dev.marksman.kraftwerk.frequency.FrequencyMapN Maven / Gradle / Ivy
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Purely functional random data generation
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package dev.marksman.kraftwerk.frequency;
import com.jnape.palatable.lambda.functions.Fn1;
import com.jnape.palatable.lambda.functions.builtin.fn2.Map;
import dev.marksman.kraftwerk.Generator;
import dev.marksman.kraftwerk.Weighted;
import java.util.TreeMap;
import static com.jnape.palatable.lambda.functions.builtin.fn2.Cons.cons;
import static com.jnape.palatable.lambda.functions.builtin.fn3.FoldLeft.foldLeft;
import static dev.marksman.kraftwerk.Generators.generateLongIndex;
final class FrequencyMapN implements FrequencyMap {
private final Iterable>> entries;
private Generator cachedGenerator;
@SuppressWarnings("unchecked")
private FrequencyMapN(Iterable>> entries) {
this.entries = (Iterable>>) entries;
}
static FrequencyMapN frequencyMapN(Weighted> first,
Iterable>> rest) {
return new FrequencyMapN<>(cons(first, rest));
}
static Generator addLabel(Generator gen) {
return gen.labeled("frequency map");
}
@Override
public boolean isEmpty() {
return false;
}
@Override
public Generator toGenerator() {
synchronized (this) {
if (cachedGenerator == null) cachedGenerator = buildGenerator();
}
return cachedGenerator;
}
private Generator buildGenerator() {
long total = 0L;
TreeMap> tree = new TreeMap<>();
for (Weighted> entry : entries) {
total += entry.getWeight();
tree.put(total, entry.getValue());
}
return addLabel(generateLongIndex(total)
.flatMap(n -> tree.ceilingEntry(1 + n).getValue()));
}
@SuppressWarnings("unchecked")
@Override
public FrequencyMap add(Weighted> weightedGenerator) {
if (weightedGenerator.getWeight() < 1) {
return this;
} else {
return new FrequencyMapN<>(cons((Weighted>) weightedGenerator, entries));
}
}
@Override
public FrequencyMap combine(FrequencyMap other) {
return foldLeft(FrequencyMap::add, other, entries);
}
@Override
public FrequencyMap fmap(Fn1 fn) {
Iterable>> mapped = Map.map(entry -> entry.fmap(gen -> gen.fmap(fn)), entries);
return new FrequencyMapN<>(mapped);
}
@Override
public FrequencyMap multiply(int positiveFactor) {
if (positiveFactor == 1) {
return this;
} else {
return new FrequencyMapN<>(Map.map(entry -> entry.multiplyBy(positiveFactor), entries));
}
}
}