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

public static class GoogleSheetComparer
{
    public static GoogleSheetDiffResult Compare<T>(List<T> oldList, List<T> newList) where T : class
    {
        var result = new GoogleSheetDiffResult();

        var oldDict = oldList.ToDictionary(x => GetId(x));
        var newDict = newList.ToDictionary(x => GetId(x));

        foreach (var newId in newDict.Keys)
        {
            if (!oldDict.ContainsKey(newId)) result.Added.Add(newId);
            else if (!IsSame(oldDict[newId], newDict[newId])) result.Modified.Add(newId);
        }

        foreach (var oldId in oldDict.Keys)
        {
            if (!newDict.ContainsKey(oldId)) result.Removed.Add(oldId);
        }

        return result;
    }

    private static string GetId(object obj)
    {
        var field = obj.GetType().GetField("Id");
        return field?.GetValue(obj)?.ToString() ?? "";
    }

    private static bool IsSame(object a, object b)
    {
        foreach (var field in a.GetType().GetFields())
        {
            var valA = field.GetValue(a);
            var valB = field.GetValue(b);
            if (!Equals(valA, valB)) return false;
        }
        return true;
    }
}