/// <summary>
/// Gets the winning vote.
/// Excludes any already chosen votes from the process.
/// </summary>
/// <param name="voterRankings">The voter rankings.</param>
/// <param name="chosenChoices">The already chosen choices.</param>
/// <returns>Returns the winning vote.</returns>
private (VoteStorageEntry vote, double score) GetWinningVote(VoteStorage votes)
{
var workingVotes = new VoteStorage(votes);
int voterCount = workingVotes.SelectMany(a => a.Value).Distinct().Count();
int winCount = voterCount / 2 + 1;
while (workingVotes.Count > 1)
{
// Invert the votes so that we can look at preferences per user.
var voterPreferences = workingVotes
.SelectMany(v => v.Value)
.GroupBy(u => u.Key)
.ToDictionary(t => t.Key, s => s.Select(q => q.Value).OrderBy(r => r.MarkerValue).ToList());
// Check to see if we have a winner.
var(vote, count) = GetMostPreferredVote(voterPreferences);
if (count >= winCount)
{
var fullVote = workingVotes.First(a => a.Key == vote);
return(fullVote, count);
}
VoteLineBlock leastPreferredChoice;
// If not, eliminate the least preferred option and try again.
if (leastPreferredChecksFullVotes)
{
leastPreferredChoice = GetLeastPreferredChoice(workingVotes);
}
else
{
leastPreferredChoice = GetLeastPreferredChoice(voterPreferences);
}
workingVotes.Remove(leastPreferredChoice);
}
// If we get to here, the only option left has to win.
return(workingVotes.First(), 1);
}
