/// <summary>
/// Calculates the winning <see cref="Runner"/>.
/// </summary>
/// <returns></returns>
public Runner RunRace()
{
if (!_canRunRace || _raceMargin == 0)
{
return(null);
}
// Calculate the chances of each of the runners winning, based on their margin.
var runnersAndChances = Runners.Select(r => new { Runner = r, Chances = r.GetMargin() / _raceMargin });
// Now, randomize the runners' chances using a randomization margin.
var runnersAndRanomizedChances = runnersAndChances.Select(r => new { Runner = r.Runner, Chances = r.Chances + Convert.ToDecimal(_random.NextDouble() * 2 - 1) * _randomMargin });
// Re-normalize the chances so that they stack up to 100%.
Decimal totalRandomizedChances = runnersAndRanomizedChances.Sum(r => r.Chances);
var runnersAndNormalizedRandomizedChances = runnersAndRanomizedChances
.Select(r => new { Runner = r.Runner, Chances = r.Chances / totalRandomizedChances })
.ToList();
// Calculate a random outcome for the race.
Decimal raceOutcome = Convert.ToDecimal(_random.NextDouble());
// Now, iterate over the runners to see if their chances of winning covers the random race outcome.
Decimal cumulativeChances = 0M;
foreach (var runnerChances in runnersAndNormalizedRandomizedChances.OrderBy(r => r.Chances))
{
Decimal runnerMinChance = cumulativeChances;
Decimal runnerMaxChance = cumulativeChances + runnerChances.Chances;
if (raceOutcome > runnerMinChance && raceOutcome <= runnerMaxChance)
{
// If the runners chances covers the outcome, we have a winner.
// Note that this case covers 1.
return(runnerChances.Runner);
}
else if (cumulativeChances == 0 && raceOutcome == 0)
{
// If the race outcome was zero and this is the first runner, then this one wins.
return(runnerChances.Runner);
}
// If we didn't find a winner, increase the cumulative chances and continue.
cumulativeChances += runnerChances.Chances;
}
// If we reach this point, its likely that the runnerMaxChance was still less than
// the race outcome due to accuracy issues. If this is the case, then last runner
// would have been the winner.
return(runnersAndNormalizedRandomizedChances.OrderBy(r => r.Chances).Last().Runner);
}
