[WIP] Add item picker

WARNING: Do not revert back to the previous commits after this one!
Doing so will give away items for free (as players will be able to take
out any items that they prevously selected with the item picker)

If you want to be able to revert then maybe it'd be better to make the
existing code store a copy of the item in its own inventory first (like
mese tubes in pipeworks).

The GUI currently uses flow because I'm lazy, if more performance is
needed then I can probably convert it to a formspec.

mod.conf

@@ -1,4 +1,4 @@
 name = exchange_shop
 description = An improved exchange shop
-depends = default
+depends = default, flow
 optional_depends = mesecons_mvps

shop.lua

@@ -9,6 +9,7 @@ local S = exchange_shop.S
 local shop_positions = {}
 
 local tconcat = table.concat
+local lower = utf8.lower
 
 local function get_exchange_shop_formspec(mode, pos, meta)
 	local name = "nodemeta:" .. pos.x .. "," .. pos.y .. "," .. pos.z
@@ -67,7 +68,20 @@ local function get_exchange_shop_formspec(mode, pos, meta)
 			main_image ..
 			"list[current_player;main;0," .. inv_pos .. ";9,4;]"
 
-		return formspec
+			return formspec
+	end
+
+	local function make_slots_btns(x, y, w, h, list, label)
+		local fs = {make_slots(x, y, w, h, list, label)}
+		local i = 0
+		for y2 = 1, h do
+			for x2 = 1, w do
+				i = i + 1
+				fs[#fs + 1] = ("image_button[%s,%s;1.2,1.2;;%s_%s;;false;false]"):format(x + x2 - 1.1, y + y2 - 1.1, list, i)
+			end
+		end
+		print(dump(fs))
+		return tconcat(fs)
 	end
 
 	if mode == "owner_custm" or mode == "owner_stock" then
@@ -75,12 +89,12 @@ local function get_exchange_shop_formspec(mode, pos, meta)
 
 		-- owner
 		local formspec = (
-			"size[10,10]" ..
+			"formspec_version[3]size[10,10]real_coordinates[false]" ..
 			"item_image[0,-0.1;1,1;".. exchange_shop.shopname .. "]" ..
 			"label[0.9,0.1;" .. S("Exchange Shop") .. "]" ..
 			default.gui_close_btn("9.3,-0.1") ..
-			make_slots(0.1, 2, 2, 2, "cust_ow", S("You need:")) ..
+			make_slots_btns(0.1, 2, 2, 2, "cust_ow", S("You need:")) ..
-			make_slots(2.6, 2, 2, 2, "cust_og", S("You give:")) ..
+			make_slots_btns(2.6, 2, 2, 2, "cust_og", S("You give:")) ..
 			"label[5,0.4;" .. S("Current stock:") .. "]"
 		)
 
@@ -140,6 +154,178 @@ local function get_exchange_shop_formspec(mode, pos, meta)
 end
 
 
+local function shop_valid(pos, player)
+	return minetest.get_node(pos).name == exchange_shop.shopname and
+	not minetest.is_protected(pos, player:get_player_name())
+end
+
+-- TODO: Maybe not use flow
+local function go_back(player, ctx)
+	if shop_valid(ctx.pos, player) then
+		local name = player:get_player_name()
+		shop_positions[name] = ctx.pos
+		minetest.show_formspec(name, "exchange_shop:shop_formspec",
+			get_exchange_shop_formspec("owner_custm", ctx.pos))
+	end
+end
+
+local items_cache = {}
+minetest.after(0, function()
+	for item, def in pairs(minetest.registered_items) do
+		if (not def.groups or (def.groups.not_in_creative_inventory ~= 1 and
+				def.groups.stairs ~= 1)) and def.description ~= "" then
+			items_cache[#items_cache + 1] = item
+		end
+	end
+
+	table.sort(items_cache)
+end)
+
+local function matches_search(query, description, lang)
+	return query == "" or
+		lower(minetest.get_translated_string(lang, description)):find(query, 1, true)
+end
+
+local gui = flow.widgets
+local item_picker = flow.make_gui(function(player, ctx)
+	local rows = {name='items', w = 11.8, h = 5.8, custom_scrollbar = {
+		w = 0.9,
+		scrollbar_bg = "inventory_creative_scrollbar_bg.png",
+		slider = "inventory_creative_slider.png",
+		arrow_up = "inventory_creative_arrow_up.png",
+		arrow_down = "inventory_creative_arrow_down.png",
+	}}
+
+	local query = ctx.form.Dsearch and lower(ctx.form.Dsearch) or ""
+
+	-- Reset items scrollbar
+	if ctx.query ~= query then
+		ctx.form["_scrollbar-items"] = 0
+		ctx.query = query
+	end
+
+	local name = player:get_player_name()
+	local info = minetest.get_player_information(name)
+	local lang = info and info.lang_code or ""
+
+	local row = {}
+	for _, item in ipairs(items_cache) do
+		local description = minetest.registered_items[item].description
+		if matches_search(query, description, lang) then
+			if #row >= 10 then
+				rows[#rows + 1] = gui.HBox(row)
+				row = {}
+			end
+			row[#row + 1] = gui.ItemImageButton{
+				w = 1, h = 1,
+				item_name = item,
+				on_event = function(p, c)
+					if c.item ~= item or c.form.amount ~= "1" then
+						c.item = item
+						c.desc = description or item
+						c.form.amount = "1"
+						return true
+					end
+				end,
+			}
+		end
+	end
+	if #rows > 0 or #row > 0 then
+		rows[#rows + 1] = gui.HBox(row)
+	else
+		rows[#rows + 1] = gui.Label{label = S("No items found.")}
+	end
+
+	local item_preview
+
+	return gui.VBox{
+		gui.HBox{
+			gui.Style{selectors = {"back"}, props = {border = false}},
+			gui.ItemImageButton{
+				item_name = exchange_shop.shopname, w = 1, h = 1,
+				on_event = go_back, name = "back",
+			},
+			gui.Label{label = S("Select item"), align_h = "left", expand = true},
+
+			-- Search box
+			gui.HBox{
+				align_v = "centre",
+				bgimg = "inventory_search_bg9.png",
+				bgimg_middle = 25,
+				spacing = 0,
+				gui.Spacer{expand = false, padding = 0.06},
+				gui.Style{selectors = {"Dsearch"}, props = {border = false, bgcolor = "transparent"}},
+				gui.Field{name = "Dsearch", w = 3, h = 0.7},
+				gui.ImageButton{
+					w = 0.7, h = 0.7, drawborder = false, padding = 0.05,
+					texture_name = "inventory_search.png",
+				},
+				gui.ImageButton{
+					w = 0.7, h = 0.7, drawborder = false, padding = 0.05,
+					texture_name = "inventory_search_clear.png",
+					on_event = function(_, c)
+						if c.form.Dsearch ~= "" then
+							c.form.Dsearch = ""
+							return true
+						end
+					end
+				},
+			}
+		},
+		gui.StyleType{
+			selectors = {"item_image_button"},
+			props = {
+				bgimg = "formspec_cell.png",
+				bgimg_hovered = "formspec_cell.png^[brighten",
+				border = false,
+			}
+		},
+		gui.ScrollableVBox(rows),
+		gui.HBox{
+			gui.ItemImage{w = 1, h = 1, item_name = ctx.item},
+			gui.Label{
+				label = ctx.desc and ctx.item ~= "" and
+					S("Selected item: @1", ctx.desc) or
+					S("No item selected")
+			},
+		},
+		gui.HBox{
+			gui.Field{name = "amount", label = S("Amount"), default = "1"},
+			gui.HBox{
+				expand = true, align_h = "end", align_v = "end",
+				gui.Button{
+					label = S("Clear"),
+					w = 3.5,
+					on_event = function(p, c)
+						c.item = ""
+						c.form.amount = "0"
+						return true
+					end,
+				},
+				gui.Button{
+					label = S("Save"),
+					w = 3.5,
+					on_event = function(p, c)
+						if shop_valid(c.pos, p) then
+							local item = ItemStack(c.item)
+							local amount = tonumber(c.form.amount)
+							if amount and amount == amount and amount >= 1 then
+								item:set_count(math.min(amount, item:get_stack_max()))
+							end
+							shop_positions[name] = c.pos
+							local meta = minetest.get_meta(c.pos)
+							meta:get_inventory():set_stack(c.list, c.idx, item)
+							minetest.show_formspec(name, "exchange_shop:shop_formspec",
+								get_exchange_shop_formspec("owner_custm", c.pos, meta))
+						end
+					end,
+				},
+			},
+		},
+	}
+end)
+
+
 minetest.register_on_player_receive_fields(function(sender, formname, fields)
 	if formname ~= "exchange_shop:shop_formspec" then
 		return
@@ -183,6 +369,23 @@ minetest.register_on_player_receive_fields(function(sender, formname, fields)
 		end
 		minetest.show_formspec(player_name, "exchange_shop:shop_formspec",
 			get_exchange_shop_formspec(mode, pos, meta))
+	else
+		for field in pairs(fields) do
+			local list, idx = field:match("(cust_o[wg])_([1-4])")
+			if list then
+				idx = tonumber(idx)
+				local stack = minetest.get_meta(pos):get_inventory():get_stack(list, idx)
+				item_picker:show(sender, {
+					pos = pos,
+					list = list,
+					idx = idx,
+					item = stack:get_name(),
+					desc = stack:get_short_description(),
+					form = {amount = stack:get_count()}
+				})
+				return
+			end
+		end
 	end
 end)
 
@@ -243,7 +446,11 @@ minetest.register_node(exchange_shop.shopname, {
 			get_exchange_shop_formspec(mode, pos, meta))
 	end,
 
-	allow_metadata_inventory_move = function(pos, _, _, _, _, count, player)
+	allow_metadata_inventory_move = function(pos, from_list, to_list, _, _, count, player)
+		if from_list:sub(1, 6) == "cust_o" or to_list:sub(1, 6) == "cust_o" then
+			return 0
+		end
+
 		local player_name = player:get_player_name()
 		return not minetest.is_protected(pos, player_name) and count or 0
 	end,
@@ -257,15 +464,19 @@ minetest.register_node(exchange_shop.shopname, {
 			return 0
 		end
 		if not minetest.is_protected(pos, player_name)
-				and listname ~= "custm_ej" then
+				and listname ~= "custm_ej" and listname:sub(1, 6) ~= "cust_o" then
 			return stack:get_count()
 		end
 		return 0
 	end,
 
-	allow_metadata_inventory_take = function(pos, _, _, stack, player)
+	allow_metadata_inventory_take = function(pos, listname, _, stack, player)
 		local player_name = player:get_player_name()
-		return not minetest.is_protected(pos, player_name) and stack:get_count() or 0
+		if minetest.is_protected(pos, player_name) or
+				listname:sub(1, 6) == "cust_o" then
+			return 0
+		end
+		return stack:get_count()
 	end
 })