Exercise.java

package org.khanacademy.core.topictree.models;

import com.google.common.base.MoreObjects;
import com.google.common.base.Preconditions;

import org.khanacademy.core.topictree.identifiers.ContentItemIdentifiable;
import org.khanacademy.core.topictree.identifiers.ContentItemIdentifier;
import org.khanacademy.core.topictree.identifiers.ContentItemKind;

/**
 * An exercise, which is a content item.
 */
public final class Exercise implements ContentItemIdentifiable {
    public final String contentId;

    public final ExerciseDescriptor descriptor;

    // TODO(mgp): Merge this into descriptor?
    public final String khanExercisesFilename;
    public final String progressKey;

    public Exercise(String contentId,
                    ExerciseDescriptor descriptor,
                    String khanExercisesFilename,
                    String progressKey) {
        this.contentId = Preconditions.checkNotNull(contentId);
        this.descriptor = Preconditions.checkNotNull(descriptor);
        this.khanExercisesFilename = Preconditions.checkNotNull(khanExercisesFilename);
        this.progressKey = Preconditions.checkNotNull(progressKey);
    }

    @Override
    public ContentItemIdentifier getIdentifier() {
        return new ContentItemIdentifier(ContentItemKind.EXERCISE, contentId);
    }

    @Override
    public String toString() {
        return MoreObjects.toStringHelper(this)
                .add("contentId", contentId)
                .add("descriptor", descriptor)
                .add("khanExercisesFilename", khanExercisesFilename)
                .add("progressKey", progressKey)
                .toString();
    }
}