Add method for fetching api versions that the mailbox supports

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

@@ -31,6 +31,9 @@ interface MailboxApi {
 	List<MailboxVersion> CLIENT_SUPPORTS = singletonList(
 			new MailboxVersion(1, 0));
 
+	List<MailboxVersion> getServerSupports(MailboxProperties properties)
+			throws IOException, ApiException;
+
 	/**
 	 * Sets up the mailbox with the setup token.
 	 *

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

@@ -56,6 +56,23 @@ class MailboxApiImpl implements MailboxApi {
 		this.httpClientProvider = httpClientProvider;
 	}
 
+	@Override
+	public List<MailboxVersion> getServerSupports(MailboxProperties properties)
+			throws IOException, ApiException {
+		if (!properties.isOwner()) throw new IllegalArgumentException();
+		Response response = sendGetRequest(properties, "/versions");
+		if (response.code() != 200) throw new ApiException();
+
+		ResponseBody body = response.body();
+		if (body == null) throw new ApiException();
+		try {
+			JsonNode node = mapper.readTree(body.string());
+			return parseServerSupports(node);
+		} catch (JacksonException e) {
+			throw new ApiException();
+		}
+	}
+
 	@Override
 	public MailboxProperties setup(MailboxProperties properties)
 			throws IOException, ApiException {
@@ -76,32 +93,37 @@ class MailboxApiImpl implements MailboxApi {
 			if (tokenNode == null) {
 				throw new ApiException();
 			}
-			List<MailboxVersion> serverSupports = new ArrayList<>();
-			ArrayNode serverSupportsNode = getArray(node, "serverSupports");
-			for (JsonNode versionNode : serverSupportsNode) {
-				if (!versionNode.isObject()) throw new ApiException();
-				ObjectNode objectNode = (ObjectNode) versionNode;
-				JsonNode majorNode = objectNode.get("major");
-				JsonNode minorNode = objectNode.get("minor");
-				if (majorNode == null || !majorNode.isNumber()) {
-					throw new ApiException();
-				}
-				if (minorNode == null || !minorNode.isNumber()) {
-					throw new ApiException();
-				}
-				int major = majorNode.asInt();
-				int minor = minorNode.asInt();
-				if (major < 0 || minor < 0) throw new ApiException();
-				serverSupports.add(new MailboxVersion(major, minor));
-			}
 			return new MailboxProperties(properties.getBaseUrl(),
 					MailboxAuthToken.fromString(tokenNode.textValue()),
-					true, serverSupports);
+					true, parseServerSupports(node));
 		} catch (JacksonException | InvalidMailboxIdException e) {
 			throw new ApiException();
 		}
 	}
 
+	private List<MailboxVersion> parseServerSupports(JsonNode node)
+			throws ApiException {
+		List<MailboxVersion> serverSupports = new ArrayList<>();
+		ArrayNode serverSupportsNode = getArray(node, "serverSupports");
+		for (JsonNode versionNode : serverSupportsNode) {
+			if (!versionNode.isObject()) throw new ApiException();
+			ObjectNode objectNode = (ObjectNode) versionNode;
+			JsonNode majorNode = objectNode.get("major");
+			JsonNode minorNode = objectNode.get("minor");
+			if (majorNode == null || !majorNode.isNumber()) {
+				throw new ApiException();
+			}
+			if (minorNode == null || !minorNode.isNumber()) {
+				throw new ApiException();
+			}
+			int major = majorNode.asInt();
+			int minor = minorNode.asInt();
+			if (major < 0 || minor < 0) throw new ApiException();
+			serverSupports.add(new MailboxVersion(major, minor));
+		}
+		return serverSupports;
+	}
+
 	@Override
 	public boolean checkStatus(MailboxProperties properties)
 			throws IOException, ApiException {

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

@@ -9,6 +9,7 @@ import org.briarproject.bramble.api.mailbox.MailboxFileId;
 import org.briarproject.bramble.api.mailbox.MailboxFolderId;
 import org.briarproject.bramble.api.mailbox.MailboxId;
 import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.mailbox.MailboxVersion;
 import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
 import org.briarproject.bramble.mailbox.MailboxApi.MailboxContact;
 import org.briarproject.bramble.mailbox.MailboxApi.MailboxFile;
@@ -79,6 +80,94 @@ public class MailboxApiTest extends BrambleTestCase {
 	private final MailboxContact mailboxContact = new MailboxContact(
 			contactId, contactToken, contactInboxId, contactOutboxId);
 
+	@Test
+	public void testGetServerSupports() throws Exception {
+		String validVersions = "[ {\"major\":1,\"minor\":0} ]";
+		String validResponse = makeVersionsResponse(validVersions);
+		String invalidResponse = "{\"foo\":\"bar\"}";
+		String invalidVersionsResponse = makeVersionsResponse("42");
+		String invalidVersionsResponse2 = makeVersionsResponse("[ 1,0 ]");
+		String invalidVersionsResponse3 =
+				makeVersionsResponse("[ {\"major\":1, \"minor\":-1} ]");
+
+		MockWebServer server = new MockWebServer();
+		server.enqueue(new MockResponse().setBody(validResponse));
+		server.enqueue(new MockResponse().setBody(invalidResponse));
+		server.enqueue(new MockResponse().setResponseCode(401));
+		server.enqueue(new MockResponse().setResponseCode(500));
+		server.enqueue(new MockResponse().setBody(invalidVersionsResponse));
+		server.enqueue(new MockResponse().setBody(invalidVersionsResponse2));
+		server.enqueue(new MockResponse().setBody(invalidVersionsResponse3));
+		server.start();
+		String baseUrl = getBaseUrl(server);
+		List<MailboxVersion> versions = singletonList(new MailboxVersion(1, 0));
+		MailboxProperties properties =
+				new MailboxProperties(baseUrl, token, true, new ArrayList<>());
+		MailboxProperties properties2 =
+				new MailboxProperties(baseUrl, token2, true, new ArrayList<>());
+
+		RecordedRequest request;
+
+		// valid response with valid token
+		assertEquals(versions, api.getServerSupports(properties));
+		request = server.takeRequest();
+		assertEquals("/versions", request.getPath());
+		assertEquals("GET", request.getMethod());
+		assertToken(request, token);
+
+		// invalid response
+		assertThrows(ApiException.class,
+				() -> api.getServerSupports(properties));
+		request = server.takeRequest();
+		assertEquals("/versions", request.getPath());
+		assertEquals("GET", request.getMethod());
+		assertToken(request, token);
+
+		// 401 response
+		assertThrows(ApiException.class,
+				() -> api.getServerSupports(properties2));
+		request = server.takeRequest();
+		assertEquals("/versions", request.getPath());
+		assertEquals("GET", request.getMethod());
+		assertToken(request, token2);
+
+		// 500 response
+		assertThrows(ApiException.class,
+				() -> api.getServerSupports(properties));
+		request = server.takeRequest();
+		assertEquals("/versions", request.getPath());
+		assertEquals("GET", request.getMethod());
+		assertToken(request, token);
+
+		// invalid non-array serverSupports response
+		assertThrows(ApiException.class,
+				() -> api.getServerSupports(properties));
+		request = server.takeRequest();
+		assertEquals("/versions", request.getPath());
+		assertEquals("GET", request.getMethod());
+		assertToken(request, token);
+
+		// invalid non-object in serverSupports array response
+		assertThrows(ApiException.class,
+				() -> api.getServerSupports(properties));
+		request = server.takeRequest();
+		assertEquals("/versions", request.getPath());
+		assertEquals("GET", request.getMethod());
+		assertToken(request, token);
+
+		// invalid negative minor version in serverSupports response
+		assertThrows(ApiException.class,
+				() -> api.getServerSupports(properties));
+		request = server.takeRequest();
+		assertEquals("/versions", request.getPath());
+		assertEquals("GET", request.getMethod());
+		assertToken(request, token);
+	}
+
+	private String makeVersionsResponse(String versions) {
+		return "{\"serverSupports\":" + versions + "}";
+	}
+
 	@Test
 	public void testSetup() throws Exception {
 		String validVersions = "[ {\"major\":1,\"minor\":0} ]";