function constrain(val, low, high)
	if val > high then 
		return high
	elseif val < low then 
		return low
	else 
		return val
	end
end

function map(value, inMin, inMax, outMin, outMax)
	local inPercent = value / (inMax - inMin)
	return (outMax - outMin) * (inPercent) + outMin
end

function lerp(a, b, amount)
	return (1 - amount) * a + (amount * b)
end

-- Write to the project tree itself (not LÖVE's save dir) so edits persist in the
-- repo during dev. Uses plain io.open against love.filesystem.getSource(), which
-- is the absolute project path when running `love .` from a folder. Falls back to
-- love.filesystem.write (save dir) if the source is a packaged .love archive.
function writeToSource(relPath, contents)
	local base = love.filesystem.getSource()
	local file = io.open(base .. "/" .. relPath, "w")
	if file then
		file:write(contents)
		file:close()
		return true
	end
	return love.filesystem.write(relPath, contents)
end

-- The editor occasionally needs to rename a source level after it has written
-- the replacement.  Keep that operation alongside writeToSource so packaged
-- games still fall back to LÖVE's writable save directory.
function removeFromSource(relPath)
	local base = love.filesystem.getSource()
	local path = base .. "/" .. relPath
	local file = io.open(path, "r")
	if file then
		file:close()
		return os.remove(path)
	end
	return love.filesystem.remove(relPath)
end

-- Runtime saves live in LÖVE's write directory.  This deliberately uses only
-- love.filesystem operations: they cannot delete files from the source tree.
function clearRuntimeSaveData()
	local removed = 0
	local function removeTree(path)
		if love.filesystem.isDirectory(path) then
			for _, child in ipairs(love.filesystem.getDirectoryItems(path)) do
				removeTree(path .. "/" .. child)
			end
		end
		if love.filesystem.remove(path) then removed = removed + 1 end
	end

	-- These are the only files this game writes through love.filesystem: room
	-- autosaves and the generated asset cache.  Source levels are read-only to
	-- this API and cannot be removed here.
	removeTree("rooms")
	if love.filesystem.remove("assets.prop") then removed = removed + 1 end
	return removed
end

-- Read from the project tree directly so a stale copy in LÖVE's save directory
-- can't shadow the real source file. Falls back to love.filesystem for a
-- packaged .love.
function readFromSource(relPath)
	local base = love.filesystem.getSource()
	local file = io.open(base .. "/" .. relPath, "r")
	if file then
		local contents = file:read("*a")
		file:close()
		return contents
	end
	return love.filesystem.read(relPath)
end

-- Cached image loader. The filesystem is the source of truth for art, so every
-- sprite is loaded on demand by path (deduped here) rather than from a
-- hand-maintained central table.
local spriteCache = {}
function loadSprite(path)
	if not spriteCache[path] then
		spriteCache[path] = love.graphics.newImage(path)
	end
	return spriteCache[path]
end

function cellShapeFromBox(box)
	local cells = {}
	for i = 1, box.w do
		for j = 1, box.h do
			table.insert(cells, {x = i, y = j})
		end
	end
	return cells
end

-- Which 16x16 cells of a sprite are non-empty, for multi-cell collision shapes.
function getCellsFromSprite(sprite)
	local w, h = sprite:getWidth(), sprite:getHeight()
	local box = {w = w / 16, h = h / 16}
	local boxCells = cellShapeFromBox(box)
	if box.w < 1 or box.h < 1 then
		return boxCells
	end

	local img = sprite:getData()
	local cellsToRemove = {}

	for _, cell in pairs(boxCells) do
		local startPixel = {x = (cell.x - 1) * 16, y = (cell.y - 1) * 16}
		local endPixel = {x = (cell.x * 16) - 1, y = (cell.y * 16) - 1}
		local empty = true

		for i = startPixel.x, endPixel.x do
			for j = startPixel.y, endPixel.y do
				local r, g, b, a = img:getPixel(i, j)
				if a > 0 and (r > 0 or g > 0 or b > 0) then
					empty = false
				end
			end
		end

		if empty then
			cellsToRemove[cell] = cell
		end
	end

	local i = 1
	while i <= #boxCells do
		if boxCells[i] == cellsToRemove[boxCells[i]] then
			table.remove(boxCells, i)
		else
			i = i + 1
		end
	end

	return boxCells
end