Fill out the sled-style tests

error-training/src/lib.rs

@@ -24,6 +24,27 @@ pub enum DatabaseError {
     NotFound,
 }
 
+#[derive(Clone, Debug, Error, PartialEq)]
+pub enum OperationError {
+    #[error("database error occurred: {0}")]
+    DatabaseError(DatabaseError),
+
+    #[error("math error occurred: {0}")]
+    MathError(MathError),
+}
+
+impl From<DatabaseError> for OperationError {
+    fn from(err: DatabaseError) -> Self {
+        Self::DatabaseError(err)
+    }
+}
+
+impl From<MathError> for OperationError {
+    fn from(err: MathError) -> Self {
+        Self::MathError(err)
+    }
+}
+
 pub mod sled {
     //! Sled-style error handling is based on Result<Result<Value, LocalError>, FatalError>.
     //! FatalErrors do not get resolved. LocalErrors get bubbled up until they can be handled.
@@ -58,5 +79,42 @@ pub mod sled {
         }
     }
 
-    pub fn run() {}
+    fn op(val: i8) -> Result<i8, MathError> {
+        if val as i32 + 120_i32 > (i8::MAX as i32) {
+            Err(MathError::ExceedsMaxint)
+        } else {
+            Ok(val + 120)
         }
+    }
+
+    /// This function exists to test several of the major cases. This is where I will figure out
+    /// how to handle everything and also have clean code.
+    /// ```rust
+    /// use error_training::{*, sled::*};
+    ///
+    /// let db = DB::new(vec![("a".to_owned(), 15), ("b".to_owned(), 0)]);
+    /// assert_eq!(run_op(&db, "a"), Ok(Ok(i8::MAX)));
+    /// assert_eq!(run_op(&db, "b"), Ok(Ok(120)));
+    /// assert_eq!(run_op(&db, "c"), Ok(Ok(0)));
+    /// assert_eq!(run_op(&db, "fail"), Err(FatalError::DatabaseCorruption));
+    /// ```
+    ///
+    /// I have defined this function such that a database miss becomes a 0 and no operation will be
+    /// performed on it. Since that is the only database error that can occur, this function can
+    /// only return a `MathError` or a `FatalError`.
+    pub fn run_op(db: &DB, key: &str) -> Result<Result<i8, MathError>, FatalError> {
+        let val = db.get(key)?;
+
+        let res = match val {
+            Err(DatabaseError::NotFound) => Ok(0),
+            Ok(val) => op(val),
+        };
+
+        Ok(match res {
+            Ok(val) => Ok(val),
+            Err(MathError::ExceedsMaxint) => Ok(127),
+            Err(err) => Err(err),
+        })
+    }
+}
+