Refactors backend

1 files changed, 53 insertions, 0 deletions

diff --git a/backend/src/utils/find_by_id_or.rs b/backend/src/utils/find_by_id_or.rs
new file mode 100644
index 0000000..f5add30
--- /dev/null
+++ b/backend/src/utils/find_by_id_or.rs
@@ -0,0 +1,53 @@
+pub fn find_by_id_or<Id: PartialEq, Val: Copy>(
+    arr: &[(Id, Option<Val>)],
+    id: Id,
+    default: Val,
+) -> Val {
+    arr.iter()
+        .find(|(elem_id, _)| *elem_id == id)
+        .map_or(default, |row| match row {
+            (_, Some(quantity)) => *quantity,
+            (_, _) => default,
+        })
+}
+
+#[cfg(test)]
+mod test {
+    use super::find_by_id_or;
+
+    #[test]
+    fn when_no_elements_then_return_default() {
+        let arr = [];
+
+        let result = find_by_id_or(&arr, 1, 42);
+
+        assert_eq!(result, 42);
+    }
+
+    #[test]
+    fn when_id_not_in_elements_then_return_default() {
+        let arr = [(0, Some(100)), (2, Some(200))];
+
+        let result = find_by_id_or(&arr, 1, 42);
+
+        assert_eq!(result, 42);
+    }
+
+    #[test]
+    fn when_value_is_none_then_return_default() {
+        let arr = [(1, None)];
+
+        let result = find_by_id_or(&arr, 1, 42);
+
+        assert_eq!(result, 42);
+    }
+
+    #[test]
+    fn when_value_is_some_then_return_value() {
+        let arr = [(1, Some(67))];
+
+        let result = find_by_id_or(&arr, 1, 42);
+
+        assert_eq!(result, 67);
+    }
+}