1 files changed, 28 insertions, 8 deletions

diff --git a/src/genlist.rs b/src/genlist.rs
index 10c614e..3a0d81a 100644
--- a/src/genlist.rs
+++ b/src/genlist.rs
@@ -1,33 +1,51 @@
+//! A list of generations on the server.
+
 use crate::chunkid::ChunkId;
-use crate::generation::FinishedGeneration;
+use crate::generation::{FinishedGeneration, GenId};
 
+/// A list of generations on the server.
 pub struct GenerationList {
     list: Vec<FinishedGeneration>,
 }
 
+/// Possible errors from listing generations.
+#[derive(Debug, thiserror::Error)]
+pub enum GenerationListError {
+    /// Server doesn't know about a generation.
+    #[error("Unknown generation: {0}")]
+    UnknownGeneration(ChunkId),
+}
+
 impl GenerationList {
+    /// Create a new list of generations.
     pub fn new(gens: Vec<FinishedGeneration>) -> Self {
-        let mut list = gens.clone();
+        let mut list = gens;
         list.sort_by_cached_key(|gen| gen.ended().to_string());
         Self { list }
     }
 
+    /// Return an iterator over the generations.
     pub fn iter(&self) -> impl Iterator<Item = &FinishedGeneration> {
         self.list.iter()
     }
 
-    pub fn resolve(&self, genref: &str) -> Option<String> {
+    /// Resolve a symbolic name of a generation into its identifier.
+    ///
+    /// For example, "latest" refers to the latest backup, but needs
+    /// to be resolved into an actual, immutable id to actually be
+    /// restored.
+    pub fn resolve(&self, genref: &str) -> Result<GenId, GenerationListError> {
         let gen = if self.list.is_empty() {
             None
         } else if genref == "latest" {
             let i = self.list.len() - 1;
             Some(self.list[i].clone())
         } else {
-            let genref: ChunkId = genref.parse().unwrap();
+            let genref = GenId::from_chunk_id(genref.parse().unwrap());
             let hits: Vec<FinishedGeneration> = self
                 .iter()
-                .filter(|gen| gen.id() == genref)
-                .map(|gen| gen.clone())
+                .filter(|gen| gen.id().as_chunk_id() == genref.as_chunk_id())
+                .cloned()
                 .collect();
             if hits.len() == 1 {
                 Some(hits[0].clone())
@@ -36,8 +54,10 @@ impl GenerationList {
             }
         };
         match gen {
-            None => None,
-            Some(gen) => Some(gen.id().to_string()),
+            None => Err(GenerationListError::UnknownGeneration(ChunkId::recreate(
+                genref,
+            ))),
+            Some(gen) => Ok(gen.id().clone()),
         }
     }
 }