Add cp -r support to cp-utility tool (#285)

*Issue #, if available:*
ADOT SDK instrumentation Docker Images only support `cp -a` copy command
so that the [CWAgentOperator can
extract](https://github.com/aws/amazon-cloudwatch-agent-operator/blob/main/pkg/instrumentation/nodejs.go#L65)
the instrumentation SDK via `cp -a`, but upstream OTel Operator has
[changed a few months
ago](open-telemetry/opentelemetry-operator@4cd6dcb)
to use `cp -r` instead of `-a` to copy files from the OTel SDK
Instrumentation Images. Today, OTel Operator is not compatible with some
of the ADOT SDKs, and in the future, CWAgent Operator may also change to
use `cp -r` as well

*Description of changes:*
- Copy changes from Java's PR to add `cp -r` support -
aws-observability/aws-otel-java-instrumentation#843
- Modify the above `cp -r` support with bug fix implemented in Python's
`cp -a` command -
#214 (comment)

*Testing:*
- Tested on PetClinic Sample App's Python Services with latest OTel
Operator + Collector


![image](https://github.com/user-attachments/assets/c08aec2b-01ce-46c4-abfd-27c5b4f16c6b)


By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice.

tools/cp-utility/src/main.rs

@@ -28,6 +28,8 @@ enum CopyType {
     SingleFile,
     /// equivalent to cp -a <source> <dest>
     Archive,
+    /// equivalent to cp -r <source> <dest>
+    Recursive,
 }
 
 /// Encapsulate a copy operation
@@ -42,18 +44,22 @@ struct CopyOperation {
 
 /// Parse command line arguments and transform into `CopyOperation`
 fn parse_args(args: Vec<&str>) -> io::Result<CopyOperation> {
-    if !(args.len() == 3 || args.len() == 4 && args[1].eq("-a")) {
+    if !(args.len() == 3 || (args.len() == 4 && (args[1] == "-a" || args[1] == "-r"))) {
         return Err(io::Error::new(
             io::ErrorKind::InvalidInput,
-            "Invalid parameters. Expected cp [-a] <source> <destination>",
+            "Invalid parameters. Expected cp [-a | -r] <source> <destination>",
         ));
     }
 
     if args.len() == 4 {
         return Ok(CopyOperation {
             source: PathBuf::from(args[2]),
             destination: PathBuf::from(args[3]),
-            copy_type: CopyType::Archive,
+            copy_type: match args[1] {
+                "-a" => CopyType::Archive,
+                "-r" => CopyType::Recursive,
+                _ => panic!("Invalid option. Expected -a or -r"),
+            },
         });
     }
 
@@ -69,10 +75,40 @@ fn do_copy(operation: CopyOperation) -> io::Result<()> {
     match operation.copy_type {
         CopyType::Archive => copy_archive(&operation.source, &operation.destination)?,
         CopyType::SingleFile => fs::copy(&operation.source, &operation.destination).map(|_| ())?,
+        CopyType::Recursive => copy_recursive(&operation.source, &operation.destination)?,
     };
     Ok(())
 }
 
+fn copy_recursive(source: &Path, dest: &Path) -> io::Result<()> {
+    let mut stack = VecDeque::new();
+    stack.push_back((source.to_path_buf(), dest.to_path_buf()));
+    while let Some((current_source, current_dest)) = stack.pop_back() {
+        if current_source.is_dir() {
+            if !current_dest.exists() {
+                fs::create_dir(&current_dest)?;
+            }
+            for entry in fs::read_dir(current_source)? {
+                let next_source = entry?.path();
+                let next_dest =
+                    current_dest
+                        .clone()
+                        .join(next_source.file_name().ok_or(io::Error::new(
+                            io::ErrorKind::InvalidInput,
+                            "Invalid source file",
+                        ))?);
+                stack.push_back((next_source, next_dest));
+            }
+        } else if current_source.is_symlink() {
+            // Follow symbolic links as regular files
+            fs::copy(current_source, current_dest)?;
+        } else if current_source.is_file() {
+            fs::copy(current_source, current_dest)?;
+        }
+    }
+    Ok(())
+}
+
 // Execute the recursive type of copy operation
 fn copy_archive(source: &Path, dest: &Path) -> io::Result<()> {
     let mut stack = VecDeque::new();
@@ -100,7 +136,6 @@ fn copy_archive(source: &Path, dest: &Path) -> io::Result<()> {
             fs::copy(current_source, current_dest)?;
         }
     }
-
     Ok(())
 }
 
@@ -163,7 +198,7 @@ mod tests {
     fn parser_failure() {
         // prepare
         let inputs = vec![
-            vec!["cp", "-r", "foo.txt", "bar.txt"],
+            vec!["cp", "-r", "foo.txt", "bar.txt", "foo1.txt"],
             vec!["cp", "-a", "param1", "param2", "param3"],
             vec!["cp", "param1", "param2", "param3"],
         ];
@@ -177,6 +212,24 @@ mod tests {
         }
     }
 
+    #[test]
+    fn parser_correct() {
+        // prepare
+        let inputs = vec![
+            vec!["cp", "-r", "foo.txt", "bar.txt"],
+            vec!["cp", "-a", "param1", "param2"],
+            vec!["cp", "param1", "param2"],
+        ];
+
+        for input in inputs.into_iter() {
+            // act
+            let result = parse_args(input.clone());
+
+            // assert
+            assert!(result.is_ok(), "input should fail {:?}", input);
+        }
+    }
+
     #[test]
     fn test_copy_single() {
         // prepare
@@ -220,6 +273,51 @@ mod tests {
         assert!(result.is_err());
     }
 
+    #[test]
+    fn test_copy_recursive() {
+        // prepare
+        let tempdir = tempfile::tempdir().unwrap();
+        let test_base = tempdir.path().to_path_buf();
+        ["foo", "foo/foo0", "foo/foo1", "foo/bar"]
+            .iter()
+            .for_each(|x| create_dir(&test_base, x));
+        let files = [
+            "foo/file1.txt",
+            "foo/file2.txt",
+            "foo/foo1/file3.txt",
+            "foo/bar/file4.txt",
+        ];
+        files.iter().for_each(|x| create_file(&test_base, x));
+        [("foo/symlink1.txt", "./file1.txt")]
+            .iter()
+            .for_each(|(x, y)| create_symlink(&test_base, x, y));
+
+        // act
+        let recursive_copy = CopyOperation {
+            copy_type: CopyType::Recursive,
+            source: test_base.join("foo"),
+            destination: test_base.join("bar"),
+        };
+        do_copy(recursive_copy).unwrap();
+
+        // assert
+        files.iter().for_each(|x| {
+            assert_same_file(
+                &test_base.join(x),
+                &test_base.join(x.replace("foo/", "bar/")),
+            )
+        });
+        assert_same_file(
+            &test_base.join("foo/symlink1.txt"),
+            &test_base.join("bar/symlink1.txt"),
+        );
+        // recursive copy will treat symlink as a file
+        assert_recursive_same_link(
+            &test_base.join("foo/symlink1.txt"),
+            &test_base.join("bar/symlink1.txt"),
+        )
+    }
+
     #[test]
     fn test_copy_archive() {
         // prepare
@@ -342,4 +440,16 @@ mod tests {
 
         assert_eq!(fs::read_link(source).unwrap(), fs::read_link(dest).unwrap());
     }
+
+    fn assert_recursive_same_link(source: &Path, dest: &Path) {
+        assert!(source.exists());
+        assert!(dest.exists());
+        assert!(source.is_symlink());
+        assert!(dest.is_file());
+
+        assert_eq!(
+            fs::read_to_string(source).unwrap(),
+            fs::read_to_string(dest).unwrap()
+        );
+    }
 }