/**
 * Injectable fault profiles.
 *
 * Each profile turns "time since injection" into a set of physics modifiers that
 * stations.js and line.js consume. Faults are progressive where a real fault
 * would be progressive - the bearing does not fail the instant you press the
 * button, it degrades, which is the whole point of showing trend extrapolation.
 */

export const FAULT_PROFILES = [
  {
    id: 'bearing-degradation',
    station: 'CNC-02',
    label: 'CNC-02 bearing degradation',
    short: 'Bearing wear',
    severity: 'major',
    headline: true,
    description:
      'Spindle bearing begins to spall. Vibration rises exponentially, spindle load creeps up, and out-of-tolerance parts start reaching inspection.',
  },
  {
    id: 'oven-burner',
    station: 'OVN-03',
    label: 'OVN-03 zone 2 burner fault',
    short: 'Burner fault',
    severity: 'major',
    description:
      'Zone 2 loses roughly 40% of its heating capacity. The controller saturates trying to hold setpoint, the cure runs cold, and quality falls downstream.',
  },
  {
    id: 'packer-jam',
    station: 'PKG-05',
    label: 'PKG-05 film jam',
    short: 'Film jam',
    severity: 'critical',
    description:
      'Film binds then tears, stopping the packer. Work in progress backs up through the line and upstream stations block.',
  },
  {
    id: 'sensor-dropout',
    station: 'INS-04',
    label: 'INS-04 sensor dropout',
    short: 'Sensor dropout',
    severity: 'minor',
    description:
      'The inspection station stops reporting. Values go stale rather than to zero, which is what a real dropout looks like and what a twin has to handle honestly.',
  },
];

export function faultProfile(id) {
  return FAULT_PROFILES.find((f) => f.id === id);
}

/** Time constant for the bearing ramp, in simulated seconds. */
const BEARING_TAU = 420;
const BEARING_GAIN = 0.35;
const BEARING_CAP = 3.2;

/**
 * Collapse the set of active faults into physics modifiers.
 *
 * active: Map of faultId -> { injectedAt } in simulated seconds.
 */
export function computeModifiers(active, simTime) {
  const mods = {
    bearingVibration: 0,
    ovenZone2Capacity: 1,
    packerJamPhase: null,
    faultedStations: new Set(),
    offlineStations: new Set(),
  };

  for (const [id, info] of active) {
    const t = Math.max(0, simTime - info.injectedAt);

    switch (id) {
      case 'bearing-degradation':
        // Exponential ramp: slow to start, unmistakable once it moves. Crosses
        // the 3.5 mm/s warn band around 13 simulated minutes.
        mods.bearingVibration = Math.min(
          BEARING_CAP,
          BEARING_GAIN * (Math.exp(t / BEARING_TAU) - 1),
        );
        break;

      case 'oven-burner': {
        // Capacity degrades over the first minute rather than cliff-edging.
        const frac = Math.min(1, t / 60);
        mods.ovenZone2Capacity = 1 - 0.38 * frac;
        break;
      }

      case 'packer-jam':
        mods.faultedStations.add('PKG-05');
        mods.packerJamPhase = t < 8 ? 'bind' : 'tear';
        break;

      case 'sensor-dropout':
        mods.offlineStations.add('INS-04');
        break;
    }
  }

  return mods;
}