haptika/packages/react-native-haptika-ppg/Tests/HaptikaSignalTests/PPGSignalPipelineTests.swift

import XCTest
@testable import HaptikaSignal

final class PPGSignalPipelineTests: XCTestCase {
  func testPRVCalculatorDerivesIntervalMetrics() throws {
    let intervals = [700.0, 720, 760, 710, 800, 730, 750, 705]
    let metrics = try PPGPRVCalculator.calculate(
      intervalsMilliseconds: intervals,
      configuration: PPGProcessingConfiguration(minimumIntervalsForPRV: 5)
    )

    XCTAssertEqual(metrics.meanIpiMs ?? 0, 734.375, accuracy: 0.001)
    XCTAssertEqual(metrics.medianIpiMs ?? 0, 725, accuracy: 0.001)
    XCTAssertEqual(metrics.pnn50Percent ?? 0, 200.0 / 7.0, accuracy: 0.001)
    XCTAssertEqual(metrics.rangeIpiMs ?? 0, 100, accuracy: 0.001)
    XCTAssertEqual(metrics.modeIpiMs ?? 0, 713, accuracy: 0.001)
    XCTAssertEqual(metrics.amo50Percent ?? 0, 62.5, accuracy: 0.001)
    XCTAssertEqual((metrics.coefficientOfVariation ?? 0) * 100, 4.68, accuracy: 0.1)
  }

  func testBPMEstimatorCorrectsSecondHarmonic() throws {
    let sampleRate = 30.0
    let duration = 30.0
    let sampleCount = Int(sampleRate * duration)
    let timestamps = (0..<sampleCount).map { Double($0) / sampleRate }
    // The spectral method sees a strong 144 BPM harmonic while the clean peak
    // intervals correctly describe a 72 BPM pulse.
    let signal = timestamps.map { sin(2 * Double.pi * 2.4 * $0) }
    let peakInterval = 60.0 / 72.0
    let peaks = (0..<35).map { index in
      DetectedPeak(
        sampleIndex: Int((Double(index) * peakInterval * sampleRate).rounded()),
        timestampSeconds: Double(index) * peakInterval,
        amplitude: 1,
        prominence: 1
      )
    }
    let intervals = zip(peaks, peaks.dropFirst()).enumerated().map { index, pair in
      PulseInterval(
        sourceIndex: index,
        startSeconds: pair.0.timestampSeconds,
        endSeconds: pair.1.timestampSeconds,
        durationMilliseconds: peakInterval * 1_000
      )
    }
    let detection = PeakDetectionResult(
      peaks: peaks,
      intervals: intervals,
      selectedPolarity: 1,
      confidence: 0.9
    )

    let estimate = try PPGBPMEstimator.estimate(
      signal: signal,
      timestampsSeconds: timestamps,
      validityMask: Array(repeating: true, count: sampleCount),
      peakDetection: detection,
      selectedChannel: .greenRedRatio,
      configuration: .production
    )

    XCTAssertNotNil(estimate.bpm)
    XCTAssertEqual(estimate.bpm ?? 0, 72, accuracy: 1.5)
    XCTAssertEqual(estimate.frequencyBpm ?? 0, 72, accuracy: 1.5)
  }

  func testProcessorProducesHeartRateFromCleanContactPPG() throws {
    let sampleRate = 30.0
    let duration = 55.0
    let sampleCount = Int(sampleRate * duration) + 1
    let samples = (0..<sampleCount).map { index -> PPGFrameSample in
      let time = Double(index) / sampleRate
      let pulse = sin(2 * Double.pi * 1.2 * time)
        + 0.18 * sin(2 * Double.pi * 2.4 * time)
      let slowLightDrift = 1 + 0.08 * sin(2 * Double.pi * 0.08 * time)
      return PPGFrameSample(
        timestampSeconds: time,
        red: 185 * slowLightDrift + 2.5 * pulse,
        green: 82 * slowLightDrift + 5.5 * pulse,
        luminance: 112 * slowLightDrift + 4 * pulse,
        contactConfidence: 0.9,
        saturationRatio: 0,
        motionArtifactScore: 0.02
      )
    }
    let configuration = PPGProcessingConfiguration(
      minimumAnalysisDurationSeconds: 45,
      filterTapCount: 61
    )

    let result = try PPGSignalProcessor(configuration: configuration)
      .analyze(samples: samples)

    XCTAssertEqual(result.status, .valid)
    XCTAssertNotNil(result.bpm.bpm)
    XCTAssertEqual(result.bpm.bpm ?? 0, 72, accuracy: 3)
    XCTAssertGreaterThan(result.quality.score, 0.65)
  }

  func testResamplerKeepsUniformGridAndMasksLongGap() throws {
    let input = [
      TimestampedValue(timestampSeconds: 0.00, value: 0),
      TimestampedValue(timestampSeconds: 0.09, value: 1),
      TimestampedValue(timestampSeconds: 0.21, value: 2),
      TimestampedValue(timestampSeconds: 0.80, value: 3),
      TimestampedValue(timestampSeconds: 0.91, value: 4),
    ]
    let result = try PPGSignalResampler.resample(
      input,
      targetSampleRateHz: 10,
      maximumInterpolationGapSeconds: 0.20
    )

    XCTAssertEqual(result.timestampsSeconds.count, result.values.count)
    XCTAssertEqual(result.timestampsSeconds[1] - result.timestampsSeconds[0], 0.1, accuracy: 1e-9)
    XCTAssertFalse(result.validityMask[4], "A long camera gap must remain unusable")
    XCTAssertGreaterThan(result.diagnostics.droppedFrameRatio, 0)
  }

  func testPRVLocalFilterRejectsArtifactWithoutRejectingGradualChange() throws {
    let intervals = [700.0, 710, 720, 730, 740, 400, 760, 770, 780, 790, 800]
    let result = try PPGPRVCalculator.calculate(
      intervals: makeIntervals(intervals),
      configuration: PPGProcessingConfiguration(
        minimumIntervalsForPRV: 5,
        maximumRejectedIntervalRatioForPRV: 0.25
      )
    )

    XCTAssertEqual(result.intervals[5].rejectionReason, .localOutlier)
    XCTAssertTrue(result.intervals[10].isAccepted, "A gradual HR change must remain usable")
    XCTAssertEqual(result.metrics.validIntervalCount, intervals.count - 1)
    XCTAssertTrue(result.metrics.reliable)
  }

  func testProcessorCanRecoverPulseCarriedByBlueChrominance() throws {
    let sampleRate = 30.0
    let duration = 55.0
    let samples = (0...Int(sampleRate * duration)).map { index -> PPGFrameSample in
      let time = Double(index) / sampleRate
      let pulse = sin(2 * Double.pi * 1.2 * time)
        + 0.20 * sin(2 * Double.pi * 2.4 * time)
      let red = 150.0
      let green = 100.0
      let blue = 80 + 9 * pulse
      let luminance = 0.2126 * red + 0.7152 * green + 0.0722 * blue
      return PPGFrameSample(
        timestampSeconds: time,
        red: red,
        green: green,
        luminance: luminance,
        contactConfidence: 0.95,
        saturationRatio: 0,
        motionArtifactScore: 0
      )
    }
    let result = try PPGSignalProcessor(
      configuration: PPGProcessingConfiguration(
        minimumAnalysisDurationSeconds: 45,
        filterTapCount: 61
      )
    ).analyze(samples: samples)

    XCTAssertEqual(result.status, .valid)
    XCTAssertTrue(
      [.blue, .greenRedRatio, .blueRedRatio, .normalizedBlend]
        .contains(result.bpm.selectedChannel)
    )
    XCTAssertEqual(result.bpm.bpm ?? 0, 72, accuracy: 3)
  }

  func testCoachingContactScoreDoesNotDiscardARealPeriodicSignal() throws {
    let sampleRate = 30.0
    let duration = 55.0
    let samples = (0...Int(sampleRate * duration)).map { index -> PPGFrameSample in
      let time = Double(index) / sampleRate
      let pulse = sin(2 * Double.pi * 1.25 * time)
        + 0.16 * sin(2 * Double.pi * 2.5 * time)
      return PPGFrameSample(
        timestampSeconds: time,
        red: 142 + 3.2 * pulse,
        green: 104 + 5.8 * pulse,
        blue: 76 + 1.4 * pulse,
        luminance: 111 + 4.9 * pulse,
        contactConfidence: 0.10,
        saturationRatio: 0,
        motionArtifactScore: 0.02
      )
    }

    let result = try PPGSignalProcessor(
      configuration: PPGProcessingConfiguration(
        minimumAnalysisDurationSeconds: 45,
        filterTapCount: 61
      )
    ).analyze(samples: samples)

    XCTAssertEqual(result.status, .valid)
    XCTAssertEqual(result.bpm.bpm ?? 0, 75, accuracy: 3)
    XCTAssertTrue(result.quality.issues.contains(.poorFingerContact))
  }

  func testBeatMorphologyScoresDistortedCycleWithoutLosingCleanBeats() throws {
    let sampleRate = 30.0
    let periodSamples = 25
    let sampleCount = periodSamples * 14 + 1
    var signal = (0..<sampleCount).map { index in
      cos(2 * Double.pi * Double(index % periodSamples) / Double(periodSamples))
    }
    // Preserve the two bounding pulse peaks but flatten one complete cycle.
    for index in (periodSamples * 6 + 1)..<(periodSamples * 7) {
      signal[index] = -0.15
    }
    let timestamps = (0..<sampleCount).map { Double($0) / sampleRate }
    let result = try PPGPeakDetector.detect(
      signal: signal,
      timestampsSeconds: timestamps,
      validityMask: Array(repeating: true, count: sampleCount),
      configuration: PPGProcessingConfiguration(
        minimumAnalysisDurationSeconds: 1,
        minimumPeakProminence: 0.10,
        minimumPeakAmplitude: 0.05
      )
    )

    let scores = result.intervals.map(\.qualityScore)
    XCTAssertLessThan(
      scores.min() ?? 1,
      SignalStatistics.median(scores) - 0.05,
      "The flattened pulse must receive a distinctly lower technical quality"
    )
    XCTAssertGreaterThan(result.acceptedIntervals.count, 8)
  }

  private func makeIntervals(_ durations: [Double]) -> [PulseInterval] {
    var elapsed = 0.0
    return durations.enumerated().map { index, duration in
      defer { elapsed += duration / 1_000 }
      return PulseInterval(
        sourceIndex: index,
        startSeconds: elapsed,
        endSeconds: elapsed + duration / 1_000,
        durationMilliseconds: duration
      )
    }
  }
}