/*
 * Copyright 2016 the original author or authors.
 *
 * Licensed 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
 *
 *      http://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.gradle.api.internal.changedetection.rules;

import com.google.common.collect.Iterators;
import org.gradle.api.internal.changedetection.state.FileCollectionSnapshot;
import org.gradle.api.internal.changedetection.state.TaskExecution;

import javax.annotation.Nullable;
import java.util.Iterator;

public class DiscoveredInputsTaskStateChanges implements TaskStateChanges {
    private final TaskExecution previous;
    private final TaskExecution current;

    public DiscoveredInputsTaskStateChanges(@Nullable TaskExecution previous, TaskExecution current) {
        this.previous = previous;
        this.current = current;
    }

    @Override
    public Iterator<TaskStateChange> iterator() {
        FileCollectionSnapshot previousDiscoveredInputs = previous != null ? previous.getDiscoveredInputFilesSnapshot() : null;
        if (previousDiscoveredInputs == null) {
            return Iterators.<TaskStateChange>singletonIterator(new DescriptiveChange("Discovered input file history is not available."));
        }
        return current.getDiscoveredInputFilesSnapshot().iterateContentChangesSince(previousDiscoveredInputs, "discovered input", true);
    }
}
