First version 🐈

README.txt

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+ Exchange Shop
+===============
+
+This mod adds an improved ("currency" compatible) shop to your world.
+
+Features:
+ * 4 buyer and 4 seller slots
+ * Much storage capacity
+ * Custom shop title settable
+ * pipeworks compatibilty
+
+Optional dependencies:
+ * currency
+ * bitchange
+ * wrench
+
+License: CC0 (for everything)

currency_migrate.lua

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+-- Combine stacks into a new list
+local function compress_list(list)
+	local items = {}
+	local new_list = {}
+	for i, stack in pairs(list or {}) do
+		if not stack:is_empty() then
+			if stack:get_stack_max() == 1 then
+				table.insert(new_list, stack)
+			else
+				items[stack:get_name()] = (items[stack:get_name()] or 0)
+					+ stack:get_count()
+			end
+		end
+	end
+	for name, count in pairs(items) do
+		local max = ItemStack(name):get_stack_max()
+
+		repeat
+			local take = math.min(max, count)
+			local stack = ItemStack(name)
+			stack:set_count(take)
+			table.insert(new_list, stack)
+			count = count - take
+		until count == 0
+	end
+	return new_list
+end
+
+local function list_add_list(inv, list_name, list)
+	local leftover_list = {}
+	for i, stack in pairs(list or {}) do
+		local leftover = inv:add_item(list_name, stack)
+		if not leftover:is_empty() then
+			table.insert(leftover_list, leftover)
+		end
+	end
+	if #leftover_list > 0 then
+		minetest.log("warning", "[exchange_shop] List " .. list_name
+			.. " is full. Possible item loss!")
+	end
+	return leftover_list
+end
+
+local function migrate_shop_node(pos, node)
+	local meta = minetest.get_meta(pos)
+	local owner = meta:get_string("owner")
+	local title = meta:get_string("infotext")
+	local inv = meta:get_inventory()
+	local def = minetest.registered_nodes[exchange_shop.shopname]
+
+	-- Create new slots
+	def.on_construct(pos)
+	meta:set_string("owner", owner)
+	meta:set_string("infotext", title)
+
+	list_add_list(inv, "custm", inv:get_list("customers_gave"))
+	inv:set_size("customers_gave", 0)
+
+	local new_owner_gives = compress_list(inv:get_list("owner_gives"))
+	local new_owner_wants = compress_list(inv:get_list("owner_wants"))
+	local dst_gives = "cust_og"
+	local dst_wants = "cust_ow"
+	if #new_owner_gives > 4 or #new_owner_wants > 4 then
+		-- Not enough space (from 6 slots to 4)
+		-- redirect everything to the stock
+		dst_gives = "stock"
+		dst_wants = "custm"
+	end
+	list_add_list(inv, dst_gives, new_owner_gives)
+	list_add_list(inv, dst_wants, new_owner_wants)
+
+	inv:set_size("owner_gives", 0)
+	inv:set_size("owner_takes", 0)
+
+	node.name = exchange_shop.shopname
+	minetest.swap_node(pos, node)
+end
+
+minetest.register_lbm({
+	label = "currency shop to exchange shop migration",
+        name = "exchange_shop:currency_migrate",
+        nodenames = { "currency:shop" },
+        run_at_every_load = true, -- TODO this for testing only
+	action = migrate_shop_node
+})
+
+-- Clean up garbage
+minetest.register_on_joinplayer(function(player)
+	local inv = player:get_inventory()
+	for i, name in pairs({"customer_gives", "customer_gets"}) do
+		if inv:get_size(name) > 0 then
+			local leftover = list_add_list(inv, "main", inv:get_list(name))
+			list_add_list(inv, "craft", leftover)
+			inv:set_size(name, 0)
+		end
+	end
+end)

currency_override.lua

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+local def = table.copy(minetest.registered_nodes["currency:shop"])
+def.groups.not_in_creative_inventory = 1
+
+minetest.override_item("currency:shop", {
+	groups = def.groups,
+	on_construct = function() end,
+	after_place_node = function(pos, ...)
+		local node = minetest.get_node(pos)
+		node.name = exchange_shop.shopname
+		minetest.swap_node(pos, node)
+
+		local new_def = minetest.registered_nodes[exchange_shop.shopname]
+		if new_def.on_construct then
+			new_def.on_construct(pos)
+		end
+		new_def.after_place_node(pos, unpack({...}))
+
+	end
+})

depends.txt

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+currency?
+bitchange?
+wrench?

init.lua

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+exchange_shop = {}
+exchange_shop.storage_size = 5 * 4
+exchange_shop.shopname = "exchange_shop:shop"
+
+local modpath = minetest.get_modpath("exchange_shop")
+local has_currency = minetest.get_modpath("currency")
+local has_bitchange = minetest.get_modpath("bitchange")
+local migrate_currency = true -- TODO testing!
+local slow_migrate_currency = false
+
+
+if has_bitchange then
+	minetest.register_alias("exchange_shop:shop", "bitchange:shop")
+	exchange_shop.shopname = "bitchange:shop"
+else
+	dofile(modpath .. "/shop_functions.lua")
+	dofile(modpath .. "/shop.lua")
+end
+
+if has_currency then
+	if migrate_currency then
+		dofile(modpath .. "/currency_migrate.lua")
+	end
+	if slow_migrate_currency then
+		dofile(modpath .. "/currency_override.lua")
+	end
+end

mod.conf

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+name = exchange_shop
+optional_depends = currency, bitchange, wrench

shop.lua

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+--[[
+	Exchange Shop
+
+This code is based on the idea of Dan Duncombe's exchange shop
+	https://web.archive.org/web/20160403113102/https://forum.minetest.net/viewtopic.php?id=7002
+]]
+
+
+local shop_positions = {}
+
+local function get_exchange_shop_formspec(mode, pos, title)
+	local name = "nodemeta:"..pos.x..","..pos.y..","..pos.z
+
+	local function listring(src)
+		return "listring[".. name ..";" .. src .. "]" ..
+			"listring[current_player;main]"
+	end
+	if mode == "customer" then
+		-- customer
+		return (
+			"size[8,9;]"..
+			"label[0,0;Exchange shop]"..
+			"label[1,0.5;Owner needs:]"..
+			"list["..name..";cust_ow;1,1;2,2;]"..
+			"button[3,2.4;2,1;exchange;Exchange]"..
+			"label[5,0.5;Owner gives:]"..
+			"list["..name..";cust_og;5,1;2,2;]"..
+			"label[0.7,3.5;Ejected items:]"..
+			"label[0.7,3.8;(Remove me!)]"..
+			"list["..name..";cust_ej;3,3.5;4,1;]"..
+			"list[current_player;main;0,5;8,4;]"..
+			listring("cust_ej")
+		)
+	end
+	if mode == "owner_custm"
+			or mode == "owner_stock" then
+		-- owner
+		local formspec = (
+			"size[11,10;]"..
+			"label[0.3,0.1;Title:]"..
+			"field[1.5,0.5;3,0.5;title;;"..title.."]"..
+			"field_close_on_enter[title;false]"..
+			"button[4.1,0.2;1,0.5;set_title;Set]"..
+			"label[0,0.7;You need:]"..
+			"list["..name..";cust_ow;0,1.2;2,2;]"..
+			"label[3,0.7;You give:]"..
+			"list["..name..";cust_og;3,1.2;2,2;]"..
+			"label[0,3.5;Ejected items: (Remove me!)]"..
+			"list["..name..";custm_ej;0,4;4,1;]"..
+			"label[6,0;You are viewing:]"..
+			"label[6,0.3;(Click to switch)]"..
+			listring("custm_ej")
+		)
+
+		if mode == "owner_custm" then
+			formspec = (formspec..
+				"button[8.5,0.2;2.5,0.5;view_stock;Customers stock]"..
+				"list["..name..";custm;6,1;5,4;]"..
+				listring("custm"))
+		else
+			formspec = (formspec..
+				"button[8.5,0.2;2.5,0.5;view_custm;Your stock]"..
+				"list["..name..";stock;6,1;5,4;]"..
+				listring("stock"))
+		end
+		return (formspec..
+			"label[1,5;Use (E) + (Right click) for customer interface]"..
+			"list[current_player;main;1,6;8,4;]")
+	end
+	return ""
+end
+
+
+minetest.register_on_player_receive_fields(function(sender, formname, fields)
+	if formname ~= "exchange_shop:shop_formspec" then
+		return
+	end
+
+	local player_name = sender:get_player_name()
+	local pos = shop_positions[player_name]
+	if not pos then
+		return
+	end
+
+	if (fields.quit and fields.quit ~= "") or
+			minetest.get_node(pos).name ~= "exchange_shop:shop" then
+		shop_positions[player_name] = nil
+		return
+	end
+
+	local meta = minetest.get_meta(pos)
+	local title = meta:get_string("title")
+	local shop_owner = meta:get_string("owner")
+
+	if fields.title and exchange_shop.has_access(meta, player_name) then
+		-- Limit title length
+		fields.title = fields.title:sub(1, 80)
+		if title ~= fields.title then
+			if fields.title ~= "" then
+				meta:set_string("infotext", "'" .. fields.title
+					.. "' (owned by " .. shop_owner .. ")")
+			else
+				meta:set_string("infotext", "Exchange shop (owned by "
+					.. shop_owner ..")")
+			end
+			meta:set_string("title", minetest.formspec_escape(fields.title))
+		end
+	end
+
+	if fields.exchange then
+		local shop_inv = meta:get_inventory()
+		local player_inv = sender:get_inventory()
+		if shop_inv:is_empty("cust_ow")
+				and shop_inv:is_empty("cust_og") then
+			return
+		end
+
+		local err_msg = exchange_shop.exchange_action(player_inv, shop_inv)
+		-- Throw error message
+		if err_msg then
+			minetest.chat_send_player(player_name, minetest.colorize("#F33",
+				"Exchange shop: " .. err_msg))
+		end
+	elseif exchange_shop.has_access(meta, player_name) then
+		local mode
+		if fields.view_custm then
+			mode = "owner_custm"
+		elseif fields.view_stock then
+			mode = "owner_stock"
+		else
+			return
+		end
+		minetest.show_formspec(player_name, "exchange_shop:shop_formspec",
+			get_exchange_shop_formspec(mode, pos, title))
+	end
+end)
+
+minetest.register_node(exchange_shop.shopname, {
+	description = "Exchange Shop",
+	tiles = {
+		"shop_top.png", "shop_top.png", 
+		"shop_side.png","shop_side.png",
+		"shop_side.png", "shop_front.png"
+	},
+	paramtype2 = "facedir",
+	groups = {choppy=2, oddly_breakable_by_hand=2, 
+		tubedevice=1, tubedevice_receiver=1},
+	tube = {
+		insert_object = function(pos, node, stack, direction)
+			local meta = minetest.get_meta(pos)
+			local inv = meta:get_inventory()
+			return inv:add_item("stock", stack)
+		end,
+		can_insert = function(pos, node, stack, direction)
+			local meta = minetest.get_meta(pos)
+			local inv = meta:get_inventory()
+			return inv:room_for_item("stock", stack)
+		end,
+		input_inventory = "custm",
+		connect_sides = {left=1, right=1, back=1, top=1, bottom=1}
+	},
+	sounds = default.node_sound_wood_defaults(),
+	after_place_node = function(pos, placer)
+		local meta = minetest.get_meta(pos)
+		local owner = placer:get_player_name()
+		meta:set_string("owner", owner)
+		meta:set_string("infotext", "Exchange shop (owned by "
+			.. owner .. ")")
+	end,
+	on_construct = function(pos)
+		local meta = minetest.get_meta(pos)
+		meta:set_string("infotext", "Exchange shop (constructing)")
+		meta:set_string("owner", "")
+		local inv = meta:get_inventory()
+		inv:set_size("stock", exchange_shop.storage_size) -- needed stock for exchanges
+		inv:set_size("custm", exchange_shop.storage_size) -- stock of the customers exchanges
+		inv:set_size("custm_ej", 4) -- ejected items if shop has no inventory room
+		inv:set_size("cust_ow", 2*2) -- owner wants
+		inv:set_size("cust_og", 2*2) -- owner gives
+		inv:set_size("cust_ej", 4) -- ejected items if player has no inventory room
+	end,
+	can_dig = function(pos,player)
+		local meta = minetest.get_meta(pos)
+		local inv = meta:get_inventory()
+		if inv:is_empty("stock") and inv:is_empty("custm")
+				and inv:is_empty("cust_ow") and inv:is_empty("custm_ej")
+				and inv:is_empty("cust_og") and inv:is_empty("cust_ej") then
+			return true
+		end
+		minetest.chat_send_player(player:get_player_name(),
+			"Cannot dig exchange shop: one or multiple stocks are in use.")
+		return false
+	end,
+	on_rightclick = function(pos, node, clicker, itemstack)
+		local meta = minetest.get_meta(pos)
+		local player_name = clicker:get_player_name()
+
+		local mode = "customer"
+		if exchange_shop.has_access(meta, player_name) and
+				not clicker:get_player_control().aux1 then
+			mode = "owner_custm"
+		end
+		shop_positions[player_name] = pos
+		minetest.show_formspec(player_name, "exchange_shop:shop_formspec",
+			get_exchange_shop_formspec(mode, pos, meta:get_string("title")))
+	end,
+	allow_metadata_inventory_move = function(pos, from_list, from_index, to_list, to_index, count, player)
+		local meta = minetest.get_meta(pos)
+		if exchange_shop.has_access(meta, player:get_player_name()) then
+			return count
+		end
+		return 0
+	end,
+	allow_metadata_inventory_put = function(pos, listname, index, stack, player)
+		if player:get_player_name() == ":pipeworks" then
+			return stack:get_count()
+		end
+		if listname == "custm" then
+			minetest.chat_send_player(player:get_player_name(),
+				"Exchange shop: Please press 'Customers stock' and insert your items there.")
+			return 0
+		end
+		local meta = minetest.get_meta(pos)
+		if exchange_shop.has_access(meta, player:get_player_name())
+				and listname ~= "cust_ej"
+				and listname ~= "custm_ej" then
+			return stack:get_count()
+		end
+		return 0
+	end,
+	allow_metadata_inventory_take = function(pos, listname, index, stack, player)
+		if player:get_player_name() == ":pipeworks" then
+			return stack:get_count()
+		end
+		local meta = minetest.get_meta(pos)
+		if exchange_shop.has_access(meta, player:get_player_name())
+				or listname == "cust_ej" then
+			return stack:get_count()
+		end
+		return 0
+	end,
+})
+
+minetest.register_craft({
+	output = "exchange_shop:shop",
+	recipe = {
+		{"default:sign_wall"},
+		{"default:chest_locked"},
+	}
+})
+
+minetest.register_on_leaveplayer(function(player)
+	shop_positions[player:get_player_name()] = nil
+end)
+
+if minetest.get_modpath("wrench") and wrench then
+	local STRING = wrench.META_TYPE_STRING
+	wrench:register_node("exchange_shop:shop", {
+		lists = {"stock", "custm", "custm_ej", "cust_ow", "cust_og", "cust_ej"},
+		metas = {
+			owner = STRING,
+			infotext = STRING,
+			title = STRING,
+		},
+		owned = true
+	})
+end

shop_functions.lua

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+function exchange_shop.has_access(meta, player_name)
+	local owner = meta:get_string("owner")
+	if player_name == owner or owner == "" then
+		return true
+	end
+	local privs = minetest.get_player_privs(player_name)
+	return privs.server or privs.protection_bypass
+end
+
+
+-- Tool wear aware replacement for contains_item.
+function exchange_shop.list_contains_item(inv, listname, stack)
+	local count = stack:get_count()
+	if count == 0 then
+		return true
+	end
+
+	local list = inv:get_list(listname)
+	local name = stack:get_name()
+	local wear = stack:get_wear()
+	for _, list_stack in pairs(list) do
+		if list_stack:get_name() == name and
+		   list_stack:get_wear() <= wear then
+			if list_stack:get_count() >= count then
+				return true
+			else
+				count = count - list_stack:get_count()
+			end
+		end
+	end
+end
+
+-- Tool wear aware replacement for remove_item.
+function exchange_shop.list_remove_item(inv, listname, stack)
+	local wanted = stack:get_count()
+	if wanted == 0 then
+		return stack
+	end
+
+	local list = inv:get_list(listname)
+	local name = stack:get_name()
+	local wear = stack:get_wear()
+	local remaining = wanted
+	local removed_wear = 0
+
+	for index, list_stack in pairs(list) do
+		if list_stack:get_name() == name and
+		   list_stack:get_wear() <= wear then
+			local taken_stack = list_stack:take_item(remaining)
+			inv:set_stack(listname, index, list_stack)
+
+			removed_wear = math.max(removed_wear, taken_stack:get_wear())
+			remaining = remaining - taken_stack:get_count()
+			if remaining == 0 then
+				break
+			end
+		end
+	end
+
+	-- Todo: Also remove kebab
+	local removed_stack = ItemStack(name)
+	removed_stack:set_count(wanted - remaining)
+	removed_stack:set_wear(removed_wear)
+	return removed_stack
+end
+
+function exchange_shop.exchange_action(player_inv, shop_inv)
+	if not shop_inv:is_empty("cust_ej")
+			or not shop_inv:is_empty("custm_ej") then
+		return "One or multiple ejection fields are filled. "..
+			"Please empty them or contact the shop owner."
+	end
+	local owner_wants = shop_inv:get_list("cust_ow")
+	local owner_gives = shop_inv:get_list("cust_og")
+
+	-- Check validness of stack "owner wants"
+	for i1, item1 in pairs(owner_wants) do
+		local name1 = item1:get_name()
+		for i2, item2 in pairs(owner_wants) do
+			if name1 == "" then
+				break
+			end
+			if i1 ~= i2 and name1 == item2:get_name() then
+				return "The field 'Owner needs' can not contain multiple "..
+					"times the same items. Please contact the shop owner."
+			end
+		end
+	end
+
+	-- Check validness of stack "owner gives"
+	for i1, item1 in pairs(owner_gives) do
+		local name1 = item1:get_name()
+		for i2, item2 in pairs(owner_gives) do
+			if name1 == "" then
+				break
+			end
+			if i1 ~= i2 and name1 == item2:get_name() then
+				return "The field 'Owner gives' can not contain multiple "..
+					"times the same items. Please contact the shop owner."
+			end
+		end
+	end
+
+	-- Check for space in the shop
+	for i, item in pairs(owner_wants) do
+		if not shop_inv:room_for_item("custm", item) then
+			return "The stock in this shop is full. "..
+				"Please contact the shop owner."
+		end
+	end
+
+	local list_contains_item = exchange_shop.list_contains_item
+
+	-- Check availability of the shop's items
+	for i, item in pairs(owner_gives) do
+		if not list_contains_item(shop_inv, "stock", item) then
+			return "This shop is sold out."
+		end
+	end
+
+	-- Check for space in the player's inventory
+	for i, item in pairs(owner_gives) do
+		if not player_inv:room_for_item("main", item) then
+			return "You do not have enough space in your inventory."
+		end
+	end
+
+	-- Check availability of the player's items
+	for i, item in pairs(owner_wants) do
+		if not list_contains_item(player_inv, "main", item) then
+			return "You do not have the required items."
+		end
+	end
+
+	local list_remove_item = exchange_shop.list_remove_item
+
+	-- Conditions are ok: (try to) exchange now
+	local fully_exchanged = true
+	for i, item in pairs(owner_wants) do
+		local stack = list_remove_item(player_inv, "main", item)
+		if shop_inv:room_for_item("custm", stack) then
+			shop_inv:add_item("custm", stack)
+		else
+			-- Move to ejection field
+			shop_inv:add_item("custm_ej", stack)
+			fully_exchanged = false
+		end
+	end
+	for i, item in pairs(owner_gives) do
+		local stack = list_remove_item(shop_inv, "stock", item)
+		if player_inv:room_for_item("main", stack) then
+			player_inv:add_item("main", stack)
+		else
+			-- Move to ejection field
+			shop_inv:add_item("cust_ej", stack)
+			fully_exchanged = false
+		end
+	end
+	if not fully_exchanged then
+		return "Warning! Stacks are overflowing somewhere!"
+	end
+end