//
//  ContentView.swift
//  Splits
//
//  Created by Isaac Greene on 4/3/22.
//

import SwiftUI
import Foundation

/// Creates the primary tab of ``SplitsApp``
///
/// e
struct ContentView: View {
	enum Field {
		case distance
		case hours
		case minutes
		case seconds
	}
	
	@FocusState private var nameIsFocused: Bool
	@FocusState private var focusedField: Field?
	var SISystem = ["km","mi"]
	@State var timeHours: String = ""
	@State var timeMinutes: String = ""
	@State var timeSeconds: String = ""
	@State var selectedSystem: String = "km"
	@State var distance: String = ""
	
	var body: some View {
		NavigationView {
			VStack {
				VStack {
					TextField("Enter distance", text: $distance)
						.padding()
						.keyboardType(.decimalPad)
						.textFieldStyle(.roundedBorder)
						.focused($nameIsFocused)
						.focused($focusedField, equals: .distance)
						.toolbar {
							ToolbarItemGroup(placement: .keyboard) {
								Button("Done") {
									nameIsFocused = false
								}
								Button("Clear") {
									distance = ""
									timeHours = ""
									timeMinutes = ""
									timeSeconds = ""
								}
								Spacer()
								Button("Next") {
									if focusedField == .distance {
										focusedField = .hours
									} else if focusedField == .hours {
										focusedField = .minutes
									} else if focusedField == .minutes {
										focusedField = .seconds
									} else {
										focusedField = nil
									}
								}
							}
						}
				}
				VStack {
					Text("Unit of measurement:")
					Picker("System of measurement", selection: $selectedSystem, content: {
						ForEach(SISystem, id: \.self, content: { unit in
							Text(unit)
						})
					})
						.pickerStyle(.segmented)
						.frame(minWidth: 60, maxWidth: 300)
					HStack {
						VStack {
							Text("Hours")
							TextField("Enter hours", text: $timeHours)
								.keyboardType(.numberPad)
								.textFieldStyle(.roundedBorder)
								.focused($nameIsFocused)
								.focused($focusedField, equals: .hours)
						}
						.frame(minWidth: 100)
						.padding(.trailing, -15)
						.padding()
						VStack {
							Text("Minutes")
							TextField("Enter minutes", text: $timeMinutes)
									.keyboardType(.numberPad)
									.textFieldStyle(.roundedBorder)
									.focused($nameIsFocused)
									.focused($focusedField, equals: .minutes)
						}
						.frame(minWidth: 100)
						.padding(.trailing, -15)
						.padding(.leading, -15)
						.padding()
						VStack {
							Text("Seconds")
							TextField("Enter seconds", text: $timeSeconds)
								.keyboardType(.numberPad)
								.textFieldStyle(.roundedBorder)
								.focused($nameIsFocused)
								.focused($focusedField, equals: .seconds)
						}
						.frame(minWidth: 100)
						.padding(.leading, -15)
						.padding()
					}
				}
				PaceResults(timeHours: $timeHours, timeMinutes: $timeMinutes, timeSeconds: $timeSeconds, selectedSystem: $selectedSystem, distance: $distance)
			}
		}
	}
}

struct PaceResults: View {
	@Binding var timeHours: String
	@Binding var timeMinutes: String
	@Binding var timeSeconds: String
	@Binding var selectedSystem: String
	@Binding var distance: String
	
	var body: some View {
		let distanceDub:Double = ((Double(distance) != 0 ? Double(removeLeadingZeros(distance: &distance)) ?? 1.0 : 1.0))
		// because of some conversions I have to do,
		// this constant is a double just to make things easier.
		// this has to be one because the pace is calculated
		// by time / distance, and you can't divide by 0.
		// I could just make the TextField have a default value
		// but then my message would disappear to let you know
		// what to enter in that box
		
		let multiplier = (selectedSystem == "mi" ? 1.609344 : 0.6213711922)
		let notSelectedSystem = (selectedSystem == "km" ? "mi" : "km")
		let convertedDistanceString:String = {
			let convertedDistance = distanceDub * multiplier
			return (distance == "" ? "0" : String(format: "%.3f", convertedDistance))
		}()
		
		let convertedSeconds:Double = (Double(timeSeconds) ?? 0) * (1.6666666666666666666666666)
		let timeSecondsInt:Int = Int(timeSeconds) ?? 0
		let timeSecondsUnderSixty:Int = (timeSecondsInt % 60)
		// this section takes the seconds and multiplies it by 1.66
		// so that 60 seconds becomes 100 (as in 100% of a minute)
		// and this means that 30 seconds becomes 50 (as in 50% of a minute)
		// which allows us to to calculate our pace. Without this
		// the pace would be all wrong.
		
		let timeSecondsToMinutes:Int = (timeSecondsInt - timeSecondsUnderSixty) / 60
		// this takes the seconde and converts it to minutes so 78
		// seconds will turn into 1 minute and 18 seconds leftover
		// with the minutes saved in this value and the seconds
		// disregarded because they're saved in timeSecondsUnderSixty
		
		let timeMinutesInt:Int = (Int(timeMinutes) ?? 0) + (timeSecondsToMinutes)
		let timeMinutesUnderSixty:Int = timeMinutesInt % 60
		let timeMinutesToHours:Int = (timeMinutesInt - timeMinutesUnderSixty) / 60
		// this section takes the minutes (which it combines the
		// minutes with the timeSecondsToMinutes) then finds out how
		// many hours (multiples of 60) are in the minutes value
		// and saves the hours in timeMinutesToHours and the remaining
		// minutes in `timeMinutesUnderSixty`
		
		let timeMinutesDouble:Double = Double(timeMinutes) ?? 0.0
		// this line of code takes the binding $timeMinutes which
		// is a string and turns it into a number of type Double.
		// while the TextField is a number pad, on iPads, Mac computers
		// and using copy/paste you can get other characters.
		// if the text field contains anything other than a number
		// or a single decimal, this value instantly becomes 0.0
		
		let pace:Double = {
			let actualTime:Double = timeMinutesDouble + (convertedSeconds / 100) + ((Double(timeHours) ?? 0) * 60)
			// adds the minutes, hours, and seconds all together to get
			// a single value in terms of minutes, so that 1:08:45
			// becomes 68.75 which is a nice number we can do math on
			// and this number is never directly seen by the user
			return actualTime / distanceDub
		}()
		
		let paceFormatted:String = {
			let paceSeconds = pace.truncatingRemainder(dividingBy: 1.0)
			let paceMinutes = (pace.truncatingRemainder(dividingBy: 60.0) - paceSeconds)
			let paceHours = String(format: "%.0f", ((pace - paceMinutes) / 60))
			let reConvertedSeconds = (paceSeconds / 1.666666666666666666) * 100
			let properTimeMS = String(format: "%02d:%02d", Int(paceMinutes), Int(reConvertedSeconds.rounded()))
			return (pace >= 60 ? "\(paceHours):\(properTimeMS)" : "\(properTimeMS)")
		}()
		
		let paceFormattedOpposite:String = {
			let paceOpposite = (selectedSystem == "km" ? (pace * 1.609344) : (pace * 0.6213711922))
			let paceSecondsOpposite = paceOpposite.truncatingRemainder(dividingBy: 1.0)
			let paceMinutesOpposite = (paceOpposite.truncatingRemainder(dividingBy: 60.0) - paceSecondsOpposite)
			let paceHoursOpposite = String(format: "%.0f", ((paceOpposite - paceMinutesOpposite) / 60))
			let reConvertedSecondsOpposite = (paceSecondsOpposite / 1.666666666666666666) * 100
			let properTimeMSOpposite = String(format: "%02d:%02d", Int(paceMinutesOpposite), Int(reConvertedSecondsOpposite.rounded()))
			return (paceOpposite >= 60 ? "\(paceHoursOpposite):\(properTimeMSOpposite)" : "\(properTimeMSOpposite)")
		}()
		
		let hoursFormatted:String = {
			let totalHours:Double = Double(timeMinutesToHours) + (Double(timeHours) ?? 0)
			// this takes the number of hours in the binding $timeHours
			// and the hours calculated in the previous section
			// and adds them together to get our total number of hours.
			return String(format: "%.0f", totalHours)
		}()

		
		let leadingZeros:String = String(format: "%02d:%02d", timeMinutesUnderSixty, timeSecondsUnderSixty)
		// this takes the minutes and the seconds and adds leading
		// zeros to them, so that 5 minutes 7 seconds will show
		// as 05:07 which is a format most people, and certainly
		// the people this app is intended for, will understand

		HStack {
			VStack (alignment: .leading) {
				Text("\(roundString(Double(removeLeadingZeros(distance: &distance)) ?? 0))\(selectedSystem)")
				Text("\(convertedDistanceString)\(notSelectedSystem)")
			}
			.frame(minWidth: 100)
			Text("\(hoursFormatted):\(leadingZeros)")
				.padding()
				.frame(minWidth: 100)
			VStack(alignment: .trailing) {
				Text("\(paceFormatted)/\(selectedSystem)")
				Text("\(paceFormattedOpposite)/\(notSelectedSystem)")
			}
			.frame(minWidth: 100)
		}
	}
	func removeLeadingZeros(distance: inout String) -> String {
		while distance.starts(with: "0") {
			distance = distance.removing(prefix: "0")
		}
		return distance
	}
	
	func roundString(_ variable: Double) -> String {
		if distance.contains(".") {
			let formattedString = String(format: "%.3f", variable)
			return formattedString
		} else {
			return distance
		}
	}
}

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