/*
 * Copyright (C) 2011 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.inputmethod.latin;

import android.content.ContentProviderClient;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.content.Context;
import android.content.res.AssetFileDescriptor;
import android.database.Cursor;
import android.net.Uri;
import android.os.RemoteException;
import android.text.TextUtils;
import android.util.Log;

import com.android.inputmethod.dictionarypack.DictionaryPackConstants;
import com.android.inputmethod.latin.DictionaryInfoUtils.DictionaryInfo;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Locale;

/**
 * Group class for static methods to help with creation and getting of the binary dictionary
 * file from the dictionary provider
 */
public final class BinaryDictionaryFileDumper {
    private static final String TAG = BinaryDictionaryFileDumper.class.getSimpleName();
    private static final boolean DEBUG = false;

    /**
     * The size of the temporary buffer to copy files.
     */
    private static final int FILE_READ_BUFFER_SIZE = 8192;
    // TODO: make the following data common with the native code
    private static final byte[] MAGIC_NUMBER_VERSION_1 =
            new byte[] { (byte)0x78, (byte)0xB1, (byte)0x00, (byte)0x00 };
    private static final byte[] MAGIC_NUMBER_VERSION_2 =
            new byte[] { (byte)0x9B, (byte)0xC1, (byte)0x3A, (byte)0xFE };

    private static final String DICTIONARY_PROJECTION[] = { "id" };

    private static final String QUERY_PARAMETER_MAY_PROMPT_USER = "mayPrompt";
    private static final String QUERY_PARAMETER_TRUE = "true";
    private static final String QUERY_PARAMETER_DELETE_RESULT = "result";
    private static final String QUERY_PARAMETER_SUCCESS = "success";
    private static final String QUERY_PARAMETER_FAILURE = "failure";

    // Using protocol version 2 to communicate with the dictionary pack
    private static final String QUERY_PARAMETER_PROTOCOL = "protocol";
    private static final String QUERY_PARAMETER_PROTOCOL_VALUE = "2";

    // The path fragment to append after the client ID for dictionary info requests.
    private static final String QUERY_PATH_DICT_INFO = "dict";
    // The path fragment to append after the client ID for dictionary datafile requests.
    private static final String QUERY_PATH_DATAFILE = "datafile";
    // The path fragment to append after the client ID for updating the metadata URI.
    private static final String QUERY_PATH_METADATA = "metadata";
    private static final String INSERT_METADATA_CLIENT_ID_COLUMN = "clientid";
    private static final String INSERT_METADATA_METADATA_URI_COLUMN = "uri";

    // Prevents this class to be accidentally instantiated.
    private BinaryDictionaryFileDumper() {
    }

    /**
     * Returns a URI builder pointing to the dictionary pack.
     *
     * This creates a URI builder able to build a URI pointing to the dictionary
     * pack content provider for a specific dictionary id.
     */
    private static Uri.Builder getProviderUriBuilder(final String path) {
        return new Uri.Builder().scheme(ContentResolver.SCHEME_CONTENT)
                .authority(DictionaryPackConstants.AUTHORITY).appendPath(path);
    }

    /**
     * Gets the content URI builder for a specified type.
     *
     * Supported types include QUERY_PATH_DICT_INFO, which takes the locale as
     * the extraPath argument, and QUERY_PATH_DATAFILE, which needs a wordlist ID
     * as the extraPath argument.
     *
     * @param clientId the clientId to use
     * @param contentProviderClient the instance of content provider client
     * @param queryPathType the path element encoding the type
     * @param extraPath optional extra argument for this type (typically word list id)
     * @return a builder that can build the URI for the best supported protocol version
     * @throws RemoteException if the client can't be contacted
     */
    private static Uri.Builder getContentUriBuilderForType(final String clientId,
            final ContentProviderClient contentProviderClient, final String queryPathType,
            final String extraPath) throws RemoteException {
        // Check whether protocol v2 is supported by building a v2 URI and calling getType()
        // on it. If this returns null, v2 is not supported.
        final Uri.Builder uriV2Builder = getProviderUriBuilder(clientId);
        uriV2Builder.appendPath(queryPathType);
        uriV2Builder.appendPath(extraPath);
        uriV2Builder.appendQueryParameter(QUERY_PARAMETER_PROTOCOL,
                QUERY_PARAMETER_PROTOCOL_VALUE);
        if (null != contentProviderClient.getType(uriV2Builder.build())) return uriV2Builder;
        // Protocol v2 is not supported, so create and return the protocol v1 uri.
        return getProviderUriBuilder(extraPath);
    }

    /**
     * Queries a content provider for the list of word lists for a specific locale
     * available to copy into Latin IME.
     */
    private static List<WordListInfo> getWordListWordListInfos(final Locale locale,
            final Context context, final boolean hasDefaultWordList) {
        final String clientId = context.getString(R.string.dictionary_pack_client_id);
        final ContentProviderClient client = context.getContentResolver().
                acquireContentProviderClient(getProviderUriBuilder("").build());
        if (null == client) return Collections.<WordListInfo>emptyList();

        try {
            final Uri.Builder builder = getContentUriBuilderForType(clientId, client,
                    QUERY_PATH_DICT_INFO, locale.toString());
            if (!hasDefaultWordList) {
                builder.appendQueryParameter(QUERY_PARAMETER_MAY_PROMPT_USER,
                        QUERY_PARAMETER_TRUE);
            }
            final Uri queryUri = builder.build();
            final boolean isProtocolV2 = (QUERY_PARAMETER_PROTOCOL_VALUE.equals(
                    queryUri.getQueryParameter(QUERY_PARAMETER_PROTOCOL)));

            Cursor c = client.query(queryUri, DICTIONARY_PROJECTION, null, null, null);
            if (isProtocolV2 && null == c) {
                reinitializeClientRecordInDictionaryContentProvider(context, client, clientId);
                c = client.query(queryUri, DICTIONARY_PROJECTION, null, null, null);
            }
            if (null == c) return Collections.<WordListInfo>emptyList();
            if (c.getCount() <= 0 || !c.moveToFirst()) {
                c.close();
                return Collections.<WordListInfo>emptyList();
            }
            final ArrayList<WordListInfo> list = CollectionUtils.newArrayList();
            do {
                final String wordListId = c.getString(0);
                final String wordListLocale = c.getString(1);
                if (TextUtils.isEmpty(wordListId)) continue;
                list.add(new WordListInfo(wordListId, wordListLocale));
            } while (c.moveToNext());
            c.close();
            return list;
        } catch (RemoteException e) {
            // The documentation is unclear as to in which cases this may happen, but it probably
            // happens when the content provider got suddenly killed because it crashed or because
            // the user disabled it through Settings.
            Log.e(TAG, "RemoteException: communication with the dictionary pack cut", e);
            return Collections.<WordListInfo>emptyList();
        } catch (Exception e) {
            // A crash here is dangerous because crashing here would brick any encrypted device -
            // we need the keyboard to be up and working to enter the password, so we don't want
            // to die no matter what. So let's be as safe as possible.
            Log.e(TAG, "Unexpected exception communicating with the dictionary pack", e);
            return Collections.<WordListInfo>emptyList();
        } finally {
            client.release();
        }
    }


    /**
     * Helper method to encapsulate exception handling.
     */
    private static AssetFileDescriptor openAssetFileDescriptor(
            final ContentProviderClient providerClient, final Uri uri) {
        try {
            return providerClient.openAssetFile(uri, "r");
        } catch (FileNotFoundException e) {
            // I don't want to log the word list URI here for security concerns. The exception
            // contains the name of the file, so let's not pass it to Log.e here.
            Log.e(TAG, "Could not find a word list from the dictionary provider."
                    /* intentionally don't pass the exception (see comment above) */);
            return null;
        } catch (RemoteException e) {
            Log.e(TAG, "Can't communicate with the dictionary pack", e);
            return null;
        }
    }

    /**
     * Caches a word list the id of which is passed as an argument. This will write the file
     * to the cache file name designated by its id and locale, overwriting it if already present
     * and creating it (and its containing directory) if necessary.
     */
    private static AssetFileAddress cacheWordList(final String wordlistId, final String locale,
            final ContentProviderClient providerClient, final Context context) {
        final int COMPRESSED_CRYPTED_COMPRESSED = 0;
        final int CRYPTED_COMPRESSED = 1;
        final int COMPRESSED_CRYPTED = 2;
        final int COMPRESSED_ONLY = 3;
        final int CRYPTED_ONLY = 4;
        final int NONE = 5;
        final int MODE_MIN = COMPRESSED_CRYPTED_COMPRESSED;
        final int MODE_MAX = NONE;

        final String clientId = context.getString(R.string.dictionary_pack_client_id);
        final Uri.Builder wordListUriBuilder;
        try {
            wordListUriBuilder = getContentUriBuilderForType(clientId,
                    providerClient, QUERY_PATH_DATAFILE, wordlistId /* extraPath */);
        } catch (RemoteException e) {
            Log.e(TAG, "Can't communicate with the dictionary pack", e);
            return null;
        }
        final String finalFileName =
                DictionaryInfoUtils.getCacheFileName(wordlistId, locale, context);
        String tempFileName;
        try {
            tempFileName = BinaryDictionaryGetter.getTempFileName(wordlistId, context);
        } catch (IOException e) {
            Log.e(TAG, "Can't open the temporary file", e);
            return null;
        }

        for (int mode = MODE_MIN; mode <= MODE_MAX; ++mode) {
            InputStream originalSourceStream = null;
            InputStream inputStream = null;
            InputStream uncompressedStream = null;
            InputStream decryptedStream = null;
            BufferedInputStream bufferedInputStream = null;
            File outputFile = null;
            BufferedOutputStream bufferedOutputStream = null;
            AssetFileDescriptor afd = null;
            final Uri wordListUri = wordListUriBuilder.build();
            try {
                // Open input.
                afd = openAssetFileDescriptor(providerClient, wordListUri);
                // If we can't open it at all, don't even try a number of times.
                if (null == afd) return null;
                originalSourceStream = afd.createInputStream();
                // Open output.
                outputFile = new File(tempFileName);
                // Just to be sure, delete the file. This may fail silently, and return false: this
                // is the right thing to do, as we just want to continue anyway.
                outputFile.delete();
                // Get the appropriate decryption method for this try
                switch (mode) {
                    case COMPRESSED_CRYPTED_COMPRESSED:
                        uncompressedStream =
                                FileTransforms.getUncompressedStream(originalSourceStream);
                        decryptedStream = FileTransforms.getDecryptedStream(uncompressedStream);
                        inputStream = FileTransforms.getUncompressedStream(decryptedStream);
                        break;
                    case CRYPTED_COMPRESSED:
                        decryptedStream = FileTransforms.getDecryptedStream(originalSourceStream);
                        inputStream = FileTransforms.getUncompressedStream(decryptedStream);
                        break;
                    case COMPRESSED_CRYPTED:
                        uncompressedStream =
                                FileTransforms.getUncompressedStream(originalSourceStream);
                        inputStream = FileTransforms.getDecryptedStream(uncompressedStream);
                        break;
                    case COMPRESSED_ONLY:
                        inputStream = FileTransforms.getUncompressedStream(originalSourceStream);
                        break;
                    case CRYPTED_ONLY:
                        inputStream = FileTransforms.getDecryptedStream(originalSourceStream);
                        break;
                    case NONE:
                        inputStream = originalSourceStream;
                        break;
                }
                bufferedInputStream = new BufferedInputStream(inputStream);
                bufferedOutputStream = new BufferedOutputStream(new FileOutputStream(outputFile));
                checkMagicAndCopyFileTo(bufferedInputStream, bufferedOutputStream);
                bufferedOutputStream.flush();
                bufferedOutputStream.close();
                final File finalFile = new File(finalFileName);
                finalFile.delete();
                if (!outputFile.renameTo(finalFile)) {
                    throw new IOException("Can't move the file to its final name");
                }
                wordListUriBuilder.appendQueryParameter(QUERY_PARAMETER_DELETE_RESULT,
                        QUERY_PARAMETER_SUCCESS);
                if (0 >= providerClient.delete(wordListUriBuilder.build(), null, null)) {
                    Log.e(TAG, "Could not have the dictionary pack delete a word list");
                }
                BinaryDictionaryGetter.removeFilesWithIdExcept(context, wordlistId, finalFile);
                // Success! Close files (through the finally{} clause) and return.
                return AssetFileAddress.makeFromFileName(finalFileName);
            } catch (Exception e) {
                if (DEBUG) {
                    Log.i(TAG, "Can't open word list in mode " + mode, e);
                }
                if (null != outputFile) {
                    // This may or may not fail. The file may not have been created if the
                    // exception was thrown before it could be. Hence, both failure and
                    // success are expected outcomes, so we don't check the return value.
                    outputFile.delete();
                }
                // Try the next method.
            } finally {
                // Ignore exceptions while closing files.
                try {
                    // inputStream.close() will close afd, we should not call afd.close().
                    if (null != inputStream) inputStream.close();
                    if (null != uncompressedStream) uncompressedStream.close();
                    if (null != decryptedStream) decryptedStream.close();
                    if (null != bufferedInputStream) bufferedInputStream.close();
                } catch (Exception e) {
                    Log.e(TAG, "Exception while closing a file descriptor", e);
                }
                try {
                    if (null != bufferedOutputStream) bufferedOutputStream.close();
                } catch (Exception e) {
                    Log.e(TAG, "Exception while closing a file", e);
                }
            }
        }

        // We could not copy the file at all. This is very unexpected.
        // I'd rather not print the word list ID to the log out of security concerns
        Log.e(TAG, "Could not copy a word list. Will not be able to use it.");
        // If we can't copy it we should warn the dictionary provider so that it can mark it
        // as invalid.
        wordListUriBuilder.appendQueryParameter(QUERY_PARAMETER_DELETE_RESULT,
                QUERY_PARAMETER_FAILURE);
        try {
            if (0 >= providerClient.delete(wordListUriBuilder.build(), null, null)) {
                Log.e(TAG, "In addition, we were unable to delete it.");
            }
        } catch (RemoteException e) {
            Log.e(TAG, "In addition, communication with the dictionary provider was cut", e);
        }
        return null;
    }

    /**
     * Queries a content provider for word list data for some locale and cache the returned files
     *
     * This will query a content provider for word list data for a given locale, and copy the
     * files locally so that they can be mmap'ed. This may overwrite previously cached word lists
     * with newer versions if a newer version is made available by the content provider.
     * @returns the addresses of the word list files, or null if no data could be obtained.
     * @throw FileNotFoundException if the provider returns non-existent data.
     * @throw IOException if the provider-returned data could not be read.
     */
    public static List<AssetFileAddress> cacheWordListsFromContentProvider(final Locale locale,
            final Context context, final boolean hasDefaultWordList) {
        final ContentProviderClient providerClient = context.getContentResolver().
                acquireContentProviderClient(getProviderUriBuilder("").build());
        if (null == providerClient) {
            Log.e(TAG, "Can't establish communication with the dictionary provider");
            return CollectionUtils.newArrayList();
        }
        try {
            final List<WordListInfo> idList = getWordListWordListInfos(locale, context,
                    hasDefaultWordList);
            final ArrayList<AssetFileAddress> fileAddressList = CollectionUtils.newArrayList();
            for (WordListInfo id : idList) {
                final AssetFileAddress afd =
                        cacheWordList(id.mId, id.mLocale, providerClient, context);
                if (null != afd) {
                    fileAddressList.add(afd);
                }
            }
            return fileAddressList;
        } finally {
            providerClient.release();
        }
    }

    /**
     * Copies the data in an input stream to a target file if the magic number matches.
     *
     * If the magic number does not match the expected value, this method throws an
     * IOException. Other usual conditions for IOException or FileNotFoundException
     * also apply.
     *
     * @param input the stream to be copied.
     * @param output an output stream to copy the data to.
     */
    public static void checkMagicAndCopyFileTo(final BufferedInputStream input,
            final BufferedOutputStream output) throws FileNotFoundException, IOException {
        // Check the magic number
        final int length = MAGIC_NUMBER_VERSION_2.length;
        final byte[] magicNumberBuffer = new byte[length];
        final int readMagicNumberSize = input.read(magicNumberBuffer, 0, length);
        if (readMagicNumberSize < length) {
            throw new IOException("Less bytes to read than the magic number length");
        }
        if (!Arrays.equals(MAGIC_NUMBER_VERSION_2, magicNumberBuffer)) {
            if (!Arrays.equals(MAGIC_NUMBER_VERSION_1, magicNumberBuffer)) {
                throw new IOException("Wrong magic number for downloaded file");
            }
        }
        output.write(magicNumberBuffer);

        // Actually copy the file
        final byte[] buffer = new byte[FILE_READ_BUFFER_SIZE];
        for (int readBytes = input.read(buffer); readBytes >= 0; readBytes = input.read(buffer))
            output.write(buffer, 0, readBytes);
        input.close();
    }

    private static void reinitializeClientRecordInDictionaryContentProvider(final Context context,
            final ContentProviderClient client, final String clientId) throws RemoteException {
        final String metadataFileUri = MetadataFileUriGetter.getMetadataUri(context);
        if (TextUtils.isEmpty(metadataFileUri)) return;
        // Tell the content provider to reset all information about this client id
        final Uri metadataContentUri = getProviderUriBuilder(clientId)
                .appendPath(QUERY_PATH_METADATA)
                .appendQueryParameter(QUERY_PARAMETER_PROTOCOL, QUERY_PARAMETER_PROTOCOL_VALUE)
                .build();
        client.delete(metadataContentUri, null, null);
        // Update the metadata URI
        final ContentValues metadataValues = new ContentValues();
        metadataValues.put(INSERT_METADATA_CLIENT_ID_COLUMN, clientId);
        metadataValues.put(INSERT_METADATA_METADATA_URI_COLUMN, metadataFileUri);
        client.insert(metadataContentUri, metadataValues);

        // Update the dictionary list.
        final Uri dictionaryContentUriBase = getProviderUriBuilder(clientId)
                .appendPath(QUERY_PATH_DICT_INFO)
                .appendQueryParameter(QUERY_PARAMETER_PROTOCOL, QUERY_PARAMETER_PROTOCOL_VALUE)
                .build();
        final ArrayList<DictionaryInfo> dictionaryList =
                DictionaryInfoUtils.getCurrentDictionaryFileNameAndVersionInfo(context);
        final int length = dictionaryList.size();
        for (int i = 0; i < length; ++i) {
            final DictionaryInfo info = dictionaryList.get(i);
            client.insert(Uri.withAppendedPath(dictionaryContentUriBase, info.mId),
                    info.toContentValues());
        }
    }

    /**
     * Initialize a client record with the dictionary content provider.
     *
     * This merely acquires the content provider and calls
     * #reinitializeClientRecordInDictionaryContentProvider.
     *
     * @param context the context for resources and providers.
     * @param clientId the client ID to use.
     */
    public static void initializeClientRecordHelper(final Context context,
            final String clientId) {
        try {
            final ContentProviderClient client = context.getContentResolver().
                    acquireContentProviderClient(getProviderUriBuilder("").build());
            if (null == client) return;
            reinitializeClientRecordInDictionaryContentProvider(context, client, clientId);
        } catch (RemoteException e) {
            Log.e(TAG, "Cannot contact the dictionary content provider", e);
        }
    }
}