/**
 * Resolves the working pressure for prediction and pushes it onto
 * predictFlow/predictPower/predictCtrl.fDimension. After every push the
 * CoG, efficiency, and distance-from-BEP are recomputed so downstream
 * state stays consistent — exactly what the pre-refactor
 * getMeasuredPressure() did.
 */

const eff = require('../prediction/efficiencyMath');

function getMeasuredPressure(host) {
  if (!host.hasCurve || !host.predictFlow || !host.predictPower || !host.predictCtrl) {
    host.logger.error('No valid curve available to calculate prediction using last known pressure');
    return 0;
  }
  const up = host._getPreferredPressureValue('upstream');
  const dn = host._getPreferredPressureValue('downstream');

  const applyDiff = (diff) => {
    host.predictFlow.fDimension = diff;
    host.predictPower.fDimension = diff;
    host.predictCtrl.fDimension = diff;
    const { cog, minEfficiency } = eff.calcCog(host);
    const efficiency = eff.calcEfficiency(host, host.predictPower.outputY, host.predictFlow.outputY, 'predicted');
    eff.calcDistanceBEP(host, efficiency, cog, minEfficiency);
  };

  if (up != null && dn != null) {
    const diff = dn - up;
    host.logger.debug(`Pressure differential: ${diff}`);
    applyDiff(diff);
    return diff;
  }
  if (dn != null) {
    host.logger.warn(`Using downstream pressure only for prediction: ${dn}. Prediction accuracy is degraded; inject upstream pressure too.`);
    applyDiff(dn);
    return dn;
  }
  if (up != null) {
    host.logger.warn(`Using upstream pressure only for prediction: ${up}. Prediction accuracy is degraded; inject downstream pressure too.`);
    applyDiff(up);
    return up;
  }
  host.logger.error('No valid pressure measurements available to calculate prediction using last known pressure');
  applyDiff(0);
  const fu = host.unitPolicy.canonical.flow;
  host.measurements.type('flow').variant('predicted').position('max').value(host.predictFlow.currentFxyYMax, Date.now(), fu);
  host.measurements.type('flow').variant('predicted').position('min').value(host.predictFlow.currentFxyYMin, Date.now(), fu);
  return 0;
}

module.exports = { getMeasuredPressure };