/*
 * 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 com.android.jack.multidex.fakelibrary;

import com.android.jack.multidex.fakeframeworks.Context;

import java.io.Closeable;
import java.io.File;
import java.io.FileFilter;
import java.io.IOException;
import java.util.List;

/**
 * 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 List<File> loadExistingExtractions(Context context, File sourceApk, File dexDir)
            throws IOException {

        final String extractedFilePrefix = sourceApk.getName() + EXTRACTED_NAME_EXT;
        int totalDexNumber = 1;
        final List<File> files = null;

        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);
            } else {
                throw new IOException("Missing extracted secondary dex file '" +
                        extractedFile.getPath() + "'");
            }
        }

        return files;
    }

    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 = null;

        return files;
    }

    /**
     * This removes any files that do not have the correct prefix.
     */
    private static void prepareDexDir(File dexDir, final String extractedFilePrefix)
            throws IOException {
        dexDir.mkdir();
        if (!dexDir.isDirectory()) {
            throw new IOException("Failed to create dex directory " + dexDir.getPath());
        }

        // Clean possible old files
        FileFilter filter = new FileFilter() {

            @Override
            public boolean accept(File pathname) {
                return !pathname.getName().startsWith(extractedFilePrefix);
            }
        };
        File[] files = dexDir.listFiles(filter);
        if (files == null) {
            return;
        }
        for (File oldFile : files) {
            if (!oldFile.delete()) {
            } else {
            }
        }
    }

    /**
     * Closes the given {@code Closeable}. Suppresses any IO exceptions.
     */
    private static void closeQuietly(Closeable closeable) {
        try {
            closeable.close();
        } catch (IOException e) {
        }
    }

}