package io.atlassian.fugue.optic.law;
   
   import io.atlassian.fugue.*;
   import io.atlassian.fugue.law.IsEq;
   import io.atlassian.fugue.optic.PLens;
   
   import java.util.Collections;
   import java.util.List;
   import java.util.function.Function;
  
  import static io.atlassian.fugue.law.IsEq.isEq;
  import static java.util.Spliterator.ORDERED;
  import static java.util.Spliterators.spliteratorUnknownSize;
  import static java.util.stream.Collectors.toList;
  import static java.util.stream.StreamSupport.stream;
  
  public final class LensLaws<S, A> {
  
    private final PLens<S, S, A, A> lens;
  
    public LensLaws(PLens<S, S, A, A> lens) {
      this.lens = lens;
    }
  
    /**
     * set what you get
     */
    public IsEq<S> getSet(S s) {
      return isEq(lens.set(lens.get(s)).apply(s), s);
    }
  
    /**
     * get what you set
     */
    public IsEq<A> setGet(S s, A a) {
      return isEq(lens.get(lens.set(a).apply(s)), a);
    }
  
    /**
     * set idempotent
     */
    public IsEq<S> setIdempotent(S s, A a) {
      return isEq(lens.set(a).apply(lens.set(a).apply(s)), lens.set(a).apply(s));
    }
  
    /**
     * modify id = id
     */
    public IsEq<S> modifyIdentity(S s) {
      return isEq(lens.modify(Function.<A> identity()).apply(s), s);
    }
  
    /**
     * modifyF Applicative.point(_) = Applicative.point(_)
     */
    public IsEq<S> modifySupplierFPoint(S s) {
      return isEq(lens.modifySupplierF(Suppliers::ofInstance).apply(s).get(), s);
    }
  
    /**
     * modifyF Applicative.point(_) = Applicative.point(_)
     */
    public IsEq<Either<String, S>> modifyEitherFPoint(S s) {
      return isEq(lens.<String> modifyEitherF(Eithers.toRight()).apply(s), Either.right(s));
    }
  
    /**
     * modifyF Applicative.point(_) = Applicative.point(_)
     */
    public IsEq<Option<S>> modifyOptionFPoint(S s) {
      return isEq(lens.modifyOptionF(Options.toOption()).apply(s), Option.some(s));
    }
  
    /**
     * modifyF Applicative.point(_) = Applicative.point(_)
     */
    public IsEq<Pair<S, S>> modifyPairFPoint(S s) {
      return isEq(lens.modifyPairF(a -> Pair.pair(a, a)).apply(s), Pair.pair(s, s));
    }
  
    /**
     * modifyF Applicative.point(_) = Applicative.point(_)
     */
    public IsEq<S> modifyFunctionFPoint(S s) {
      return isEq(lens.<String> modifyFunctionF(a -> __ -> a).apply(s).apply(""), s);
    }
  
    /**
     * modifyF Applicative.point(_) = Applicative.point(_)
     */
    public IsEq<List<S>> modifyIterableFPoint(S s) {
      return isEq(stream(spliteratorUnknownSize(lens.modifyIterableF(Collections::singleton).apply(s).iterator(), ORDERED), false).collect(toList()),
        Collections.singletonList(s));
    }
  }