util: Replace regex with custom iterator

src/util.rs

@@ -1,8 +1,6 @@
-use regex::Regex;
 use std::cmp::Ordering;
-use std::sync::OnceLock;
 
-#[derive(Eq, PartialEq)]
+#[derive(Eq, PartialEq, Debug)]
 enum VersionComponent {
     Number(u64),
     Text(String),
@@ -30,30 +28,93 @@ impl PartialOrd for VersionComponent {
     }
 }
 
+// takes a version string and outputs the different components
+//
+// a component is delimited by '-' or '.' and consists of just digits or letters
+struct VersionComponentIterator<'a> {
+    v: &'a str,
+    pos: usize,
+}
+
+impl<'a> VersionComponentIterator<'a> {
+    pub fn new<I: Into<&'a str>>(v: I) -> Self {
+        Self {
+            v: v.into(),
+            pos: 0,
+        }
+    }
+}
+
+impl Iterator for VersionComponentIterator<'_> {
+    type Item = VersionComponent;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        // check if there is something left
+        if self.pos >= self.v.len() {
+            return None;
+        }
+
+        // skip all '-' and '.' in the beginning
+        let mut skipped_chars = 0;
+        let mut chars = self.v[self.pos..].chars().peekable();
+        while let Some('.' | '-') = chars.peek() {
+            skipped_chars += 1;
+            chars.next();
+        }
+
+        // get the next character and decide if it is a digit or char
+        let c = chars.peek()?;
+        let is_digit = c.is_ascii_digit();
+        // based on this collect characters after this into the component
+        let component: String = chars
+            .take_while(|&c| c.is_ascii_digit() == is_digit && c != '.' && c != '-')
+            .collect();
+
+        // remember what chars we used
+        self.pos += component.len() + skipped_chars;
+
+        if component.is_empty() {
+            None
+        } else if is_digit {
+            component.parse::<u64>().ok().map(VersionComponent::Number)
+        } else {
+            Some(VersionComponent::Text(component))
+        }
+    }
+}
+
 /// Compares two strings of package versions, and figures out the greater one.
 ///
 /// # Returns
 ///
 /// * Ordering
 pub fn compare_versions(a: &str, b: &str) -> Ordering {
-    let iter_a = version_split_regex().find_iter(a).map(|m| {
-        use VersionComponent::{Number, Text};
-        let bla = m.as_str();
-        bla.parse().map_or_else(|_| Text(bla.to_string()), Number)
-    });
-
-    let iter_b = version_split_regex().find_iter(b).map(|m| {
-        use VersionComponent::{Number, Text};
-        let bla = m.as_str();
-        bla.parse().map_or_else(|_| Text(bla.to_string()), Number)
-    });
+    let iter_a = VersionComponentIterator::new(a);
+    let iter_b = VersionComponentIterator::new(b);
 
     iter_a.cmp(iter_b)
 }
 
-fn version_split_regex() -> &'static Regex {
-    static REGEX: OnceLock<Regex> = OnceLock::new();
-    REGEX.get_or_init(|| {
-        Regex::new(r"(\d+|[a-zA-Z]+)").expect("Failed to compile regex pattern for nix store paths")
-    })
+mod test {
+
+    #[test]
+    fn test_version_component_iter() {
+        use super::VersionComponent::{Number, Text};
+        use crate::util::VersionComponentIterator;
+        let v = "132.1.2test234-1-man----.--.......---------..---";
+
+        let comp: Vec<_> = VersionComponentIterator::new(v).collect();
+        assert_eq!(
+            comp,
+            [
+                Number(132),
+                Number(1),
+                Number(2),
+                Text("test".into()),
+                Number(234),
+                Number(1),
+                Text("man".into())
+            ]
+        );
+    }
 }