technic/technic/machines/register/battery_box.lua

local S = technic.getter

technic.register_power_tool("technic:battery", 10000)
technic.register_power_tool("technic:red_energy_crystal", 50000)
technic.register_power_tool("technic:green_energy_crystal", 150000)
technic.register_power_tool("technic:blue_energy_crystal", 450000)

minetest.register_craft({
	output = 'technic:battery',
	recipe = {
		{'group:wood', 'default:copper_ingot', 'group:wood'},
		{'group:wood', 'moreores:tin_ingot',   'group:wood'},
		{'group:wood', 'default:copper_ingot', 'group:wood'},
	}
})

minetest.register_tool("technic:battery", {
	description = S("RE Battery"),
	inventory_image = "technic_battery.png",
	wear_represents = "technic_RE_charge",
	on_refill = technic.refill_RE_charge,
	tool_capabilities = {
		charge = 0,
		max_drop_level = 0,
		groupcaps = {
			fleshy = {times={}, uses=10000, maxlevel=0}
		}
	}
})

local tube = {
	insert_object = function(pos, node, stack, direction)
		if direction.y == 0 then
			return stack
		end
		local meta = minetest.get_meta(pos)
		local inv = meta:get_inventory()
		if direction.y > 0 then
			return inv:add_item("src", stack)
		else
			return inv:add_item("dst", stack)
		end
	end,
	can_insert = function(pos, node, stack, direction)
		if direction.y == 0 then
			return false
		end
		local meta = minetest.get_meta(pos)
		local inv = meta:get_inventory()
		if direction.y > 0 then
			return inv:room_for_item("src", stack)
		else
			return inv:room_for_item("dst", stack)
		end
	end,
	connect_sides = {left=1, right=1, back=1, top=1, bottom=1},
}

function technic.register_battery_box(data)
	local tier = data.tier
	local ltier = string.lower(tier)

	local formspec =
		"invsize[8,9;]"..
		"image[1,1;1,2;technic_power_meter_bg.png]"..
		"list[current_name;src;3,1;1,1;]"..
		"image[4,1;1,1;technic_battery_reload.png]"..
		"list[current_name;dst;5,1;1,1;]"..
		"label[0,0;"..S("%s Battery Box"):format(tier).."]"..
		"label[3,0;"..S("Charge").."]"..
		"label[5,0;"..S("Discharge").."]"..
		"label[1,3;"..S("Power level").."]"..
		"list[current_player;main;0,5;8,4;]"..
		"listring[current_name;dst]"..
		"listring[current_player;main]"..
		"listring[current_name;src]"..
		"listring[current_player;main]"

	if data.upgrade then
		formspec = formspec..
			"list[current_name;upgrade1;3.5,3;1,1;]"..
			"list[current_name;upgrade2;4.5,3;1,1;]"..
			"label[3.5,4;"..S("Upgrade Slots").."]"..
			"listring[current_name;upgrade1]"..
			"listring[current_player;main]"..
			"listring[current_name;upgrade2]"..
			"listring[current_player;main]"
	end

	local run = function(pos, node)
		local meta           = minetest.get_meta(pos)
		local eu_input       = meta:get_int(tier.."_EU_input")
		local current_charge = meta:get_int("internal_EU_charge")

		local EU_upgrade, tube_upgrade = 0, 0
		if data.upgrade then
			EU_upgrade, tube_upgrade = technic.handle_machine_upgrades(meta)
		end
		local max_charge = data.max_charge * (1 + EU_upgrade / 10)
			
		-- Charge/discharge the battery with the input EUs
		if eu_input >= 0 then
			current_charge = math.min(current_charge + eu_input, max_charge)
		else
			current_charge = math.max(current_charge + eu_input, 0)
		end

		-- Charging/discharging tools here
		local tool_full, tool_empty
		current_charge, tool_full = technic.charge_tools(meta,
				current_charge, data.charge_step)
		current_charge, tool_empty = technic.discharge_tools(meta,
				current_charge, data.discharge_step,
				max_charge)
			
		if data.tube then
			local inv = meta:get_inventory()
			technic.handle_machine_pipeworks(pos, tube_upgrade,
			function(pos, x_velocity, z_velocity)
				if tool_full and not inv:is_empty("src") then
					technic.send_items(pos, x_velocity, z_velocity, "src")
				elseif tool_empty and not inv:is_empty("dst") then
					technic.send_items(pos, x_velocity, z_velocity, "dst")
				end
			end)
		end

		-- We allow batteries to charge on less than the demand
		meta:set_int(tier.."_EU_demand",
				math.min(data.charge_rate, max_charge - current_charge))
		meta:set_int(tier.."_EU_supply",
				math.min(data.discharge_rate, current_charge))
			meta:set_int("internal_EU_charge", current_charge)

		-- Select node textures
		local charge_count = math.ceil((current_charge / max_charge) * 8)
		charge_count = math.min(charge_count, 8)
		charge_count = math.max(charge_count, 0)
		local last_count = meta:get_float("last_side_shown")
		if charge_count ~= last_count then
			technic.swap_node(pos,"technic:"..ltier.."_battery_box"..charge_count)
			meta:set_float("last_side_shown", charge_count)
		end

		local charge_percent = math.floor(current_charge / max_charge * 100)
		meta:set_string("formspec",
			formspec..
			"image[1,1;1,2;technic_power_meter_bg.png"
			.."^[lowpart:"..charge_percent
			..":technic_power_meter_fg.png]")

		local infotext = S("@1 Battery Box: @2/@3", tier,
				technic.pretty_num(current_charge), technic.pretty_num(max_charge))
		if eu_input == 0 then
			infotext = S("%s Idle"):format(infotext)
		end
		meta:set_string("infotext", infotext)
	end
	
	for i = 0, 8 do
		local groups = {snappy=2, choppy=2, oddly_breakable_by_hand=2,
				technic_machine=1, ["technic_"..ltier]=1}
		if i ~= 0 then
			groups.not_in_creative_inventory = 1
		end
		
		if data.tube then
			groups.tubedevice = 1
			groups.tubedevice_receiver = 1
		end
		
		minetest.register_node("technic:"..ltier.."_battery_box"..i, {
			description = S("%s Battery Box"):format(tier),
			tiles = {"technic_"..ltier.."_battery_box_top.png",
			         "technic_"..ltier.."_battery_box_bottom.png",
				 "technic_"..ltier.."_battery_box_side.png^technic_power_meter"..i..".png",
				 "technic_"..ltier.."_battery_box_side.png^technic_power_meter"..i..".png",
				 "technic_"..ltier.."_battery_box_side.png^technic_power_meter"..i..".png",
				 "technic_"..ltier.."_battery_box_side.png^technic_power_meter"..i..".png"},
			groups = groups,
			connect_sides = {"bottom"},
			tube = data.tube and tube or nil,
			paramtype2 = "facedir",
			sounds = default.node_sound_wood_defaults(),
			drop = "technic:"..ltier.."_battery_box0",
			on_construct = function(pos)
				local meta = minetest.get_meta(pos)
				local inv = meta:get_inventory()
				local node = minetest.get_node(pos)

				meta:set_string("infotext", S("%s Battery Box"):format(tier))
				meta:set_string("formspec", formspec)
				meta:set_int(tier.."_EU_demand", 0)
				meta:set_int(tier.."_EU_supply", 0)
				meta:set_int(tier.."_EU_input",  0)
				meta:set_float("internal_EU_charge", 0)
				inv:set_size("src", 1)
				inv:set_size("dst", 1)
				inv:set_size("upgrade1", 1)
				inv:set_size("upgrade2", 1)
			end,
			can_dig = technic.machine_can_dig,
			allow_metadata_inventory_put = technic.machine_inventory_put,
			allow_metadata_inventory_take = technic.machine_inventory_take,
			allow_metadata_inventory_move = technic.machine_inventory_move,
			technic_run = run,
			after_place_node = data.tube and pipeworks.after_place,
			after_dig_node = technic.machine_after_dig_node
		})
	end

	-- Register as a battery type
	-- Battery type machines function as power reservoirs and can both receive and give back power
	for i = 0, 8 do
		technic.register_machine(tier, "technic:"..ltier.."_battery_box"..i, technic.battery)
	end

end -- End registration


function technic.charge_tools(meta, batt_charge, charge_step)
	local inv = meta:get_inventory()
	if inv:is_empty("src") then
		return batt_charge, false
	end
	local src_stack = inv:get_stack("src", 1)

	local tool_name = src_stack:get_name()
	if not technic.power_tools[tool_name] then
		return batt_charge, false
	end
	-- Set meta data for the tool if it didn't do it itself
	local src_meta = minetest.deserialize(src_stack:get_metadata()) or {}
	if not src_meta.charge then
		src_meta.charge = 0
	end
	-- Do the charging
	local item_max_charge = technic.power_tools[tool_name]
	local tool_charge     = src_meta.charge
	if tool_charge >= item_max_charge then
		return batt_charge, true
	elseif batt_charge <= 0 then
		return batt_charge, false
	end
	charge_step = math.min(charge_step, batt_charge)
	charge_step = math.min(charge_step, item_max_charge - tool_charge)
	tool_charge = tool_charge + charge_step
	batt_charge = batt_charge - charge_step
	technic.set_RE_wear(src_stack, tool_charge, item_max_charge)
	src_meta.charge = tool_charge
	src_stack:set_metadata(minetest.serialize(src_meta))
	inv:set_stack("src", 1, src_stack)
	return batt_charge, (tool_charge == item_max_charge)
end


function technic.discharge_tools(meta, batt_charge, charge_step, max_charge)
	local inv = meta:get_inventory()
	if inv:is_empty("dst") then
		return batt_charge, false
	end
	srcstack = inv:get_stack("dst", 1)
	local toolname = srcstack:get_name()
	if technic.power_tools[toolname] == nil then
		return batt_charge, false
	end
	-- Set meta data for the tool if it didn't do it itself :-(
	local src_meta = minetest.deserialize(srcstack:get_metadata())
	src_meta = src_meta or {}
	if not src_meta.charge then
		src_meta.charge = 0
	end

	-- Do the discharging
	local item_max_charge = technic.power_tools[toolname]
	local tool_charge     = src_meta.charge
	if tool_charge <= 0 then
		return batt_charge, true
	elseif batt_charge >= max_charge then
		return batt_charge, false
	end
	charge_step = math.min(charge_step, max_charge - batt_charge)
	charge_step = math.min(charge_step, tool_charge)
	tool_charge = tool_charge - charge_step
	batt_charge = batt_charge + charge_step
	technic.set_RE_wear(srcstack, tool_charge, item_max_charge)
	src_meta.charge = tool_charge
	srcstack:set_metadata(minetest.serialize(src_meta))
	inv:set_stack("dst", 1, srcstack)
	return batt_charge, (tool_charge == 0)
end