'use strict';

const { HealthStatus } = require('generalFunctions');

/**
 * PredictionHealth — composes per-metric drift snapshots + pressure
 * initialization status into a single HealthStatus plus a numeric
 * confidence figure.
 *
 * Per OPEN_QUESTIONS.md 2026-05-10: HealthStatus carries the standard
 * five fields; `confidence` is returned as a sibling on the result.
 */

class PredictionHealth {
  /**
   * @param {object} ctx
   *   - getPressureInitializationStatus() -> { initialized, hasDifferential, source, ... }
   *   - isOperational() -> boolean
   *   - applyDriftPenalty(drift, confidence, flags, prefix) -> confidence (from DriftAssessor)
   *   - resolveSetpointBounds?() -> { min, max }
   *   - getCurrentPosition?() -> number
   */
  constructor(ctx = {}) {
    this.getPressureInitializationStatus = ctx.getPressureInitializationStatus;
    this.isOperational = ctx.isOperational || (() => true);
    this.applyDriftPenalty = ctx.applyDriftPenalty || ((_d, c) => c);
    this.resolveSetpointBounds = ctx.resolveSetpointBounds;
    this.getCurrentPosition = ctx.getCurrentPosition;
  }

  /**
   * @param {object} driftSnapshots — { flow, power, pressure }
   *   pressure: { level, flags, source } (already-assessed pressure-drift status)
   * @returns {{ health: object, confidence: number }}
   *   health is a frozen HealthStatus shape; confidence ∈ [0,1].
   */
  evaluate(driftSnapshots = {}) {
    const pressureDrift = driftSnapshots.pressure || { level: 0, flags: [], source: null };
    const status = this._safePressureStatus();
    const flags = Array.isArray(pressureDrift.flags) ? [...pressureDrift.flags] : [];

    let confidence = this._baseConfidenceFromSource(status.source);
    if (!this.isOperational()) {
      confidence = 0;
      flags.push('not_operational');
    }

    confidence = this._penaltyForPressureDriftLevel(pressureDrift.level, confidence);
    confidence = this._penaltyForCurveEdge(confidence, flags);

    confidence = this.applyDriftPenalty(driftSnapshots.flow, confidence, flags, 'flow');
    confidence = this.applyDriftPenalty(driftSnapshots.power, confidence, flags, 'power');

    confidence = Math.max(0, Math.min(1, confidence));

    const dedupedFlags = flags.length ? Array.from(new Set(flags)) : ['nominal'];
    const worstLevel = this._worstLevelFromSnapshots(pressureDrift, driftSnapshots, dedupedFlags);
    const hasNonNominal = dedupedFlags.some((f) => f !== 'nominal');
    const effectiveLevel = hasNonNominal ? Math.max(1, worstLevel) : worstLevel;
    const sourceTag = pressureDrift.source ?? status.source ?? null;

    const health = effectiveLevel === 0
      ? HealthStatus.ok(this._qualityLabel(confidence), sourceTag)
      : HealthStatus.degraded(
          effectiveLevel,
          dedupedFlags,
          this._qualityLabel(confidence),
          sourceTag,
        );

    return { health, confidence };
  }

  _safePressureStatus() {
    if (typeof this.getPressureInitializationStatus !== 'function') {
      return { initialized: false, hasDifferential: false, source: null };
    }
    return this.getPressureInitializationStatus() || { source: null };
  }

  _baseConfidenceFromSource(source) {
    if (source === 'differential') return 0.9;
    if (source === 'upstream' || source === 'downstream') return 0.55;
    return 0.2;
  }

  _penaltyForPressureDriftLevel(level, confidence) {
    if (level >= 3) return confidence - 0.35;
    if (level === 2) return confidence - 0.2;
    if (level === 1) return confidence - 0.1;
    return confidence;
  }

  _penaltyForCurveEdge(confidence, flags) {
    if (typeof this.getCurrentPosition !== 'function' || typeof this.resolveSetpointBounds !== 'function') {
      return confidence;
    }
    const cur = Number(this.getCurrentPosition());
    const bounds = this.resolveSetpointBounds() || {};
    const { min, max } = bounds;
    if (Number.isFinite(cur) && Number.isFinite(min) && Number.isFinite(max) && max > min) {
      const span = max - min;
      const edgeDist = Math.min(Math.abs(cur - min), Math.abs(max - cur));
      if (edgeDist < span * 0.05) {
        flags.push('near_curve_edge');
        return confidence - 0.1;
      }
    }
    return confidence;
  }

  _worstLevelFromSnapshots(pressureDrift, snaps, flags) {
    let worst = Number.isFinite(pressureDrift.level) ? pressureDrift.level : 0;
    for (const id of ['flow', 'power']) {
      const d = snaps[id];
      if (!d || !d.valid) continue;
      const lvl = Math.max(d.immediateLevel || 0, d.longTermLevel || 0);
      if (lvl > worst) worst = lvl;
    }
    if (flags.includes('not_operational') && worst < 2) worst = 2;
    return Math.max(0, Math.min(3, worst));
  }

  _qualityLabel(confidence) {
    if (confidence >= 0.8) return 'high';
    if (confidence >= 0.55) return 'medium';
    if (confidence >= 0.3) return 'low';
    return 'invalid';
  }
}

module.exports = PredictionHealth;