Issue #76: Add fileSize method to retrieve remote file size via SFTP

src/main/java/org/metricshub/ssh/SshClient.java

@@ -327,7 +327,7 @@
 			.append("\t")
 			.append(fileAttributes.atime.toString())
 			.append("\t-\t")
 			.append(Integer.toString(fileAttributes.permissions & 0000777, 8))
 			.append("\t")
 			.append(fileAttributes.size.toString())
 			.append("\t-\t")
@@ -346,6 +346,34 @@
 		return pslFileResult.toString();
 	}
 
+	/**
+	 * Returns the file size.
+	 *
+	 * @param filePath Path to the file on the remote system
+	 * @return the file size
+	 * @throws IOException if the file does not exist
+	 */
+	public long fileSize(final String filePath) throws IOException {
+		SFTPv3Client sftpClient = null;
+		try {
+			// Sanity check
+			checkIfAuthenticated();
+
+			// Create the SFTP client
+			sftpClient = new SFTPv3Client(sshConnection);
+
+			// Read the file attributes
+			final SFTPv3FileAttributes attributes = sftpClient.stat(filePath);
+
+			return attributes.size;
+		} finally {
+			// Deallocate
+			if (sftpClient != null) {
+				sftpClient.close();
+			}
+		}
+	}
+
 	private StringBuilder listSubDirectory(
 		SFTPv3Client sftpClient,
 		String remoteDirectoryPath,
@@ -374,17 +402,17 @@
 				SFTPv3FileAttributes fileAttributes = file.attributes;
 				String filePath = remoteDirectoryPath + "/" + filename;
 
 				if ((fileAttributes.permissions & 0120000) == 0120000) {
 					// Symbolic link
 					continue;
 				}
 
 				// CHECKSTYLE:OFF
 				if (
 					((fileAttributes.permissions & 0100000) == 0100000) ||
 					((fileAttributes.permissions & 0060000) == 0060000) ||
 					((fileAttributes.permissions & 0020000) == 0020000) ||
 					((fileAttributes.permissions & 0140000) == 0140000)
 				) {
 					// Regular/Block/Character/Socket files
 					final Matcher m = fileMaskPattern.matcher(filename);
@@ -401,12 +429,12 @@
 				}
 				// CHECKSTYLE:ON
 
 				if ((fileAttributes.permissions & 0040000) == 0040000) {
 					// Directory
 					if (includeSubfolders) {
 						resultBuilder =
 							listSubDirectory(sftpClient, filePath, fileMaskPattern, includeSubfolders, depth, resultBuilder);
 					}
 				}
 			}
 		}
@@ -541,7 +569,7 @@
 		sftpClient.close();
 
 		// Metricshub Collection format
 		return out.toString();
 	}
 
 	/**
@@ -611,24 +639,24 @@
 		/**
 		 * Whether the command was successful or not
 		 */
 		public boolean success = true;
 
 		/**
 		 * How much time was taken by the execution itself (not counting the
 		 * connection time), in seconds
 		 */
 		public float executionTime = 0;
 
 		/**
 		 * The exit code (status) returned by the command (process return code).
 		 * <code>null</code> if unsupported by the remote platform.
 		 */
 		public Integer exitStatus = null;
 
 		/**
 		 * The result of the command (stdout and stderr is merged into result)
 		 */
 		public String result = "";
 	}
 
 	/**
@@ -712,7 +740,7 @@
 				// We completed in time
 
 				// Execution time (in seconds)
 				commandResult.executionTime = (currentTime - startTime) / 1000;
 
 				// Read exit status, when available
 				waitForCondition = sshSession.waitForCondition(ChannelCondition.EXIT_STATUS, 5000);
@@ -744,7 +772,7 @@
 		openTerminal();
 
 		// Pipe specified InputStream to SSH's stdin -- use a separate thread
 		BufferedReader inputReader = new BufferedReader(new InputStreamReader(in));
 		OutputStream outputWriter = sshSession.getStdin();
 		Thread stdinPipeThread = new Thread() {
 			@Override
@@ -752,12 +780,12 @@
 				try {
 					String line;
 					while ((line = inputReader.readLine()) != null) {
 						outputWriter.write(line.getBytes());
 						outputWriter.write('\n');
 					}
 				} catch (Exception e) {
 					// Things ended up badly. Exit thread.
 				}
 				// End of the input stream. We need to exit.
 				// Let's close the session so the main thread exits nicely.
 				sshSession.close();
@@ -1009,7 +1037,7 @@
 	 * Check if already authenticate.
 	 */
 	void checkIfAuthenticated() {
-		if (!getSshConnection().isAuthenticationComplete()) {
+		if (getSshConnection() == null || !getSshConnection().isAuthenticationComplete()) {
 			throw new IllegalStateException("Authentication is required first");
 		}
 	}

src/test/java/org/metricshub/ssh/SSHClientTest.java

@@ -2,13 +2,17 @@
 
 import com.trilead.ssh2.ChannelCondition;
 import com.trilead.ssh2.Connection;
+import com.trilead.ssh2.SFTPv3Client;
+import com.trilead.ssh2.SFTPv3FileAttributes;
 import com.trilead.ssh2.Session;
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
+import java.io.IOException;
 import java.nio.charset.Charset;
 import java.util.Optional;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
+import org.mockito.MockedConstruction;
 import org.mockito.Mockito;
 
 class SSHClientTest {
@@ -525,4 +529,95 @@ void testRead() throws Exception {
 			Assertions.assertEquals(Optional.of("Hello WorldError"), sshClient.read(0, 5));
 		}
 	}
+
+	@Test
+	void testFileSize() throws Exception {
+		final Connection sshConnection = Mockito.mock(Connection.class);
+		final String filePath = "/path/to/file.txt";
+
+		// Case not Connected
+		try (final SshClient sshClient = Mockito.spy(new SshClient(HOSTNAME))) {
+			Mockito.verify(sshClient, Mockito.never()).checkIfAuthenticated();
+
+			Assertions.assertThrows(IllegalStateException.class, () -> sshClient.fileSize(filePath));
+		}
+
+		// Case not authenticated
+		try (final SshClient sshClient = Mockito.spy(new SshClient(HOSTNAME))) {
+			Mockito.doReturn(sshConnection).when(sshClient).getSshConnection();
+			Mockito.doReturn(false).when(sshConnection).isAuthenticationComplete();
+
+			Assertions.assertThrows(IllegalStateException.class, () -> sshClient.fileSize(filePath));
+		}
+
+		// Case file does not exist (IOException)
+		try (
+			final SshClient sshClient = Mockito.spy(new SshClient(HOSTNAME));
+			final MockedConstruction<SFTPv3Client> mockedConstruction = Mockito.mockConstruction(
+				SFTPv3Client.class,
+				(mock, context) -> {
+					Mockito.when(mock.stat(filePath)).thenThrow(new IOException("File not found"));
+				}
+			)
+		) {
+			Mockito.doReturn(sshConnection).when(sshClient).getSshConnection();
+			Mockito.doReturn(true).when(sshConnection).isAuthenticationComplete();
+
+			Assertions.assertThrows(IOException.class, () -> sshClient.fileSize(filePath));
+		}
+
+		// Case file size is 0
+		try (
+			final SshClient sshClient = Mockito.spy(new SshClient(HOSTNAME));
+			final MockedConstruction<SFTPv3Client> mockedConstruction = Mockito.mockConstruction(
+				SFTPv3Client.class,
+				(mock, context) -> {
+					final SFTPv3FileAttributes attributes = new SFTPv3FileAttributes();
+					attributes.size = 0L;
+					Mockito.when(mock.stat(filePath)).thenReturn(attributes);
+				}
+			)
+		) {
+			Mockito.doReturn(sshConnection).when(sshClient).getSshConnection();
+			Mockito.doReturn(true).when(sshConnection).isAuthenticationComplete();
+
+			Assertions.assertEquals(0L, sshClient.fileSize(filePath));
+		}
+
+		// Case file size is small (100 bytes)
+		try (
+			final SshClient sshClient = Mockito.spy(new SshClient(HOSTNAME));
+			final MockedConstruction<SFTPv3Client> mockedConstruction = Mockito.mockConstruction(
+				SFTPv3Client.class,
+				(mock, context) -> {
+					final SFTPv3FileAttributes attributes = new SFTPv3FileAttributes();
+					attributes.size = 100L;
+					Mockito.when(mock.stat(filePath)).thenReturn(attributes);
+				}
+			)
+		) {
+			Mockito.doReturn(sshConnection).when(sshClient).getSshConnection();
+			Mockito.doReturn(true).when(sshConnection).isAuthenticationComplete();
+
+			Assertions.assertEquals(100L, sshClient.fileSize(filePath));
+		}
+
+		// Case file size is large (1GB)
+		try (
+			final SshClient sshClient = Mockito.spy(new SshClient(HOSTNAME));
+			final MockedConstruction<SFTPv3Client> mockedConstruction = Mockito.mockConstruction(
+				SFTPv3Client.class,
+				(mock, context) -> {
+					final SFTPv3FileAttributes attributes = new SFTPv3FileAttributes();
+					attributes.size = 1073741824L;
+					Mockito.when(mock.stat(filePath)).thenReturn(attributes);
+				}
+			)
+		) {
+			Mockito.doReturn(sshConnection).when(sshClient).getSshConnection();
+			Mockito.doReturn(true).when(sshConnection).isAuthenticationComplete();
+
+			Assertions.assertEquals(1073741824L, sshClient.fileSize(filePath));
+		}
+	}
 }