--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,
	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)
		return advtrains.pcall(function()
			if not self.wagon or not player or player:get_player_name()=="" then
				--our new animal damage code seems to generate problems
				return
			end
			--only if player owns at least one wagon next to this
			local own=player:get_player_name()
			if self.wagon.owner and self.wagon.owner==own and not self.wagon.lock_couples then
				local train=advtrains.trains[self.wagon.train_id]
				local nextwgn_id=train.trainparts[self.wagon.pos_in_trainparts-1]
				for aoi, le in pairs(minetest.luaentities) do
					if le and le.is_wagon then
						if le.unique_id==nextwgn_id then
							if le.owner and le.owner~=own then
								minetest.chat_send_player(own, attrans("You need to own at least one neighboring wagon to destroy this couple."))
								return
							end
						end
					end
				end
				atprint("Discouple punched. Splitting train", self.wagon.train_id)
				advtrains.split_train_at_wagon(self.wagon)--found in trainlogic.lua
				self.object:remove()
			elseif self.wagon.lock_couples then
				minetest.chat_send_player(own, "Couples of one of the wagons are locked, can't discouple!")
			else
				minetest.chat_send_player(own, attrans("You need to own at least one neighboring wagon to destroy this couple."))
			end
		end)
	end,
	on_step=function(self, dtime)
		return advtrains.pcall(function()
			local t=os.clock()
			if not self.wagon then
				self.object:remove()
				atprint("Discouple: no wagon, destroying")
				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:getyaw() then
				atprint("Discouple: wagon no longer loaded, destroying")
				self.object:remove()
				return
			end
			local velocityvec=self.wagon.object:getvelocity()
			self.updatepct_timer=(self.updatepct_timer or 0)-dtime
			if not self.old_velocity_vector or not vector.equals(velocityvec, self.old_velocity_vector) or self.updatepct_timer<=0 then--only send update packet if something changed
				local flipsign=self.wagon.wagon_flipped and -1 or 1
				self.object:setpos(vector.add(self.wagon.object:getpos(), {y=0, x=-math.sin(self.wagon.object:getyaw())*self.wagon.wagon_span*flipsign, z=math.cos(self.wagon.object:getyaw())*self.wagon.wagon_span*flipsign}))
				self.object:setvelocity(velocityvec)
				self.updatepct_timer=2
			end
			atprintbm("discouple_step", t)
		end)
	end,
})

--advtrains:couple
--when two trains overlap with their end-positions, this entity will be spawned and both trains set its id into appropiate fields for them to know when to free them again. The entity will destroy automatically when it recognizes that any of the trains left the common position. 
--[[fields
train_id_1
train_id_2
train1_is_backpos
train2_is_backpos
]]


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,
	on_activate=function(self, staticdata)
		return advtrains.pcall(function()
			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)
	end,
	get_staticdata=function(self) return "COUPLE" end,
	on_rightclick=function(self, clicker)
		return advtrains.pcall(function()
			if not self.train_id_1 or not self.train_id_2 then return end
			
			local id1, id2=self.train_id_1, self.train_id_2
			if self.train1_is_backpos and not self.train2_is_backpos then
				advtrains.do_connect_trains(id1, id2, clicker)
				--case 2 (second train is front)
			elseif self.train2_is_backpos and not self.train1_is_backpos then
				advtrains.do_connect_trains(id2, id1, clicker)
				--case 3 
			elseif self.train1_is_backpos and self.train2_is_backpos then
				advtrains.invert_train(id2)
				advtrains.do_connect_trains(id1, id2, clicker)
				--case 4 
			elseif not self.train1_is_backpos and not self.train2_is_backpos then
				advtrains.invert_train(id1)
				advtrains.do_connect_trains(id1, id2, clicker)
			end
			atprint("Coupled trains", id1, id2)
			self.object:remove()
		end)
	end,
	on_step=function(self, dtime)
		return advtrains.pcall(function()
			advtrains.atprint_context_tid=sid(self.train_id_1)
			advtrains.atprint_context_tid_full=self.train_id_1
			local t=os.clock()
			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
			if not train1.path or not train2.path or not train1.index or not train2.index or not train1.end_index or not train2.end_index then
				atprint("Couple: paths or end_index missing. Might happen when paths got cleared")
				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 not self.train1_is_backpos then
					tp1=advtrains.get_real_index_position(train1.path, train1.index)
				else
					tp1=advtrains.get_real_index_position(train1.path, train1.end_index)
				end
				local tp2
				if not self.train2_is_backpos then
					tp2=advtrains.get_real_index_position(train2.path, train2.index)
				else
					tp2=advtrains.get_real_index_position(train2.path, train2.end_index)
				end
				local pos_median=advtrains.pos_median(tp1, tp2)
				if not vector.equals(pos_median, self.object:getpos()) then
					self.object:setpos(pos_median)
				end
				self.position_set=true
			end
			atprintbm("couple step", t)
			advtrains.atprint_context_tid=nil
			advtrains.atprint_context_tid_full=nil
		end)
	end,
})