/*
 * Copyright 2018 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.internal.execution;

import com.google.common.collect.ImmutableSortedMap;
import org.gradle.api.Describable;
import org.gradle.api.file.FileCollection;
import org.gradle.internal.execution.caching.CachingDisabledReason;
import org.gradle.internal.execution.caching.CachingState;
import org.gradle.internal.execution.history.ExecutionHistoryStore;
import org.gradle.internal.execution.history.changes.InputChangesInternal;
import org.gradle.internal.file.TreeType;
import org.gradle.internal.fingerprint.CurrentFileCollectionFingerprint;
import org.gradle.internal.fingerprint.FileCollectionFingerprint;
import org.gradle.internal.fingerprint.overlap.OverlappingOutputs;
import org.gradle.internal.reflect.TypeValidationContext;
import org.gradle.internal.snapshot.ValueSnapshot;
import org.gradle.internal.snapshot.impl.ImplementationSnapshot;

import javax.annotation.Nullable;
import java.io.File;
import java.time.Duration;
import java.util.Map;
import java.util.Optional;
import java.util.function.Supplier;

public interface UnitOfWork extends Describable {
    /**
     * Determine the identity of the work unit that uniquely identifies it
     * among the other work units of the same type in the current build.
     */
    Identity identify(Map<String, ValueSnapshot> identityInputs, Map<String, CurrentFileCollectionFingerprint> identityFileInputs);

    interface Identity {
        String getUniqueId();

        /**
         * Returns the {@link ExecutionHistoryStore} to use to store the execution state of this work.
         * When {@link Optional#empty()} no execution history will be maintained.
         */
        default Optional<ExecutionHistoryStore> getHistory() {
            return Optional.empty();
        }
    }

    /**
     * Executes the work synchronously.
     */
    WorkResult execute(@Nullable InputChangesInternal inputChanges, InputChangesContext context);

    default Optional<Duration> getTimeout() {
        return Optional.empty();
    }

    default InputChangeTrackingStrategy getInputChangeTrackingStrategy() {
        return InputChangeTrackingStrategy.NONE;
    }

    void visitImplementations(ImplementationVisitor visitor);

    interface ImplementationVisitor {
        void visitImplementation(Class<?> implementation);
        void visitImplementation(ImplementationSnapshot implementation);
        void visitAdditionalImplementation(ImplementationSnapshot implementation);
    }

    void visitInputProperties(InputPropertyVisitor visitor);

    interface InputPropertyVisitor {
        void visitInputProperty(String propertyName, Object value, IdentityKind identity);
    }

    void visitInputFileProperties(InputFilePropertyVisitor visitor);

    interface InputFilePropertyVisitor {
        void visitInputFileProperty(String propertyName, @Nullable Object value, InputPropertyType type, IdentityKind identity, Supplier<CurrentFileCollectionFingerprint> fingerprinter);
    }

    enum InputPropertyType {
        /**
         * Non-incremental inputs.
         */
        NON_INCREMENTAL(false, false),

        /**
         * Incremental inputs.
         */
        INCREMENTAL(true, false),

        /**
         * These are the primary inputs to the incremental work item;
         * if they are empty the work item shouldn't be executed.
         */
        PRIMARY(true, true);

        private final boolean incremental;
        private final boolean skipWhenEmpty;

        InputPropertyType(boolean incremental, boolean skipWhenEmpty) {
            this.incremental = incremental;
            this.skipWhenEmpty = skipWhenEmpty;
        }

        public boolean isIncremental() {
            return incremental;
        }

        public boolean isSkipWhenEmpty() {
            return skipWhenEmpty;
        }
    }

    enum IdentityKind {
        NON_IDENTITY, IDENTITY
    }

    void visitOutputProperties(OutputPropertyVisitor visitor);

    interface OutputPropertyVisitor {
        void visitOutputProperty(String propertyName, TreeType type, File root, FileCollection contents);
    }

    default void visitLocalState(LocalStateVisitor visitor) {}

    interface LocalStateVisitor {
        void visitLocalStateRoot(File localStateRoot);
    }

    default void visitDestroyableRoots(DestroyableVisitor visitor) {}

    interface DestroyableVisitor {
        void visitDestroyableRoot(File destroyableRoot);
    }

    long markExecutionTime();

    /**
     * Validate the work definition and configuration.
     */
    default void validate(WorkValidationContext validationContext) {}

    interface WorkValidationContext {
        TypeValidationContext createContextFor(Class<?> type, boolean cacheable);
    }

    /**
     * Return a reason to disable caching for this work.
     * When returning {@link Optional#empty()} if caching can still be disabled further down the pipeline.
     */
    default Optional<CachingDisabledReason> shouldDisableCaching(@Nullable OverlappingOutputs detectedOverlappingOutputs) {
        return Optional.empty();
    }

    /**
     * Checks if this work has empty inputs. If the work cannot be skipped, {@link Optional#empty()} is returned.
     * If it can, either {@link ExecutionOutcome#EXECUTED_NON_INCREMENTALLY} or {@link ExecutionOutcome#SHORT_CIRCUITED} is
     * returned depending on whether cleanup of existing outputs had to be performed.
     */
    default Optional<ExecutionOutcome> skipIfInputsEmpty(ImmutableSortedMap<String, FileCollectionFingerprint> outputFilesAfterPreviousExecution) {
        return Optional.empty();
    }

    /**
     * Is this work item allowed to load from the cache, or if we only allow it to be stored.
     */
    // TODO Make this part of CachingState instead
    default boolean isAllowedToLoadFromCache() {
        return true;
    }

    /**
     * Whether overlapping outputs should be allowed or ignored.
     */
    default OverlappingOutputHandling getOverlappingOutputHandling() {
        return OverlappingOutputHandling.IGNORE_OVERLAPS;
    }

    enum OverlappingOutputHandling {
        /**
         * Overlapping outputs are detected and handled.
         */
        DETECT_OVERLAPS,

        /**
         * Overlapping outputs are not detected.
         */
        IGNORE_OVERLAPS
    }

    /**
     * Whether the outputs should be cleanup up when the work is executed non-incrementally.
     */
    default boolean shouldCleanupOutputsOnNonIncrementalExecution() {
        return true;
    }

    enum WorkResult {
        DID_WORK,
        DID_NO_WORK
    }

    enum InputChangeTrackingStrategy {
        /**
         * No incremental parameters, nothing to track.
         */
        NONE(false),
        /**
         * Only the incremental parameters should be tracked for input changes.
         */
        INCREMENTAL_PARAMETERS(true),
        /**
         * All parameters are considered incremental.
         *
         * @deprecated Only used for {@code IncrementalTaskInputs}. Should be removed once {@code IncrementalTaskInputs} is gone.
         */
        @SuppressWarnings("DeprecatedIsStillUsed")
        @Deprecated
        ALL_PARAMETERS(true);

        private final boolean requiresInputChanges;

        InputChangeTrackingStrategy(boolean requiresInputChanges) {
            this.requiresInputChanges = requiresInputChanges;
        }

        public boolean requiresInputChanges() {
            return requiresInputChanges;
        }
    }

    /**
     * This is a temporary measure for Gradle tasks to track a legacy measurement of all input snapshotting together.
     */
    default void markLegacySnapshottingInputsStarted() {}

    /**
     * This is a temporary measure for Gradle tasks to track a legacy measurement of all input snapshotting together.
     */
    default void markLegacySnapshottingInputsFinished(CachingState cachingState) {}

    /**
     * This is a temporary measure for Gradle tasks to track a legacy measurement of all input snapshotting together.
     */
    default void ensureLegacySnapshottingInputsClosed() {}
}

@@ -2010,24 +2010,194 @@
  Identity %7B%0A
+        /**%0A         * The identity of the work unit that uniquely identifies it%0A         * among the other work units of the same type in the current build.%0A         */%0A
         Stri

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