build-system/manifest-merger/src/main/java/com/android/manifmerger/ElementsTrimmer.java

/*
 * Copyright (C) 2014 The Android Open Source Project
 *
 * 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 com.android.manifmerger;

import static com.android.SdkConstants.ANDROID_URI;

import com.android.SdkConstants;
import com.android.annotations.NonNull;
import com.android.xml.AndroidManifest;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;
import org.w3c.dom.Attr;

/**
 * Trims the document from unwanted, repeated elements.
 */
public class ElementsTrimmer {

    /**
     * Trims unwanted, duplicated elements from the merged document.
     * <p>
     * Current trimmed elements are :
     * <ul>
     *     <li>uses-features with glEsVersion key
     * <ul>
     *     <li>The highest 1.x version element will be kept regardless of 'required' flag value</li>
     *     <li>If the above element is present and has a 'false' required flag, there can be at most
     *     one element of a lesser version with 'required' attribute set to true.</li>
     *     <li>The highest 2.x or superior element will be kept regardless of 'required' flag value
     *     </li>
     *     <li>If the above element is present and has a 'false' required flag, there can be at
     *     most one element of a lesser version (but higher than 2.0) with a 'required' attribute
     *     set to true.</li>
     * </ul>
     * </li>
     * </ul>
     *
     * @param xmlDocument the xml document to trim.
     * @param mergingReport the report to log errors and actions.
     */
    public static void trim(
            @NonNull XmlDocument xmlDocument,
            @NonNull MergingReport.Builder mergingReport) {

        // I sort the glEsVersion declaration by value.
        NavigableMap<Integer, XmlElement> glEsVersionDeclarations = new TreeMap<Integer, XmlElement>();

        for (XmlElement childElement : xmlDocument.getRootNode().getMergeableElements()) {
            if (childElement.getType().equals(ManifestModel.NodeTypes.USES_FEATURE)) {
                Integer value = getGlEsVersion(childElement);
                if (value != null) {
                    glEsVersionDeclarations.put(value, childElement);
                }
            }
        }

        // now eliminate all unwanted declarations, revert the sorted map, so we get the
        // higher elements first.
        glEsVersionDeclarations = glEsVersionDeclarations.descendingMap();
        boolean doneWithAboveTwoTrue = false;
        boolean doneWithAboveTwoFalse = false;
        boolean doneWithBelowTwoTrue = false;
        boolean doneWithBelowTwoFalse = false;
        for (Map.Entry<Integer, XmlElement> glEsVersionDeclaration :
                glEsVersionDeclarations.entrySet()) {

            boolean removeElement;

            Attr requiredAttribute = glEsVersionDeclaration.getValue().getXml().getAttributeNodeNS(
                    ANDROID_URI, AndroidManifest.ATTRIBUTE_REQUIRED);

            boolean isRequired = requiredAttribute == null ||
                    Boolean.parseBoolean(requiredAttribute.getValue());

            if (glEsVersionDeclaration.getKey() < 0x20000) {
                // version one.
                removeElement = (doneWithBelowTwoFalse && doneWithBelowTwoTrue)
                        || (isRequired && doneWithBelowTwoTrue)
                        || (!isRequired && doneWithBelowTwoFalse);

                if (!removeElement) {
                    doneWithBelowTwoFalse = true;
                    doneWithBelowTwoTrue = isRequired;
                }
            } else {
                // version two or above.
                removeElement = (doneWithAboveTwoFalse && doneWithAboveTwoTrue)
                        || (isRequired && doneWithAboveTwoTrue)
                        || (!isRequired && doneWithAboveTwoFalse);

                if (!removeElement) {
                    doneWithAboveTwoFalse = true;
                    doneWithAboveTwoTrue = isRequired;
                }
            }
            if (removeElement) {
                // if the node only contains glEsVersion, then remove the entire node,
                // if it also contains android:name, just remove the glEsVersion attribute
                if (glEsVersionDeclaration.getValue().getXml().getAttributeNodeNS(ANDROID_URI,
                        SdkConstants.ATTR_NAME) != null) {
                    glEsVersionDeclaration.getValue().getXml().removeAttributeNS(ANDROID_URI,
                            AndroidManifest.ATTRIBUTE_GLESVERSION);
                    mergingReport.getActionRecorder().recordAttributeAction(
                            glEsVersionDeclaration.getValue().getAttribute(XmlNode.fromXmlName(
                                    "android:" + AndroidManifest.ATTRIBUTE_GLESVERSION)).get(),
                            Actions.ActionType.REJECTED,
                            null /* attributeOperationType */);
                } else {
                    xmlDocument.getRootNode().getXml().removeChild(
                            glEsVersionDeclaration.getValue().getXml());
                    mergingReport.getActionRecorder().recordNodeAction(
                            glEsVersionDeclaration.getValue(),
                            Actions.ActionType.REJECTED);

                }
            }

        }

    }

    private static Integer getGlEsVersion(@NonNull XmlElement xmlElement) {
        Attr glEsVersion = xmlElement.getXml()
                .getAttributeNodeNS(ANDROID_URI, AndroidManifest.ATTRIBUTE_GLESVERSION);
        if (glEsVersion == null) {
            return null;
        }
        return getHexValue(glEsVersion);
    }

    private static Integer getHexValue(@NonNull Attr attribute) {
        return Integer.decode(attribute.getValue());
    }
}