Aurora.3/code/modules/lighting/lighting_source.dm

// This is where the fun begins.
// These are the main datums that emit light.

/datum/light_source
	var/atom/top_atom        // The atom we're emitting light from (for example a mob if we're from a flashlight that's being held).
	var/atom/source_atom     // The atom that we belong to.

	var/turf/source_turf     // The turf under the above.
	var/light_power    // Intensity of the emitter light.
	var/light_range      // The range of the emitted light.
	var/light_color    // The colour of the light, string, decomposed by parse_light_color()
	var/light_uv		// The intensity of UV light, between 0 and 255.

	// Variables for keeping track of the colour.
	var/lum_r
	var/lum_g
	var/lum_b
	var/lum_u

	// The lumcount values used to apply the light.
	var/tmp/applied_lum_r
	var/tmp/applied_lum_g
	var/tmp/applied_lum_b
	var/tmp/applied_lum_u

	var/list/datum/lighting_corner/effect_str     // List used to store how much we're affecting corners.
	var/list/turf/affecting_turfs

	var/applied = FALSE // Whether we have applied our light yet or not.

	var/vis_update      // Whether we should smartly recalculate visibility. and then only update tiles that became (in)visible to us.
	var/needs_update    // Whether we are queued for an update.
	var/destroyed       // Whether we are destroyed and need to stop emitting light.
	var/force_update

/datum/light_source/New(var/atom/owner, var/atom/top)
	source_atom = owner // Set our new owner.
	if (!source_atom.light_sources)
		source_atom.light_sources = list()

	source_atom.light_sources += src // Add us to the lights of our owner.
	top_atom = top
	if (top_atom != source_atom)
		if (!top.light_sources)
			top.light_sources     = list()

		top_atom.light_sources += src

	source_turf = top_atom
	light_power = source_atom.light_power
	light_range = source_atom.light_range
	light_color = source_atom.light_color
	light_uv    = source_atom.uv_intensity

	parse_light_color()

	effect_str      = list()
	affecting_turfs = list()

	update()

	L_PROF(source_atom, "source_new")

	return ..()

// Kill ourselves.
/datum/light_source/proc/destroy(var/no_update = FALSE)
	L_PROF(source_atom, "source_destroy")

	destroyed = TRUE
	if (!no_update)
		force_update()
	if (source_atom && source_atom.light_sources)
		source_atom.light_sources -= src

	if (top_atom && top_atom.light_sources)
		top_atom.light_sources    -= src

// Process the light RIGHT NOW.
#define DO_UPDATE 								\
	if (destroyed || check() || force_update) {	\
		remove_lum(TRUE);						\
		if (!destroyed) {						\
			apply_lum(TRUE);					\
		}										\
	}											\
	else if (vis_update) {						\
		smart_vis_update(TRUE);					\
	}											\
	vis_update   = FALSE;						\
	force_update = FALSE;						\
	needs_update = FALSE;

// Queue an update.
#define QUEUE_UPDATE                    \
	if (!needs_update)                  \
	{                                   \
		lighting_update_lights += src;  \
		needs_update            = TRUE; \
	}

// Picks either scheduled or instant updates based on current server load.
#define INTELLIGENT_UPDATE 							\
	if (world.tick_usage > TICK_LIMIT || !ticker || ticker.current_state <= GAME_STATE_SETTING_UP) {	\
		QUEUE_UPDATE;								\
	}												\
	else {											\
		DO_UPDATE;									\
	}

// This proc will cause the light source to update the top atom, and add itself to the update queue.
/datum/light_source/proc/update(var/atom/new_top_atom)
	// This top atom is different.
	if (new_top_atom && new_top_atom != top_atom)
		if(top_atom != source_atom) // Remove ourselves from the light sources of that top atom.
			top_atom.light_sources -= src

		top_atom = new_top_atom

		if (top_atom != source_atom)
			if(!top_atom.light_sources)
				top_atom.light_sources = list()

			top_atom.light_sources += src // Add ourselves to the light sources of our new top atom.

	L_PROF(source_atom, "source_update")

	INTELLIGENT_UPDATE

// Will force an update without checking if it's actually needed.
/datum/light_source/proc/force_update()
	L_PROF(source_atom, "source_forceupdate")
	force_update = 1

	INTELLIGENT_UPDATE

// Will cause the light source to recalculate turfs that were removed or added to visibility only.
/datum/light_source/proc/vis_update()
	L_PROF(source_atom, "source_visupdate")
	vis_update = 1

	INTELLIGENT_UPDATE

// Will check if we actually need to update, and update any variables that may need to be updated.
/datum/light_source/proc/check()
	if (!source_atom || !light_range || !light_power)
		destroy(no_update = TRUE)
		return 1

	if (!top_atom)
		top_atom = source_atom
		. = 1

	if (istype(top_atom, /turf))
		if (source_turf != top_atom)
			source_turf = top_atom
			. = 1
	else if (top_atom.loc != source_turf)
		source_turf = top_atom.loc
		. = 1

	if (source_atom.light_power != light_power)
		light_power = source_atom.light_power
		. = 1

	if (source_atom.light_range != light_range)
		light_range = source_atom.light_range
		. = 1

	if (light_range && light_power && !applied)
		. = 1

	if (source_atom.light_color != light_color)
		light_color = source_atom.light_color
		parse_light_color()
		. = 1

// Decompile the hexadecimal colour into lumcounts of each perspective.
/datum/light_source/proc/parse_light_color()
	if (light_color)
		lum_r = GetRedPart   (light_color) / 255
		lum_g = GetGreenPart (light_color) / 255
		lum_b = GetBluePart  (light_color) / 255
	else
		lum_r = 1
		lum_g = 1
		lum_b = 1

	if (light_uv)
		lum_u = light_uv / 255
	else
		lum_u = 0

// Macro that applies light to a new corner.
// It is a macro in the interest of speed, yet not having to copy paste it.
// If you're wondering what's with the backslashes, the backslashes cause BYOND to not automatically end the line.
// As such this all gets counted as a single line.
// The braces and semicolons are there to be able to do this on a single line.

#define APPLY_CORNER(C,now)              \
	. = LUM_FALLOFF(C, source_turf); \
                                     \
	. *= light_power;                \
                                     \
	effect_str[C] = .;               \
                                     \
	C.update_lumcount                \
	(                                \
		. * applied_lum_r,           \
		. * applied_lum_g,           \
		. * applied_lum_b,           \
		. * applied_lum_u,           \
		now							 \
	);

// I don't need to explain what this does, do I?
#define REMOVE_CORNER(C,now)             \
	. = -effect_str[C];              \
	C.update_lumcount                \
	(                                \
		. * applied_lum_r,           \
		. * applied_lum_g,           \
		. * applied_lum_b,           \
		. * applied_lum_u,           \
		now                          \
	);

// This is the define used to calculate falloff.
#define LUM_FALLOFF(C, T) (1 - CLAMP01(sqrt((C.x - T.x) ** 2 + (C.y - T.y) ** 2 + LIGHTING_HEIGHT) / max(1, light_range)))

/datum/light_source/proc/apply_lum(var/now = FALSE)
	var/static/update_gen = 1
	applied = 1

	// Keep track of the last applied lum values so that the lighting can be reversed
	applied_lum_r = lum_r
	applied_lum_g = lum_g
	applied_lum_b = lum_b
	applied_lum_u = lum_u

	FOR_DVIEW(var/turf/T, light_range, source_turf, INVISIBILITY_LIGHTING)
		if (!T.lighting_corners_initialised)
			T.generate_missing_corners()

		for (var/datum/lighting_corner/C in T.get_corners())
			if (C.update_gen == update_gen)
				continue

			C.update_gen = update_gen
			C.affecting += src

			if (!C.active)
				effect_str[C] = 0
				continue

			APPLY_CORNER(C, now)

		if (!T.affecting_lights)
			T.affecting_lights = list()

		T.affecting_lights += src
		affecting_turfs    += T

	update_gen++

/datum/light_source/proc/remove_lum(var/now = FALSE)
	applied = FALSE

	for (var/turf/T in affecting_turfs)
		if (!T.affecting_lights)
			T.affecting_lights = list()
		else
			T.affecting_lights -= src

	affecting_turfs.Cut()

	for (var/datum/lighting_corner/C in effect_str)
		REMOVE_CORNER(C,now)

		C.affecting -= src

	effect_str.Cut()

/datum/light_source/proc/recalc_corner(var/datum/lighting_corner/C, var/now = FALSE)
	if (effect_str.Find(C)) // Already have one.
		REMOVE_CORNER(C,now)

	APPLY_CORNER(C,now)

/datum/light_source/proc/smart_vis_update(var/now = FALSE)
	L_PROF(source_atom, "source_smartvisupdate")
	var/list/datum/lighting_corner/corners = list()
	var/list/turf/turfs                    = list()
	FOR_DVIEW(var/turf/T, light_range, source_turf, 0)
		if (!T.lighting_corners_initialised)
			T.generate_missing_corners()
		corners |= T.get_corners()
		turfs   += T

	var/list/L = turfs - affecting_turfs // New turfs, add us to the affecting lights of them.
	affecting_turfs += L
	for (var/turf/T in L)
		if (!T.affecting_lights)
			T.affecting_lights = list(src)
		else
			T.affecting_lights += src

	L = affecting_turfs - turfs // Now-gone turfs, remove us from the affecting lights.
	affecting_turfs -= L
	for (var/turf/T in L)
		T.affecting_lights -= src

	for (var/datum/lighting_corner/C in corners - effect_str) // New corners
		C.affecting += src
		if (!C.active)
			effect_str[C] = 0
			continue

		APPLY_CORNER(C,now)

	for (var/datum/lighting_corner/C in effect_str - corners) // Old, now gone, corners.
		REMOVE_CORNER(C,now)
		C.affecting -= src
		effect_str -= C

#undef QUEUE_UPDATE
#undef DO_UPDATE
#undef INTELLIGENT_UPDATE
#undef LUM_FALLOFF
#undef REMOVE_CORNER
#undef APPLY_CORNER