local function XPopupWindowWithSearch(anchor, title, create_children_func)
	local popup = OpenDialog("GedNestedElementsList", terminal.desktop)
	popup.OnShortcut = function(self, shortcut)
		if shortcut == "Escape" then
			popup:Close()
			return "break"
		elseif shortcut == "Down" then
			popup.idLeftList.idWin.idList:SetFocus()
		end
	end
	
	local list = popup.idLeftList.idWin.idList
	popup.idTitle:SetText(title)
	local edit = popup.idLeftList.idSearch
	local container = popup.idRightList
	
	edit.OnTextChanged = function(edit) 
		create_children_func(popup, list, container, edit:GetText())
	end
	
	edit.OnShortcut = function(edit, shortcut, source, ...)
		if shortcut == "Escape" then
			return
		elseif shortcut == "Enter" and edit:GetText() then
			local list = edit.parent.idWin.idList
			if list[1] and list[1]:IsKindOf("XTextButton") then
				list[1]:OnPress()
				return
			end
		end
		return XEdit.OnShortcut(edit, shortcut, source, ...)
	end
	
	list.OnShortcut = function(list, shortcut, source, ...)
		local relation = XShortcutToRelation[shortcut]
		if shortcut == "Down" or shortcut == "Up" or relation == "down" or relation == "up" then
			local focus = list.desktop.keyboard_focus
			local order = focus and focus:GetFocusOrder()
			if shortcut == "Down" or relation == "down" then
				focus = list:GetRelativeFocus(order or point(0, 0), "next")
			else
				focus = list:GetRelativeFocus(order or point(1000000000, 1000000000), "prev")
			end
			if focus then
				list:ScrollIntoView(focus)
				focus:SetFocus()
			end
			return "break"
		end
	end
	
	create_children_func(popup, list, container, "", "create")
	popup:SetModal(true)
	edit:SetFocus()
end

local function XPopupListWithSearch(anchor, create_children_func)
	local popup = XPopup:new({}, terminal.desktop)
	popup.OnKillFocus = function(self)
		if self.window_state == "open" then
			popup:Close()
		end
	end
	popup.OnShortcut = function(self, shortcut)
		if shortcut == "Escape" then
			popup:Close()
			return "break"
		elseif shortcut == "Down" then
			popup.idPopupList:SetFocus()
		end
	end
	local list = XPopupList:new({
		Id = "idPopupList",
		AutoFocus = false,
		Dock = "bottom",
		MaxItems = 10,
		BorderWidth = 0,
		min_width = false,
		OnShortcut = function(list, shortcut, source, ...) -- let the popup handle escapes
			if shortcut == "Escape" then
				return
			end
			return XPopupList.OnShortcut(list, shortcut, source, ...)
		end,
		Measure = function(self, max_width, max_height) -- do not fold the search popup after items have been filtered
			local _, height
			if not self.min_width then
				self.min_width, height = XPopupList.Measure(self, max_width, max_height)
			else
				_, height =  XPopupList.Measure(self, max_width, max_height)
			end
			return self.min_width, height
		end,
		OnKillFocus = function(self, new_focus) end,
	}, popup)
	
	local edit = XEdit:new({
		Dock = "top",
		Id = "idSearch",
		Margins = box(2, 2, 2, 2),
		OnTextChanged = function(edit) 
			create_children_func(popup, list.idContainer, edit:GetText())
		end,
		OnShortcut = function(list, shortcut, source, ...)
			if shortcut == "Escape" then
				return
			end
			return XEdit.OnShortcut(list, shortcut, source, ...)
		end,
	}, popup)
	
	popup:SetAnchor(anchor.box)
	popup:SetAnchorType("drop-right")
	popup:SetScaleModifier(anchor.scale)
	popup:SetOutsideScale(point(1000, 1000))
	popup:Open()
	
	create_children_func(popup, list.idContainer, "")
	if #list.idContainer > 5 then
		edit:SetFocus()
	else
		edit:delete()
		popup:SetFocus()
	end
end

function FillUsageSegments(list, segments)
	local sum = 0
	local sorted = {}
	for _, item in ipairs(list) do
		if item.use_count then
			sum = sum + item.use_count
			table.insert(sorted, item)
		end
	end
	
	table.sortby_field(sorted, "use_count")
	
	local tally, target, segment = 0, 0, 0
	for _, item in ipairs(sorted) do
		tally = tally + item.use_count
		if tally > target then
			segment = segment + 1
			target = MulDivRound(sum, segment, segments)
		end
		item.usage_segment = segment
	end
	return sum
end

function GedOpenCreateItemPopup(panel, title, items, button, create_callback)
	if items and #items == 1 then
		create_callback(items[1].value)
		return
	end
	
	local defined = 0
	for i = 1, #items do
		local cat = items[i].category
		if cat and cat ~= "" and cat ~= "General" then
			defined = defined + 1
		end
	end
	if defined >= 3 then
		XPopupWindowWithSearch(button, title, function(popup, list, container, search_text, create)
			local least_dim = GetDarkModeSetting() and 255 or 32
			local most_dim = GetDarkModeSetting() and 128 or 140
			local modifiable_zone = most_dim - least_dim
			
			local suffixes = {
				"",
				"<right>•",
				"<right>••",
				"<right>•••",
			}
			local uses_total = FillUsageSegments(items, 3)
			
			local create_button = function(idx, item, container, popup, right)
				local entry = XTextButton:new({ UseXTextControl = true }, container)
				entry:SetFocusOrder(point(1, idx))
				entry:SetLayoutMethod("Box")
				entry.idLabel:SetHAlign("stretch")
				if right and search_text == "" and uses_total ~= 0 then
					local gamma = most_dim - MulDivRound(modifiable_zone, item.usage_segment, 3)
					entry:SetText(string.format("<color %d %d %d>%s%s", gamma, gamma, gamma, item.text, suffixes[item.usage_segment + 1]))
				elseif right and item.usage_segment then
					entry:SetText(item.text .. suffixes[item.usage_segment + 1])
				else
					entry:SetText(item.text)
				end
				entry.OnPress = function(entry)
					button:SetFocus()
					create_callback(item.value)
					button:SetFocus(false)
					if popup.window_state ~= "destroying" then
						popup:Close()
					end
				end
				
				if item.documentation or item.use_count then
					local texts = {}
					table.insert(texts, item.documentation or string.format("<style GedTitle><center>%s</style>", item.value))
					if item.use_count_in_preset then
						table.insert(texts, item.use_count and string.format("<style GedSmall>Used %d times in %s presets.", item.use_count, item.use_count_in_preset))
					end
					entry:SetRolloverText(table.concat(texts, "\n\n"))
					entry:SetRolloverTemplate("GedToolbarRollover")
					entry:SetRolloverAnchor("bottom")
				end
				
				return entry
			end
			
			local categories_list = {}
			local currently_searching = false
			
			-- left side
			list:DeleteChildren()
			local to_find = string.lower(search_text)
			for i, item in ipairs(items) do
				if string.lower(item.text):find(to_find, 1, true) then
					create_button(i, item, list, popup)
				end
				local category = item.category ~= "" and item.category or "General"
				local list = categories_list[category] or {}
				list[#list + 1] = item
				categories_list[category] = list
			end
			if #list == 0 then
				XText:new({}, list):SetText("No items to choose from.")
			end
			
			-- right side
			local categories_list_indexed = {}
			for name, list in sorted_pairs(categories_list) do
				categories_list_indexed[#categories_list_indexed + 1] = { category = name, elements = list }
			end		
			
			for idx, info in ipairs(categories_list_indexed) do
				local win
				if not create then
					for _, pane in ipairs(container) do
						local title = pane:ResolveId("idCategoryTitle")
						if title and title:GetText() == info.category then
							win = pane
							break
						end
					end
				end
				if not win then
					win = XTemplateSpawn("GedNestedElementsCategory", container)
					win:ResolveId("idCategoryTitle"):SetText(info.category)
				end
				
				local sublist = win:ResolveId("idCategoryElements")
				if sublist then
					sublist:DeleteChildren()
					local items = info.elements
					for i, item in ipairs(items) do
						local entry = create_button(i, item, sublist, popup, "right")
						entry:SetEnabled(not not string.lower(item.text):find(to_find, 1, true))
					end
				end
			end
			panel.app:UpdateChildrenDarkMode(popup)
		end)
	else
		XPopupListWithSearch(button, function(popup, container, search_text)
			container:DeleteChildren()
			local to_find = string.lower(search_text)
			for i, item in ipairs(items) do
				if string.lower(item.text):find(to_find, 1, true) then
					local entry = XTemplateSpawn("XComboListItem", container, false)
					entry:SetFocusOrder(point(1, i))
					entry:SetFontProps(XCombo)
					entry:SetText(item.text)
					entry:SetMinHeight(entry:GetFontHeight())
					entry.OnPress = function(entry)
						button:SetFocus()
						create_callback(item.value)
						button:SetFocus(false)
						if popup.window_state ~= "destroying" then
							popup:Close()
						end
					end
				end
			end
			if #container == 0 then
				XText:new({}, container):SetText("No items to choose from.")
			end
			panel.app:UpdateChildrenDarkMode(popup)
		end)
	end
end