1 files changed, 66 insertions, 0 deletions
diff --git a/src/attributes/port_position.rs b/src/attributes/port_position.rs
new file mode 100644
index 0000000..a492b14
--- /dev/null
+++ b/src/attributes/port_position.rs
@@ -0,0 +1,66 @@
+use crate::attributes::compass_point::CompassPoint;
+use crate::dot::DotString;
+use std::borrow::Cow;
+
+/// Modifier indicating where on a node an edge should be aimed.
+/// If Port is used, the corresponding node must either have record shape with one of its
+/// fields having the given portname, or have an HTML-like label, one of whose components has a
+/// PORT attribute set to portname.
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub enum PortPosition {
+    Port {
+        port_name: String,
+        compass_point: Option<CompassPoint>,
+    },
+    Compass(CompassPoint),
+}
+
+// TODO: AsRef vs this?
+// See https://github.com/Peternator7/strum/blob/96ee0a9a307ec7d1a39809fb59037bd4e11557cc/strum/src/lib.rs
+impl<'a> DotString<'a> for PortPosition {
+    fn dot_string(&self) -> Cow<'a, str> {
+        match self {
+            PortPosition::Port {
+                port_name,
+                compass_point,
+            } => {
+                let mut dot_string = port_name.to_owned();
+                if let Some(compass_point) = compass_point {
+                    dot_string
+                        .push_str(format!(":{}", compass_point.dot_string()).as_str());
+                }
+                dot_string.into()
+            }
+            PortPosition::Compass(p) => p.dot_string().into(),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::attributes::{PortPosition, CompassPoint};
+    use crate::DotString;
+
+    #[test]
+    fn port_dot_string() {
+        assert_eq!(
+            "port_0",
+            PortPosition::Port {
+                port_name: "port_0".to_string(),
+                compass_point: None
+            }.dot_string()
+        );
+        assert_eq!(
+            "port_0:ne",
+            PortPosition::Port {
+                port_name: "port_0".to_string(),
+                compass_point: Some(CompassPoint::NE)
+            }.dot_string()
+        );
+    }
+
+    #[test]
+    fn compass_dot_string() {
+        assert_eq!("ne", PortPosition::Compass(CompassPoint::NE).dot_string());
+    }
+}
+\ No newline at end of file