/atom
	/// Intensity of the light.
	var/light_power = 1
	/// Range in tiles of the light.
	var/light_range = 0
	/// Hexadecimal RGB string representing the colour of the light.
	var/light_color
	/// The angle that the light's emission should be restricted to. null for omnidirectional.
	var/light_wedge
	// These two vars let you override the default light offset detection (pixel_x/y).
	//  Useful for objects like light fixtures that aren't visually in the middle of the turf, but aren't offset either.
	var/light_offset_x
	var/light_offset_y

	/// Our light source. Don't fuck with this directly unless you have a good reason!
	var/tmp/datum/light_source/light
	/// Any light sources that are "inside" of us, for example, if src here was a mob that's carrying a flashlight, that flashlight's light source would be part of this list.
	var/tmp/list/light_source_multi
	/// Same as above - this is a shortcut to avoid allocating the above list if we can
	var/tmp/datum/light_source/light_source_solo

// Nonsensical value for l_color default, so we can detect if it gets set to null.
#define NONSENSICAL_VALUE -99999

/// The proc you should always use to set the light of this atom.
/atom/proc/set_light(l_range, l_power, l_color = NONSENSICAL_VALUE, angle = NONSENSICAL_VALUE, no_update = FALSE)
	if (l_range > LIGHTING_HARD_MAXIMUM_RANGE)
		CRASH("light_range [l_range] > [LIGHTING_HARD_MAXIMUM_RANGE]; ignored")
	if (l_range > LIGHTING_SOFT_MAXIMUM_RANGE)
		STACK_TRACE("light_range [l_range] > [LIGHTING_SOFT_MAXIMUM_RANGE]; going to lag")

	if (l_power > LIGHTING_SOFT_MAXIMUM_POWER)
		STACK_TRACE("light_power [l_power] > [LIGHTING_SOFT_MAXIMUM_POWER] is not useful")

	if(l_range > 0 && l_range < MINIMUM_USEFUL_LIGHT_RANGE)
		l_range = MINIMUM_USEFUL_LIGHT_RANGE	//Brings the range up to 1.4
	if (l_power != null)
		light_power = l_power

	if (l_range != null)
		light_range = l_range

	if (l_color != NONSENSICAL_VALUE)
		light_color = l_color

	if (angle != NONSENSICAL_VALUE)
		light_wedge = angle

	if (no_update)
		return

	update_light()

#undef NONSENSICAL_VALUE

// Will update the light (duh).
// Creates or destroys it if needed, makes it update values, makes sure it's got the correct source turf...
/atom/proc/update_light()
	if (QDELING(src))
		return

	switch (light_range)
		if (LIGHTING_SOFT_MAXIMUM_RANGE + 1 to LIGHTING_HARD_MAXIMUM_RANGE)
			STACK_TRACE("light_range > [LIGHTING_SOFT_MAXIMUM_RANGE]; going to lag")
		if (LIGHTING_HARD_MAXIMUM_RANGE + 1 to INFINITY)
			light_range = 0
			STACK_TRACE("light_range > [LIGHTING_HARD_MAXIMUM_RANGE]; ignored")

	if (light_power > LIGHTING_SOFT_MAXIMUM_RANGE)
		STACK_TRACE("light_power > [LIGHTING_SOFT_MAXIMUM_POWER]; not useful")

	if (!light_power || !light_range) // We won't emit light anyways, destroy the light source.
		QDEL_NULL(light)
	else
		if (!istype(loc, /atom/movable)) // We choose what atom should be the top atom of the light here.
			. = src
		else
			. = loc

		if (light)
			light.update(.)
		else
			light = new /datum/light_source(src, .)

/**
 * Updates the atom's opacity value.
 *
 * Should always be used to change the opacity of an atom.
 * This exists to act as a hook for associated behavior.
 * It notifies (potentially) affected light sources so they can update (if needed).
 */
/atom/proc/set_opacity(new_opacity)
	if (new_opacity == opacity)
		return FALSE
	. = TRUE
	SEND_SIGNAL(src, COMSIG_ATOM_SET_OPACITY, new_opacity)
	opacity = new_opacity

	var/turf/T = loc
	if (!isturf(T))
		return

	if (new_opacity == TRUE)
		T.has_opaque_atom = TRUE
		T.reconsider_lights()
#ifdef AO_USE_LIGHTING_OPACITY
		T.regenerate_ao()
#endif
	else
		var/old_has_opaque_atom = T.has_opaque_atom
		T.recalc_atom_opacity()
		if (old_has_opaque_atom != T.has_opaque_atom)
			T.reconsider_lights()

/atom/movable/forceMove()
	. = ..()

	if (light_source_solo)
		light_source_solo.source_atom.update_light()
	else if (light_source_multi)
		var/datum/light_source/L
		var/thing
		for (thing in light_source_multi)
			L = thing
			L.source_atom.update_light()

/atom/vv_edit_var(var_name, var_value)
	switch (var_name)
		if (NAMEOF(src, light_range))
			set_light(l_range=var_value)
			datum_flags |= DF_VAR_EDITED
			return TRUE

		if (NAMEOF(src, light_power))
			set_light(l_power=var_value)
			datum_flags |= DF_VAR_EDITED
			return TRUE

		if (NAMEOF(src, light_color))
			set_light(l_color=var_value)
			datum_flags |= DF_VAR_EDITED
			return TRUE

		if (NAMEOF(src, light_wedge))
			set_light(angle=var_value)
			datum_flags |= DF_VAR_EDITED
			return TRUE

	return ..()


/atom/setDir(newdir)
	. = ..()
	if (light_source_solo)
		if (light_source_solo.light_angle)
			light_source_solo.source_atom.update_light()
	else if (light_source_multi)
		var/datum/light_source/L
		for (var/thing in light_source_multi)
			L = thing
			if (L.light_angle)
				L.source_atom.update_light()