/**

* Copyright (c) Rich Hickey. All rights reserved.

* The use and distribution terms for this software are covered by the

* Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)

* which can be found in the file epl-v10.html at the root of this distribution.

* By using this software in any fashion, you are agreeing to be bound by

* the terms of this license.

* You must not remove this notice, or any other, from this software.

**/

package clojure.lang;

/* Alex Miller, Dec 5, 2014 */

import java.io.IOException;

public class Iterate extends ASeq implements IReduce, IPending {

private static final long serialVersionUID = -78221705247226450L;

private static final Object UNREALIZED_SEED = new Object();

private final IFn f; // never null

private final Object prevSeed;

private volatile Object _seed; // lazily realized

private volatile ISeq _next; // cached

private Iterate(IFn f, Object prevSeed, Object seed){

this.f = f;

this.prevSeed = prevSeed;

this._seed = seed;

}

private Iterate(IPersistentMap meta, IFn f, Object prevSeed, Object seed, ISeq next){

super(meta);

this.f = f;

this.prevSeed = prevSeed;

this._seed = seed;

this._next = next;

}

public static ISeq create(IFn f, Object seed){

return new Iterate(f, null, seed);

}

public boolean isRealized() {

return _seed != UNREALIZED_SEED;

}

public Object first(){

if(_seed == UNREALIZED_SEED) {

_seed = f.invoke(prevSeed);

}

return _seed;

}

public ISeq next(){

if(_next == null) {

_next = new Iterate(f, first(), UNREALIZED_SEED);

}

return _next;

}

public Iterate withMeta(IPersistentMap meta){

if(meta() == meta)

return this;

return new Iterate(meta, f, prevSeed, _seed, _next);

}

public Object reduce(IFn rf){

Object first = first();

Object ret = first;

Object v = f.invoke(first);

while(true){

ret = rf.invoke(ret, v);

if(RT.isReduced(ret))

return ((IDeref)ret).deref();

v = f.invoke(v);

}

}

public Object reduce(IFn rf, Object start){

Object ret = start;

Object v = first();

while(true){

ret = rf.invoke(ret, v);

if(RT.isReduced(ret))

return ((IDeref)ret).deref();

v = f.invoke(v);

}

}

public int hashCode(){

throw new UnsupportedOperationException();

}

public int hasheq(){

throw new UnsupportedOperationException();

}

// serialization not supported

private void writeObject(java.io.ObjectOutputStream out) throws IOException {

throw new UnsupportedOperationException();

}

// deserialization not supported

private void readObject(java.io.ObjectInputStream in) throws IOException, ClassNotFoundException {

throw new UnsupportedOperationException();

}

}