InstallationId.java

/*
 * Copyright (c) 2015-present, Parse, LLC.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */
package com.parse;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.UUID;

/**
 * Since we cannot save dirty ParseObjects to disk and we must be able to persist UUIDs across
 * restarts even if the ParseInstallation is not saved, we use this legacy file still as a
 * bootstrapping environment as well until the full ParseInstallation is cached to disk.
 * <p>
 * TODO: Allow dirty objects to be saved to disk.
 */
/* package */ class InstallationId {

    private static final String TAG = "InstallationId";

    private final Object lock = new Object();
    private final File file;
    private String installationId;

    public InstallationId(File file) {
        this.file = file;
    }

    /**
     * Loads the installationId from memory, then tries to loads the legacy installationId from disk
     * if it is present, or creates a new random UUID.
     */
    public String get() {
        synchronized (lock) {
            if (installationId == null) {
                try {
                    installationId = ParseFileUtils.readFileToString(file, "UTF-8");
                } catch (FileNotFoundException e) {
                    PLog.i(TAG, "Couldn't find existing installationId file. Creating one instead.");
                } catch (IOException e) {
                    PLog.e(TAG, "Unexpected exception reading installation id from disk", e);
                }
            }

            if (installationId == null) {
                setInternal(UUID.randomUUID().toString());
            }
        }

        return installationId;
    }

    /**
     * Sets the installationId and persists it to disk.
     */
    public void set(String newInstallationId) {
        synchronized (lock) {
            if (ParseTextUtils.isEmpty(newInstallationId)
                    || newInstallationId.equals(get())) {
                return;
            }
            setInternal(newInstallationId);
        }
    }

    private void setInternal(String newInstallationId) {
        synchronized (lock) {
            try {
                ParseFileUtils.writeStringToFile(file, newInstallationId, "UTF-8");
            } catch (IOException e) {
                PLog.e(TAG, "Unexpected exception writing installation id to disk", e);
            }

            installationId = newInstallationId;
        }
    }

    /* package for tests */ void clear() {
        synchronized (lock) {
            installationId = null;
            ParseFileUtils.deleteQuietly(file);
        }
    }
}