spacerace/Assets/Src/Laps.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;

using UnityEngine;
using UnityEngine.UIElements;

public enum NoticeCategory {
    Initial,
    Slower,
    Faster,
    Fastest,
}

public class TimingNotice {
    public double Seconds;
    NoticeCategory Category = NoticeCategory.Initial;

    public TimingNotice Compare(double comparison) {
        double s = Math.Abs(comparison - Seconds);
        NoticeCategory cat = comparison switch {
            double c when Seconds < c => NoticeCategory.Faster,
            _ => NoticeCategory.Slower,
        };

        return new TimingNotice {
            Seconds = s,
            Category = cat,
        };
    }

    public Label ToLabel() {
        Label l = Category switch {
            NoticeCategory.Initial =>   new Label($"{TimeSpan.FromSeconds(Seconds):m\\:ss\\.fff}"),
            NoticeCategory.Slower =>    new Label($"+{Seconds:0.000}"),
            NoticeCategory.Faster =>    new Label($"-{Seconds:0.000}"),
            NoticeCategory.Fastest =>   new Label($"-{Seconds:0.000}"),
            _ =>                        new Label($"-{Seconds:0.000}"),
        };

        string colourClass = Category switch {
            NoticeCategory.Initial =>   "",
            NoticeCategory.Slower =>    "yellow",
            NoticeCategory.Faster =>    "green",
            NoticeCategory.Fastest =>   "purple",
            _ => "",
        };

        l.AddToClassList(colourClass);
        return l;
    }
}

public enum DiffColour {
    Green,
    Purple,
    White,
    Yellow,
}

[Serializable]
public class SectorTime {
    public int Sector;
    public double Seconds;
    public override string ToString() => $"{Seconds:0.000}";
}

[Serializable]
public class Lap {
    public string Map;
    public List<SectorTime> Sectors;

    // 0:1:39
    public override string ToString() {
        return $"{TimeSpan.FromSeconds(TotalTime):m\\:ss\\.fff}";
    }

    public double TotalTime =>  Sectors.Sum(s => s.Seconds);
}


[Serializable]
public class LapJSON {
    public string Map;
    public List<Lap> Laps = new();
}

// We can't save a dictionary with the Unity JSONUtility
// so we use this to hold a list of maps
public class LapStorage {
    public List<LapJSON> Laps = new();
}

static class LapStorageService {
    static Dictionary<string, LapJSON> lapsByMap = new();
    static string lapStoragePath = Path.Combine(Application.persistentDataPath, "lapStorage.json");

    static LapStorageService() {
        LapStorage lapStorage = new LapStorage();

        try {
            string json = File.ReadAllText(lapStoragePath);
            JsonUtility.FromJsonOverwrite(json, lapStorage);
        } catch {
            Debug.Log("No existing lapStorage.json");
        }

        lapsByMap = lapStorage.Laps.ToDictionary((lapJson) => lapJson.Map);
    }

    public static LapJSON GetPlayerLaps(string mapName) {
        LapJSON currentLaps;
        bool found = lapsByMap.TryGetValue(mapName, out currentLaps);
        if (!found) return EnsureMap(mapName);
        return currentLaps;
    }

    public static LapJSON EnsureMap(string mapName) {
        LapJSON lapJson = new LapJSON { Map = mapName, Laps = new List<Lap>() };
        lapsByMap[mapName] = lapJson;
        return lapJson;
    }

    static void Persist() {
        LapStorage lapStorage = new LapStorage { Laps = lapsByMap.Values.ToList() };
        File.WriteAllText(lapStoragePath, JsonUtility.ToJson(lapStorage));
    }

    // laps.count
    public static int NumberOfCompletions() { return 0; }

    // finds your PB in all completions
    public static int Position() { return 1; }

    public static void PersistLap(Lap lap) {
        LapJSON lapJson = GetPlayerLaps(lap.Map);
        lapJson.Laps.Add(lap);
        lapsByMap[lap.Map] = lapJson; // not needed?
        Persist();
    }

    public static Lap PB(string mapName) {
        return lapsByMap[mapName].Laps
            .MinBy(l => l.TotalTime);
    }
}

// Add this magic code, you will be able to use record and init.
// I only tested in editor, not sure whether it would work on other platforms.
namespace System.Runtime.CompilerServices {
    class IsExternalInit {}
}