require "defines"


function startOffshoreDumps(event)
	-- Work around the "onload" event triggering when a save occurs.
	if global.startedOffshoreDumps == nil then
		global.offshoreDumps = {}
		
		global.startedOffshoreDumps = true
	end
end

function stepOffshoreDumps(event)
	for offshoreDump, magicFurnace in pairs(global.offshoreDumps) do
		-- Work around the lack of a proper stop event.
		if not offshoreDump.valid then
			if magicFurnace.valid then
				-- Also remove the invisible furnace from the game.
				magicFurnace.destroy()
			end
			
			global.offshoreDumps[offshoreDump] = nil
		end
		
		-- If all is well then we can just do our thing.
		if offshoreDump.valid and magicFurnace.valid then
			-- The game will set the fluidbox property to nil if there is no fluid in it anymore.
			if offshoreDump.fluidbox[1] ~= nil then
				-- Decrease the amount of fluid at a rate similar to the offshore pump. We have to
				-- completely replace the table, adjusting only the amount value has no effect.
				local fluid = {
					type = offshoreDump.fluidbox[1].type,
					amount = offshoreDump.fluidbox[1].amount,
					temperature = offshoreDump.fluidbox[1].temperature
				}
				
				fluid.amount = fluid.amount - 1
				
				if fluid.amount < 0 then
					fluid.amount = 0
				end
				
				offshoreDump.fluidbox[1] = fluid
				
				-- Produce pollution if the amount of a fluid other than water is being decreased
				-- by running an invisible furnace.
				if fluid.type ~= "water" then
					-- Make sure there is iron ore in the furnace, otherwise no pollution will be
					-- produced.
					local sourceInventory = magicFurnace.get_inventory(2)
					
					local ironOreCount = sourceInventory.get_item_count("iron-ore")
					
					if ironOreCount < 1 then
						sourceInventory.insert({
							name = "iron-ore",
							count = 1
						})
					end
				end
			end
			
			-- Make sure there is always fuel in the furnace, otherwise an out-of-fuel icon will
			-- be shown.
			local fuelInventory = magicFurnace.get_inventory(1)
			
			local coalCount = fuelInventory.get_item_count("coal")

			if coalCount < 1 then
				fuelInventory.insert({
					name = "coal",
					count = 1
				})
			end
			
			-- Make sure there is never iron in the furnace, otherwise it will become backed up.
			local resultInventory = magicFurnace.get_inventory(3)
			
			local ironCount = resultInventory.get_item_count("iron-plate")
			
			if ironCount > 0 then
				resultInventory.remove({
					name = "iron-plate",
					count = ironCount
				})
			end
		end
	end
end


function startOffshoreDump(event)
	local entity = event.created_entity
		if event.created_entity.name == "offshore-dump" then
			-- Place an invisible furnace on top of the entity.
			local magicFurnace = game.get_surface("nauvis").create_entity({
				name = "magic-furnace",
				position = event.created_entity.position
			})

			-- Remember the entity and the furnace together.
			global.offshoreDumps[entity] = magicFurnace
		end
end


script.on_init(startOffshoreDumps)
script.on_load(startOffshoreDumps)
script.on_event(defines.events.on_tick, stepOffshoreDumps)

script.on_event(defines.events.on_built_entity, startOffshoreDump)
script.on_event(defines.events.on_robot_built_entity, startOffshoreDump)