/**
 * Centralised measurement update routing for rotatingMachine.
 *
 * Wraps the four measurement types coming from child measurement nodes
 * (flow / power / temperature / pressure) and dispatches each to the
 * appropriate handler. Pressure is delegated to the host's pressureRouter
 * (built in P5.4); the other three are normalised + written + drift-tracked
 * here.
 *
 * The handlers reach back into the host for `_resolveMeasurementUnit`,
 * `_updateMetricDrift`, `_updatePredictionHealth`, `updatePosition` and the
 * measurements container. Behaviour is preserved 1:1 from the original
 * specificClass methods.
 */

class MeasurementHandlers {
  constructor(ctx) {
    if (!ctx || !ctx.host) {
      throw new Error('MeasurementHandlers: ctx.host is required');
    }
    this.host = ctx.host;
    this.logger = ctx.logger || ctx.host.logger;
  }

  /**
   * Single entry point used by child-measurement event listeners.
   * Unknown types warn and fall back to a no-op position refresh so a
   * mis-configured child can't silently break the FSM tick.
   */
  dispatch(measurementType, value, position, context = {}) {
    switch (measurementType) {
      case 'pressure':
        return this.host.updateMeasuredPressure(value, position, context);
      case 'flow':
        return this.updateMeasuredFlow(value, position, context);
      case 'power':
        return this.updateMeasuredPower(value, position, context);
      case 'temperature':
        return this.updateMeasuredTemperature(value, position, context);
      default:
        this.logger.warn(`No handler for measurement type: ${measurementType}`);
        return this.host.updatePosition();
    }
  }

  updateMeasuredTemperature(value, position, context = {}) {
    const host = this.host;
    this.logger.debug(
      `Temperature update: ${value} at ${position} from ${context.childName || 'child'} (${context.childId || 'unknown-id'})`,
    );
    let unit;
    try {
      unit = host._resolveMeasurementUnit('temperature', context.unit);
    } catch (error) {
      this.logger.warn(`Rejected temperature update: ${error.message}`);
      return;
    }
    host.measurements
      .type('temperature')
      .variant('measured')
      .position(position || 'atEquipment')
      .child(context.childId)
      .value(value, context.timestamp, unit);
  }

  updateMeasuredFlow(value, position, context = {}) {
    const host = this.host;
    if (!host._isOperationalState()) {
      this.logger.warn(`Machine not operational, skipping flow update from ${context.childName || 'unknown'}`);
      return;
    }
    this.logger.debug(`Flow update: ${value} at ${position} from ${context.childName || 'child'}`);
    let unit;
    try {
      unit = host._resolveMeasurementUnit('flow', context.unit);
    } catch (error) {
      this.logger.warn(`Rejected flow update: ${error.message}`);
      return;
    }

    host.measurements
      .type('flow').variant('measured').position(position).child(context.childId)
      .value(value, context.timestamp, unit);

    if (host.predictFlow) {
      const canonical = host.unitPolicy.canonical.flow;
      const predicted = host.predictFlow.outputY || 0;
      host.measurements.type('flow').variant('predicted').position('downstream')
        .value(predicted, Date.now(), canonical);
      host.measurements.type('flow').variant('predicted').position('atEquipment')
        .value(predicted, Date.now(), canonical);
    }

    const measuredCanonical = host.measurements
      .type('flow').variant('measured').position(position)
      .getCurrentValue(host.unitPolicy.canonical.flow);

    host._updateMetricDrift('flow', measuredCanonical, context);
    host._updatePredictionHealth();
  }

  updateMeasuredPower(value, position, context = {}) {
    const host = this.host;
    if (!host._isOperationalState()) {
      this.logger.warn(`Machine not operational, skipping power update from ${context.childName || 'unknown'}`);
      return;
    }
    this.logger.debug(`Power update: ${value} at ${position} from ${context.childName || 'child'}`);
    let unit;
    try {
      unit = host._resolveMeasurementUnit('power', context.unit);
    } catch (error) {
      this.logger.warn(`Rejected power update: ${error.message}`);
      return;
    }
    host.measurements
      .type('power').variant('measured').position(position).child(context.childId)
      .value(value, context.timestamp, unit);

    if (host.predictPower) {
      host.measurements.type('power').variant('predicted').position('atEquipment')
        .value(host.predictPower.outputY || 0, Date.now(), host.unitPolicy.canonical.power);
    }

    const measuredCanonical = host.measurements
      .type('power').variant('measured').position(position)
      .getCurrentValue(host.unitPolicy.canonical.power);

    host._updateMetricDrift('power', measuredCanonical, context);
    host._updatePredictionHealth();
  }
}

module.exports = MeasurementHandlers;