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

local math_random = math.random

local vector_multiply = vector.multiply
local vector_add      = vector.add

local minetest_yaw_to_dir                   = minetest.yaw_to_dir
local minetest_get_item_group               = minetest.get_item_group
local minetest_get_node                     = minetest.get_node
local minetest_line_of_sight                = minetest.line_of_sight


local state_list_wandering = {"stand", "walk"}

local DOUBLE_PI = math.pi * 2
local THIRTY_SECONDTH_PI = DOUBLE_PI * 0.03125


--this is basically reverse jump_check
local cliff_check = function(self,dtime)
	--mobs will flip out if they are falling without this
	if self.object:get_velocity().y ~= 0 then
		return false
	end

	local pos = self.object:get_pos()
    local dir = minetest_yaw_to_dir(self.yaw)
	local collisionbox = self.object:get_properties().collisionbox
	local radius = collisionbox[4] + 0.5

	dir = vector_multiply(dir,radius)

	local free_fall, blocker = minetest_line_of_sight(
		{x = pos.x + dir.x, y = pos.y, z = pos.z + dir.z},
		{x = pos.x + dir.x, y = pos.y - self.fear_height, z = pos.z + dir.z})

	return free_fall
end

--a simple helper function which is too small to move into movement.lua
local quick_rotate_45 = function(self,dtime)
	self.yaw = self.yaw + THIRTY_SECONDTH_PI
	if self.yaw > DOUBLE_PI then
		self.yaw = self.yaw - DOUBLE_PI
	end
end

--check if a mob needs to jump
local 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



-- state switching logic (stand, walk, run, attacks)
local state_switch = function(self, dtime)
	self.state_timer = self.state_timer - dtime
	if self.wandering and self.state_timer <= 0 then
		self.state_timer = math.random(4,10) + math.random()
		self.state = state_list_wandering[math.random(1,#state_list_wandering)]
	end
end

-- states are executed here (goto would have been helpful :<)
local state_execution = function(self,dtime)

	--local yaw = self.object:get_yaw() or 0

	if self.state == "stand" then

		--do animation
		mobs.set_mob_animation(self, "stand")

		--set the velocity of the mob
		mobs.set_velocity(self,0)

		--print("stand")

	elseif self.state == "walk" then

		self.walk_timer = self.walk_timer - dtime

		--reset the walk timer
		if self.walk_timer <= 0 then

			--re-randomize the walk timer
			self.walk_timer = math.random(1,6) + math.random()

			--set the mob into a random direction
			self.yaw = (math_random() * (math.pi * 2))
		end

		--do animation
		mobs.set_mob_animation(self, "walk")

		--enable rotation locking
		mobs.movement_rotation_lock(self)

		--check for nodes to jump over
		local node_in_front_of = jump_check(self)

		if node_in_front_of == 1 then
			mobs.jump(self)
		
		--turn if on the edge of cliff
		--(this is written like this because unlike
		--jump_check which simply tells the mob to jump
		--this requires a mob to turn, removing the
		--ease of a full implementation for it in a single
		--function)
		elseif node_in_front_of == 2 or (self.fear_height ~= 0 and cliff_check(self,dtime)) then
			--turn 45 degrees if so
			quick_rotate_45(self,dtime)
			--stop the mob so it doesn't fall off
			mobs.set_velocity(self,0)
		end

		--only move forward if path is clear
		if node_in_front_of == 0 or node_in_front_of == 1 then
			--set the velocity of the mob
			mobs.set_velocity(self,1)
		end

		--print("walk")

	elseif self.state == "run" then

		print("run")

	elseif self.state == "attack" then

		print("attack")

	end	
	
end






mobs.mob_step = function(self, dtime)

	--do not continue if non-existent
	if not self or not self.object or not self.object:get_luaentity() then
		return false
	end

	--print(self.object:get_yaw())

	state_switch(self, dtime)

	state_execution(self,dtime)


	-- can mob be pushed, if so calculate direction -- do this last (overrides everything)
	if self.pushable then
		mobs.collision(self)
	end

    self.old_velocity = self.object:get_velocity()
end