-- Developer-only CPU sampler. It is inert until F9 is pressed.
--
-- On stop it writes `chroma-solstice.folded` in LÖVE's save directory. The
-- file uses Brendan Gregg's folded-stack format and can be given directly to
-- FlameGraph's flamegraph.pl.
PerfProfiler = {
	active = false,
	samples = {},
	status = "F9: start CPU profile",
}

local ok, profile = pcall(require, "jit.profile")
PerfProfiler.available = ok
if not ok then
	PerfProfiler.status = "LuaJIT sampler unavailable"
end

local function sample(thread, count, vmstate)
	-- Negative depth produces caller -> callee order, which is what folded
	-- flamegraphs expect. Function-level samples keep the output compact.
	local stack = profile.dumpstack(thread, "pF;", -64):gsub(";$", "")
	if stack ~= "" then
		PerfProfiler.samples[stack] = (PerfProfiler.samples[stack] or 0) + count
	end
end

function PerfProfiler:toggle()
	if not self.available then return false end
	if not self.active then
		self.samples = {}
		profile.start("fi2", sample)
		self.active = true
		self.status = "CPU profile recording (F9 to write)"
		return true
	end

	profile.stop()
	self.active = false
	local lines, sampleCount = {}, 0
	for stack, count in pairs(self.samples) do
		table.insert(lines, stack .. " " .. count)
		sampleCount = sampleCount + count
	end
	table.sort(lines)
	local path = "chroma-solstice.folded"
	local saved = love.filesystem.write(path, table.concat(lines, "\n") .. "\n")
	local directory = love.filesystem.getSaveDirectory()
	self.status = saved and ("CPU profile saved (" .. sampleCount .. " samples); see terminal")
		or "Could not write CPU profile"
	if saved then print("CPU profile: " .. directory .. "/" .. path) else print(self.status) end
	return saved
end

function PerfProfiler:draw()
	if not self.active and self.status == "F9: start CPU profile" then return end
	love.graphics.setColor(self.active and 1 or 0.6, self.active and 0.75 or 1, self.active and 0.2 or 0.6, 1)
	love.graphics.print(self.active and "PROFILING: F9 to save flamegraph data" or self.status, 10, 28)
	love.graphics.setColor(1, 1, 1, 1)
end