'use strict';

const PA_PER_MBAR = 100;
const SECONDS_PER_HOUR = 3600;

function withinTolerance(observed, expected, absTol, relTol) {
  if (!Number.isFinite(observed) || !Number.isFinite(expected)) return false;
  const absErr = Math.abs(observed - expected);
  if (absErr <= absTol) return true;
  if (Math.abs(expected) > 0) return absErr / Math.abs(expected) <= relTol;
  return false;
}

function assertMassBalance({ inflowKgPerS, outflowKgPerS, accumulationKgPerS = 0, label = 'mass', absTol = 1e-6, relTol = 1e-3 } = {}) {
  const expected = inflowKgPerS - accumulationKgPerS;
  const ok = withinTolerance(outflowKgPerS, expected, absTol, relTol);
  return {
    ok,
    label,
    inflowKgPerS,
    outflowKgPerS,
    accumulationKgPerS,
    residualKgPerS: inflowKgPerS - outflowKgPerS - accumulationKgPerS,
    relErr: expected === 0 ? null : (outflowKgPerS - expected) / expected,
  };
}

function assertHydraulicBalance({ headerSuctionPa, headerDischargePa, pumpHeadPa, frictionPa = 0, staticHeadPa = 0, label = 'hydraulic', absTol = 50, relTol = 1e-3 } = {}) {
  const lhs = headerDischargePa - headerSuctionPa;
  const rhs = pumpHeadPa - frictionPa - staticHeadPa;
  const ok = withinTolerance(lhs, rhs, absTol, relTol);
  return {
    ok,
    label,
    lhsPa: lhs,
    rhsPa: rhs,
    residualPa: lhs - rhs,
    residualMbar: (lhs - rhs) / PA_PER_MBAR,
  };
}

function assertHydraulicPower({ flowM3PerS, headPa, shaftPowerW, efficiency, label = 'hydraulic-power', absTol = 1, relTol = 5e-3 } = {}) {
  if (!Number.isFinite(efficiency) || efficiency <= 0 || efficiency > 1.0) {
    return { ok: false, label, msg: `efficiency=${efficiency} outside (0,1]` };
  }
  const expectedShaftPowerW = (flowM3PerS * headPa) / efficiency;
  const ok = withinTolerance(shaftPowerW, expectedShaftPowerW, absTol, relTol);
  return {
    ok,
    label,
    flowM3PerS,
    headPa,
    efficiency,
    expectedShaftPowerW,
    observedShaftPowerW: shaftPowerW,
    residualW: shaftPowerW - expectedShaftPowerW,
  };
}

function assertEnergyBalance({ heatInW = 0, workInW = 0, heatOutW = 0, workOutW = 0, accumulationW = 0, label = 'energy', absTol = 1, relTol = 1e-3 } = {}) {
  const inputs = heatInW + workInW;
  const outputs = heatOutW + workOutW + accumulationW;
  const ok = withinTolerance(inputs, outputs, absTol, relTol);
  return {
    ok,
    label,
    inputsW: inputs,
    outputsW: outputs,
    residualW: inputs - outputs,
  };
}

function assertOxygenTransfer({ klaPerS, csMgPerL, cMgPerL, otrKgPerS, volumeM3, label = 'OTR', absTol = 1e-4, relTol = 5e-3 } = {}) {
  if (!Number.isFinite(klaPerS) || klaPerS < 0) return { ok: false, label, msg: `KLa=${klaPerS} invalid` };
  if (!Number.isFinite(volumeM3) || volumeM3 <= 0) return { ok: false, label, msg: `volume=${volumeM3} invalid` };
  const driveMgPerL = csMgPerL - cMgPerL;
  const expectedKgPerS = klaPerS * driveMgPerL * volumeM3 * 1e-3 / SECONDS_PER_HOUR * SECONDS_PER_HOUR / 1000;
  const expectedKgPerS_corrected = klaPerS * driveMgPerL * volumeM3 / 1e6;
  const ok = withinTolerance(otrKgPerS, expectedKgPerS_corrected, absTol, relTol);
  return {
    ok,
    label,
    klaPerS,
    csMgPerL,
    cMgPerL,
    driveMgPerL,
    volumeM3,
    expectedKgPerS: expectedKgPerS_corrected,
    observedKgPerS: otrKgPerS,
    residualKgPerS: otrKgPerS - expectedKgPerS_corrected,
  };
}

function reportToString(r) {
  if (r.ok) return `OK   ${r.label}`;
  const fields = Object.entries(r)
    .filter(([k]) => !['ok', 'label'].includes(k))
    .map(([k, v]) => `${k}=${typeof v === 'number' ? v.toExponential(3) : v}`)
    .join(' ');
  return `FAIL ${r.label}  ${fields}`;
}

module.exports = {
  assertMassBalance,
  assertHydraulicBalance,
  assertHydraulicPower,
  assertEnergyBalance,
  assertOxygenTransfer,
  reportToString,
  PA_PER_MBAR,
};