Race Pace Calculator

racepace.swift

//
//  ContentView.swift
//  RunningPaceCalculator
//
//  Created by Chris Eidhof on 19.02.20.
//  Copyright © 2020 Chris Eidhof. All rights reserved.
//

import SwiftUI

struct Pace: Codable, Equatable, Hashable {
    var secondsPerKM: Double
    
    var secondsPerMile: Double {
        return secondsPerKM * 1.60934
    }
}

struct Meters: Codable, Equatable, Hashable {
    var meters: Double
    init(floatLiteral: Double) { self.meters = floatLiteral }
}

extension Meters: ExpressibleByFloatLiteral, ExpressibleByIntegerLiteral {
    init(integerLiteral value: Double) {
        meters = value
    }
}

enum Distance {
    case marathon
    case halfMarathon
    case other(Meters)
    
    var displayName: String {
        switch self {
        case .marathon: return "Marathon"
        case .halfMarathon: return "Half Marathon"
        case .other(let m): return "\(Int(m.meters))m"
        }
    }
    
    var distance: Meters {
        switch self {
        case .marathon: return 42195
        case .halfMarathon: return 21097.5
        case .other(let m): return m
        }
    }
    
    static let builtin: [Distance] = [
        .marathon,
        .halfMarathon,
        .other(10000),
        .other(5000),
        .other(1500),
        .other(800),
        .other(400),
        .other(200)
    ]
}

struct Time: Codable, Equatable, Hashable {
    var seconds: Double
}

let timeFormatter: DateComponentsFormatter = {
    var t = DateComponentsFormatter()
    t.allowedUnits = [.hour, .minute, .second]
    t.unitsStyle = .positional
    return t
}()

extension Time {
    var formatted: String {
        return timeFormatter.string(from: TimeInterval(seconds))!
    }
}

func *(lhs: Pace, rhs: Meters) -> Time {
    return Time(seconds: lhs.secondsPerKM * rhs.meters/1000)
}

func *(lhs: Pace, rhs: Double) -> Pace {
    return Pace(secondsPerKM: lhs.secondsPerKM * rhs)
}

extension Pace {
    var minutesPerKM: String {
        let formatted = timeFormatter.string(from: TimeInterval(secondsPerKM))!
        return "\(formatted)/km"
    }
    
    var minutesPerMile: String {
        let formatted = timeFormatter.string(from: TimeInterval(secondsPerMile))!
        return "\(formatted)/mi"
    }
}

struct TimeSlider: View {
    @Binding var pace: Pace
    var body: some View {
        HStack(alignment: .bottom, spacing: 5) {
            ForEach(0..<(10*60)) { tick in
                Rectangle()
                    .fill(Color.black)
                    .frame(width: 2, height: (tick % 10 == 0) ? 30 : 15)
            }
        }
    }
}

struct ContentView: View {
    @State var pace: Pace = Pace(secondsPerKM: 180+46)
    var body: some View {
        let separator = Rectangle()
        .frame(height: 1)
        .padding()
        return VStack {
            HStack {
                Button("-") { self.pace.secondsPerKM -= 1 }
                Text(pace.minutesPerKM)
                Button("+") { self.pace.secondsPerKM += 1 }
            }.font(Font.largeTitle.monospacedDigit())
            Text(pace.minutesPerMile).font(Font.body.monospacedDigit())
            Text("")
            separator
            ForEach(Array(Distance.builtin.enumerated()), id: \.offset) { (offset, el) in
                HStack {
                    Text(el.displayName).frame(maxWidth: .infinity, alignment: .trailing)
                    Text((self.pace * el.distance).formatted).frame(maxWidth: .infinity, alignment: .leading)
                }
            }.font(Font.body.monospacedDigit())
            separator
            ForEach([10, 15, 20], id: \.self) { perc in
                HStack {
                    Text("\(perc)% slower")
                        .frame(maxWidth: .infinity, alignment: .trailing)
                    Text((self.pace * (1 + Double(perc)/100)).minutesPerKM)
                        .frame(maxWidth: .infinity, alignment: .leading)
                }
            }.font(Font.body.monospacedDigit())
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}