/var/datum/lighting_corner/dummy/dummy_lighting_corner = new
// Because we can control each corner of every lighting overlay.
// And corners get shared between multiple turfs (unless you're on the corners of the map, then 1 corner doesn't).
// For the record: these should never ever ever be deleted, even if the turf doesn't have dynamic lighting.

// This list is what the code that assigns corners listens to, the order in this list is the order in which corners are added to the /turf/corners list.
/var/list/LIGHTING_CORNER_DIAGONAL = list(NORTHEAST, SOUTHEAST, SOUTHWEST, NORTHWEST)

// This is the reverse of the above - the position in the array is a dir. Update this if the above changes.
var/list/REVERSE_LIGHTING_CORNER_DIAGONAL = list(0, 0, 0, 0, 3, 4, 0, 0, 2, 1)

/datum/lighting_corner
	var/turf/t1	// These are in no particular order.
	var/turf/t2
	var/turf/t3
	var/turf/t4

	var/list/datum/light_source/affecting // Light sources affecting us.
	var/active                            = FALSE  // TRUE if one of our masters has dynamic lighting.

	var/x     = 0
	var/y     = 0
	var/z     = 0

	var/lum_r = 0
	var/lum_g = 0
	var/lum_b = 0
	var/lum_u = 0	// UV Radiation, not visible.

	var/needs_update = FALSE

	var/cache_r  = LIGHTING_SOFT_THRESHOLD
	var/cache_g  = LIGHTING_SOFT_THRESHOLD
	var/cache_b  = LIGHTING_SOFT_THRESHOLD
	var/cache_mx = 0

/datum/lighting_corner/New(var/turf/new_turf, var/diagonal)
	SSlighting.lighting_corners += src

	t1 = new_turf
	z = new_turf.z

	var/vertical   = diagonal & ~(diagonal - 1) // The horizontal directions (4 and 8) are bigger than the vertical ones (1 and 2), so we can reliably say the lsb is the horizontal direction.
	var/horizontal = diagonal & ~vertical       // Now that we know the horizontal one we can get the vertical one.

	x = new_turf.x + (horizontal == EAST  ? 0.5 : -0.5)
	y = new_turf.y + (vertical   == NORTH ? 0.5 : -0.5)

	// My initial plan was to make this loop through a list of all the dirs (horizontal, vertical, diagonal).
	// Issue being that the only way I could think of doing it was very messy, slow and honestly overengineered.
	// So we'll have this hardcode instead.
	var/turf/T
	var/i

	// Diagonal one is easy.
	T = get_step(new_turf, diagonal)
	if (T) // In case we're on the map's border.
		if (!T.corners)
			T.corners = list(null, null, null, null)

		t2 = T
		i = REVERSE_LIGHTING_CORNER_DIAGONAL[diagonal]
		T.corners[i] = src

	// Now the horizontal one.
	T = get_step(new_turf, horizontal)
	if (T) // Ditto.
		if (!T.corners)
			T.corners = list(null, null, null, null)

		t3 = T
		i = REVERSE_LIGHTING_CORNER_DIAGONAL[((T.x > x) ? EAST : WEST) | ((T.y > y) ? NORTH : SOUTH)] // Get the dir based on coordinates.
		T.corners[i] = src

	// And finally the vertical one.
	T = get_step(new_turf, vertical)
	if (T)
		if (!T.corners)
			T.corners = list(null, null, null, null)

		t4 = T
		i = REVERSE_LIGHTING_CORNER_DIAGONAL[((T.x > x) ? EAST : WEST) | ((T.y > y) ? NORTH : SOUTH)] // Get the dir based on coordinates.
		T.corners[i] = src

	update_active()

#define OVERLAY_PRESENT(T) (T && T.lighting_overlay)

/datum/lighting_corner/proc/update_active()
	active = FALSE

	if (OVERLAY_PRESENT(t1) || OVERLAY_PRESENT(t2) || OVERLAY_PRESENT(t3) || OVERLAY_PRESENT(t4))
		active = TRUE

#undef OVERLAY_PRESENT

// God that was a mess, now to do the rest of the corner code! Hooray!
/datum/lighting_corner/proc/update_lumcount(var/delta_r, var/delta_g, var/delta_b, var/delta_u, var/now = FALSE)
	lum_r += delta_r
	lum_g += delta_g
	lum_b += delta_b
	lum_u += delta_u

	if (needs_update || !(delta_r + delta_g + delta_b))	// Don't check u since the overlay doesn't care about it.
		return

	if (!now)
		needs_update = TRUE
		update_overlays(FALSE)
		SSlighting.corner_queue += src
	else
		update_overlays(TRUE)

#define UPDATE_MASTER(T) \
	if (T && T.lighting_overlay) { \
		if (now) { \
			T.lighting_overlay.update_overlay(); \
		} \
		else if (!T.lighting_overlay.needs_update) { \
			T.lighting_overlay.needs_update = TRUE; \
			SSlighting.overlay_queue += T.lighting_overlay; \
		} \
	}

/datum/lighting_corner/proc/update_overlays(var/now = FALSE)
	// Cache these values a head of time so 4 individual lighting overlays don't all calculate them individually.
	var/mx = max(lum_r, lum_g, lum_b) // Scale it so 1 is the strongest lum, if it is above 1.
	. = 1 // factor
	if (mx > 1)
		. = 1 / mx

	else if (mx < LIGHTING_SOFT_THRESHOLD)
		. = 0 // 0 means soft lighting.

	cache_r  = round(lum_r * ., LIGHTING_ROUND_VALUE) || LIGHTING_SOFT_THRESHOLD
	cache_g  = round(lum_g * ., LIGHTING_ROUND_VALUE) || LIGHTING_SOFT_THRESHOLD
	cache_b  = round(lum_b * ., LIGHTING_ROUND_VALUE) || LIGHTING_SOFT_THRESHOLD
	cache_mx = round(mx, LIGHTING_ROUND_VALUE)

	UPDATE_MASTER(t1)
	UPDATE_MASTER(t2)
	UPDATE_MASTER(t3)
	UPDATE_MASTER(t4)

#undef UPDATE_MASTER

/datum/lighting_corner/Destroy(force = FALSE)
	crash_with("Some fuck [force ? "force-" : ""]deleted a lighting corner.")
	if (!force)
		return QDEL_HINT_LETMELIVE

	SSlighting.lighting_corners -= src
	return ..()

/datum/lighting_corner/dummy/New()
	return