packages/MtpDocumentsProvider/src/com/android/mtp/MtpDatabase.java

/*
 * Copyright (C) 2015 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.mtp;

import static com.android.mtp.MtpDatabaseConstants.*;

import android.content.ContentValues;
import android.content.Context;
import android.content.res.Resources;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteQueryBuilder;
import android.media.MediaFile;
import android.mtp.MtpConstants;
import android.mtp.MtpObjectInfo;
import android.provider.DocumentsContract;
import android.provider.DocumentsContract.Document;
import android.provider.DocumentsContract.Root;

import com.android.internal.annotations.VisibleForTesting;

import java.io.FileNotFoundException;
import java.util.HashSet;
import java.util.Objects;
import java.util.Set;

/**
 * Database for MTP objects.
 * The object handle which is identifier for object in MTP protocol is not stable over sessions.
 * When we resume the process, we need to remap our document ID with MTP's object handle.
 *
 * If the remote MTP device is backed by typical file system, the file name
 * is unique among files in a directory. However, MTP protocol itself does
 * not guarantee the uniqueness of name so we cannot use fullpath as ID.
 *
 * Instead of fullpath, we use artificial ID generated by MtpDatabase itself. The database object
 * remembers the map of document ID and object handle, and remaps new object handle with document ID
 * by comparing the directory structure and object name.
 *
 * To start putting documents into the database, the client needs to call
 * {@link Mapper#startAddingChildDocuments(String)} with the parent document ID. Also it
 * needs to call {@link Mapper#stopAddingChildDocuments(String)} after putting all child
 * documents to the database. (All explanations are same for root documents)
 *
 * database.getMapper().startAddingChildDocuments();
 * database.getMapper().putChildDocuments();
 * database.getMapper().stopAddingChildDocuments();
 *
 * To update the existing documents, the client code can repeat to call the three methods again.
 * The newly added rows update corresponding existing rows that have same MTP identifier like
 * objectHandle.
 *
 * The client can call putChildDocuments multiple times to add documents by chunk, but it needs to
 * put all documents under the parent before calling stopAddingChildDocuments. Otherwise missing
 * documents are regarded as deleted, and will be removed from the database.
 *
 * If the client calls clearMtpIdentifier(), it clears MTP identifier in the database. In this case,
 * the database tries to find corresponding rows by using document's name instead of MTP identifier
 * at the next update cycle.
 *
 * TODO: Improve performance by SQL optimization.
 */
class MtpDatabase {
    private final SQLiteDatabase mDatabase;
    private final Mapper mMapper;

    SQLiteDatabase getSQLiteDatabase() {
        return mDatabase;
    }

    MtpDatabase(Context context, int flags) {
        final OpenHelper helper = new OpenHelper(context, flags);
        mDatabase = helper.getWritableDatabase();
        mMapper = new Mapper(this);
    }

    void close() {
        mDatabase.close();
    }

    /**
     * Returns operations for mapping.
     * @return Mapping operations.
     */
    Mapper getMapper() {
        return mMapper;
    }

    /**
     * Queries roots information.
     * @param columnNames Column names defined in {@link android.provider.DocumentsContract.Root}.
     * @return Database cursor.
     */
    Cursor queryRoots(String[] columnNames) {
        return mDatabase.query(
                VIEW_ROOTS,
                columnNames,
                COLUMN_ROW_STATE + " IN (?, ?)",
                strings(ROW_STATE_VALID, ROW_STATE_INVALIDATED),
                null,
                null,
                null);
    }

    /**
     * Queries root documents information.
     * @param columnNames Column names defined in
     *     {@link android.provider.DocumentsContract.Document}.
     * @return Database cursor.
     */
    @VisibleForTesting
    Cursor queryRootDocuments(String[] columnNames) {
        return mDatabase.query(
                TABLE_DOCUMENTS,
                columnNames,
                COLUMN_ROW_STATE + " IN (?, ?)",
                strings(ROW_STATE_VALID, ROW_STATE_INVALIDATED),
                null,
                null,
                null);
    }

    /**
     * Queries documents information.
     * @param columnNames Column names defined in
     *     {@link android.provider.DocumentsContract.Document}.
     * @return Database cursor.
     */
    Cursor queryChildDocuments(String[] columnNames, String parentDocumentId) {
        return mDatabase.query(
                TABLE_DOCUMENTS,
                columnNames,
                COLUMN_ROW_STATE + " IN (?, ?) AND " + COLUMN_PARENT_DOCUMENT_ID + " = ?",
                strings(ROW_STATE_VALID, ROW_STATE_INVALIDATED, parentDocumentId),
                null,
                null,
                null);
    }

    /**
     * Queries a single document.
     * @param documentId
     * @param projection
     * @return Database cursor.
     */
    public Cursor queryDocument(String documentId, String[] projection) {
        return mDatabase.query(
                TABLE_DOCUMENTS,
                projection,
                SELECTION_DOCUMENT_ID,
                strings(documentId),
                null,
                null,
                null,
                "1");
    }

    /**
     * Remove all rows belong to a device.
     * @param deviceId Device ID.
     */
    void removeDeviceRows(int deviceId) {
        // Call non-recursive version because it anyway deletes all rows in the devices.
        deleteDocumentsAndRoots(COLUMN_DEVICE_ID + "=?", strings(deviceId));
    }

    /**
     * Obtains parent document ID.
     * @param documentId
     * @return parent document ID.
     * @throws FileNotFoundException
     */
    String getParentId(String documentId) throws FileNotFoundException {
        final Cursor cursor = mDatabase.query(
                TABLE_DOCUMENTS,
                strings(COLUMN_PARENT_DOCUMENT_ID),
                SELECTION_DOCUMENT_ID,
                strings(documentId),
                null,
                null,
                null,
                "1");
        try {
            if (cursor.moveToNext()) {
                return cursor.getString(0);
            } else {
                throw new FileNotFoundException("Cannot find a row having ID=" + documentId);
            }
        } finally {
            cursor.close();
        }
    }

    /**
     * Adds new document under the parent.
     * The method does not affect invalidated and pending documents because we know the document is
     * newly added and never mapped with existing ones.
     * @param parentDocumentId
     * @param info
     * @return Document ID of added document.
     */
    String putNewDocument(int deviceId, String parentDocumentId, MtpObjectInfo info) {
        final ContentValues values = new ContentValues();
        getChildDocumentValues(values, deviceId, parentDocumentId, info);
        mDatabase.beginTransaction();
        try {
            final long id = mDatabase.insert(TABLE_DOCUMENTS, null, values);
            mDatabase.setTransactionSuccessful();
            return Long.toString(id);
        } finally {
            mDatabase.endTransaction();
        }
    }

    /**
     * Deletes document and its children.
     * @param documentId
     */
    void deleteDocument(String documentId) {
        deleteDocumentsAndRootsRecursively(SELECTION_DOCUMENT_ID, strings(documentId));
    }

    /**
     * Gets identifier from document ID.
     * @param documentId Document ID.
     * @return Identifier.
     * @throws FileNotFoundException
     */
    Identifier createIdentifier(String documentId) throws FileNotFoundException {
        // Currently documentId is old format.
        final Cursor cursor = mDatabase.query(
                TABLE_DOCUMENTS,
                strings(COLUMN_DEVICE_ID, COLUMN_STORAGE_ID, COLUMN_OBJECT_HANDLE),
                SELECTION_DOCUMENT_ID,
                strings(documentId),
                null,
                null,
                null,
                "1");
        try {
            if (cursor.getCount() == 0) {
                throw new FileNotFoundException("ID is not found.");
            } else {
                cursor.moveToNext();
                return new Identifier(
                        cursor.getInt(0),
                        cursor.getInt(1),
                        cursor.isNull(2) ? Identifier.DUMMY_HANDLE_FOR_ROOT : cursor.getInt(2),
                        documentId);
            }
        } finally {
            cursor.close();
        }
    }

    /**
     * Deletes a document, and its root information if the document is a root document.
     * @param selection Query to select documents.
     * @param args Arguments for selection.
     * @return Whether the method deletes rows.
     */
    boolean deleteDocumentsAndRootsRecursively(String selection, String[] args) {
        mDatabase.beginTransaction();
        try {
            boolean changed = false;
            final Cursor cursor = mDatabase.query(
                    TABLE_DOCUMENTS,
                    strings(Document.COLUMN_DOCUMENT_ID),
                    selection,
                    args,
                    null,
                    null,
                    null);
            try {
                while (cursor.moveToNext()) {
                    if (deleteDocumentsAndRootsRecursively(
                            COLUMN_PARENT_DOCUMENT_ID + "=?",
                            strings(cursor.getString(0)))) {
                        changed = true;
                    }
                }
            } finally {
                cursor.close();
            }
            if (deleteDocumentsAndRoots(selection, args)) {
                changed = true;
            }
            mDatabase.setTransactionSuccessful();
            return changed;
        } finally {
            mDatabase.endTransaction();
        }
    }

    /**
     * Returns the set of device ID stored in the database.
     */
    int[] getDeviceIds() {
        final Cursor cursor = mDatabase.query(
                true,
                TABLE_DOCUMENTS,
                strings(COLUMN_DEVICE_ID),
                null,
                null,
                null,
                null,
                null,
                null);
        try {
            final int[] ids = new int[cursor.getCount()];
            for (int i = 0; i < ids.length; i++) {
                cursor.moveToNext();
                ids[i] = cursor.getInt(0);
            }
            return ids;
        } finally {
            cursor.close();
        }
    }

    private boolean deleteDocumentsAndRoots(String selection, String[] args) {
        mDatabase.beginTransaction();
        try {
            int deleted = 0;
            deleted += mDatabase.delete(
                    TABLE_ROOT_EXTRA,
                    Root.COLUMN_ROOT_ID + " IN (" + SQLiteQueryBuilder.buildQueryString(
                            false,
                            TABLE_DOCUMENTS,
                            new String[] { Document.COLUMN_DOCUMENT_ID },
                            selection,
                            null,
                            null,
                            null,
                            null) + ")",
                    args);
            deleted += mDatabase.delete(TABLE_DOCUMENTS, selection, args);
            mDatabase.setTransactionSuccessful();
            // TODO Remove mappingState.
            return deleted != 0;
        } finally {
            mDatabase.endTransaction();
        }
    }

    private static class OpenHelper extends SQLiteOpenHelper {
        public OpenHelper(Context context, int flags) {
            super(context,
                  flags == FLAG_DATABASE_IN_MEMORY ? null : DATABASE_NAME,
                  null,
                  DATABASE_VERSION);
        }

        @Override
        public void onCreate(SQLiteDatabase db) {
            db.execSQL(QUERY_CREATE_DOCUMENTS);
            db.execSQL(QUERY_CREATE_ROOT_EXTRA);
            db.execSQL(QUERY_CREATE_VIEW_ROOTS);
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            throw new UnsupportedOperationException();
        }
    }

    @VisibleForTesting
    static void deleteDatabase(Context context) {
        context.deleteDatabase(DATABASE_NAME);
    }

    /**
     * Gets {@link ContentValues} for the given root.
     * @param values {@link ContentValues} that receives values.
     * @param resources Resources used to get localized root name.
     * @param root Root to be converted {@link ContentValues}.
     */
    static void getRootDocumentValues(ContentValues values, Resources resources, MtpRoot root) {
        values.clear();
        values.put(COLUMN_DEVICE_ID, root.mDeviceId);
        values.put(COLUMN_STORAGE_ID, root.mStorageId);
        values.putNull(COLUMN_OBJECT_HANDLE);
        values.putNull(COLUMN_PARENT_DOCUMENT_ID);
        values.put(COLUMN_ROW_STATE, ROW_STATE_VALID);
        values.put(COLUMN_DOCUMENT_TYPE, DOCUMENT_TYPE_STORAGE);
        values.put(Document.COLUMN_MIME_TYPE, Document.MIME_TYPE_DIR);
        values.put(Document.COLUMN_DISPLAY_NAME, root.getRootName(resources));
        values.putNull(Document.COLUMN_SUMMARY);
        values.putNull(Document.COLUMN_LAST_MODIFIED);
        values.put(Document.COLUMN_ICON, R.drawable.ic_root_mtp);
        values.put(Document.COLUMN_FLAGS, 0);
        values.put(Document.COLUMN_SIZE,
                (int) Math.min(root.mMaxCapacity - root.mFreeSpace, Integer.MAX_VALUE));
    }

    /**
     * Gets {@link ContentValues} for the given MTP object.
     * @param values {@link ContentValues} that receives values.
     * @param deviceId Device ID of the object.
     * @param parentId Parent document ID of the object.
     * @param info MTP object info.
     */
    static void getChildDocumentValues(
            ContentValues values, int deviceId, String parentId, MtpObjectInfo info) {
        values.clear();
        final String mimeType = info.getFormat() == MtpConstants.FORMAT_ASSOCIATION ?
                DocumentsContract.Document.MIME_TYPE_DIR :
                MediaFile.getMimeTypeForFormatCode(info.getFormat());
        int flag = 0;
        if (info.getProtectionStatus() == 0) {
            flag |= Document.FLAG_SUPPORTS_DELETE |
                    Document.FLAG_SUPPORTS_WRITE;
            if (mimeType == Document.MIME_TYPE_DIR) {
                flag |= Document.FLAG_DIR_SUPPORTS_CREATE;
            }
        }
        if (info.getThumbCompressedSize() > 0) {
            flag |= Document.FLAG_SUPPORTS_THUMBNAIL;
        }
        values.put(COLUMN_DEVICE_ID, deviceId);
        values.put(COLUMN_STORAGE_ID, info.getStorageId());
        values.put(COLUMN_OBJECT_HANDLE, info.getObjectHandle());
        values.put(COLUMN_PARENT_DOCUMENT_ID, parentId);
        values.put(COLUMN_ROW_STATE, ROW_STATE_VALID);
        values.put(COLUMN_DOCUMENT_TYPE, DOCUMENT_TYPE_OBJECT);
        values.put(Document.COLUMN_MIME_TYPE, mimeType);
        values.put(Document.COLUMN_DISPLAY_NAME, info.getName());
        values.putNull(Document.COLUMN_SUMMARY);
        values.put(
                Document.COLUMN_LAST_MODIFIED,
                info.getDateModified() != 0 ? info.getDateModified() : null);
        values.putNull(Document.COLUMN_ICON);
        values.put(Document.COLUMN_FLAGS, flag);
        values.put(Document.COLUMN_SIZE, info.getCompressedSize());
    }

    static String[] strings(Object... args) {
        final String[] results = new String[args.length];
        for (int i = 0; i < args.length; i++) {
            results[i] = Objects.toString(args[i]);
        }
        return results;
    }
}