using System;
using System.Collections.Generic;
using System.Linq;
using Sony.Filtr.Utility.Extensions;

namespace Sony.Filtr.AdminAPI.ViewModels.Graph
{
    public static class GraphViewModelHelper
    {
        public static IEnumerable<GraphEntry<int>> BuildDailyChange(List<GraphEntry<int>> stats)
        {
            return stats.OrderBy(e => e.Date).SelectWithPrevious((previous, current) =>
            {
                if (previous.Date.Date == current.Date.AddDays(-1))
                {
                    return new GraphEntry<int>()
                    {
                        Date = current.Date,
                        Value = current.Value - previous.Value
                    };
                }
                return null;
            }).Where(s => s != null);
        }

        public static ulong SumSafe<TSource>(this IEnumerable<TSource> source, Func<TSource, int> projection)
        {
            ulong sum = 0;

            foreach (var item in source)
            {
                sum = sum + (ulong)checked((uint)projection(item));
            }

            return sum;
        }
    }
}