Add convenience method for converting mailbox pairing text into QR code payload

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxManager.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.api.mailbox;
 
+import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
@@ -34,6 +35,16 @@ public interface MailboxManager {
 	 */
 	MailboxPairingTask startPairingTask(String qrCodePayload);
 
+	/**
+	 * Takes a textual QR code representation in
+	 * {@link org.briarproject.bramble.util.Base32} format and converts it
+	 * into a qrCodePayload as expected by {@link #startPairingTask(String)}.
+	 *
+	 * @throws FormatException when the provided payload did not include a
+	 * proper briar-mailbox:// link.
+	 */
+	String convertBase32Payload(String base32Payload) throws FormatException;
+
 	/**
 	 * Can be used by the UI to test the mailbox connection.
 	 *

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxManagerImpl.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.mailbox;
 
+import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.db.TransactionManager;
@@ -11,12 +12,15 @@ import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
 import org.briarproject.bramble.api.mailbox.MailboxStatus;
 import org.briarproject.bramble.api.mailbox.MailboxVersion;
 import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.util.Base32;
 import org.briarproject.nullsafety.NotNullByDefault;
 
 import java.io.IOException;
 import java.util.List;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.GuardedBy;
@@ -26,6 +30,7 @@ import javax.inject.Inject;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.StringUtils.ISO_8859_1;
 
 @Immutable
 @NotNullByDefault
@@ -98,6 +103,22 @@ class MailboxManagerImpl implements MailboxManager {
 		return created;
 	}
 
+	@Override
+	public String convertBase32Payload(String base32Payload)
+			throws FormatException {
+		Pattern regex = Pattern.compile("(briar-mailbox://)?([a-z2-7]{104})");
+		Matcher matcher = regex.matcher(base32Payload);
+		if (!matcher.find()) throw new FormatException();
+		String base32 = matcher.group(2);
+		byte[] payloadBytes;
+		try {
+			payloadBytes = Base32.decode(base32, false);
+		} catch (IllegalArgumentException e) {
+			throw new FormatException();
+		}
+		return new String(payloadBytes, ISO_8859_1);
+	}
+
 	@Override
 	public boolean checkConnection() {
 		List<MailboxVersion> versions = null;

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxManagerImplTest.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.mailbox;
 
+import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.db.TransactionManager;
@@ -9,17 +10,23 @@ import org.briarproject.bramble.api.mailbox.event.OwnMailboxConnectionStatusEven
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.DbExpectations;
+import org.briarproject.bramble.util.Base32;
 import org.junit.Test;
 
 import java.io.IOException;
+import java.util.Locale;
 import java.util.Random;
 import java.util.concurrent.Executor;
 
+import static org.briarproject.bramble.util.StringUtils.ISO_8859_1;
 import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
 import static org.briarproject.bramble.test.TestUtils.getMailboxProperties;
+import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.hasEvent;
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 
 public class MailboxManagerImplTest extends BrambleMockTestCase {
 
@@ -125,4 +132,32 @@ public class MailboxManagerImplTest extends BrambleMockTestCase {
 		assertTrue(manager.checkConnection());
 	}
 
+	@Test
+	public void testConvertBase32Payload() throws FormatException {
+		byte[] payload = getRandomBytes(65);
+		String base32payload = Base32.encode(payload).toLowerCase(Locale.ROOT);
+		String expected = new String(payload, ISO_8859_1);
+		try {
+			manager.convertBase32Payload("foo bar");
+			fail();
+		} catch (FormatException e) {
+			// expected
+		}
+		try { // doesn't work with shorter link
+			manager.convertBase32Payload("briar-mailbox://" +
+					base32payload.substring(0, base32payload.length() - 1));
+			fail();
+		} catch (FormatException e) {
+			// expected
+		}
+		// works with white-spaces
+		assertEquals(expected, manager.convertBase32Payload(
+				"foo bar  briar-mailbox://" + base32payload + " foo bar"));
+		// even works without white-space at the end
+		assertEquals(expected, manager.convertBase32Payload(
+				"foo bar  briar-mailbox://" + base32payload + "foobar"));
+		// even works without schema and extra chars at end
+		assertEquals(expected, manager.convertBase32Payload(
+				"foo bar " + base32payload + "foobar"));
+	}
 }