Calculate the Available Time of a Shared Resource

Introduction

Shared resources are often limited by their usage count, like jobs per person or beds per room. This tip demonstrates based on the Time Period Library for .NET, how you can calculate the available time of such a resource.

Algorithm

// ----------------------------------------------------------------------
public ITimePeriodCollection GetOccupiedPeriods<t>( ITimePeriodCollection periods, int usageCount )
  where T : ITimeRange, new()
{
  TimePeriodCollection occupiedPeriods = new TimePeriodCollection();

  if ( periods.Count > 0)
  {
    TimeLineMomentCollection timeLineMoments = new TimeLineMomentCollection( periods );
    DateTime? start = null;
    int balance = 0;
    foreach ( ITimeLineMoment timeLineMoment in timeLineMoments )
    {
      balance += timeLineMoment.BalanceCount;
      if ( !start.HasValue )
      {
        // start
        if ( balance >= usageCount )
        {
          start = timeLineMoment.Moment;
        }
      }
      else if ( balance < usageCount )
      {
        // end
        T period = new T();
        period.Setup( start.Value, timeLineMoment.Moment );
        occupiedPeriods.Add( period );
        start = null;
      }
    }
  }

  return occupiedPeriods;
} // GetOccupiedPeriods

Using the Code

The following example calculates the occupation periods (step one) of a resource using GetOccupiedPeriods. Based on the occupied periods, the library tool TimeGapCalculator (step two) calculates the available time periods of the resource:

// ----------------------------------------------------------------------
public void FreePeriodFinder()
{
  // resource
  ITimePeriodCollection resourcePeriods = new TimePeriodCollection();
  resourcePeriods.Add( 
    new TimeRange( new DateTime( 2014, 7, 19, 08, 15, 0 ), new DateTime( 2014, 7, 19, 14, 00, 0 ) ) );
  resourcePeriods.Add( 
    new TimeRange( new DateTime( 2014, 7, 19, 12, 45, 0 ), new DateTime( 2014, 7, 19, 20, 30, 0 ) ) );
  resourcePeriods.Add( 
    new TimeRange( new DateTime( 2014, 7, 19, 18, 00, 0 ), new DateTime( 2014, 7, 19, 23, 00, 0 ) ) );

  // step 1: calculate occupied periods
  ITimePeriodCollection occupiedPeriods = GetOccupiedPeriods<TimeRange>( resourcePeriods, 2 );
  foreach ( ITimePeriod occupiedPeriod in occupiedPeriods )
  {
    Console.WriteLine( "occupied: {0}", occupiedPeriod );
  }
  // > occupied: 19.07.2014 12:45:00 - 14:00:00 | 0.01:15
  // > occupied: 19.07.2014 18:00:00 - 20:30:00 | 0.02:30

  // step 2: calculate free periods
  ITimePeriod freePeriodLimits = resourcePeriods; // can be any other period like week, month...
  ITimePeriodCollection freePeriods = new TimeGapCalculator<TimeRange>().
    GetGaps( occupiedPeriods, freePeriodLimits );
  foreach ( ITimePeriod freePeriod in freePeriods )
  {
    Console.WriteLine( "free: {0}", freePeriod );
  }
  // > free: 19.07.2014 08:15:00 - 12:45:00 | 0.04:30
  // > free: 19.07.2014 14:00:00 - 18:00:00 | 0.04:00
  // > free: 19.07.2014 20:30:00 - 23:00:00 | 0.02:30
} // FreePeriodFinder