package water.udf;

import water.fvec.Chunk;
import water.fvec.RawChunk;
import water.fvec.Vec;
import water.util.fp.Function;
import static water.util.Java7.*;

/**
 * This column depends on another column
 */
public class FunColumn<X, Y> extends FunColumnBase<Y> {
  private final Function<X, Y> f;
  private final Column<X> xs;

  @Override public int rowLayout() { return xs.rowLayout(); }

  /**
   * deserialization :(
   */
  public FunColumn() {
    f = null; xs = null;
  }

  public FunColumn(Function<X, Y> f, Column<X> xs) {
    super(xs);
    this.f = f;
    this.xs = xs;
  }
  
  @Override public TypedChunk<Y> chunkAt(int i) {
    return new FunChunk(xs.chunkAt(i));
  }

  public Y get(long idx) { return isNA(idx) ? null : f.apply(xs.apply(idx)); }

  @Override public boolean isNA(long idx) { return xs.isNA(idx); }

  /**
   * Pretends to be a chunk of a column, for distributed calculations.
   * Has type, and is not materialized
   */
  public class FunChunk extends DependentChunk<Y> {
    private final TypedChunk<X> cx;
  
    public FunChunk(TypedChunk<X> cx) { 
      super(cx);
      this.cx = cx; 
    }

    @Override public Vec vec() { return FunColumn.this.vec(); }

    @Override public int length() { return cx.length(); }

    private RawChunk myChunk = new RawChunk(this);

    @Override public Chunk rawChunk() { return myChunk; }

    @Override public boolean isNA(int i) { return cx.isNA(i); }

    @Override public Y get(int i) { return f.apply(cx.get(i)); }
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) return true;
    if (o instanceof FunColumn) {
      FunColumn other = (FunColumn) o;
      return Objects.equals(f, other.f) && xs.equals(other.xs);
    }
    return false;

  }

  @Override
  public int hashCode() {
    return 61 * xs.hashCode() + Objects.hashCode(f);
  }

  @Override public String toString() { return "FunColumn(" + f.getClass().getSimpleName() + "," + xs + ")"; }
}