PruneDeletionTree.java

package com.octodecillion.learn.rxjava;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import rx.Observable;

/**
 * 
 * @author jbetancourt
 *
 */
public class PruneDeletionTree {
    /** A struct */
    private class State{
        public String deletedPath = "";
        public boolean isDeleting = false;
    }
    
    /**
     * 
     * <p>
     * @param list  sorted list of Folders
     * @return pruned list of those Folders
     * @since Dec 18, 2015
     */
    public List<Folder> pruneDeletedFoldersRx(List<Folder> list){
        final State state = new State();
        
        final List<Folder> prunedList = new ArrayList<>();
        
        Observable.from(list).filter(folder -> {
            String path = folder.getPath();
            if (state.isDeleting) {
                if (path.startsWith(state.deletedPath)) {
                    return false;
                } else {
                    state.isDeleting = false;
                    state.deletedPath = "";
                }
            } else { 
                if (folder.isDeleted()) {
                    state.isDeleting = true;
                    state.deletedPath = path;
                }
            }           
            
            return true;
        }).subscribe(prunedList::add);
        
        return prunedList;
    }
    
    /**
     * 
     * <p>
     * @param list  list of sorted Folders
     * @return pruned list of those Folders
     * @since Dec 18, 2015
     */
    public List<Folder> pruneDeletedFoldersJavaStream(List<Folder> list){       
        final State state = new State();
        
        List<Folder> prunedList = new ArrayList<>();
        
        prunedList =  list.stream().filter(folder -> {
            String path = folder.getPath();
            if (state.isDeleting) {
                if (path.startsWith(state.deletedPath)) {
                    return false;
                } else {
                    state.isDeleting = false;
                    state.deletedPath = "";
                }
            } else { 
                if (folder.isDeleted()) {
                    state.isDeleting = true;
                    state.deletedPath = path;
                }
            }           
            
            return true;
            
        }).collect(Collectors.toList());

        return prunedList;
    }
}

PruneDeletionTreeTest.java

package com.octodecillion.learn.rxjava;

import static org.junit.Assert.fail;

import java.util.List;

import org.junit.Test;

/**
 * Test {@link PruneDeletionTree}.
 * @author jbetancourt
 *
 */
public class PruneDeletionTreeTest {
    private static final String EXPECTED_TREE_JSON = "/expectedTree.json";
    private static final String TEST_TREE_JSON = "/tree.json";
    
    
    /**
     * Test method for {@link com.octodecillion.learn.rxjava.Iterative#pruneDeletedFolders(java.util.List)}.
     */
    @Test
    public void testPruneDeletedFoldersRx() {
        final List<Folder> expectedList = TestUtils.readData(EXPECTED_TREE_JSON);

        final List<Folder> prunedList = new PruneDeletionTree().pruneDeletedFoldersRx(TestUtils.readData(TEST_TREE_JSON));
        
        boolean sizesMatch = prunedList.size() == expectedList.size();
        
        if(!sizesMatch && expectedList.stream().noneMatch(f-> prunedList.contains(f))){
            fail("Failed pruning list");
        }
    }
    
    /**
     * Test method for {@link com.octodecillion.learn.rxjava.Iterative#pruneDeletedFolders(java.util.List)}.
     */
    @Test
    public void testPruneDeletedFoldersJavaStream() {
        final List<Folder> expectedList = TestUtils.readData(EXPECTED_TREE_JSON);

        final List<Folder> prunedList = new PruneDeletionTree().pruneDeletedFoldersJavaStream(TestUtils.readData(TEST_TREE_JSON));
        
        boolean sizesMatch = prunedList.size() == expectedList.size();
        
        if(!sizesMatch && expectedList.stream().noneMatch(f-> prunedList.contains(f))){
            fail("Failed pruning list");
        }
    }
}