public override IEnumerable <Song> VisitRatioExpression([NotNull] HaGrammarParser.RatioExpressionContext context)
{
var expressions = context.booleanExpression();
var evaluator = new ExpressionEvaluator();
if (expressions.Length == 1)
{
var parsed_expression = evaluator.Visit(expressions.First());
return(library.RandomSelect(parsed_expression));
}
else
{
var song_lists = new List <List <Song> >();
var weights = new List <int>();
double min_unit_size = double.MaxValue;
for (int i = 0; i < expressions.Length; i++)
{
BooleanExpression parsed_expression = evaluator.Visit(expressions[i]);
var list = library.RandomSelect(parsed_expression).ToList();
song_lists.Add(list);
int weight = int.Parse(context.GetToken(HaGrammarLexer.NUMBER, i).GetText());
weights.Add(weight);
double unit_size = list.Count / (double)weight;
if (unit_size < min_unit_size)
{
min_unit_size = unit_size;
}
}
var result_song_lists = new List <IEnumerable <Song> >();
for (int i = 0; i < expressions.Length; i++)
{
int songs_amount = (int)Math.Floor(weights[i] * min_unit_size);
result_song_lists.Add(song_lists[i].Take(songs_amount));
}
return(SongLibrary.Shuffle(new HashSet <Song>(result_song_lists.Aggregate((x, y) => x.Concat(y)))));
}
}
public QueryEvaluator(SongLibrary library)
{
this.library = library;
}
