// derived from https://sustainablewebdesign.org/estimating-digital-emissions/

const GRID = 494; // in gCO2e/kWh

// operational energy intensity (kWh/GB)
const OP = { dc: 0.055, net: 0.059, ud: 0.08 };

// embodied energy intensity (kWh/GB)
const EM = { dc: 0.012, net: 0.013, ud: 0.081 };

// this function uses some defaults from the spec.
// green hosting factor is prob the most important 
// one to change here
function estimateEmissions(
	bytes: number,
	{
		greenHostingFactor = 1,
		returnVisitorRatio = 0,
		dataCacheRatio = 0.02,
	} = {},
) {
	const newVisitorRatio = 1 - returnVisitorRatio;
	const gb = bytes / 1e9;

	// operational emissions data centers
	const OPDC = gb * OP.dc * GRID * (1 - greenHostingFactor);

	// embodied emissions data centers
	const EMDC = gb * EM.dc * GRID;

	// operational emissions networks
	const OPN = gb * OP.net * GRID;

	// embodied emissions networks
	const EMN = gb * EM.net * GRID;

	// operational emissions user devices
	const OPUD = gb * OP.ud * GRID;

	// embodied emissions user devices
	const EMUD = gb * EM.ud * GRID;

	const perVisit = OPDC + EMDC + OPN + EMN + OPUD + EMUD;

	return (
		perVisit * newVisitorRatio +
		perVisit * returnVisitorRatio * (1 - dataCacheRatio)
	);
}