/**
 * Read-only snapshots of the active machine curves and the centre-of-gravity
 * statistics. These back the rotatingMachine admin endpoints used by the
 * editor (`/rotatingMachine/working-curves`, `/rotatingMachine/cog`).
 *
 * Both functions accept a single `predictors` argument — an object describing
 * the current curve state. By taking everything via that one parameter the
 * helpers stay pure and trivially testable with a plain fixture; the host
 * just passes itself (or a slim adapter) in.
 *
 * Expected shape of `predictors`:
 * {
 *   hasCurve: boolean,
 *   predictFlow, predictPower,        // generalFunctions/predict instances
 *   getCurrentCurves(): { powerCurve, flowCurve },
 *   calcCog(): { cog, cogIndex, NCog, minEfficiency },
 *   cog, cogIndex, NCog,
 *   minEfficiency,
 *   currentEfficiencyCurve,
 *   absDistFromPeak, relDistFromPeak,
 * }
 */

const NO_CURVE_ERROR = 'No curve data available';

function showCoG(predictors) {
  if (!predictors || !predictors.hasCurve) {
    return { error: NO_CURVE_ERROR, cog: 0, NCog: 0, cogIndex: 0 };
  }
  const { cog, cogIndex, NCog, minEfficiency } = predictors.calcCog();
  return {
    cog,
    cogIndex,
    NCog,
    NCogPercent: Math.round(NCog * 100 * 100) / 100,
    minEfficiency,
    currentEfficiencyCurve: predictors.currentEfficiencyCurve,
    absDistFromPeak: predictors.absDistFromPeak,
    relDistFromPeak: predictors.relDistFromPeak,
  };
}

function showWorkingCurves(predictors) {
  if (!predictors || !predictors.hasCurve) {
    return { error: NO_CURVE_ERROR };
  }
  const { powerCurve, flowCurve } = predictors.getCurrentCurves();
  return {
    powerCurve,
    flowCurve,
    cog: predictors.cog,
    cogIndex: predictors.cogIndex,
    NCog: predictors.NCog,
    minEfficiency: predictors.minEfficiency,
    currentEfficiencyCurve: predictors.currentEfficiencyCurve,
    absDistFromPeak: predictors.absDistFromPeak,
    relDistFromPeak: predictors.relDistFromPeak,
  };
}

module.exports = { showWorkingCurves, showCoG };