1using System;
 2using System.Collections.Generic;
 3using System.Linq;
 4using Gorilla.Commons.Utility;
 5
 6namespace presentation.windows.server.domain.payroll
 7{
 8    public class History<T>
 9    {
10        Stack<Event<T>> events = new Stack<Event<T>>();
11
12        public void record(T change)
13        {
14            events.Push(new Event<T>(change));
15        }
16
17        public T recorded(Date date)
18        {
19            return events.Where(x => x.occurred_on_or_before(date)).Max();
20        }
21
22        class Event<K> : IComparable<Event<K>>
23        {
24            public Event(K adjustment)
25            {
26                date_of_change = Calendar.now();
27                this.adjustment = adjustment;
28            }
29
30            K adjustment;
31            Date date_of_change;
32
33            public int CompareTo(Event<K> other)
34            {
35                return date_of_change.CompareTo(other.date_of_change);
36            }
37
38            public bool occurred_on_or_before(Date date)
39            {
40                return date_of_change.Equals(date) || date_of_change.is_before(date);
41            }
42
43            static public implicit operator K(Event<K> eventA)
44            {
45                return eventA.adjustment;
46            }
47        }
48    }
49}