error: add variants to RuntimeError

database/src/error.rs

@@ -32,30 +32,73 @@ pub enum InitError<BackendError: Debug> {
 
 //---------------------------------------------------------------------------------------------------- RuntimeError
 /// Database errors that occur _after_ successful initialization.
+///
+/// There are no errors for:
+/// 1. Missing tables
+/// 2. (De)serialization
+///
+/// as `cuprate_database` upholds the invariant that:
+///
+/// 1. All tables exist
+/// 2. (De)serialization never fails
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 #[cfg_attr(
     feature = "borsh",
     derive(borsh::BorshSerialize, borsh::BorshDeserialize)
 )]
 #[derive(thiserror::Error, Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
-pub enum RuntimeError {
-    // TODO: replace string with actual error type.
+pub enum RuntimeError<BackendError: Debug> {
+    /// The given key already existed in the database.
     ///
-    /// An error occurred when attempting to
-    /// serialize the key data into bytes.
-    #[error("serialize error: {0}")]
-    Serialize(String),
+    /// The string inside is the output of
+    /// [`std::any::type_name`] on the key type.
+    #[error("key of type `{0}` already existed")]
+    KeyExists(&'static str),
 
-    // TODO: replace string with actual error type.
+    /// The given key did not exist in the database.
     ///
-    /// An error occurred when attempting to
-    /// deserialize the response value from
-    /// the database.
-    #[error("deserialize error: {0}")]
-    Deserialize(String),
+    /// The string inside is the output of
+    /// [`std::any::type_name`] on the key type.
+    #[error("key/value pair was not found: {0}")]
+    KeyNotFound(&'static str),
 
-    /// TODO
+    /// The database environment has reached
+    /// maximum memory map size, it must be
+    /// increased.
+    //
+    // TODO: `sanakirja` automatically resizes, `heed` does not.
+    // I guess this should be `unreachable!()` for `sanakirja`?
+    #[error("not enough space in database environment memory map")]
+    MapFull,
+
+    /// A database page does not have enough
+    /// space for more key/values.
+    #[error("not enough space in database page")]
+    PageFull,
+
+    /// A [`std::io::Error`].
+    #[error("I/O error: {0}")]
+    Io(#[from] std::io::Error),
+
+    /// The expected database version was not the version found.
+    #[error("database version mismatch: expected {expected}, found {found}")]
+    VersionMismatch {
+        expected: &'static str,
+        found: &'static str,
+    },
+
+    /// The database has reached maximum parallel readers.
     ///
+    /// TODO: this can be used for retry logic in reader threads,
+    /// although, does this error ever actually occur in practice?
+    #[error("database maximum parallel readers reached")]
+    MaxReaders,
+
+    /// An unknown backend-specific error occured.
+    #[error("{DATABASE_BACKEND} error: {0}")]
+    Backend(BackendError),
+
+    // TODO: this could be removed once we have all errors figured out.
     /// An unknown error occurred.
     #[error("unknown error: {0}")]
     Unknown(Cow<'static, str>),