/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.collections4.iterators;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTimeoutPreemptively;
import static org.junit.jupiter.api.Assertions.assertTrue;

import java.time.Duration;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.NoSuchElementException;
import java.util.Set;

import org.apache.commons.collections4.IteratorUtils;
import org.apache.commons.collections4.Predicate;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

/**
 * Tests the IteratorChain class.
 */
public class IteratorChainTest extends AbstractIteratorTest<String> {

    protected String[] testArray = {
        "One", "Two", "Three", "Four", "Five", "Six"
    };
    protected String[] testArray1234 = {
        "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight"
    };

    protected List<String> list1;
    protected List<String> list2;
    protected List<String> list3;
    protected List<String> list4;

    public List<String> getList1() {
        return list1;
    }

    public List<String> getList2() {
        return list2;
    }

    public List<String> getList3() {
        return list3;
    }

    public String[] getTestArray() {
        return testArray;
    }

    @Override
    public IteratorChain<String> makeEmptyIterator() {
        final ArrayList<String> list = new ArrayList<>();
        return new IteratorChain<>(list.iterator());
    }

    @Override
    public IteratorChain<String> makeObject() {
        final IteratorChain<String> chain = new IteratorChain<>();
        chain.addIterator(list1.iterator());
        chain.addIterator(list2.iterator());
        chain.addIterator(list3.iterator());
        return chain;
    }

    @BeforeEach
    public void setUp() {
        list1 = new ArrayList<>();
        list1.add("One");
        list1.add("Two");
        list1.add("Three");
        list2 = new ArrayList<>();
        list2.add("Four");
        list3 = new ArrayList<>();
        list3.add("Five");
        list3.add("Six");
        list4 = new ArrayList<>();
        list4.add("Seven");
        list4.add("Eight");
    }

    @Test
    public void testChaining() {
        IteratorChain<String> chain = new IteratorChain<>();
        chain.addIterator(list1.iterator());
        chain = new IteratorChain<>(chain);
        chain.addIterator(list2.iterator());
        chain = new IteratorChain<>(chain);
        chain.addIterator(list3.iterator());

        for (final String testValue : testArray) {
            assertTrue(chain.hasNext(), "chain contains values");
            assertTrue(chain.hasNext(), "hasNext doesn't change on 2nd invocation");
            final String iterValue = chain.next();
            assertEquals(testValue, iterValue, "Iteration value is correct");
            if (!iterValue.equals("Four")) {
                chain.remove();
            }
        }
        assertFalse(chain.hasNext(), "all values got iterated");
        assertTrue(list1.isEmpty(), "List is empty");
        assertEquals(1, list2.size(), "List is empty");
        assertTrue(list3.isEmpty(), "List is empty");
    }

    @Test
    public void testChainingPerformsWell() {
        Iterator<String> iter = makeObject();
        for (int i = 0; i < 150; i++) {
            final IteratorChain<String> chain = new IteratorChain<>();
            chain.addIterator(iter);
            iter = chain;
        }
        final Iterator<String> iterFinal = iter;
        assertTimeoutPreemptively(Duration.ofSeconds(1), () -> {
                for (final String testValue : testArray) {
                    final String iterValue = iterFinal.next();
                    assertEquals(testValue, iterValue, "Iteration value is correct");
                    if (!iterValue.equals("Four")) {
                        iterFinal.remove();
                    }
                }
                assertFalse(iterFinal.hasNext(), "all values got iterated");
                assertTrue(list1.isEmpty(), "List is empty");
                assertEquals(1, list2.size(), "List is empty");
                assertTrue(list3.isEmpty(), "List is empty");
            });
    }

    @Test
    public void testChainOfChains() {
        final Iterator<String> iteratorChain1 = new IteratorChain<>(list1.iterator(), list2.iterator());
        final Iterator<String> iteratorChain2 = new IteratorChain<>(list3.iterator(), list4.iterator());
        final Iterator<String> iteratorChainOfChains = new IteratorChain<>(iteratorChain1, iteratorChain2);

        for (final String testValue : testArray1234) {
            final String iterValue = (String) iteratorChainOfChains.next();
            assertEquals(testValue, iterValue, "Iteration value is correct");
        }

        assertFalse(iteratorChainOfChains.hasNext(), "Iterator should now be empty");
        assertThrows(NoSuchElementException.class, iteratorChainOfChains::next, "NoSuchElementException must be thrown");
    }

    @Test
    public void testChainOfUnmodifiableChains() {
        final Iterator<String> iteratorChain1 = new IteratorChain<>(list1.iterator(), list2.iterator());
        final Iterator<String> unmodifiableChain1 = IteratorUtils.unmodifiableIterator(iteratorChain1);
        final Iterator<String> iteratorChain2 = new IteratorChain<>(list3.iterator(), list4.iterator());
        final Iterator<String> unmodifiableChain2 = IteratorUtils.unmodifiableIterator(iteratorChain2);
        final Iterator<String> iteratorChainOfChains = new IteratorChain<>(unmodifiableChain1, unmodifiableChain2);

        for (final String testValue : testArray1234) {
            final String iterValue = (String) iteratorChainOfChains.next();
            assertEquals(testValue, iterValue, "Iteration value is correct");
        }

        assertFalse(iteratorChainOfChains.hasNext(), "Iterator should now be empty");
        assertThrows(NoSuchElementException.class, iteratorChainOfChains::next, "NoSuchElementException must be thrown");
    }

    @Test
    public void testChainOfUnmodifiableChainsRetainsUnmodifiableBehaviourOfNestedIterator() {
        final Iterator<String> iteratorChain1 = new IteratorChain<>(list1.iterator(), list2.iterator());
        final Iterator<String> unmodifiableChain1 = IteratorUtils.unmodifiableIterator(iteratorChain1);
        final Iterator<String> iteratorChain2 = new IteratorChain<>(list3.iterator(), list4.iterator());
        final Iterator<String> unmodifiableChain2 = IteratorUtils.unmodifiableIterator(iteratorChain2);
        final Iterator<String> iteratorChainOfChains = new IteratorChain<>(unmodifiableChain1, unmodifiableChain2);

        iteratorChainOfChains.next();
        assertThrows(UnsupportedOperationException.class, iteratorChainOfChains::remove,
                     "Calling remove must fail when nested iterator is unmodifiable");
    }

    @Test
    void testConstructList() {
        final List<Iterator<String>> list = new ArrayList<>();
        list.add(list1.iterator());
        list.add(list2.iterator());
        list.add(list3.iterator());
        final List<String> expected = new ArrayList<>(list1);
        expected.addAll(list2);
        expected.addAll(list3);
        final IteratorChain<String> iter = new IteratorChain<>(list);
        assertEquals(iter.size(), list.size());
        assertFalse(iter.isLocked());
        final List<String> actual = new ArrayList<>();
        iter.forEachRemaining(actual::add);
        assertEquals(actual, expected);
        assertTrue(iter.isLocked());
        assertThrows(UnsupportedOperationException.class, () -> iter.addIterator(list1.iterator()),
                     "adding iterators after iteratorChain has been traversed must fail");
    }

    @Test
    void testEmptyChain() {
        final IteratorChain<Object> chain = new IteratorChain<>();
        assertFalse(chain.hasNext());
        assertThrows(NoSuchElementException.class, () -> chain.next());
        assertThrows(IllegalStateException.class, () -> chain.remove());
    }

    @Test
    void testFirstIteratorIsEmptyBug() {
        final List<String> empty = new ArrayList<>();
        final List<String> notEmpty = new ArrayList<>();
        notEmpty.add("A");
        notEmpty.add("B");
        notEmpty.add("C");
        final IteratorChain<String> chain = new IteratorChain<>();
        chain.addIterator(empty.iterator());
        chain.addIterator(notEmpty.iterator());
        assertTrue(chain.hasNext(), "should have next");
        assertEquals("A", chain.next());
        assertTrue(chain.hasNext(), "should have next");
        assertEquals("B", chain.next());
        assertTrue(chain.hasNext(), "should have next");
        assertTrue(chain.hasNext(), "should not change");
        assertEquals("C", chain.next());
        assertFalse(chain.hasNext(), "should not have next");
        assertFalse(chain.hasNext(), "should not change");
    }

    @Test
    public void testHasNextIsInvokedOnEdgeBeforeRemove() {
        final Iterator<String> iter = makeObject();
        assertEquals(iter.next(), "One");
        assertEquals(iter.next(), "Two");
        assertEquals(iter.next(), "Three");
        assertTrue(iter.hasNext(), "next elements exists");
        iter.remove();  // though hasNext() on next iterator has been invoked, removing an element on old iterator must still work
        assertTrue(iter.hasNext(), "next elements exists");
        assertEquals(iter.next(), "Four");

        assertEquals(list1, Arrays.asList("One", "Two")); // Three must be gone
        assertEquals(list2, Arrays.asList("Four")); // Four still be there
        assertEquals(list3, Arrays.asList("Five", "Six")); // Five+Six anyway
    }

    @Test
    void testIterator() {
        final Iterator<String> iter = makeObject();
        for (final String testValue : testArray) {
            final Object iterValue = iter.next();
            assertEquals(testValue, iterValue, "Iteration value is correct");
        }
        assertFalse(iter.hasNext(), "Iterator should now be empty");
        assertThrows(NoSuchElementException.class, iter::next);
    }

    @Test
    public void testMultipleChainedIteratorPerformWellCollections722() {
        final Map<Integer, List<Integer>> source = new HashMap<>();
        for (int i = 0; i < 50; i++) {
            source.put(i, Arrays.asList(1, 2, 3));
        }

        Iterator<Integer> iterator = IteratorUtils.emptyIterator();
        final Set<Entry<Integer, List<Integer>>> entries = source.entrySet();
        for (final Entry<Integer, List<Integer>> entry : entries) {
            final Iterator<Integer> next = entry.getValue().iterator();
            iterator = IteratorUtils.chainedIterator(iterator, next);
        }
        final Iterator<Integer> lastIterator = iterator;
        assertTimeoutPreemptively(Duration.ofSeconds(2), () -> {
                      while (lastIterator.hasNext()) {
                          lastIterator.next().toString();
                      }
            });
    }

    @Test
    @Override
    public void testRemove() {
        final Iterator<String> iter = makeObject();
        assertThrows(IllegalStateException.class, () -> iter.remove(), "Calling remove before the first call to next() should throw an exception");
        assertTrue(iter.hasNext(), "initial has next should be true");
        assertThrows(IllegalStateException.class, () -> iter.remove(), "Calling remove before the first call to next() should throw an exception");

        for (final String testValue : testArray) {
            final String iterValue = iter.next();
            assertEquals(testValue, iterValue, "Iteration value is correct");
            if (!iterValue.equals("Four")) {
                iter.remove();
            }
        }
        assertTrue(list1.isEmpty(), "List is empty");
        assertEquals(1, list2.size(), "List is empty");
        assertTrue(list3.isEmpty(), "List is empty");
    }

    @Test
    public void testRemoveDoubleCallShouldFail() {
        final Iterator<String> iter = makeObject();
        assertEquals(iter.next(), "One");
        iter.remove();
        assertThrows(IllegalStateException.class, () -> iter.remove());
    }

    @Test
    void testRemoveFromFilteredIterator() {

        final Predicate<Integer> myPredicate = i -> i.compareTo(Integer.valueOf(4)) < 0;

        final List<Integer> list1 = new ArrayList<>();
        final List<Integer> list2 = new ArrayList<>();

        list1.add(Integer.valueOf(1));
        list1.add(Integer.valueOf(2));
        list2.add(Integer.valueOf(3));
        list2.add(Integer.valueOf(4)); // will be ignored by the predicate

        final Iterator<Integer> it1 = IteratorUtils.filteredIterator(list1.iterator(), myPredicate);
        final Iterator<Integer> it2 = IteratorUtils.filteredIterator(list2.iterator(), myPredicate);

        final Iterator<Integer> it = IteratorUtils.chainedIterator(it1, it2);
        while (it.hasNext()) {
            it.next();
            it.remove();
        }
        assertEquals(0, list1.size());
        assertEquals(1, list2.size());
    }
}
