/*
 * 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.externalstorage;

import android.content.ContentResolver;
import android.content.Context;
import android.content.res.AssetFileDescriptor;
import android.database.Cursor;
import android.database.MatrixCursor;
import android.database.MatrixCursor.RowBuilder;
import android.graphics.Point;
import android.net.Uri;
import android.os.CancellationSignal;
import android.os.Environment;
import android.os.FileObserver;
import android.os.ParcelFileDescriptor;
import android.os.storage.StorageManager;
import android.os.storage.StorageVolume;
import android.provider.DocumentsContract;
import android.provider.DocumentsContract.Document;
import android.provider.DocumentsContract.Root;
import android.provider.DocumentsProvider;
import android.util.Log;
import android.webkit.MimeTypeMap;

import com.android.internal.annotations.GuardedBy;
import com.google.android.collect.Lists;
import com.google.android.collect.Maps;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;

public class ExternalStorageProvider extends DocumentsProvider {
    private static final String TAG = "ExternalStorage";

    private static final boolean LOG_INOTIFY = false;

    public static final String AUTHORITY = "com.android.externalstorage.documents";

    // docId format: root:path/to/file

    private static final String[] DEFAULT_ROOT_PROJECTION = new String[] {
            Root.COLUMN_ROOT_ID, Root.COLUMN_FLAGS, Root.COLUMN_ICON, Root.COLUMN_TITLE,
            Root.COLUMN_DOCUMENT_ID, Root.COLUMN_AVAILABLE_BYTES,
    };

    private static final String[] DEFAULT_DOCUMENT_PROJECTION = new String[] {
            Document.COLUMN_DOCUMENT_ID, Document.COLUMN_MIME_TYPE, Document.COLUMN_DISPLAY_NAME,
            Document.COLUMN_LAST_MODIFIED, Document.COLUMN_FLAGS, Document.COLUMN_SIZE,
    };

    private static class RootInfo {
        public String rootId;
        public int flags;
        public String title;
        public String docId;
    }

    private static final String ROOT_ID_PRIMARY_EMULATED = "primary";

    private StorageManager mStorageManager;

    private final Object mRootsLock = new Object();

    @GuardedBy("mRootsLock")
    private ArrayList<RootInfo> mRoots;
    @GuardedBy("mRootsLock")
    private HashMap<String, RootInfo> mIdToRoot;
    @GuardedBy("mRootsLock")
    private HashMap<String, File> mIdToPath;

    @GuardedBy("mObservers")
    private Map<File, DirectoryObserver> mObservers = Maps.newHashMap();

    @Override
    public boolean onCreate() {
        mStorageManager = (StorageManager) getContext().getSystemService(Context.STORAGE_SERVICE);

        mRoots = Lists.newArrayList();
        mIdToRoot = Maps.newHashMap();
        mIdToPath = Maps.newHashMap();

        updateVolumes();

        return true;
    }

    public void updateVolumes() {
        synchronized (mRootsLock) {
            updateVolumesLocked();
        }
    }

    private void updateVolumesLocked() {
        mRoots.clear();
        mIdToPath.clear();
        mIdToRoot.clear();

        final StorageVolume[] volumes = mStorageManager.getVolumeList();
        for (StorageVolume volume : volumes) {
            final boolean mounted = Environment.MEDIA_MOUNTED.equals(volume.getState())
                    || Environment.MEDIA_MOUNTED_READ_ONLY.equals(volume.getState());
            if (!mounted) continue;

            final String rootId;
            if (volume.isPrimary() && volume.isEmulated()) {
                rootId = ROOT_ID_PRIMARY_EMULATED;
            } else if (volume.getUuid() != null) {
                rootId = volume.getUuid();
            } else {
                Log.d(TAG, "Missing UUID for " + volume.getPath() + "; skipping");
                continue;
            }

            if (mIdToPath.containsKey(rootId)) {
                Log.w(TAG, "Duplicate UUID " + rootId + "; skipping");
                continue;
            }

            try {
                final File path = volume.getPathFile();
                mIdToPath.put(rootId, path);

                final RootInfo root = new RootInfo();
                root.rootId = rootId;
                root.flags = Root.FLAG_SUPPORTS_CREATE | Root.FLAG_LOCAL_ONLY | Root.FLAG_ADVANCED
                        | Root.FLAG_SUPPORTS_SEARCH;
                if (ROOT_ID_PRIMARY_EMULATED.equals(rootId)) {
                    root.title = getContext().getString(R.string.root_internal_storage);
                } else {
                    root.title = volume.getUserLabel();
                }
                root.docId = getDocIdForFile(path);
                mRoots.add(root);
                mIdToRoot.put(rootId, root);
            } catch (FileNotFoundException e) {
                throw new IllegalStateException(e);
            }
        }

        Log.d(TAG, "After updating volumes, found " + mRoots.size() + " active roots");

        getContext().getContentResolver()
                .notifyChange(DocumentsContract.buildRootsUri(AUTHORITY), null, false);
    }

    private static String[] resolveRootProjection(String[] projection) {
        return projection != null ? projection : DEFAULT_ROOT_PROJECTION;
    }

    private static String[] resolveDocumentProjection(String[] projection) {
        return projection != null ? projection : DEFAULT_DOCUMENT_PROJECTION;
    }

    private String getDocIdForFile(File file) throws FileNotFoundException {
        String path = file.getAbsolutePath();

        // Find the most-specific root path
        Map.Entry<String, File> mostSpecific = null;
        synchronized (mRootsLock) {
            for (Map.Entry<String, File> root : mIdToPath.entrySet()) {
                final String rootPath = root.getValue().getPath();
                if (path.startsWith(rootPath) && (mostSpecific == null
                        || rootPath.length() > mostSpecific.getValue().getPath().length())) {
                    mostSpecific = root;
                }
            }
        }

        if (mostSpecific == null) {
            throw new FileNotFoundException("Failed to find root that contains " + path);
        }

        // Start at first char of path under root
        final String rootPath = mostSpecific.getValue().getPath();
        if (rootPath.equals(path)) {
            path = "";
        } else if (rootPath.endsWith("/")) {
            path = path.substring(rootPath.length());
        } else {
            path = path.substring(rootPath.length() + 1);
        }

        return mostSpecific.getKey() + ':' + path;
    }

    private File getFileForDocId(String docId) throws FileNotFoundException {
        final int splitIndex = docId.indexOf(':', 1);
        final String tag = docId.substring(0, splitIndex);
        final String path = docId.substring(splitIndex + 1);

        File target;
        synchronized (mRootsLock) {
            target = mIdToPath.get(tag);
        }
        if (target == null) {
            throw new FileNotFoundException("No root for " + tag);
        }
        if (!target.exists()) {
            target.mkdirs();
        }
        target = new File(target, path);
        if (!target.exists()) {
            throw new FileNotFoundException("Missing file for " + docId + " at " + target);
        }
        return target;
    }

    private void includeFile(MatrixCursor result, String docId, File file)
            throws FileNotFoundException {
        if (docId == null) {
            docId = getDocIdForFile(file);
        } else {
            file = getFileForDocId(docId);
        }

        int flags = 0;

        if (file.canWrite()) {
            if (file.isDirectory()) {
                flags |= Document.FLAG_DIR_SUPPORTS_CREATE;
            } else {
                flags |= Document.FLAG_SUPPORTS_WRITE;
            }
            flags |= Document.FLAG_SUPPORTS_DELETE;
        }

        final String displayName = file.getName();
        final String mimeType = getTypeForFile(file);
        if (mimeType.startsWith("image/")) {
            flags |= Document.FLAG_SUPPORTS_THUMBNAIL;
        }

        final RowBuilder row = result.newRow();
        row.add(Document.COLUMN_DOCUMENT_ID, docId);
        row.add(Document.COLUMN_DISPLAY_NAME, displayName);
        row.add(Document.COLUMN_SIZE, file.length());
        row.add(Document.COLUMN_MIME_TYPE, mimeType);
        row.add(Document.COLUMN_FLAGS, flags);

        // Only publish dates reasonably after epoch
        long lastModified = file.lastModified();
        if (lastModified > 31536000000L) {
            row.add(Document.COLUMN_LAST_MODIFIED, lastModified);
        }
    }

    @Override
    public Cursor queryRoots(String[] projection) throws FileNotFoundException {
        final MatrixCursor result = new MatrixCursor(resolveRootProjection(projection));
        synchronized (mRootsLock) {
            for (String rootId : mIdToPath.keySet()) {
                final RootInfo root = mIdToRoot.get(rootId);
                final File path = mIdToPath.get(rootId);

                final RowBuilder row = result.newRow();
                row.add(Root.COLUMN_ROOT_ID, root.rootId);
                row.add(Root.COLUMN_FLAGS, root.flags);
                row.add(Root.COLUMN_TITLE, root.title);
                row.add(Root.COLUMN_DOCUMENT_ID, root.docId);
                row.add(Root.COLUMN_AVAILABLE_BYTES, path.getFreeSpace());
            }
        }
        return result;
    }

    @Override
    public String createDocument(String docId, String mimeType, String displayName)
            throws FileNotFoundException {
        final File parent = getFileForDocId(docId);
        File file;

        if (Document.MIME_TYPE_DIR.equals(mimeType)) {
            file = new File(parent, displayName);
            if (!file.mkdir()) {
                throw new IllegalStateException("Failed to mkdir " + file);
            }
        } else {
            displayName = removeExtension(mimeType, displayName);
            file = new File(parent, addExtension(mimeType, displayName));

            // If conflicting file, try adding counter suffix
            int n = 0;
            while (file.exists() && n++ < 32) {
                file = new File(parent, addExtension(mimeType, displayName + " (" + n + ")"));
            }

            try {
                if (!file.createNewFile()) {
                    throw new IllegalStateException("Failed to touch " + file);
                }
            } catch (IOException e) {
                throw new IllegalStateException("Failed to touch " + file + ": " + e);
            }
        }
        return getDocIdForFile(file);
    }

    @Override
    public void deleteDocument(String docId) throws FileNotFoundException {
        final File file = getFileForDocId(docId);
        if (!file.delete()) {
            throw new IllegalStateException("Failed to delete " + file);
        }
    }

    @Override
    public Cursor queryDocument(String documentId, String[] projection)
            throws FileNotFoundException {
        final MatrixCursor result = new MatrixCursor(resolveDocumentProjection(projection));
        includeFile(result, documentId, null);
        return result;
    }

    @Override
    public Cursor queryChildDocuments(
            String parentDocumentId, String[] projection, String sortOrder)
            throws FileNotFoundException {
        final File parent = getFileForDocId(parentDocumentId);
        final MatrixCursor result = new DirectoryCursor(
                resolveDocumentProjection(projection), parentDocumentId, parent);
        for (File file : parent.listFiles()) {
            includeFile(result, null, file);
        }
        return result;
    }

    @Override
    public Cursor querySearchDocuments(String rootId, String query, String[] projection)
            throws FileNotFoundException {
        final MatrixCursor result = new MatrixCursor(resolveDocumentProjection(projection));

        final File parent;
        synchronized (mRootsLock) {
            parent = mIdToPath.get(rootId);
        }

        final LinkedList<File> pending = new LinkedList<File>();
        pending.add(parent);
        while (!pending.isEmpty() && result.getCount() < 24) {
            final File file = pending.removeFirst();
            if (file.isDirectory()) {
                for (File child : file.listFiles()) {
                    pending.add(child);
                }
            }
            if (file.getName().toLowerCase().contains(query)) {
                includeFile(result, null, file);
            }
        }
        return result;
    }

    @Override
    public String getDocumentType(String documentId) throws FileNotFoundException {
        final File file = getFileForDocId(documentId);
        return getTypeForFile(file);
    }

    @Override
    public ParcelFileDescriptor openDocument(
            String documentId, String mode, CancellationSignal signal)
            throws FileNotFoundException {
        final File file = getFileForDocId(documentId);
        return ParcelFileDescriptor.open(file, ParcelFileDescriptor.parseMode(mode));
    }

    @Override
    public AssetFileDescriptor openDocumentThumbnail(
            String documentId, Point sizeHint, CancellationSignal signal)
            throws FileNotFoundException {
        final File file = getFileForDocId(documentId);
        return DocumentsContract.openImageThumbnail(file);
    }

    private static String getTypeForFile(File file) {
        if (file.isDirectory()) {
            return Document.MIME_TYPE_DIR;
        } else {
            return getTypeForName(file.getName());
        }
    }

    private static String getTypeForName(String name) {
        final int lastDot = name.lastIndexOf('.');
        if (lastDot >= 0) {
            final String extension = name.substring(lastDot + 1).toLowerCase();
            final String mime = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
            if (mime != null) {
                return mime;
            }
        }

        return "application/octet-stream";
    }

    /**
     * Remove file extension from name, but only if exact MIME type mapping
     * exists. This means we can reapply the extension later.
     */
    private static String removeExtension(String mimeType, String name) {
        final int lastDot = name.lastIndexOf('.');
        if (lastDot >= 0) {
            final String extension = name.substring(lastDot + 1).toLowerCase();
            final String nameMime = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
            if (mimeType.equals(nameMime)) {
                return name.substring(0, lastDot);
            }
        }
        return name;
    }

    /**
     * Add file extension to name, but only if exact MIME type mapping exists.
     */
    private static String addExtension(String mimeType, String name) {
        final String extension = MimeTypeMap.getSingleton()
                .getExtensionFromMimeType(mimeType);
        if (extension != null) {
            return name + "." + extension;
        }
        return name;
    }

    private void startObserving(File file, Uri notifyUri) {
        synchronized (mObservers) {
            DirectoryObserver observer = mObservers.get(file);
            if (observer == null) {
                observer = new DirectoryObserver(
                        file, getContext().getContentResolver(), notifyUri);
                observer.startWatching();
                mObservers.put(file, observer);
            }
            observer.mRefCount++;

            if (LOG_INOTIFY) Log.d(TAG, "after start: " + observer);
        }
    }

    private void stopObserving(File file) {
        synchronized (mObservers) {
            DirectoryObserver observer = mObservers.get(file);
            if (observer == null) return;

            observer.mRefCount--;
            if (observer.mRefCount == 0) {
                mObservers.remove(file);
                observer.stopWatching();
            }

            if (LOG_INOTIFY) Log.d(TAG, "after stop: " + observer);
        }
    }

    private static class DirectoryObserver extends FileObserver {
        private static final int NOTIFY_EVENTS = ATTRIB | CLOSE_WRITE | MOVED_FROM | MOVED_TO
                | CREATE | DELETE | DELETE_SELF | MOVE_SELF;

        private final File mFile;
        private final ContentResolver mResolver;
        private final Uri mNotifyUri;

        private int mRefCount = 0;

        public DirectoryObserver(File file, ContentResolver resolver, Uri notifyUri) {
            super(file.getAbsolutePath(), NOTIFY_EVENTS);
            mFile = file;
            mResolver = resolver;
            mNotifyUri = notifyUri;
        }

        @Override
        public void onEvent(int event, String path) {
            if ((event & NOTIFY_EVENTS) != 0) {
                if (LOG_INOTIFY) Log.d(TAG, "onEvent() " + event + " at " + path);
                mResolver.notifyChange(mNotifyUri, null, false);
            }
        }

        @Override
        public String toString() {
            return "DirectoryObserver{file=" + mFile.getAbsolutePath() + ", ref=" + mRefCount + "}";
        }
    }

    private class DirectoryCursor extends MatrixCursor {
        private final File mFile;

        public DirectoryCursor(String[] columnNames, String docId, File file) {
            super(columnNames);

            final Uri notifyUri = DocumentsContract.buildChildDocumentsUri(
                    AUTHORITY, docId);
            setNotificationUri(getContext().getContentResolver(), notifyUri);

            mFile = file;
            startObserving(mFile, notifyUri);
        }

        @Override
        public void close() {
            super.close();
            stopObserving(mFile);
        }
    }
}