/// <summary>判断两个区间是否重叠
/// </summary>
/// <param name="segment1"></param>
/// <param name="segment2"></param>
/// <returns></returns>
private bool IsSegmentIntersect(Segment segment1, Segment segment2)
{
return (segment1.StartNo > segment2.StartNo && segment1.StartNo < segment2.EndNo)
|| (segment1.EndNo > segment2.StartNo && segment1.EndNo < segment2.EndNo)
|| (segment1.StartNo <= segment2.StartNo && segment1.EndNo >= segment2.EndNo)
|| (segment1.StartNo >= segment2.StartNo && segment1.EndNo <= segment2.EndNo);
}
/// <summary>判断当前座位是否可以出售给给定的区间
/// </summary>
/// <param name="segment"></param>
/// <returns></returns>
public bool CanSellToSegment(Segment segment)
{
//如果当前座位的已出售区间中有任何一个区间和当前区间重叠，则认为当前座位不允许出售给当前区间
foreach (var soldSegment in _soldSegments)
{
if (IsSegmentIntersect(soldSegment, segment))
{
return false;
}
}
return true;
}
/// <summary>将给定座位出售给给定的订票区间
/// </summary>
/// <param name="seat"></param>
/// <param name="segment"></param>
/// <param name="atomSegments"></param>
private void SellSeat(Seat seat, Segment segment, IEnumerable<Segment> atomSegments)
{
foreach (var atomSegment in atomSegments)
{
_atomSegments[atomSegment] = _atomSegments[atomSegment] - 1;
}
seat.AddSoldSegment(segment);
if (!_soldSeats.ContainsKey(seat.No))
{
_soldSeats.Add(seat.No, seat);
_cleanSeats.Remove(seat.No);
}
}
/// <summary>添加一个已出售的区间
/// </summary>
/// <param name="segment"></param>
public void AddSoldSegment(Segment segment)
{
_soldSegments.Add(segment);
}
/// <summary>为给定的订票区间选择一个可用的座位，优先回收已出售的座位
/// </summary>
/// <param name="segment"></param>
/// <returns></returns>
private Seat SelectSeat(Segment segment)
{
//优先回收已出售的座位
foreach (var seat in _soldSeats.Values)
{
if (seat.CanSellToSegment(segment))
{
return seat;
}
}
//如果已出售的座位不符合当前区间的出售条件，则尝试从座位池取出第一个座位进行出售
return _cleanSeats.Values.FirstOrDefault();
}
/// <summary>获取给定区间的原子区间列表
/// </summary>
/// <param name="segment"></param>
/// <returns></returns>
private IEnumerable<Segment> GetAtomSegments(Segment segment)
{
return _atomSegments.Where(x => x.Key.StartNo >= segment.StartNo && x.Key.EndNo <= segment.EndNo).Select(x => x.Key).ToList();
}
/// <summary>创建一张票
/// </summary>
/// <param name="seat"></param>
/// <param name="segment"></param>
/// <returns></returns>
private Ticket CreateTicket(Seat seat, Segment segment)
{
var startStation = _stations.Single(x => x.No == segment.StartNo);
var endStation = _stations.Single(x => x.No == segment.EndNo);
return new Ticket(seat.No, startStation, endStation);
}
/// <summary>订票领域方法，实现订票的核心业务逻辑
/// </summary>
/// <param name="segment"></param>
/// <returns></returns>
public Ticket BookTicket(Segment segment)
{
var atomSegments = GetAtomSegments(segment);
if (!IsAllAtomSegmentHaveSeat(atomSegments))
{
return null;
}
var seat = SelectSeat(segment);
if (seat != null)
{
SellSeat(seat, segment, atomSegments);
return CreateTicket(seat, segment);
}
return null;
}
private static bool IsEqual(Segment left, Segment right)
{
if (ReferenceEquals(left, null) ^ ReferenceEquals(right, null))
{
return false;
}
return ReferenceEquals(left, null) || left.Equals(right);
}
