	return corners

/turf/proc/generate_missing_corners()
	lighting_corners_initialised = TRUE
	if (!corners)
		corners = list(null, null, null, null)

	for (var/i = 1 to 4)
		if (corners[i]) // Already have a corner on this direction.
			continue

		corners[i] = new/datum/lighting_corner(src, GLOB.LIGHTING_CORNER_DIAGONAL[i])


/turf/ChangeTurf(path)
	if (!path || (!GLOB.use_preloader && path == type) || !SSlighting.initialized)
		return ..()

	var/old_opacity = opacity
	var/old_dynamic_lighting = dynamic_lighting
	var/old_affecting_lights = affecting_lights
	var/old_lighting_object = lighting_object
	var/old_corners = corners

	. = ..() //At this point the turf has changed

	recalc_atom_opacity()
	lighting_object = old_lighting_object
	affecting_lights = old_affecting_lights
	corners = old_corners
	if (old_opacity != opacity || dynamic_lighting != old_dynamic_lighting)
		reconsider_lights()

	if (dynamic_lighting != old_dynamic_lighting)
		if (IS_DYNAMIC_LIGHTING(src))
			lighting_build_overlay()
		else
			lighting_clear_overlay()

	for(var/turf/open/space/S in RANGE_TURFS(1, src)) //RANGE_TURFS is in code\__HELPERS\game.dm
		S.update_starlight()