-- Define target box cleanup routine
function SelectionBoxPool.Cleanup(SelectionBox)
	SelectionBox.Adornee = nil
	SelectionBox.Visible = nil
end

function CreateSelectionBoxes(Item)
	-- Creates selection boxes for the given item

	-- Only create selection boxes if in tool mode
	if GetCore().Mode ~= 'Tool' then
		return;
	end;

	-- Ensure selection boxes don't already exist for item
	if Selection.Outlines[Item] then
		return
	end

	-- Get targetable items
	local Items = Support.FlipTable { Item }
	if not IsVisible(Item) then
		Items = Support.FlipTable(GetVisibleChildren(Item))
	end

	-- Create selection box for each targetable item
	local SelectionBoxes = {}
	for Item in pairs(Items) do

		-- Create the selection box
		local SelectionBox = SelectionBoxPool:Get()
		SelectionBox.Adornee = Item
		SelectionBox.Visible = true

		-- Register the outline
		SelectionBoxes[Item] = SelectionBox

	end

	-- Register selection boxes for this item
	Selection.Outlines[Item] = SelectionBoxes

end;

function RemoveSelectionBoxes(Item)
	-- Removes the given item's selection boxes

	-- Only proceed if outlines exist for item
	local SelectionBoxes = Selection.Outlines[Item]
	if not SelectionBoxes then
		return
	end

	-- Remove each item's outline
	for _, SelectionBox in pairs(SelectionBoxes) do
		SelectionBoxPool:Release(SelectionBox)
	end

	-- Clear list of outlines for item
	Selection.Outlines[Item] = nil

end

function Selection.RecolorOutlines(Color)
	-- Updates selection outline colors

	-- Set `Color` as the new color
	Selection.Color = Color;

	-- Recolor existing outlines
	for Outline in pairs(SelectionBoxPool.All) do
		Outline.Color = Selection.Color;
	end;

end;

function Selection.RecolorOutline(Item, Color)
	-- Updates outline colors for `Item`

	-- Make sure `Item` has outlines
	local Outlines = Selection.Outlines[Item]
	if not Outlines then
		return
	end

	-- Recolor all outlines for item
	for VisibleItem, Outline in pairs(Outlines) do
		Outline.Color = Color
	end
end

function Selection.FlashOutlines()
	-- Flashes selection outlines for emphasis

	-- Fade in from complete to normal transparency
	for Transparency = 1, 0.5, -0.1 do

		-- Update each outline
		for Outline in pairs(SelectionBoxPool.InUse) do
			Outline.Transparency = Transparency;
		end;

		-- Fade over time
		wait(0.1);

	end;

end;

function Selection.EnableMultiselectionHotkeys()
	-- Enables hotkeys for multiselecting

	-- Determine multiselection hotkeys
	local Hotkeys = Support.FlipTable { 'LeftShift', 'RightShift', 'LeftControl', 'RightControl' };

	-- Get core API
	local Core = GetCore();

	-- Listen for matching key presses
	Core.Connections.MultiselectionHotkeys = Support.AddUserInputListener('Began', 'Keyboard', false, function (Input)
		if Hotkeys[Input.KeyCode.Name] then
			Selection.Multiselecting = true;
		end;
	end);

	-- Listen for matching key releases
	Core.Connections.MultiselectingReleaseHotkeys = Support.AddUserInputListener('Ended', 'Keyboard', true, function (Input)

		-- Get currently pressed keys
		local PressedKeys = Support.GetListMembers(Support.GetListMembers(Game:GetService('UserInputService'):GetKeysPressed(), 'KeyCode'), 'Name');

		-- Continue multiselection if a hotkey is still pressed
		for _, PressedKey in pairs(PressedKeys) do
			if Hotkeys[PressedKey] then
				return;
			end;
		end;

		-- Disable multiselection if matching key not found
		Selection.Multiselecting = false;

	end);

end;

function Selection.EnableOutlines()
	-- Enables selection outlines

	-- Create outlines for each item
	for Item in pairs(Selection.ItemIndex) do
		CreateSelectionBoxes(Item)
	end
end

function Selection.HideOutlines()
	-- Hides selection outlines

	-- Remove every item's outlines
	for Item in pairs(Selection.Outlines) do
		RemoveSelectionBoxes(Item)
	end
end

function TrackSelectionChange(OldSelection)
	-- Registers a history record for a change in the selection

	-- Avoid overwriting history for selection actions
	if History.Index ~= #History.Stack then
		return;
	end;

	-- Add the history record
	History.Add({

		Before = OldSelection;
		After = Selection.Items;

		Unapply = function (HistoryRecord)
			-- Reverts this change

			-- Restore the old selection
			Selection.Replace(HistoryRecord.Before);

		end;

		Apply = function (HistoryRecord)
			-- Reapplies this change

			-- Restore the new selection
			Selection.Replace(HistoryRecord.After);

		end;
	});

end;

return Selection;