1 files changed, 32 insertions, 7 deletions

diff --git a/src/dot.rs b/src/dot.rs
index c211bdb..f328e1a 100644
--- a/src/dot.rs
+++ b/src/dot.rs
@@ -53,7 +53,7 @@ impl<'a> Dot<'a> {
         write!(w, "{}{}", strict, &graph.graph_type())?;
 
         if let Some(id) = &graph.id {
-            write!(w, r#" "{}""#, escape_doublequotes(id))?;
+            write!(w, " {}", format_id(id))?;
         }
 
         writeln!(w, " {{")?;
@@ -185,11 +185,11 @@ impl<'a> Dot<'a> {
 
         write!(
             w,
-            r#"{}"{}" {} "{}""#,
+            r#"{}{} {} {}"#,
             get_indentation(indentation_level),
-            escape_doublequotes(&edge_source),
+            format_id(&edge_source),
             edge_op,
-            escape_doublequotes(&edge_source)
+            format_id(&edge_target)
         )?;
         write!(w, "{}", fmt_attributes(&edge.attributes))?;
         writeln!(w, ";")
@@ -638,7 +638,7 @@ impl<'a> Node<'a> {
 
 impl<'a> DotString<'a> for Node<'a> {
     fn dot_string(&self) -> Cow<'a, str> {
-        let mut dot_string = format!(r#""{}""#, escape_doublequotes(&self.id));
+        let mut dot_string = format!("{}", format_id(&self.id));
         dot_string.push_str(fmt_attributes(&self.attributes).as_str());
         dot_string.push_str(";");
         dot_string.into()
@@ -966,6 +966,31 @@ fn get_indentation(indentation_level: usize) -> String {
     INDENT.repeat(indentation_level)
 }
 
-fn escape_doublequotes(val: &String) -> String {
-    val.chars().map(|c| if c == '"' { format!("\\{}", c) } else { format!("{}", c)}).collect()
+fn is_alphanum(val: &String) -> bool {
+    for byte in val.bytes() {
+        if !((byte >= b'a' && byte <= b'z') || (byte >= b'A' && byte <= b'Z') ||
+            (byte >= b'0' && byte <= b'9') || byte == b'_' || byte >= 128)
+        {
+            return false;
+        }
+    }
+    true
+}
+
+// According to https://graphviz.org/doc/info/lang.html we should wrap any strings containing
+// non-alphanumerical characters, as escape double quotes within those strings.
+// This probably needs to be more robust but I think for now it fixes a but around double-quoted
+// strings
+fn format_id(val: &String) -> String {
+    if is_alphanum(val) {
+        val.to_string()
+    } else {
+        format!("\"{}\"", val.chars().map(
+            |c| if c == '"' {
+                format!("\\{}", c)
+            } else {
+                format!("{}", c)
+            }).collect::<String>()
+        )
+    }
 }