/*
 * Copyright (C) 2013 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 android.support.multidex;

import android.content.Context;
import android.content.SharedPreferences;
import android.content.pm.ApplicationInfo;
import android.os.Build;
import android.util.Log;

import java.io.BufferedOutputStream;
import java.io.Closeable;
import java.io.File;
import java.io.FileFilter;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.util.ArrayList;
import java.util.List;
import java.util.zip.ZipEntry;
import java.util.zip.ZipException;
import java.util.zip.ZipFile;
import java.util.zip.ZipOutputStream;

/**
 * Exposes application secondary dex files as files in the application data
 * directory.
 */
final class MultiDexExtractor {

    private static final String TAG = MultiDex.TAG;

    /**
     * We look for additional dex files named {@code classes2.dex},
     * {@code classes3.dex}, etc.
     */
    private static final String DEX_PREFIX = "classes";
    private static final String DEX_SUFFIX = ".dex";

    private static final String EXTRACTED_NAME_EXT = ".classes";
    private static final String EXTRACTED_SUFFIX = ".zip";
    private static final int MAX_EXTRACT_ATTEMPTS = 3;

    private static final String PREFS_FILE = "multidex.version";
    private static final String KEY_TIME_STAMP = "timestamp";
    private static final String KEY_CRC = "crc";
    private static final String KEY_DEX_NUMBER = "dex.number";

    /**
     * Size of reading buffers.
     */
    private static final int BUFFER_SIZE = 0x4000;
    /* Keep value away from 0 because it is a too probable time stamp value */
    private static final long NO_VALUE = -1L;

    private static final String LOCK_FILENAME = "MultiDex.lock";

    /**
     * Extracts application secondary dexes into files in the application data
     * directory.
     *
     * @return a list of files that were created. The list may be empty if there
     *         are no secondary dex files. Never return null.
     * @throws IOException if encounters a problem while reading or writing
     *         secondary dex files
     */
    static List<File> load(Context context, ApplicationInfo applicationInfo, File dexDir,
            boolean forceReload) throws IOException {
        Log.i(TAG, "MultiDexExtractor.load(" + applicationInfo.sourceDir + ", " + forceReload + ")");
        final File sourceApk = new File(applicationInfo.sourceDir);

        long currentCrc = getZipCrc(sourceApk);

        // Validity check and extraction must be done only while the lock file has been taken.
        File lockFile = new File(dexDir, LOCK_FILENAME);
        RandomAccessFile lockRaf = new RandomAccessFile(lockFile, "rw");
        FileChannel lockChannel = null;
        FileLock cacheLock = null;
        List<File> files;
        IOException releaseLockException = null;
        try {
            lockChannel = lockRaf.getChannel();
            Log.i(TAG, "Blocking on lock " + lockFile.getPath());
            cacheLock = lockChannel.lock();
            Log.i(TAG, lockFile.getPath() + " locked");

            if (!forceReload && !isModified(context, sourceApk, currentCrc)) {
                try {
                    files = loadExistingExtractions(context, sourceApk, dexDir);
                } catch (IOException ioe) {
                    Log.w(TAG, "Failed to reload existing extracted secondary dex files,"
                            + " falling back to fresh extraction", ioe);
                    files = performExtractions(sourceApk, dexDir);
                    putStoredApkInfo(context,
                            getTimeStamp(sourceApk), currentCrc, files.size() + 1);

                }
            } else {
                Log.i(TAG, "Detected that extraction must be performed.");
                files = performExtractions(sourceApk, dexDir);
                putStoredApkInfo(context, getTimeStamp(sourceApk), currentCrc, files.size() + 1);
            }
        } finally {
            if (cacheLock != null) {
                try {
                    cacheLock.release();
                } catch (IOException e) {
                    Log.e(TAG, "Failed to release lock on " + lockFile.getPath());
                    // Exception while releasing the lock is bad, we want to report it, but not at
                    // the price of overriding any already pending exception.
                    releaseLockException = e;
                }
            }
            if (lockChannel != null) {
                closeQuietly(lockChannel);
            }
            closeQuietly(lockRaf);
        }

        if (releaseLockException != null) {
            throw releaseLockException;
        }

        Log.i(TAG, "load found " + files.size() + " secondary dex files");
        return files;
    }

    /**
     * Load previously extracted secondary dex files. Should be called only while owning the lock on
     * {@link #LOCK_FILENAME}.
     */
    private static List<File> loadExistingExtractions(Context context, File sourceApk, File dexDir)
            throws IOException {
        Log.i(TAG, "loading existing secondary dex files");

        final String extractedFilePrefix = sourceApk.getName() + EXTRACTED_NAME_EXT;
        int totalDexNumber = getMultiDexPreferences(context).getInt(KEY_DEX_NUMBER, 1);
        final List<File> files = new ArrayList<File>(totalDexNumber);

        for (int secondaryNumber = 2; secondaryNumber <= totalDexNumber; secondaryNumber++) {
            String fileName = extractedFilePrefix + secondaryNumber + EXTRACTED_SUFFIX;
            File extractedFile = new File(dexDir, fileName);
            if (extractedFile.isFile()) {
                files.add(extractedFile);
                if (!verifyZipFile(extractedFile)) {
                    Log.i(TAG, "Invalid zip file: " + extractedFile);
                    throw new IOException("Invalid ZIP file.");
                }
            } else {
                throw new IOException("Missing extracted secondary dex file '" +
                        extractedFile.getPath() + "'");
            }
        }

        return files;
    }


    /**
     * Compare current archive and crc with values stored in {@link SharedPreferences}. Should be
     * called only while owning the lock on {@link #LOCK_FILENAME}.
     */
    private static boolean isModified(Context context, File archive, long currentCrc) {
        SharedPreferences prefs = getMultiDexPreferences(context);
        return (prefs.getLong(KEY_TIME_STAMP, NO_VALUE) != getTimeStamp(archive))
                || (prefs.getLong(KEY_CRC, NO_VALUE) != currentCrc);
    }

    private static long getTimeStamp(File archive) {
        long timeStamp = archive.lastModified();
        if (timeStamp == NO_VALUE) {
            // never return NO_VALUE
            timeStamp--;
        }
        return timeStamp;
    }


    private static long getZipCrc(File archive) throws IOException {
        long computedValue = ZipUtil.getZipCrc(archive);
        if (computedValue == NO_VALUE) {
            // never return NO_VALUE
            computedValue--;
        }
        return computedValue;
    }

    private static List<File> performExtractions(File sourceApk, File dexDir)
            throws IOException {

        final String extractedFilePrefix = sourceApk.getName() + EXTRACTED_NAME_EXT;

        // Ensure that whatever deletions happen in prepareDexDir only happen if the zip that
        // contains a secondary dex file in there is not consistent with the latest apk.  Otherwise,
        // multi-process race conditions can cause a crash loop where one process deletes the zip
        // while another had created it.
        prepareDexDir(dexDir, extractedFilePrefix);

        List<File> files = new ArrayList<File>();

        final ZipFile apk = new ZipFile(sourceApk);
        try {

            int secondaryNumber = 2;

            ZipEntry dexFile = apk.getEntry(DEX_PREFIX + secondaryNumber + DEX_SUFFIX);
            while (dexFile != null) {
                String fileName = extractedFilePrefix + secondaryNumber + EXTRACTED_SUFFIX;
                File extractedFile = new File(dexDir, fileName);
                files.add(extractedFile);

                Log.i(TAG, "Extraction is needed for file " + extractedFile);
                int numAttempts = 0;
                boolean isExtractionSuccessful = false;
                while (numAttempts < MAX_EXTRACT_ATTEMPTS && !isExtractionSuccessful) {
                    numAttempts++;

                    // Create a zip file (extractedFile) containing only the secondary dex file
                    // (dexFile) from the apk.
                    extract(apk, dexFile, extractedFile, extractedFilePrefix);

                    // Verify that the extracted file is indeed a zip file.
                    isExtractionSuccessful = verifyZipFile(extractedFile);

                    // Log the sha1 of the extracted zip file
                    Log.i(TAG, "Extraction " + (isExtractionSuccessful ? "success" : "failed") +
                            " - length " + extractedFile.getAbsolutePath() + ": " +
                            extractedFile.length());
                    if (!isExtractionSuccessful) {
                        // Delete the extracted file
                        extractedFile.delete();
                        if (extractedFile.exists()) {
                            Log.w(TAG, "Failed to delete corrupted secondary dex '" +
                                    extractedFile.getPath() + "'");
                        }
                    }
                }
                if (!isExtractionSuccessful) {
                    throw new IOException("Could not create zip file " +
                            extractedFile.getAbsolutePath() + " for secondary dex (" +
                            secondaryNumber + ")");
                }
                secondaryNumber++;
                dexFile = apk.getEntry(DEX_PREFIX + secondaryNumber + DEX_SUFFIX);
            }
        } finally {
            try {
                apk.close();
            } catch (IOException e) {
                Log.w(TAG, "Failed to close resource", e);
            }
        }

        return files;
    }

    /**
     * Save {@link SharedPreferences}. Should be called only while owning the lock on
     * {@link #LOCK_FILENAME}.
     */
    private static void putStoredApkInfo(Context context, long timeStamp, long crc,
            int totalDexNumber) {
        SharedPreferences prefs = getMultiDexPreferences(context);
        SharedPreferences.Editor edit = prefs.edit();
        edit.putLong(KEY_TIME_STAMP, timeStamp);
        edit.putLong(KEY_CRC, crc);
        edit.putInt(KEY_DEX_NUMBER, totalDexNumber);
        /* Use commit() and not apply() as advised by the doc because we need synchronous writing of
         * the editor content and apply is doing an "asynchronous commit to disk".
         */
        edit.commit();
    }

    /**
     * Get the MuliDex {@link SharedPreferences} for the current application. Should be called only
     * while owning the lock on {@link #LOCK_FILENAME}.
     */
    private static SharedPreferences getMultiDexPreferences(Context context) {
        return context.getSharedPreferences(PREFS_FILE,
                Build.VERSION.SDK_INT < 11 /* Build.VERSION_CODES.HONEYCOMB */
                        ? Context.MODE_PRIVATE
                        : Context.MODE_PRIVATE | 0x0004 /* Context.MODE_MULTI_PROCESS */);
    }

    /**
     * This removes old files.
     */
    private static void prepareDexDir(File dexDir, final String extractedFilePrefix) {
        FileFilter filter = new FileFilter() {

            @Override
            public boolean accept(File pathname) {
                String name = pathname.getName();
                return !(name.startsWith(extractedFilePrefix)
                        || name.equals(LOCK_FILENAME));
            }
        };
        File[] files = dexDir.listFiles(filter);
        if (files == null) {
            Log.w(TAG, "Failed to list secondary dex dir content (" + dexDir.getPath() + ").");
            return;
        }
        for (File oldFile : files) {
            Log.i(TAG, "Trying to delete old file " + oldFile.getPath() + " of size " +
                    oldFile.length());
            if (!oldFile.delete()) {
                Log.w(TAG, "Failed to delete old file " + oldFile.getPath());
            } else {
                Log.i(TAG, "Deleted old file " + oldFile.getPath());
            }
        }
    }

    private static void extract(ZipFile apk, ZipEntry dexFile, File extractTo,
            String extractedFilePrefix) throws IOException, FileNotFoundException {

        InputStream in = apk.getInputStream(dexFile);
        ZipOutputStream out = null;
        File tmp = File.createTempFile(extractedFilePrefix, EXTRACTED_SUFFIX,
                extractTo.getParentFile());
        Log.i(TAG, "Extracting " + tmp.getPath());
        try {
            out = new ZipOutputStream(new BufferedOutputStream(new FileOutputStream(tmp)));
            try {
                ZipEntry classesDex = new ZipEntry("classes.dex");
                // keep zip entry time since it is the criteria used by Dalvik
                classesDex.setTime(dexFile.getTime());
                out.putNextEntry(classesDex);

                byte[] buffer = new byte[BUFFER_SIZE];
                int length = in.read(buffer);
                while (length != -1) {
                    out.write(buffer, 0, length);
                    length = in.read(buffer);
                }
                out.closeEntry();
            } finally {
                out.close();
            }
            Log.i(TAG, "Renaming to " + extractTo.getPath());
            if (!tmp.renameTo(extractTo)) {
                throw new IOException("Failed to rename \"" + tmp.getAbsolutePath() +
                        "\" to \"" + extractTo.getAbsolutePath() + "\"");
            }
        } finally {
            closeQuietly(in);
            tmp.delete(); // return status ignored
        }
    }

    /**
     * Returns whether the file is a valid zip file.
     */
    static boolean verifyZipFile(File file) {
        try {
            ZipFile zipFile = new ZipFile(file);
            try {
                zipFile.close();
                return true;
            } catch (IOException e) {
                Log.w(TAG, "Failed to close zip file: " + file.getAbsolutePath());
            }
        } catch (ZipException ex) {
            Log.w(TAG, "File " + file.getAbsolutePath() + " is not a valid zip file.", ex);
        } catch (IOException ex) {
            Log.w(TAG, "Got an IOException trying to open zip file: " + file.getAbsolutePath(), ex);
        }
        return false;
    }

    /**
     * Closes the given {@code Closeable}. Suppresses any IO exceptions.
     */
    private static void closeQuietly(Closeable closeable) {
        try {
            closeable.close();
        } catch (IOException e) {
            Log.w(TAG, "Failed to close resource", e);
        }
    }
}