From c6f0cd94049bc3a127e1f1afdda6520e1ecf9286 Mon Sep 17 00:00:00 2001
From: Hirrolot <hirrolot@gmail.com>
Date: Sun, 20 Mar 2022 09:06:21 +0600
Subject: [PATCH] Implement `ErasedStorage`

---
 CHANGELOG.md                            |  5 ++
 src/dispatching/dialogue/mod.rs         |  2 +-
 src/dispatching/dialogue/storage/mod.rs | 82 +++++++++++++++++++++++++
 src/dispatching2/dialogue/mod.rs        |  3 +-
 4 files changed, 90 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 48f67379..aaaf25d1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## unreleased
 
+### Added
+
+- The `StorageExt` trait with a single function `erase` that returns `ErasedStorage`.
+- `ErasedStorage`, a storage with an erased error type.
+
 ## 0.7.1 - 2022-03-09
 
 ### Fixed
diff --git a/src/dispatching/dialogue/mod.rs b/src/dispatching/dialogue/mod.rs
index 3f336d73..8c6e6bae 100644
--- a/src/dispatching/dialogue/mod.rs
+++ b/src/dispatching/dialogue/mod.rs
@@ -169,4 +169,4 @@ pub use storage::{RedisStorage, RedisStorageError};
 #[cfg(feature = "sqlite-storage")]
 pub use storage::{SqliteStorage, SqliteStorageError};
 
-pub use storage::{serializer, InMemStorage, InMemStorageError, Serializer, Storage, TraceStorage};
+pub use storage::*;
diff --git a/src/dispatching/dialogue/storage/mod.rs b/src/dispatching/dialogue/storage/mod.rs
index 506e18bf..c20855ed 100644
--- a/src/dispatching/dialogue/storage/mod.rs
+++ b/src/dispatching/dialogue/storage/mod.rs
@@ -73,3 +73,85 @@ pub trait Storage<D> {
         chat_id: i64,
     ) -> BoxFuture<'static, Result<Option<D>, Self::Error>>;
 }
+
+/// A storage with an erased error type.
+pub type ErasedStorage<D> = Arc<dyn Storage<D, Error = Box<dyn std::error::Error>>>;
+
+/// Extension methods for working with [`Storage`].
+pub trait StorageExt<D> {
+    /// Returns [`ErasedStorage`].
+    fn erase(self: Arc<Self>) -> ErasedStorage<D>;
+}
+
+impl<S, D> StorageExt<D> for S
+where
+    S: Storage<D> + Send + Sync + 'static,
+    S::Error: std::error::Error + 'static,
+{
+    fn erase(self: Arc<Self>) -> ErasedStorage<D> {
+        struct Eraser<S>(Arc<S>);
+
+        impl<D, S> Storage<D> for Eraser<S>
+        where
+            S: Storage<D> + Send + Sync + 'static,
+            S::Error: std::error::Error + 'static,
+        {
+            type Error = Box<dyn std::error::Error>;
+
+            fn remove_dialogue(
+                self: Arc<Self>,
+                chat_id: i64,
+            ) -> BoxFuture<'static, Result<(), Self::Error>>
+            where
+                D: Send + 'static,
+            {
+                Box::pin(async move {
+                    Arc::clone(&self.0).remove_dialogue(chat_id).await.map_err(|e| e.into())
+                })
+            }
+
+            fn update_dialogue(
+                self: Arc<Self>,
+                chat_id: i64,
+                dialogue: D,
+            ) -> BoxFuture<'static, Result<(), Self::Error>>
+            where
+                D: Send + 'static,
+            {
+                Box::pin(async move {
+                    Arc::clone(&self.0)
+                        .update_dialogue(chat_id, dialogue)
+                        .await
+                        .map_err(|e| e.into())
+                })
+            }
+
+            fn get_dialogue(
+                self: Arc<Self>,
+                chat_id: i64,
+            ) -> BoxFuture<'static, Result<Option<D>, Self::Error>> {
+                Box::pin(async move {
+                    Arc::clone(&self.0).get_dialogue(chat_id).await.map_err(|e| e.into())
+                })
+            }
+        }
+
+        Arc::new(Eraser(self))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[tokio::test]
+    async fn test_erased() {
+        let chat_id = 123;
+
+        let erased = InMemStorage::new().erase();
+        Arc::clone(&erased).update_dialogue(chat_id, 1).await.unwrap();
+        assert_eq!(Arc::clone(&erased).get_dialogue(chat_id).await.unwrap().unwrap(), 1);
+        Arc::clone(&erased).remove_dialogue(chat_id).await.unwrap();
+        assert_eq!(Arc::clone(&erased).get_dialogue(chat_id).await.unwrap(), None);
+    }
+}
diff --git a/src/dispatching2/dialogue/mod.rs b/src/dispatching2/dialogue/mod.rs
index cf9867ed..a492b77c 100644
--- a/src/dispatching2/dialogue/mod.rs
+++ b/src/dispatching2/dialogue/mod.rs
@@ -92,7 +92,8 @@ pub use crate::dispatching::dialogue::{RedisStorage, RedisStorageError};
 pub use crate::dispatching::dialogue::{SqliteStorage, SqliteStorageError};
 
 pub use crate::dispatching::dialogue::{
-    serializer, InMemStorage, InMemStorageError, Serializer, Storage, TraceStorage,
+    serializer, ErasedStorage, InMemStorage, InMemStorageError, Serializer, Storage, StorageExt,
+    TraceStorage,
 };
 pub use get_chat_id::GetChatId;