/*
 * Copyright (C) 2012-2014 Dominik Schürmann <dominik@dominikschuermann.de>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package org.sufficientlysecure.keychain.util;


import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.security.SecureRandom;
import java.text.DecimalFormat;
import java.util.List;

import android.annotation.TargetApi;
import android.content.ActivityNotFoundException;
import android.content.ContentResolver;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.content.pm.ResolveInfo;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.Point;
import android.net.Uri;
import android.os.Build;
import android.os.Build.VERSION_CODES;
import android.os.Environment;
import android.provider.DocumentsContract;
import android.provider.OpenableColumns;
import android.support.v4.app.Fragment;
import android.widget.Toast;

import org.sufficientlysecure.keychain.Constants;
import org.sufficientlysecure.keychain.R;

/** This class offers a number of helper functions for saving documents.
 *
 * There are three entry points here: openDocument, saveDocument and
 * saveDocumentDialog. Each behaves a little differently depending on whether
 * the Android version used is pre or post KitKat.
 *
 * - openDocument queries for a document for reading. Used in "open encrypted
 *   file" ui flow. On pre-kitkat, this relies on an external file manager,
 *   and will fail with a toast message if none is installed.
 *
 * - saveDocument queries for a document name for saving. on pre-kitkat, this
 *   shows a dialog where a filename can be input.  on kitkat and up, it
 *   directly triggers a "save document" intent. Used in "save encrypted file"
 *   ui flow.
 *
 * - saveDocumentDialog queries for a document. this shows a dialog on all
 *   versions of android. the browse button opens an external browser on
 *   pre-kitkat or the "save document" intent on post-kitkat devices. Used in
 *   "backup key" ui flow.
 *
 *   It is noteworthy that the "saveDocument" call is essentially substituted
 *   by the "saveDocumentDialog" on pre-kitkat devices.
 *
 */
public class FileHelper {

    private static Boolean hasOpenDocumentIntent;

    @TargetApi(VERSION_CODES.KITKAT)
    public static void saveDocument(Fragment fragment, String targetName, int requestCode) {
        saveDocument(fragment, targetName, "*/*", requestCode);
    }

    /** Opens the storage browser on Android 4.4 or later for saving a file. */
    @TargetApi(VERSION_CODES.KITKAT)
    public static void saveDocument(Fragment fragment, String suggestedName, String mimeType, int requestCode) {
        Intent intent = new Intent(Intent.ACTION_CREATE_DOCUMENT);
        intent.addCategory(Intent.CATEGORY_OPENABLE);
        intent.setType(mimeType);
        // Note: This is not documented, but works: Show the Internal Storage menu item in the drawer!
        intent.putExtra("android.content.extra.SHOW_ADVANCED", true);
        intent.putExtra(Intent.EXTRA_TITLE, suggestedName);
        fragment.startActivityForResult(intent, requestCode);
    }

    public static void openDocument(Fragment fragment, Uri last, String mimeType, boolean multiple, int requestCode) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT
                && hasOpenDocumentIntent(fragment.getContext())) {
            openDocumentKitKat(fragment, mimeType, multiple, requestCode);
        } else {
            openDocumentPreKitKat(fragment, last, mimeType, multiple, requestCode);
        }
    }

    /** Opens the preferred installed file manager on Android and shows a toast
     * if no manager is installed. */
    private static void openDocumentPreKitKat(
            Fragment fragment, Uri last, String mimeType, boolean multiple, int requestCode) {

        Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
        intent.addCategory(Intent.CATEGORY_OPENABLE);
        if (Build.VERSION.SDK_INT >= VERSION_CODES.JELLY_BEAN_MR2) {
            intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, multiple);
        }
        intent.setData(last);
        intent.setType(mimeType);

        try {
            fragment.startActivityForResult(intent, requestCode);
        } catch (ActivityNotFoundException e) {
            // No compatible file manager was found.
            Toast.makeText(fragment.getActivity(), R.string.no_filemanager_installed,
                    Toast.LENGTH_SHORT).show();
        }

    }

    /** Opens the storage browser on Android 4.4 or later for opening a file */
    @TargetApi(Build.VERSION_CODES.KITKAT)
    private static void openDocumentKitKat(Fragment fragment, String mimeType, boolean multiple, int requestCode) {
        Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
        intent.addCategory(Intent.CATEGORY_OPENABLE);
        intent.setType(mimeType);
        // Note: This is not documented, but works: Show the Internal Storage menu item in the drawer!
        intent.putExtra("android.content.extra.SHOW_ADVANCED", true);
        intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, multiple);

        fragment.startActivityForResult(intent, requestCode);
    }

    /**
     * Does the device actually have a ACTION_OPEN_DOCUMENT Intent? Looks like some Android
     * distributions are missing the ACTION_OPEN_DOCUMENT Intent even on Android 4.4,
     * see https://github.com/open-keychain/open-keychain/issues/1625
     *
     * @return True, if the device supports ACTION_OPEN_DOCUMENT. False, otherwise.
     */
    @TargetApi(VERSION_CODES.KITKAT)
    private static boolean hasOpenDocumentIntent(Context context) {
        if (hasOpenDocumentIntent == null) {
            PackageManager packageManager = context.getPackageManager();
            List<ResolveInfo> resolveInfoList = packageManager.queryIntentActivities(
                    new Intent(Intent.ACTION_OPEN_DOCUMENT), 0);
            hasOpenDocumentIntent = !resolveInfoList.isEmpty();
        }

        return hasOpenDocumentIntent;
    }

    public static String getFilename(Context context, Uri uri) {
        String filename = null;
        try {
            Cursor cursor = context.getContentResolver().query(uri, new String[]{OpenableColumns.DISPLAY_NAME}, null, null, null);

            if (cursor != null) {
                if (cursor.moveToNext()) {
                    filename = cursor.getString(0);
                }
                cursor.close();
            }
        } catch (Exception ignored) {
            // This happens in rare cases (eg: document deleted since selection) and should not cause a failure
        }
        if (filename == null) {
            String[] split = uri.toString().split("/");
            filename = split[split.length - 1];
        }
        return filename;
    }

    public static long getFileSize(Context context, Uri uri) {
        return getFileSize(context, uri, -1);
    }

    public static long getFileSize(Context context, Uri uri, long def) {
        if (ContentResolver.SCHEME_FILE.equals(uri.getScheme())) {
            long size = new File(uri.getPath()).length();
            if (size == 0) {
                size = def;
            }
            return size;
        }

        long size = def;
        try {
            Cursor cursor = context.getContentResolver().query(uri, new String[]{OpenableColumns.SIZE}, null, null, null);

            if (cursor != null) {
                if (cursor.moveToNext()) {
                    size = cursor.getLong(0);
                }
                cursor.close();
            }
        } catch (Exception ignored) {
            // This happens in rare cases (eg: document deleted since selection) and should not cause a failure
        }
        return size;
    }

    /**
     * Retrieve thumbnail of file, document api feature and thus KitKat only
     */
    public static Bitmap getThumbnail(Context context, Uri uri, Point size) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            return DocumentsContract.getDocumentThumbnail(context.getContentResolver(), uri, size, null);
        } else {
            return null;
        }
    }

    public static boolean isEncryptedFile(Context context, Uri uri) throws IOException {
        boolean isEncrypted = false;

        BufferedReader br = null;
        try {
            InputStream is = context.getContentResolver().openInputStream(uri);
            br = new BufferedReader(new InputStreamReader(is));

            String header = "-----BEGIN PGP MESSAGE-----";
            int length = header.length();
            char[] buffer = new char[length];
            if (br.read(buffer, 0, length) == length) {
                isEncrypted = new String(buffer).equals(header);
            }
        } finally {
            try {
                if (br != null)
                    br.close();
            } catch (IOException e) {
                Log.e(Constants.TAG, "Error closing file", e);
            }
        }
        return isEncrypted;
    }

    public static String readableFileSize(long size) {
        if (size <= 0) return "0";
        final String[] units = new String[]{"B", "KB", "MB", "GB", "TB"};
        int digitGroups = (int) (Math.log10(size) / Math.log10(1024));
        return new DecimalFormat("#,##0.#").format(size / Math.pow(1024, digitGroups)) + " " + units[digitGroups];
    }

    public static String readTextFromUri(Context context, Uri outputUri, String charset)
        throws IOException {

        byte[] decryptedMessage;
        {
            InputStream in = context.getContentResolver().openInputStream(outputUri);
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            byte[] buf = new byte[256];
            int read;
            while ( (read = in.read(buf)) > 0) {
                out.write(buf, 0, read);
            }
            in.close();
            out.close();
            decryptedMessage = out.toByteArray();
        }

        String plaintext;
        if (charset != null) {
            try {
                plaintext = new String(decryptedMessage, charset);
            } catch (UnsupportedEncodingException e) {
                // if we can't decode properly, just fall back to utf-8
                plaintext = new String(decryptedMessage);
            }
        } else {
            plaintext = new String(decryptedMessage);
        }

        return plaintext;

    }

    public static void copyUriData(Context context, Uri fromUri, Uri toUri) throws IOException {
        BufferedInputStream bis = null;
        BufferedOutputStream bos = null;

        try {
            ContentResolver resolver = context.getContentResolver();
            bis = new BufferedInputStream(resolver.openInputStream(fromUri));
            bos = new BufferedOutputStream(resolver.openOutputStream(toUri));
            byte[] buf = new byte[1024];
            int len;
            while ( (len = bis.read(buf)) > 0) {
                bos.write(buf, 0, len);
            }
        } finally {
            try {
                if (bis != null) {
                    bis.close();
                }
                if (bos != null) {
                    bos.close();
                }
            } catch (IOException e) {
                // ignore, it's just stream closin'
            }
        }
    }

    /**
     * Deletes data at a URI securely by overwriting it with random data
     * before deleting it. This method is fail-fast - if we can't securely
     * delete the file, we don't delete it at all.
     */
    public static int deleteFileSecurely(Context context, Uri uri)
            throws IOException {

        ContentResolver resolver = context.getContentResolver();
        long lengthLeft = FileHelper.getFileSize(context, uri);

        if (lengthLeft == -1) {
            throw new IOException("Error opening file!");
        }

        SecureRandom random = new SecureRandom();
        byte[] randomData = new byte[1024];

        OutputStream out = resolver.openOutputStream(uri, "w");
        if (out == null) {
            throw new IOException("Error opening file!");
        }
        out = new BufferedOutputStream(out);
        while (lengthLeft > 0) {
            random.nextBytes(randomData);
            out.write(randomData, 0, lengthLeft > randomData.length ? randomData.length : (int) lengthLeft);
            lengthLeft -= randomData.length;
        }
        out.close();

        if (ContentResolver.SCHEME_FILE.equals(uri.getScheme())) {
            return new File(uri.getPath()).delete() ? 1 : 0;
        } else {
            return resolver.delete(uri, null, null);
        }

    }

    /** Checks if external storage is mounted if file is located on external storage. */
    public static boolean isStorageMounted(String file) {
        if (file.startsWith(Environment.getExternalStorageDirectory().getAbsolutePath())) {
            if (!Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
                return false;
            }
        }

        return true;
    }

    /** A replacement for ContentResolver.openInputStream() that does not allow
     * the usage of "file" Uris that point to private files owned by the
     * application only, *on Lollipop devices*.
     *
     * The check will be performed on devices >= Lollipop only, which have the
     * necessary API to stat filedescriptors.
     *
     * @see FileHelperLollipop
     */
    public static InputStream openInputStreamSafe(ContentResolver resolver, Uri uri)
        throws FileNotFoundException {

        // Not supported on Android < 5
        if (Build.VERSION.SDK_INT >= VERSION_CODES.LOLLIPOP) {
            return FileHelperLollipop.openInputStreamSafe(resolver, uri);
        } else {
            return resolver.openInputStream(uri);
        }
    }

}