MeasurementColorInterpolation.swift

extension Measurement where UnitType == UnitTemperature {
  var color: Color {
    /// Convert input temperature to Celsius for consistency
    let temperatureInCelsius = self.converted(to: .celsius)

    /// Find the two closest color values in Celsius
    var lowerIndex = 0
    var upperIndex = 0

    for i in 0..<colorSteps.count {
      let stepTemperatureInCelsius = colorSteps[i].temperature.converted(to: .celsius)
      if stepTemperatureInCelsius <= temperatureInCelsius {
        lowerIndex = i
      }
      if stepTemperatureInCelsius >= temperatureInCelsius {
        upperIndex = i
        break
      }
    }

    /// Interpolate the color in the HSBA color space
    let lowerValue = colorSteps[lowerIndex].temperature.converted(to: .celsius)
    let lowerColor = colorSteps[lowerIndex].color
    let upperValue = colorSteps[upperIndex].temperature.converted(to: .celsius)
    let upperColor = colorSteps[upperIndex].color

    let progress: Double
    if upperValue == lowerValue {
      progress = 0.5  // Set progress to 0.5 if the values are the same
    } else {
      progress = (temperatureInCelsius - lowerValue).value / (upperValue - lowerValue).value
    }

    /// Interpolating hue with wrap-around handling
    /// When interpolating between two hue values, ensure that you take the shortest path around the color wheel.
    let deltaHue = upperColor.hue - lowerColor.hue
    let interpolatedHue: Double
    if deltaHue > 0.5 {
      interpolatedHue = lowerColor.hue + (deltaHue - 1.0) * progress
    } else if deltaHue < -0.5 {
      interpolatedHue = lowerColor.hue + (deltaHue + 1.0) * progress
    } else {
      interpolatedHue = lowerColor.hue + deltaHue * progress
    }

    /// Wrap the hue around
    let wrappedHue = interpolatedHue.truncatingRemainder(dividingBy: 1.0)

    let interpolatedSaturation =
      lowerColor.saturation + (upperColor.saturation - lowerColor.saturation) * progress
    let interpolatedBrightness =
      lowerColor.brightness + (upperColor.brightness - lowerColor.brightness) * progress
    let interpolatedAlpha = lowerColor.alpha + (upperColor.alpha - lowerColor.alpha) * progress

    return Color(
      hue: wrappedHue,
      saturation: interpolatedSaturation,
      brightness: interpolatedBrightness,
      opacity: interpolatedAlpha
    )
  }