solana-ibc: introduce ClientStateUpdate event (#315)

Introduce ClientStateUpdate event which is emitted when client state
is updated and includes the updated serialised client state.

---------

Co-authored-by: Michal Nazarewicz <mina86@mina86.com>

solana/solana-ibc/programs/solana-ibc/src/client_state.rs

@@ -237,7 +237,7 @@ impl cf_guest::CommonContext<sigverify::ed25519::PubKey>
         client_id: &ibc::ClientId,
         state: Self::AnyClientState,
     ) -> Result<()> {
-        Self::set_client_state(self, client_id, state)
+        self.store_client_state_impl(client_id, state)
     }
 
     fn consensus_state(

solana/solana-ibc/programs/solana-ibc/src/events.rs

@@ -22,6 +22,7 @@ pub enum Event<'a> {
     NewBlock(NewBlock<'a>),
     BlockSigned(BlockSigned),
     BlockFinalised(BlockFinalised),
+    ClientStateUpdate(ClientStateUpdate<'a>),
 }
 
 /// Event emitted once blockchain is implemented.
@@ -112,6 +113,24 @@ pub struct BlockFinalised {
     pub block_height: guestchain::BlockHeight,
 }
 
+/// Event emitted each time IBC client state is updated.
+#[derive(
+    Clone,
+    Debug,
+    PartialEq,
+    Eq,
+    borsh::BorshSerialize,
+    borsh::BorshDeserialize,
+    derive_more::From,
+)]
+pub struct ClientStateUpdate<'a> {
+    /// Client identifier which got updated.
+    pub client_id: CowClientId<'a>,
+
+    /// Borsh-serialised [`crate::client_state::AnyClientState`].
+    pub state: alloc::borrow::Cow<'a, [u8]>,
+}
+
 impl Event<'_> {
     pub fn emit(&self) -> Result<(), String> {
         borsh::BorshSerialize::try_to_vec(self)
@@ -205,6 +224,19 @@ macro_rules! impl_cow {
 impl_cow!(header: BlockHeader, CowHeader, BoxedHeader);
 impl_cow!(epoch: Epoch, CowEpoch, BoxedEpoch);
 
+pub type CowClientId<'a> = alloc::borrow::Cow<'a, crate::ibc::ClientId>;
+
+#[inline]
+pub fn client_id(value: &crate::ibc::ClientId) -> CowClientId {
+    alloc::borrow::Cow::Borrowed(value)
+}
+
+#[inline]
+pub fn bytes(value: &[u8]) -> alloc::borrow::Cow<'_, [u8]> {
+    alloc::borrow::Cow::Borrowed(value)
+}
+
+
 #[cfg(test)]
 // insta uses open to read the snapshot file which is not available when running
 // through Miri.

solana/solana-ibc/programs/solana-ibc/src/execution_context.rs

@@ -4,8 +4,8 @@ use lib::hash::CryptoHash;
 
 use crate::client_state::AnyClientState;
 use crate::consensus_state::AnyConsensusState;
-use crate::ibc;
 use crate::storage::{self, IbcStorage};
+use crate::{events, ibc};
 
 type Result<T = (), E = ibc::ContextError> = core::result::Result<T, E>;
 
@@ -19,7 +19,8 @@ impl ibc::ClientExecutionContext for IbcStorage<'_, '_> {
         path: ibc::path::ClientStatePath,
         state: Self::AnyClientState,
     ) -> Result {
-        self.set_client_state(&path.0, state).map_err(ibc::ContextError::from)
+        self.store_client_state_impl(&path.0, state)
+            .map_err(ibc::ContextError::from)
     }
 
     fn store_consensus_state(
@@ -78,7 +79,7 @@ impl IbcStorage<'_, '_> {
         height: ibc::Height,
         state: AnyConsensusState,
     ) -> Result<(), ibc::ClientError> {
-        msg!("store_consensus_state({}, {:?})", client_id, state);
+        msg!("store_consensus_state({})", client_id);
         let mut store = self.borrow_mut();
         let (processed_time, processed_height) = {
             let head = store.chain.head()?;
@@ -288,7 +289,7 @@ impl ibc::ExecutionContext for IbcStorage<'_, '_> {
     }
 
     fn emit_ibc_event(&mut self, event: ibc::IbcEvent) -> Result {
-        crate::events::emit(event).map_err(ctx_error)
+        events::emit(event).map_err(ctx_error)
     }
 
     fn log_message(&mut self, message: String) -> Result {
@@ -300,15 +301,23 @@ impl ibc::ExecutionContext for IbcStorage<'_, '_> {
 }
 
 impl storage::IbcStorage<'_, '_> {
-    pub(crate) fn set_client_state(
+    pub(crate) fn store_client_state_impl(
         &mut self,
         client_id: &ibc::ClientId,
         state: AnyClientState,
     ) -> Result<(), ibc::ClientError> {
-        msg!("store_client_state({}, {:?})", client_id, state);
+        msg!("store_client_state({})", client_id);
         let mut store = self.borrow_mut();
+
         let mut client = store.private.client_mut(client_id, true)?;
         client.client_state.set(&state)?;
+
+        events::emit(events::ClientStateUpdate {
+            client_id: events::client_id(client_id),
+            state: events::bytes(client.client_state.as_bytes()),
+        })
+        .map_err(client_error)?;
+
         let state_any = state.encode_vec();
         let hash =
             cf_guest::digest_with_client_id(client_id, state_any.as_slice());

solana/solana-ibc/programs/solana-ibc/src/lib.rs

@@ -371,13 +371,6 @@ pub mod solana_ibc {
             .map_err(error::Error::ContextError)
             .map_err(move |err| error!((&err)))?;
 
-        // Log client state only when it is updated which is when `UpdateClient` message
-        // sent.
-        if ctx.remaining_accounts.split_last().is_some() {
-            let storage = &store.borrow().private;
-            let client_state = &storage.clients[0].client_state;
-            msg!("This is updated client state {:?}", client_state.as_bytes());
-        }
         Ok(())
     }