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package au.id.zancanaro;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.function.Function;
public interface Generator<T> {
RoseTree<T> generate(Random random, int size);
static <T> Generator<T> pure(T value) {
return (random, size) -> RoseTree.pure(value);
}
default <R> Generator<R> genFlatmap(Function<RoseTree<T>, Generator<R>> f) {
return (random, size) -> {
RoseTree<T> inner = this.generate(random, size);
Generator<R> generator = f.apply(inner);
return generator.generate(random, size);
};
}
default <R> Generator<R> genFmap(Function<RoseTree<T>, RoseTree<R>> f) {
return (random, size) -> f.apply(this.generate(random, size));
}
@SafeVarargs
static <T> Generator<T[]> tuple(Generator<T>... generators) {
return (random, size) -> {
@SuppressWarnings("unchecked")
RoseTree<T>[] result = (RoseTree<T>[]) new RoseTree[generators.length];
int index = 0;
for (Generator<T> generator : generators) {
result[index++] = generator.generate(random, size);
}
return RoseTree.zip(Function.identity(), result);
};
}
default <R> Generator<R> fmap(Function<T, R> f) {
return (random, size) -> this.generate(random, size).fmap(f);
}
default <R> Generator<R> flatMap(Function<T, Generator<R>> action) {
return this.genFlatmap(rose -> {
Generator<RoseTree<R>> generator = (random, size) ->
rose.fmap(action).fmap(g -> g.generate(random, size));
return generator.<R>genFmap(RoseTree::join);
});
}
}
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