1 files changed, 17 insertions, 4 deletions

diff --git a/src/main.rs b/src/main.rs
index d3839b2..181d64a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -83,6 +83,19 @@ impl StdError for NotFound {}
 /// 2. We don't want yet another error kind with a lot of kinds.
 type MainResult<T> = Result<T, Box<dyn StdError>>;
 
+/// A trait for containers that only contain a single item.
+trait SingleContainer<T> {
+    /// Extract the single element by consuming the container.
+    fn single(self) -> T;
+}
+
+impl<T> SingleContainer<T> for Vec<T> {
+    fn single(self) -> T {
+        assert_eq!(self.len(), 1, "this container must have exactly 1 element.");
+        self.into_iter().next().unwrap()
+    }
+}
+
 /// Find the profession by the given name.
 fn find_profession(api: &mut Api, name: &str) -> MainResult<Profession> {
     let profession_ids = api.get_profession_ids()?;
@@ -93,7 +106,7 @@ fn find_profession(api: &mut Api, name: &str) -> MainResult<Profession> {
         .ok_or_else(|| NotFound::Profession(name.to_owned()))?
         .clone();
 
-    Ok(api.get_professions(&[profession_id])?.remove(0))
+    Ok(api.get_professions(&[profession_id])?.single())
 }
 
 /// Resolve a skill.
@@ -106,7 +119,7 @@ fn resolve_skill(api: &mut Api, profession: &Profession, text: &str) -> MainResu
     if let Ok(num_id) = numeric {
         let exists = profession.skills.iter().any(|s| s.id == num_id);
         if exists {
-            return Ok(api.get_skills(&[num_id])?.remove(0));
+            return Ok(api.get_skills(&[num_id])?.single());
         } else {
             return Err(NotFound::SkillId(num_id).into());
         }
@@ -191,10 +204,10 @@ fn run_searching(api: &mut Api, matches: &ArgMatches) -> MainResult<BuildTemplat
             .map(|s| resolve_skill(api, &profession, s))
             .collect::<Result<Vec<_>, _>>()?
     } else if let Some(l) = legends.first() {
-        let l = api.get_legends(&[l.get_api_id().unwrap()])?.remove(0);
+        let l = api.get_legends(&[l.api_id().unwrap()])?.single();
         let mut result = Vec::new();
         for skill_id in (&[l.heal]).iter().chain(&l.utilities).chain(&[l.elite]) {
-            let skill = api.get_skills(&[*skill_id])?.remove(0);
+            let skill = api.get_skills(&[*skill_id])?.single();
             result.push(skill);
         }
         result