/*
 * Copyright 2019 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.tasks.execution;

import org.gradle.api.execution.internal.TaskInputsListener;
import org.gradle.api.file.FileCollection;
import org.gradle.api.internal.TaskInternal;
import org.gradle.api.internal.file.FileCollectionInternal;
import org.gradle.internal.Cast;
import org.gradle.internal.cleanup.BuildOutputCleanupRegistry;
import org.gradle.internal.execution.ExecutionOutcome;
import org.gradle.internal.execution.OutputChangeListener;
import org.gradle.internal.execution.impl.OutputsCleaner;
import org.gradle.internal.file.Deleter;
import org.gradle.internal.fingerprint.FileCollectionFingerprint;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.Map;
import java.util.Optional;

public class DefaultEmptySourceTaskSkipper implements EmptySourceTaskSkipper {
    private static final Logger LOGGER = LoggerFactory.getLogger(DefaultEmptySourceTaskSkipper.class);

    private final BuildOutputCleanupRegistry buildOutputCleanupRegistry;
    private final Deleter deleter;
    private final OutputChangeListener outputChangeListener;
    private final TaskInputsListener taskInputsListener;

    public DefaultEmptySourceTaskSkipper(
        BuildOutputCleanupRegistry buildOutputCleanupRegistry,
        Deleter deleter,
        OutputChangeListener outputChangeListener,
        TaskInputsListener taskInputsListener
    ) {
        this.buildOutputCleanupRegistry = buildOutputCleanupRegistry;
        this.deleter = deleter;
        this.outputChangeListener = outputChangeListener;
        this.taskInputsListener = taskInputsListener;
    }

    @Override
    public Optional<ExecutionOutcome> skipIfEmptySources(TaskInternal task, boolean hasSourceFiles, FileCollection inputFiles, FileCollection sourceFiles, Map<String, FileCollectionFingerprint> outputFileSnapshots) {
        if (hasSourceFiles && sourceFiles.isEmpty()) {
            ExecutionOutcome skipOutcome;
            if (outputFileSnapshots.isEmpty()) {
                LOGGER.info("Skipping {} as it has no source files and no previous output files.", task);
                skipOutcome = ExecutionOutcome.SHORT_CIRCUITED;
            } else {
                OutputsCleaner outputsCleaner = new OutputsCleaner(
                    deleter,
                    buildOutputCleanupRegistry::isOutputOwnedByBuild,
                    buildOutputCleanupRegistry::isOutputOwnedByBuild
                );
                for (FileCollectionFingerprint outputFingerprints : outputFileSnapshots.values()) {
                    try {
                        outputChangeListener.beforeOutputChange(outputFingerprints.getRootPaths());
                        outputsCleaner.cleanupOutputs(outputFingerprints);
                    } catch (IOException e) {
                        throw new UncheckedIOException(e);
                    }
                }
                if (outputsCleaner.getDidWork()) {
                    LOGGER.info("Cleaned previous output of {} as it has no source files.", task);
                    skipOutcome = ExecutionOutcome.EXECUTED_NON_INCREMENTALLY;
                } else {
                    skipOutcome = ExecutionOutcome.SHORT_CIRCUITED;
                }
            }
            taskInputsListener.onExecute(task, Cast.cast(FileCollectionInternal.class, sourceFiles));
            return Optional.of(skipOutcome);
        } else {
            taskInputsListener.onExecute(task, Cast.cast(FileCollectionInternal.class, inputFiles));
            return Optional.empty();
        }
    }

}
