minetest-mm/mods/advtrains/advtrains/couple.lua

--couple.lua
--defines couple entities.

--advtrains:discouple
--set into existing trains to split them when punched.
--they are attached to the wagons.
--[[fields
wagon

wagons keep their couple entity minetest-internal id inside the field discouple_id. if it refers to nowhere, they will spawn a new one if player is near
]]

local couple_max_dist=3

minetest.register_entity("advtrains:discouple", {
	visual="sprite",
	textures = {"advtrains_discouple.png"},
	collisionbox = {-0.3,-0.3,-0.3, 0.3,0.3,0.3},
	visual_size = {x=0.7, y=0.7},
	initial_sprite_basepos = {x=0, y=0},
	
	is_discouple=true,
	static_save = false,
	on_activate=function(self, staticdata) 
		if staticdata=="DISCOUPLE" then
			--couple entities have no right to exist further...
			atprint("Discouple loaded from staticdata, destroying")
			self.object:remove()
			return
		end
		self.object:set_armor_groups({immortal=1})
	end,
	get_staticdata=function() return "DISCOUPLE" end,
	on_punch=function(self, player)
			local pname = player:get_player_name()
			if pname and pname~="" and self.wagon then
				if advtrains.safe_decouple_wagon(self.wagon.id, pname) then
					self.object:remove()
				else
					minetest.add_entity(self.object:getpos(), "advtrains:lockmarker")
				end
			end
	end,
	on_step=function(self, dtime)
			if not self.wagon then
				self.object:remove()
				return
			end
			--getyaw seems to be a reliable method to check if an object is loaded...if it returns nil, it is not.
			if not self.wagon.object:get_yaw() then
				self.object:remove()
				return
			end
			if not self.wagon:train() or self.wagon:train().velocity > 0 then
				self.object:remove()
				return
			end
	end,
})

-- advtrains:couple
-- Couple entity 
local function lockmarker(obj)
	minetest.add_entity(obj:get_pos(), "advtrains:lockmarker")
	obj:remove()
end

minetest.register_entity("advtrains:couple", {
	visual="sprite",
	textures = {"advtrains_couple.png"},
	collisionbox = {-0.3,-0.3,-0.3, 0.3,0.3,0.3},
	visual_size = {x=0.7, y=0.7},
	initial_sprite_basepos = {x=0, y=0},
	
	is_couple=true,
	static_save = false,
	on_activate=function(self, staticdata)
			if staticdata=="COUPLE" then
				--couple entities have no right to exist further...
				atprint("Couple loaded from staticdata, destroying")
				self.object:remove()
				return
			end
			self.object:set_armor_groups({immmortal=1})
	end,
	get_staticdata=function(self) return "COUPLE" end,
	on_rightclick=function(self, clicker)
			if not self.train_id_1 or not self.train_id_2 then return end
			
			local pname=clicker
			if type(clicker)~="string" then pname=clicker:get_player_name() end
			
			if advtrains.safe_couple_trains(self.train_id_1, self.train_id_2, self.t1_is_front, self.t2_is_front, pname) then
				self.object:remove()
			else
				lockmarker(self.object)
			end
	end,
	on_step=function(self, dtime)
			if advtrains.wagon_outside_range(self.object:getpos()) then
				self.object:remove()
				return
			end

			if not self.train_id_1 or not self.train_id_2 then atprint("Couple: train ids not set!") self.object:remove() return end
			local train1=advtrains.trains[self.train_id_1]
			local train2=advtrains.trains[self.train_id_2]
			if not train1 or not train2 then
				atprint("Couple: trains missing, destroying")
				self.object:remove()
				return
			end
			
			--shh, silence here, this is an on-step callback!
			if not advtrains.train_ensure_init(self.train_id_1, train1) then
				--atwarn("Train",self.train_id_1,"is not initialized! Operation aborted!")
				return
			end
			if not advtrains.train_ensure_init(self.train_id_2, train2) then
				--atwarn("Train",self.train_id_2,"is not initialized! Operation aborted!")
				return
			end
			
			if train1.velocity>0 or train2.velocity>0 then
				if not self.position_set then --ensures that train stands a single time before check fires. Using flag below
					return
				end
				atprint("Couple: train is moving, destroying")
				self.object:remove()
				return
			end
			
			if not self.position_set then
				local tp1
				if self.t1_is_front then
					tp1=advtrains.path_get_interpolated(train1, train1.index)
				else
					tp1=advtrains.path_get_interpolated(train1, train1.end_index)
				end
				local tp2
				if self.t2_is_front then
					tp2=advtrains.path_get_interpolated(train2, train2.index)
				else
					tp2=advtrains.path_get_interpolated(train2, train2.end_index)
				end
				local pos_median=advtrains.pos_median(tp1, tp2)
				if not vector.equals(pos_median, self.object:getpos()) then
					self.object:set_pos(pos_median)
				end
				self.position_set=true
			end
			atprintbm("couple step", t)
			advtrains.atprint_context_tid=nil
	end,
})
minetest.register_entity("advtrains:lockmarker", {
	visual="sprite",
	textures = {"advtrains_cpl_lock.png"},
	collisionbox = {-0.3,-0.3,-0.3, 0.3,0.3,0.3},
	visual_size = {x=0.7, y=0.7},
	initial_sprite_basepos = {x=0, y=0},
	
	is_lockmarker=true,
	static_save = false,
	on_activate=function(self, staticdata)
			if staticdata=="COUPLE" then
				--couple entities have no right to exist further...
				atprint("Couple loaded from staticdata, destroying")
				self.object:remove()
				return
			end
			self.object:set_armor_groups({immmortal=1})
			self.life=5
	end,
	get_staticdata=function(self) return "COUPLE" end,
	on_step=function(self, dtime)
		self.life=(self.life or 5)-dtime
		if self.life<0 then
			self.object:remove()
		end
	end,
})