Add display trait for OpticPorts

src/optic_ports.rs

 use crate::error::OpossumError;
-use std::collections::HashSet;
+use std::{collections::HashSet, fmt::Display};
 
 /// Structure defining the optical ports (input / output terminals) of an [`OpticNode`](crate::optic_node::OpticNode).
 #[derive(Default, Debug, Clone)]
@@ -57,6 +57,34 @@ impl OpticPorts {
     }
 }
 
+impl Display for OpticPorts {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        writeln!(f, "inputs:").unwrap();
+        if !&self.inputs.is_empty() {
+            let mut ports=self.inputs();
+            ports.sort();
+            for port in ports {
+                writeln!(f, "  <{}>", port).unwrap();
+            }
+        } else {
+            writeln!(f, "  None").unwrap();
+        }
+        writeln!(f, "output:").unwrap();
+        if !&self.outputs.is_empty() {
+            let mut ports=self.outputs();
+            ports.sort();
+            for port in ports {
+                writeln!(f, "  <{}>", port).unwrap();
+            }
+        } else {
+            writeln!(f, "  None").unwrap();
+        }
+        if self.inverted {
+            writeln!(f, "ports are inverted").unwrap();
+        }
+        Ok(())
+    }
+}
 #[cfg(test)]
 mod test {
     use crate::optic_ports::OpticPorts;
@@ -151,4 +179,28 @@ mod test {
         ports.set_inverted(true);
         assert_eq!(ports.inverted(), true);
     }
+    #[test]
+    fn display_empty() {
+        let ports = OpticPorts::new();
+        assert_eq!(ports.to_string(), "inputs:\n  None\noutput:\n  None\n".to_owned());
+    }
+    #[test]
+    fn display_entries() {
+        let mut ports = OpticPorts::new();
+        ports.add_input("test1").unwrap();
+        ports.add_input("test2").unwrap();
+        ports.add_output("test3").unwrap();
+        ports.add_output("test4").unwrap();
+        assert_eq!(ports.to_string(), "inputs:\n  <test1>\n  <test2>\noutput:\n  <test3>\n  <test4>\n".to_owned());
+    }
+    #[test]
+    fn display_entries_inverted() {
+        let mut ports = OpticPorts::new();
+        ports.add_input("test1").unwrap();
+        ports.add_input("test2").unwrap();
+        ports.add_output("test3").unwrap();
+        ports.add_output("test4").unwrap();
+        ports.set_inverted(true);
+        assert_eq!(ports.to_string(), "inputs:\n  <test3>\n  <test4>\noutput:\n  <test1>\n  <test2>\nports are inverted\n".to_owned());
+    }
 }