package eu.siacs.conversations.services;

import android.app.Notification;
import android.app.NotificationManager;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.DatabaseUtils;
import android.database.sqlite.SQLiteDatabase;
import android.os.IBinder;
import android.support.v4.app.NotificationCompat;
import android.util.Log;

import java.io.DataOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.PrintWriter;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.zip.GZIPOutputStream;

import javax.crypto.Cipher;
import javax.crypto.CipherOutputStream;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;

import eu.siacs.conversations.Config;
import eu.siacs.conversations.R;
import eu.siacs.conversations.crypto.axolotl.SQLiteAxolotlStore;
import eu.siacs.conversations.entities.Account;
import eu.siacs.conversations.entities.Conversation;
import eu.siacs.conversations.entities.Message;
import eu.siacs.conversations.persistance.DatabaseBackend;
import eu.siacs.conversations.persistance.FileBackend;
import eu.siacs.conversations.utils.BackupFileHeader;
import eu.siacs.conversations.utils.Compatibility;

public class ExportBackupService extends Service {

    public static final String KEYTYPE = "AES";
    public static final String CIPHERMODE = "AES/GCM/NoPadding";
    public static final String PROVIDER = "BC";

    private static final int NOTIFICATION_ID = 19;
    private static AtomicBoolean running = new AtomicBoolean(false);
    private DatabaseBackend mDatabaseBackend;
    private List<Account> mAccounts;
    private NotificationManager notificationManager;

    @Override
    public void onCreate() {
        mDatabaseBackend = DatabaseBackend.getInstance(getBaseContext());
        mAccounts = mDatabaseBackend.getAccounts();
        notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        if (running.compareAndSet(false, true)) {
            new Thread(() -> {
                export();
                stopForeground(true);
                running.set(false);
                stopSelf();
            }).start();
        }
        return START_NOT_STICKY;
    }

    private static void accountExport(SQLiteDatabase db, String uuid, PrintWriter writer) {
        StringBuilder builder = new StringBuilder();
        final Cursor accountCursor = db.query(Account.TABLENAME, null, Account.UUID + "=?", new String[]{uuid}, null, null, null);
        while (accountCursor != null && accountCursor.moveToNext()) {
            builder.append("INSERT INTO ").append(Account.TABLENAME).append("(");
            for (int i = 0; i < accountCursor.getColumnCount(); ++i) {
                if (i != 0) {
                    builder.append(',');
                }
                builder.append(accountCursor.getColumnName(i));
            }
            builder.append(") VALUES(");
            for (int i = 0; i < accountCursor.getColumnCount(); ++i) {
                if (i != 0) {
                    builder.append(',');
                }
                final String value = accountCursor.getString(i);
                if (value == null || Account.ROSTERVERSION.equals(accountCursor.getColumnName(i))) {
                    builder.append("NULL");
                } else if (value.matches("\\d+")) {
                    int intValue = Integer.parseInt(value);
                    Log.d(Config.LOGTAG,"reading int value. "+intValue);
                    if (Account.OPTIONS.equals(accountCursor.getColumnName(i))) {
                        intValue |= 1 << Account.OPTION_DISABLED;
                        Log.d(Config.LOGTAG,"modified int value "+intValue);
                    }
                    builder.append(intValue);
                } else {
                    DatabaseUtils.appendEscapedSQLString(builder, value);
                }
            }
            builder.append(")");
            builder.append(';');
            builder.append('\n');
        }
        Log.d(Config.LOGTAG,builder.toString());
        if (accountCursor != null) {
            accountCursor.close();
        }
        writer.append(builder.toString());
    }

    private void messageExport(SQLiteDatabase db, String uuid, PrintWriter writer, Progress progress) {
        Cursor cursor = db.rawQuery("select messages.* from messages join conversations on conversations.uuid=messages.conversationUuid where conversations.accountUuid=?", new String[]{uuid});
        int size = cursor != null ? cursor.getCount() : 0;
        Log.d(Config.LOGTAG, "exporting " + size + " messages");
        int i = 0;
        int p = 0;
        while (cursor != null && cursor.moveToNext()) {
            writer.write(cursorToString(Message.TABLENAME, cursor, 20));
            if (i + 20 > size) {
                i = size;
            } else {
                i += 20;
            }
            final int percentage = i * 100 / size;
            if (p < percentage) {
                p = percentage;
                notificationManager.notify(NOTIFICATION_ID,progress.build(p));
                Log.d(Config.LOGTAG, "percentage=" + p);
            }
        }
        if (cursor != null) {
            cursor.close();
        }
    }

    private static void simpleExport(SQLiteDatabase db, String table, String column, String uuid, PrintWriter writer) {
        final Cursor cursor = db.query(table, null, column + "=?", new String[]{uuid}, null, null, null);
        while (cursor != null && cursor.moveToNext()) {
            writer.write(cursorToString(table, cursor, 20));
        }
        if (cursor != null) {
            cursor.close();
        }
    }

    private void export() {
        NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(getBaseContext(), "backup");
        mBuilder.setContentTitle(getString(R.string.notification_create_backup_title))
                .setSmallIcon(R.drawable.ic_archive_white_24dp)
                .setProgress(1, 0, false);
        startForeground(NOTIFICATION_ID, mBuilder.build());
        try {
            int count = 0;
            final int max = this.mAccounts.size();
            final SecureRandom secureRandom = new SecureRandom();
            for (Account account : this.mAccounts) {
                final byte[] IV = new byte[12];
                final byte[] salt = new byte[16];
                secureRandom.nextBytes(IV);
                secureRandom.nextBytes(salt);
                final BackupFileHeader backupFileHeader = new BackupFileHeader(getString(R.string.app_name),account.getJid(),System.currentTimeMillis(),IV,salt);
                final Progress progress = new Progress(mBuilder, max, count);
                final File file = new File(FileBackend.getBackupDirectory(this)+account.getJid().asBareJid().toEscapedString()+".ceb");
                if (file.getParentFile().mkdirs()) {
                    Log.d(Config.LOGTAG,"created backup directory "+file.getParentFile().getAbsolutePath());
                }
                final FileOutputStream fileOutputStream = new FileOutputStream(file);
                final DataOutputStream dataOutputStream = new DataOutputStream(fileOutputStream);
                backupFileHeader.write(dataOutputStream);
                dataOutputStream.flush();

                final Cipher cipher = Compatibility.twentyEight() ? Cipher.getInstance(CIPHERMODE) : Cipher.getInstance(CIPHERMODE, PROVIDER);
                byte[] key = getKey(account.getPassword(), salt);
                Log.d(Config.LOGTAG,backupFileHeader.toString());
                SecretKeySpec keySpec = new SecretKeySpec(key, KEYTYPE);
                IvParameterSpec ivSpec = new IvParameterSpec(IV);
                cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
                CipherOutputStream cipherOutputStream = new CipherOutputStream(fileOutputStream, cipher);

                GZIPOutputStream gzipOutputStream = new GZIPOutputStream(cipherOutputStream);
                PrintWriter writer = new PrintWriter(gzipOutputStream);
                SQLiteDatabase db = this.mDatabaseBackend.getReadableDatabase();
                final String uuid = account.getUuid();
                accountExport(db, uuid, writer);
                simpleExport(db, Conversation.TABLENAME, Conversation.ACCOUNT, uuid, writer);
                messageExport(db, uuid, writer, progress);
                for(String table : Arrays.asList(SQLiteAxolotlStore.PREKEY_TABLENAME, SQLiteAxolotlStore.SIGNED_PREKEY_TABLENAME, SQLiteAxolotlStore.SESSION_TABLENAME, SQLiteAxolotlStore.IDENTITIES_TABLENAME)) {
                    simpleExport(db, table, SQLiteAxolotlStore.ACCOUNT,uuid,writer);
                }
                writer.flush();
                writer.close();
                Log.d(Config.LOGTAG, "written backup to " + file.getAbsoluteFile());
                count++;
            }
        } catch (Exception e) {
            Log.d(Config.LOGTAG, "unable to create backup ", e);
        }
    }

    public static byte[] getKey(String password, byte[] salt) {
        try {
            SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
            return factory.generateSecret(new PBEKeySpec(password.toCharArray(), salt, 1024, 128)).getEncoded();
        } catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
            throw new AssertionError(e);
        }
    }

    private static String cursorToString(String tablename, Cursor cursor, int max) {
        StringBuilder builder = new StringBuilder();
        builder.append("INSERT INTO ").append(tablename).append("(");
        for (int i = 0; i < cursor.getColumnCount(); ++i) {
            if (i != 0) {
                builder.append(',');
            }
            builder.append(cursor.getColumnName(i));
        }
        builder.append(") VALUES");
        for (int i = 0; i < max; ++i) {
            if (i != 0) {
                builder.append(',');
            }
            appendValues(cursor, builder);
            if (!cursor.moveToNext()) {
                break;
            }
        }
        builder.append(';');
        builder.append('\n');
        return builder.toString();
    }

    private static void appendValues(Cursor cursor, StringBuilder builder) {
        builder.append("(");
        for (int i = 0; i < cursor.getColumnCount(); ++i) {
            if (i != 0) {
                builder.append(',');
            }
            final String value = cursor.getString(i);
            if (value == null) {
                builder.append("NULL");
            } else if (value.matches("\\d+")) {
                builder.append(value);
            } else {
                DatabaseUtils.appendEscapedSQLString(builder, value);
            }
        }
        builder.append(")");

    }

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    private class Progress {
        private final NotificationCompat.Builder builder;
        private final int max;
        private final int count;

        private Progress(NotificationCompat.Builder builder, int max, int count) {
            this.builder = builder;
            this.max = max;
            this.count = count;
        }

        private Notification build(int percentage) {
            builder.setProgress(max * 100,count * 100 + percentage,false);
            return builder.build();
        }
    }
}