add recipe_id, to deal with recipes in federated repos

tools/src/lib.rs

@@ -4,3 +4,7 @@ pub use recipe::Recipe;
 pub mod repo;
 pub use repo::Repo;
 pub use repo::RepoLoadError;
+
+pub mod recipe_id;
+pub use recipe_id::RecipeId;
+pub use recipe_id::RecipeIdParseError;

tools/src/recipe_id.rs

@@ -0,0 +1,73 @@
+use std::str::FromStr;
+
+use thiserror::Error;
+
+#[derive(Debug, PartialEq)]
+pub struct RecipeId {
+    pub repo: Option<String>,
+    pub recipe: String,
+}
+
+#[derive(Debug, Error, PartialEq)]
+pub enum RecipeIdParseError {
+    #[error("syntax error: {0}")]
+    SyntaxError(String),
+}
+
+impl FromStr for RecipeId {
+    type Err = RecipeIdParseError;
+    fn from_str(recipe_id: &str) -> Result<RecipeId, Self::Err> {
+        let substrings: Vec<&str> = recipe_id.split(':').collect();
+        match substrings.len() {
+            1 => Ok(RecipeId {
+                repo: None,
+                recipe: String::from(recipe_id),
+            }),
+            2 => Ok(RecipeId {
+                repo: Some(String::from(substrings[0])),
+                recipe: String::from(substrings[1]),
+            }),
+            _ => Err(RecipeIdParseError::SyntaxError(String::from(recipe_id))),
+        }
+    }
+}
+
+mod test {
+    #[cfg(test)]
+    use crate::recipe_id::{FromStr, RecipeId, RecipeIdParseError};
+
+    #[test]
+    fn parse_simple() {
+        let r = RecipeId::from_str("hello");
+        assert_eq!(
+            r,
+            Ok(RecipeId {
+                repo: None,
+                recipe: "hello".into(),
+            })
+        );
+    }
+
+    #[test]
+    fn parse_with_repo() {
+        let r = RecipeId::from_str("my_repo:my_recipe");
+        assert_eq!(
+            r,
+            Ok(RecipeId {
+                repo: Some("my_repo".into()),
+                recipe: "my_recipe".into(),
+            })
+        );
+    }
+
+    #[test]
+    fn parse_too_many_colons() {
+        let r = RecipeId::from_str("my_repo:my_recipe:something_else");
+        assert_eq!(
+            r,
+            Err(RecipeIdParseError::SyntaxError(
+                "my_repo:my_recipe:something_else".into()
+            ))
+        );
+    }
+}