MeasurementScaler.swift

//
//  MeasurementScaler.swift
//
//  Copyright © 2019 Paul Wilkinson. 
//


extension Measurement where UnitType: Dimension {
    
    /// Attempt to find a  `UnitType` that produces a value less than `target`
    /// 
    /// See [Scaling Measurement in Swift](https://wilko.me/wordpress/?p=371)
    /// - Parameters:
    ///   - scales: An array of `UnitTypes` that will be applied in order seeking a value less than `target`.  \
    ///   This array should be in increasing order of coefficient
    ///   - target: The target value
    /// - Returns:
    ///   `Self` converted to the `UnitType` that produces a value less than `target` or
    ///   scaled by the last `UnitType` in the `scales` array
    
    func scaled (scales:[UnitType], target: Double) -> Measurement {
        guard !scales.isEmpty else {
            return self
        }
        var returnMeasure = self.converted(to: scales.first!)
        if returnMeasure.value.magnitude > target {            
            for unit in scales {
                returnMeasure.convert(to: unit)
                if returnMeasure.value.magnitude < target {
                    break
                }
            }
        }
        return returnMeasure
    }
}