VoxeLibre/mods/ENTITIES/mcl_mobs/api/mob_functions/environment.lua

local minetest_line_of_sight = minetest.line_of_sight
local minetest_dir_to_yaw    = minetest.dir_to_yaw
local minetest_yaw_to_dir    = minetest.yaw_to_dir
local minetest_get_node      = minetest.get_node
local minetest_get_item_group = minetest.get_item_group
local minetest_get_objects_inside_radius = minetest.get_objects_inside_radius
local minetest_get_node_or_nil = minetest.get_node_or_nil
local minetest_registered_nodes = minetest.registered_nodes
local minetest_get_connected_players = minetest.get_connected_players

local vector_new = vector.new
local vector_add = vector.add
local vector_multiply = vector.multiply
local vector_distance = vector.distance

local table_copy = table.copy

local math_abs = math.abs

-- default function when mobs are blown up with TNT
local do_tnt = function(obj, damage)

	obj.object:punch(obj.object, 1.0, {
		full_punch_interval = 1.0,
		damage_groups = {fleshy = damage},
	}, nil)

	return false, true, {}
end

--a fast function to be able to detect only players without using objects_in_radius
mobs.detect_closest_player_within_radius = function(self, line_of_sight, radius, object_height_adder)
	
	local pos1 = self.object:get_pos()
	local players_in_area = {}
	local winner_player = nil
	local players_detected = 0

	--get players in radius
	for _,player in pairs(minetest.get_connected_players()) do
		if player and player:get_hp() > 0 then

			local pos2 = player:get_pos()

			local distance = vector_distance(pos1,pos2)

			if distance <= radius then
				if line_of_sight then
					--must add eye height or stuff breaks randomly because of
					--seethrough nodes being a blocker (like grass)
					if minetest_line_of_sight(
							vector_new(pos1.x, pos1.y + object_height_adder, pos1.z), 
							vector_new(pos2.x, pos2.y + player:get_properties().eye_height, pos2.z)
						) then
						players_detected = players_detected + 1
						players_in_area[player] = distance
					end
				else
					players_detected = players_detected + 1
					players_in_area[player] = distance
				end
			end
		end
	end


	--return if there's no one near by
	if players_detected <= 0 then --handle negative numbers for some crazy error that could possibly happen
		return nil
	end

	--do a default radius max
	local shortest_distance = radius + 1

	--sort through players and find the closest player
	for player,distance in pairs(players_in_area) do
		if distance < shortest_distance then
			shortest_distance = distance
			winner_player = player
		end
	end

	return(winner_player)
end


--check if a mob needs to jump
mobs.jump_check = function(self,dtime)

    local pos = self.object:get_pos()
    pos.y = pos.y + 0.1
    local dir = minetest_yaw_to_dir(self.yaw)

    local collisionbox = self.object:get_properties().collisionbox
	local radius = collisionbox[4] + 0.5

    vector_multiply(dir, radius)

	--only jump if there's a node and a non-solid node above it
    local test_dir = vector_add(pos,dir)

	local green_flag_1 = minetest_get_item_group(minetest_get_node(test_dir).name, "solid") ~= 0

	test_dir.y = test_dir.y + 1

	local green_flag_2 = minetest_get_item_group(minetest_get_node(test_dir).name, "solid") == 0

    if green_flag_1 and green_flag_2 then
		--can jump over node
        return(1)
	elseif green_flag_1 and not green_flag_2 then 
		--wall in front of mob
		return(2)
    end

	--nothing to jump over
	return(0)
end

-- a helper function to quickly turn neutral passive mobs hostile
local turn_hostile = function(self,detected_mob)
	--drop in variables for attacking (stops crash)
	detected_mob.punch_timer = 0
	--set to hostile
	detected_mob.hostile = true
	--hostile_cooldown timer is initialized here
	detected_mob.hostile_cooldown_timer = detected_mob.hostile_cooldown
	--set target to the same
	detected_mob.attacking = self.attacking
end

--allow hostile mobs to signal to other mobs
--to switch from neutal passive to neutral hostile
mobs.group_attack_initialization = function(self)

	--get basic data
	local friends_list

	if self.group_attack == true then
		friends_list = {self.name}
	else
		friends_list = table_copy(self.group_attack)
	end

	local objects_in_area = minetest_get_objects_inside_radius(self.object:get_pos(), self.view_range)

	--get the player's name
	local name = self.attacking:get_player_name()

	--re-use local variable
	local detected_mob

	--run through mobs in viewing distance
	for _,object in pairs(objects_in_area) do
		if object and object:get_luaentity() then
			detected_mob = object:get_luaentity()
			-- only alert members of same mob or friends
			if detected_mob._cmi_is_mob and detected_mob.state ~= "attack" and detected_mob.owner ~= name then
				if detected_mob.name == self.name then
					turn_hostile(self,detected_mob)
				else
					for _,id in pairs(friends_list) do
						if detected_mob.name == id then
							turn_hostile(self,detected_mob)
							break
						end
					end
				end
			end

			--THIS NEEDS TO BE RE-IMPLEMENTED AS A GLOBAL HIT IN MOB_PUNCH!!
			-- have owned mobs attack player threat
			--if obj.owner == name and obj.owner_loyal then
			--	do_attack(obj, self.object)
			--end
		end
	end
end

-- check if within physical map limits (-30911 to 30927)
-- within_limits, wmin, wmax = nil, -30913, 30928
mobs.within_limits = function(pos, radius)
	if mcl_vars then
		if mcl_vars.mapgen_edge_min and mcl_vars.mapgen_edge_max then
			wmin, wmax = mcl_vars.mapgen_edge_min, mcl_vars.mapgen_edge_max
			within_limits = function(pos, radius)
				return pos
					and (pos.x - radius) > wmin and (pos.x + radius) < wmax
					and (pos.y - radius) > wmin and (pos.y + radius) < wmax
					and (pos.z - radius) > wmin and (pos.z + radius) < wmax
			end
		end
	end
	return pos
		and (pos.x - radius) > wmin and (pos.x + radius) < wmax
		and (pos.y - radius) > wmin and (pos.y + radius) < wmax
		and (pos.z - radius) > wmin and (pos.z + radius) < wmax
end

-- get node but use fallback for nil or unknown
mobs.node_ok = function(pos, fallback)

	fallback = fallback or mobs.fallback_node

	local node = minetest_get_node_or_nil(pos)

	if node and minetest_registered_nodes[node.name] then
		return node
	end

	return minetest_registered_nodes[fallback]
end


--a teleport functoin
mobs.teleport = function(self, target)
	if self.do_teleport then
		if self.do_teleport(self, target) == false then
			return
		end
	end
end

--a function used for despawning mobs
mobs.check_for_player_within_area = function(self, radius)
	local pos1 = self.object:get_pos()
	--get players in radius
	for _,player in pairs(minetest_get_connected_players()) do
		if player and player:get_hp() > 0 then
			local pos2 = player:get_pos()
			local distance = vector_distance(pos1,pos2)
			if distance < radius then
				--found a player
				return(true)
			end
		end
	end
	--did not find a player
	return(false)
end


--a simple helper function for mobs following
mobs.get_2d_distance = function(pos1,pos2)
	pos1.y = 0
	pos2.y = 0
	return(vector_distance(pos1, pos2))
end

-- fall damage onto solid ground
mobs.calculate_fall_damage = function(self)
	if self.old_velocity and self.old_velocity.y < -7 and self.object:get_velocity().y == 0 then
		local vel = self.object:get_velocity()
		if vel then
			local damage = math_abs(self.old_velocity.y + 7) * 2
			self.pause_timer = 0.4
			self.health = self.health - damage
		end
	end
end