refactor: Add GetState request

gear-programs/checkpoint-light-client/io/src/lib.rs

@@ -80,6 +80,7 @@ pub enum Handle {
         headers: Vec<BeaconBlockHeader>,
     },
     ReplayBack(Vec<BeaconBlockHeader>),
+    GetState(meta::StateRequest),
 }
 
 #[derive(Debug, Clone, Encode, Decode, TypeInfo)]
@@ -88,4 +89,5 @@ pub enum HandleResult {
     SyncUpdate(Result<(), sync_update::Error>),
     ReplayBackStart(Result<replay_back::StatusStart, replay_back::Error>),
     ReplayBack(Option<replay_back::Status>),
+    State(meta::State),
 }

gear-programs/checkpoint-light-client/io/src/meta.rs

@@ -1,6 +1,6 @@
 use super::*;
 
-use gmeta::{In, InOut, Out};
+use gmeta::{In, InOut};
 use gstd::prelude::*;
 
 pub struct Metadata;
@@ -11,13 +11,35 @@ impl gmeta::Metadata for Metadata {
     type Others = ();
     type Reply = ();
     type Signal = ();
-    type State = Out<State>;
+    type State = InOut<StateRequest, State>;
 }
 
 #[derive(Debug, Clone, Default, Encode, Decode, TypeInfo)]
 pub struct State {
     pub checkpoints: Vec<(Slot, Hash256)>,
-    /// The field contains the last processed header if the program is
+    /// The field contains the data if the program is
     /// replaying checkpoints back.
-    pub replay_back: Option<BeaconBlockHeader>,
+    pub replay_back: Option<ReplayBack>,
+}
+
+/// The struct contains slots of the finalized and the last checked headers.
+#[derive(Debug, Clone, Encode, Decode, TypeInfo)]
+pub struct ReplayBack {
+    pub finalized_header: Slot,
+    pub last_header: Slot,
+}
+
+#[derive(Debug, Clone, Encode, Decode, TypeInfo)]
+pub enum Order {
+    Direct,
+    Reverse,
+}
+
+#[derive(Debug, Clone, Encode, Decode, TypeInfo)]
+pub struct StateRequest {
+    // The flag specifies the subslice position
+    pub order: Order,
+    // Parameters determine checkpoints count in the response
+    pub index_start: u32,
+    pub count: u32,
 }

gear-programs/checkpoint-light-client/io/src/sync_update.rs

@@ -27,7 +27,7 @@ pub enum Error {
     InvalidNextSyncCommitteeProof,
     InvalidPublicKeys,
     ReplayBackRequired {
-        replayed_slot: Option<Slot>,
+        replay_back: Option<meta::ReplayBack>,
         checkpoint: (Slot, Hash256),
     },
 }

gear-programs/checkpoint-light-client/src/wasm/mod.rs

@@ -1,5 +1,6 @@
 use super::*;
 use ark_serialize::CanonicalSerialize;
+use core::{cmp, num::Saturating};
 use gstd::{msg, vec};
 use io::{
     ethereum_common::{
@@ -9,6 +10,7 @@ use io::{
         tree_hash::TreeHash,
         utils as eth_utils, Hash256, SYNC_COMMITTEE_SIZE,
     },
+    meta,
     sync_update::Error as SyncCommitteeUpdateError,
     BeaconBlockHeader, Handle, HandleResult, Init, SyncCommitteeKeys, SyncCommitteeUpdate, G1, G2,
 };
@@ -107,28 +109,21 @@ async fn main() {
         } => replay_back::handle_start(state, sync_update, headers).await,
 
         Handle::ReplayBack(headers) => replay_back::handle(state, headers),
+
+        Handle::GetState(request) => {
+            let reply = utils::construct_state_reply(request, state);
+            msg::reply(HandleResult::State(reply), 0)
+                .expect("Unable to reply with `HandleResult::State`");
+        }
     }
 }
 
 #[no_mangle]
 extern "C" fn state() {
-    let state = unsafe { STATE.as_ref() };
-    let checkpoints = state
-        .map(|state| state.checkpoints.checkpoints())
-        .unwrap_or(vec![]);
-    let replay_back = state.and_then(|state| {
-        state
-            .replay_back
-            .as_ref()
-            .map(|replay_back| replay_back.last_header.clone())
-    });
-
-    msg::reply(
-        io::meta::State {
-            checkpoints,
-            replay_back,
-        },
-        0,
-    )
-    .expect("Failed to encode or reply with `<AppMetadata as Metadata>::State` from `state()`");
+    let request = msg::load().expect("Unable to decode `StateRequest` message");
+    let state = unsafe { STATE.as_ref() }.expect("The program should be initialized");
+    let reply = utils::construct_state_reply(request, state);
+
+    msg::reply(reply, 0)
+        .expect("Failed to encode or reply with `<AppMetadata as Metadata>::State` from `state()`");
 }

gear-programs/checkpoint-light-client/src/wasm/sync_update.rs

@@ -28,10 +28,13 @@ pub async fn handle(state: &mut State<STORED_CHECKPOINTS_COUNT>, sync_update: Sy
         {
             let result =
                 HandleResult::SyncUpdate(Err(io::sync_update::Error::ReplayBackRequired {
-                    replayed_slot: state
+                    replay_back: state
                         .replay_back
                         .as_ref()
-                        .map(|replay_back| replay_back.last_header.slot),
+                        .map(|replay_back| meta::ReplayBack {
+                            finalized_header: replay_back.finalized_header.slot,
+                            last_header: replay_back.last_header.slot,
+                        }),
                     checkpoint: state
                         .checkpoints
                         .last()

gear-programs/checkpoint-light-client/src/wasm/utils.rs

@@ -1,11 +1,7 @@
 use super::*;
-use io::{
-    ethereum_common::{
-        base_types::{BytesFixed, FixedArray},
-        beacon::{BLSPubKey, SyncCommittee},
-        SYNC_COMMITTEE_SIZE,
-    },
-    SyncCommitteeKeys,
+use io::ethereum_common::{
+    base_types::BytesFixed,
+    beacon::{BLSPubKey, SyncCommittee},
 };
 
 pub fn construct_sync_committee(
@@ -41,3 +37,48 @@ pub fn get_participating_keys(
         .filter_map(|(bit, pub_key)| bit.then_some(pub_key.clone().0 .0))
         .collect::<Vec<_>>()
 }
+
+pub fn construct_state_reply(
+    request: meta::StateRequest,
+    state: &State<STORED_CHECKPOINTS_COUNT>,
+) -> meta::State {
+    use meta::Order;
+
+    let count = Saturating(request.count as usize);
+    let checkpoints_all = state.checkpoints.checkpoints();
+    let (start, end) = match request.order {
+        Order::Direct => {
+            let start = Saturating(request.index_start as usize);
+            let Saturating(end) = start + count;
+
+            (start.0, cmp::min(end, checkpoints_all.len()))
+        }
+
+        Order::Reverse => {
+            let len = Saturating(checkpoints_all.len());
+            let index_last = Saturating(request.index_start as usize);
+            let end = len - index_last;
+            let Saturating(start) = end - count;
+
+            (start, end.0)
+        }
+    };
+
+    let checkpoints = checkpoints_all
+        .get(start..end)
+        .map(|slice| slice.to_vec())
+        .unwrap_or(vec![]);
+
+    let replay_back = state
+        .replay_back
+        .as_ref()
+        .map(|replay_back| meta::ReplayBack {
+            finalized_header: replay_back.finalized_header.slot,
+            last_header: replay_back.last_header.slot,
+        });
+
+    meta::State {
+        checkpoints,
+        replay_back,
+    }
+}

relayer/src/ethereum_checkpoints/mod.rs

@@ -101,7 +101,7 @@ pub async fn relay(args: RelayCheckpointsArgs) {
             return;
         }
         Ok(Err(sync_update::Error::ReplayBackRequired {
-            replayed_slot,
+            replay_back,
             checkpoint,
         })) => {
             if let Err(e) = replay_back::execute(
@@ -111,7 +111,7 @@ pub async fn relay(args: RelayCheckpointsArgs) {
                 &mut listener,
                 program_id,
                 gas_limit,
-                replayed_slot,
+                replay_back.map(|r| r.last_header),
                 checkpoint,
                 sync_update,
             )