1 files changed, 77 insertions, 0 deletions
diff --git a/src/util/mod.rs b/src/util/mod.rs
new file mode 100644
index 0000000..84ea114
--- /dev/null
+++ b/src/util/mod.rs
@@ -0,0 +1,77 @@
+use serde::Deserialize;
+
+#[derive(Deserialize, Debug, Hash, Eq, PartialEq, Ord, PartialOrd)]
+pub struct EnvironmentVariableName(String);
+
+pub mod docker {
+    use anyhow::Result;
+    use anyhow::anyhow;
+    use serde::Deserialize;
+
+    #[derive(Deserialize, Debug, Hash, Eq, PartialEq, Ord, PartialOrd)]
+    pub struct ImageName(String);
+
+    /// Check whether a string is a valid docker tag name
+    ///
+    /// From the docker spec:
+    ///
+    /// > A tag name must be valid ASCII and may contain lowercase and uppercase letters, digits,
+    /// > underscores, periods and dashes. A tag name may not start with a period or a dash and may
+    /// > contain a maximum of 128 characters.
+    ///
+    /// Returns Ok(()) if `s` is a valid docker tag name, otherwise an explanatory error message
+    pub fn is_valid_tag_name(s: &str) -> Result<()> {
+        let valid_chars = s.chars().all(|c| {
+            c == '_' ||
+            c == ':' ||
+            c == '-' ||
+            c.is_ascii_alphanumeric()
+        });
+
+        if !valid_chars {
+            return Err(anyhow!("Invalid characters"))
+        }
+
+        if s.chars().count() > 128 {
+            return Err(anyhow!("Too long"))
+        }
+
+
+        if s.chars().next().map(|c| c == '.' || c == '-').unwrap_or(false) {
+            return Err(anyhow!("Starts with invalid character"))
+        }
+
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod docker_test {
+    extern crate env_logger;
+    fn setup_logging() {
+        let _ = env_logger::try_init();
+    }
+
+    use super::docker::*;
+
+    #[test]
+    fn is_valid_tag_name_test_1() {
+        setup_logging();
+        let test = |s| {
+            debug!("check if valid: '{}'", s);
+            let e = is_valid_tag_name(s);
+            debug!("Result = {:?}", e);
+            e
+        };
+
+        assert!(test("foo").is_ok());
+        assert!(test("foo:bar").is_ok());
+        assert!(test("foo123").is_ok());
+        assert!(test("1f23oo").is_ok());
+        assert!(test(":foo").is_ok());
+        assert!(test(".foo").is_err());
+        assert!(test("-foo").is_err());
+    }
+
+}
+