RotationBug.swift

//
//  ContentView.swift
//  ClockRotationBug
//
//  Created by David Smith on 11/6/23.
//

import SwiftUI

struct ContentView: View {
    @State var date:Date = Date.dateOn(year: 2023, month: 12, day: 31, hour: 23, minute: 58, second: 0)
    
    var body: some View {
        VStack {
            rotationBugEntryView(date: date)
                .frame(width:200, height:200)
            
            HStack {
                Button(action: {
                    withAnimation {
                        self.date = date.addingTimeInterval(-60)
                    }
                }, label: {
                    Text("Last")
                })
                
                Button(action: {
                    withAnimation {
                        self.date = date.addingTimeInterval(60)
                    }
                }, label: {
                    Text("Next")
                })
            }
            
        }
    }
}

#Preview {
    ContentView()
}



struct rotationBugEntryView : View {
    var date: Date

    var hourAngle:Angle {

        let anchor = Date.dateOn(year: 2023, month: 1, day: 1, hour: 0, minute: 0, second: 0)
        let startOfDay = Calendar.current.startOfDay(for: date)

        let daysBetween = Calendar.current.dateComponents([.day], from: anchor, to: startOfDay)
        guard let numberOfDays = daysBetween.day else {
            return .zero
        }

        let dayStartAngle = Double(numberOfDays) * (360.0 * 2.0)

        let components = Calendar.current.dateComponents ([.hour, .minute], from: date)
        if let hour = components.hour, let minute = components.minute {
            let percentHourOfDay = ((Double(hour) + Double(minute) / 60.0)) / 24.0
            let hourAngleInDay = (percentHourOfDay * (360.0 * 2.0))
            return Angle.degrees(dayStartAngle + hourAngleInDay )
        }
        return .zero
    }
    
    var minuteAngle:Angle {
        let anchor = Date.dateOn(year: 2023, month: 1, day: 1, hour: 0, minute: 0, second: 0)
        let startOfDay = Calendar.current.startOfDay(for: date)

        let daysBetween = Calendar.current.dateComponents([.day], from: anchor, to: startOfDay)
        guard let numberOfDays = daysBetween.day else {
            return .zero
        }

        let dayStartAngle = Double(numberOfDays) * (360.0 * 24.0)

        let components = Calendar.current.dateComponents ([.hour, .minute], from: date)
        if let hour = components.hour, let minute = components.minute {
            let percentMinuteInDay = Double(hour * 60 + minute) / (24.0 * 60.0)
            let minuteAngleInDay   = percentMinuteInDay * (360.0 * 24.0)
            return Angle.degrees(dayStartAngle + minuteAngleInDay)
        }
        return Angle.zero
    }
    
    var body: some View {
        VStack {
            GeometryReader { proxy in
                ZStack {
                    Circle()
                        .fill(Color.gray)

                    ForEach(0..<12) { hour in
                        VStack(spacing:2) {
                            Rectangle()
                                .fill(.white)
                                .frame(width: 2, height: 5)
                            Text("\(hour == 0 ? 12 : hour)")
                                .font(.system(size: 8))
                                .foregroundStyle(.white)
                                .rotationEffect(Angle(degrees:-360.0 * ( Double(hour) / 12.0)))
                                .frame(width: 10, height: 5)
                            Spacer()
                        }
                        .rotationEffect(Angle(degrees:360.0 * ( Double(hour) / 12.0)))
                    }
                    
                    ClockHand(lengthPercent: 1.0)
                        .stroke(.black, style: StrokeStyle(lineWidth: 7, lineCap: .round))
                        .shadow(radius: 1)
                        .rotationEffect(minuteAngle)

                    ClockHand(lengthPercent: 0.7)
                        .stroke(.white, style: StrokeStyle(lineWidth: 7, lineCap: .round))
                        .shadow(radius: 1)
                        .rotationEffect(hourAngle)
                    

                }
                
                
            }
            Text(date, style: .time)
            Text(formatDate())
        }
    }
    
    func formatDate() -> String {
        let formatter = DateFormatter()
        formatter.timeStyle = .none
        formatter.dateStyle = .medium
        return formatter.string(from: date)
    }
    
}

struct ClockHand:Shape {
    let lengthPercent:Double
    func path(in rect: CGRect) -> Path {
        var path = Path()
        path.move(to: CGPoint(x: rect.midX, y: rect.midY))
        path.addLine(to: CGPoint(x: rect.midX, y: 3.5 + rect.height * (0.5 * (1.0 - lengthPercent))))
        return path
    }
}

extension Date {
    static func dateOn(year:Int, month:Int, day:Int, hour:Int, minute:Int, second:Int) -> Date {
        var components = DateComponents()
        components.year = year
        components.month = month
        components.day = day

        components.minute = minute
        components.hour = hour
        components.second = second
        
        return Calendar.current.date(from: components)!
    }
}
extension Date {
    static func dateSince(days:Int, hour:Int, minute:Int, second:Int) -> Date {
        let anchor = Date.dateOn(year: 2023, month: 1, day: 1, hour: 0, minute: 0, second: 0)
        var sum:Double = 0.0
        sum += Double(days) * (24.0 * 60 * 60)
        sum += Double(hour) * (60 * 60)
        sum += Double(minute) * (60)
        sum += Double(second)
        return anchor.addingTimeInterval(sum)
    }
    
}