1 files changed, 103 insertions, 0 deletions

diff --git a/lib/src/session.rs b/lib/src/session.rs
new file mode 100644
index 0000000..8d142ec
--- /dev/null
+++ b/lib/src/session.rs
@@ -0,0 +1,103 @@
+use std::{cmp::Ordering, str::FromStr};
+
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub struct Version {
+    major: u16,
+    minor: u16,
+    patch: Option<u16>,
+}
+
+impl Ord for Version {
+    fn cmp(&self, other: &Self) -> Ordering {
+        let score = |v: &Version| v.major * 100 + v.minor * 10 + v.patch.unwrap_or(0);
+        score(self).cmp(&score(other))
+    }
+}
+
+impl PartialOrd for Version {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+fn parse_number(s: &str) -> Option<u16> {
+    s.chars()
+        .take_while(|c| c.is_digit(10))
+        .collect::<String>()
+        .parse::<u16>()
+        .ok()
+}
+
+fn parse_version(s: &str) -> Option<Version> {
+    match s.split(' ').collect::<Vec<_>>().as_slice() {
+        [_, _, version] => {
+            let mut parts = version.split('.');
+            let major = parse_number(parts.next()?)?;
+            let minor = parse_number(parts.next()?)?;
+            let patch = parts.next().map(|p| parse_number(p)).flatten();
+            Some(Version {
+                major,
+                minor,
+                patch,
+            })
+        }
+        _ => None,
+    }
+}
+
+impl FromStr for Version {
+    type Err = ();
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        parse_version(s).ok_or(())
+    }
+}
+
+#[non_exhaustive]
+pub struct SessionInfo {
+    nix_version: Version,
+}
+
+impl SessionInfo {
+    pub fn from_version(nix_version: Version) -> Self {
+        Self { nix_version }
+    }
+
+    pub fn version(&self) -> &Version {
+        &self.nix_version
+    }
+}
+
+pub fn get_nix_version() -> Option<Version> {
+    "nix (Nix) 2.4pre20211006_53e4794".parse::<Version>().ok()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parse_trivial() {
+        let v = "nix (Nix) 1.6.1".parse::<Version>().ok();
+        assert!(v.is_some())
+    }
+
+    #[test]
+    fn parse() {
+        let v = "nix (Nix) 2.4pre20211006_53e4794".parse::<Version>().ok();
+        assert!(v.is_some())
+    }
+
+    #[test]
+    fn compare_trivial() {
+        let v1 = "nix (Nix) 1.6.1".parse::<Version>().ok();
+        let v2 = "nix (Nix) 1.7.2".parse::<Version>().ok();
+        assert!(v2 > v1);
+    }
+
+    #[test]
+    fn compare() {
+        let v1 = "nix (Nix) 1.7".parse::<Version>().ok();
+        let v2 = "nix (Nix) 2.4pre20211006_53e4794".parse::<Version>().ok();
+        assert!(v2 >= v1);
+    }
+}