TendermintApi, compilation fixes

Cargo.lock

@@ -5115,6 +5115,8 @@ dependencies = [
  "parity-scale-codec",
  "scale-info",
  "sp-application-crypto",
+ "sp-core",
+ "sp-std",
 ]
 
 [[package]]
@@ -7439,6 +7441,7 @@ dependencies = [
  "sp-inherents",
  "sp-runtime",
  "sp-staking",
+ "sp-tendermint",
  "sp-timestamp",
  "substrate-prometheus-endpoint",
  "tendermint-machine",
@@ -7558,6 +7561,7 @@ dependencies = [
  "sp-runtime",
  "sp-session",
  "sp-std",
+ "sp-tendermint",
  "sp-transaction-pool",
  "sp-version",
  "substrate-wasm-builder",
@@ -8318,6 +8322,15 @@ dependencies = [
  "sp-std",
 ]
 
+[[package]]
+name = "sp-tendermint"
+version = "0.1.0"
+dependencies = [
+ "sp-api",
+ "sp-core",
+ "sp-std",
+]
+
 [[package]]
 name = "sp-timestamp"
 version = "4.0.0-dev"

substrate/node/Cargo.toml

@@ -47,9 +47,9 @@ sc-rpc-api = { git = "https://github.com/serai-dex/substrate" }
 substrate-frame-rpc-system = { git = "https://github.com/serai-dex/substrate" }
 pallet-transaction-payment-rpc = { git = "https://github.com/serai-dex/substrate" }
 
-pallet-tendermint = { path = "../pallet-tendermint", default-features = false }
+pallet-tendermint = { path = "../tendermint/pallet", default-features = false }
 serai-runtime = { path = "../runtime" }
-serai-consensus = { path = "../consensus" }
+serai-consensus = { path = "../tendermint/client" }
 
 [build-dependencies]
 substrate-build-script-utils = { git = "https://github.com/serai-dex/substrate.git" }

substrate/runtime/Cargo.toml

@@ -29,6 +29,8 @@ sp-block-builder = { git = "https://github.com/serai-dex/substrate", default-fea
 sp-runtime = { git = "https://github.com/serai-dex/substrate", default-features = false }
 sp-api = { git = "https://github.com/serai-dex/substrate", default-features = false }
 
+sp-tendermint = { path = "../tendermint/primitives", default-features = false }
+
 frame-system = { git = "https://github.com/serai-dex/substrate", default-features = false }
 frame-support = { git = "https://github.com/serai-dex/substrate", default-features = false }
 frame-executive = { git = "https://github.com/serai-dex/substrate", default-features = false }
@@ -43,7 +45,7 @@ pallet-contracts-primitives = { git = "https://github.com/serai-dex/substrate",
 pallet-contracts = { git = "https://github.com/serai-dex/substrate", default-features = false }
 
 pallet-session = { git = "https://github.com/serai-dex/substrate", default-features = false }
-pallet-tendermint = { path = "../pallet-tendermint", default-features = false }
+pallet-tendermint = { path = "../tendermint/pallet", default-features = false }
 
 frame-system-rpc-runtime-api = { git = "https://github.com/serai-dex/substrate", default-features = false }
 pallet-transaction-payment-rpc-runtime-api = { git = "https://github.com/serai-dex/substrate", default-features = false }
@@ -68,6 +70,8 @@ std = [
   "sp-runtime/std",
   "sp-api/std",
 
+  "sp-tendermint/std",
+
   "frame-system/std",
   "frame-support/std",
   "frame-executive/std",

substrate/runtime/src/lib.rs

@@ -361,6 +361,16 @@ sp_api::impl_runtime_apis! {
     }
   }
 
+  impl sp_tendermint::TendermintApi<Block> for Runtime {
+    fn current_session() -> u32 {
+      Tendermint::session()
+    }
+
+    fn validators() -> Vec<Public> {
+      Session::validators()
+    }
+  }
+
   impl frame_system_rpc_runtime_api::AccountNonceApi<Block, AccountId, Index> for Runtime {
     fn account_nonce(account: AccountId) -> Index {
       System::account_nonce(account)

substrate/tendermint/client/Cargo.toml

@@ -30,6 +30,8 @@ sp-runtime = { git = "https://github.com/serai-dex/substrate" }
 sp-api = { git = "https://github.com/serai-dex/substrate" }
 sp-consensus = { git = "https://github.com/serai-dex/substrate" }
 
+sp-tendermint = { path = "../primitives" }
+
 sc-transaction-pool = { git = "https://github.com/serai-dex/substrate" }
 sc-basic-authorship = { git = "https://github.com/serai-dex/substrate" }
 sc-executor = { git = "https://github.com/serai-dex/substrate" }
@@ -43,6 +45,6 @@ pallet-session = { git = "https://github.com/serai-dex/substrate" }
 
 substrate-prometheus-endpoint = { git = "https://github.com/serai-dex/substrate" }
 
-tendermint-machine = { path = "../tendermint", features = ["substrate"] }
+tendermint-machine = { path = "../machine", features = ["substrate"] }
 
-serai-runtime = { path = "../runtime" }
+serai-runtime = { path = "../../runtime" }

substrate/tendermint/client/src/block_import.rs

@@ -2,7 +2,6 @@ use std::{sync::Arc, collections::HashMap};
 
 use async_trait::async_trait;
 
-use sp_core::sr25519::Public;
 use sp_inherents::CreateInherentDataProviders;
 use sp_runtime::traits::Block;
 use sp_api::TransactionFor;
@@ -12,7 +11,7 @@ use sc_consensus::{BlockCheckParams, BlockImportParams, ImportResult, BlockImpor
 
 use sc_client_api::Backend;
 
-use frame_support::traits::ValidatorSet;
+use sp_tendermint::TendermintApi;
 
 use crate::{
   tendermint::{TendermintClient, TendermintImport},
@@ -32,7 +31,7 @@ where
   TransactionFor<C, B>: Send + Sync + 'static,
   Arc<C>: BlockImport<B, Transaction = TransactionFor<C, B>>,
   <Arc<C> as BlockImport<B>>::Error: Into<Error>,
-  C::Api: ValidatorSet<Public>,
+  C::Api: TendermintApi<B>,
 {
   type Error = Error;
   type Transaction = TransactionFor<C, B>;

substrate/tendermint/client/src/import_queue.rs

@@ -6,7 +6,7 @@ use std::{
   time::{UNIX_EPOCH, SystemTime},
 };
 
-use sp_core::{Decode, sr25519::Public};
+use sp_core::Decode;
 use sp_inherents::CreateInherentDataProviders;
 use sp_runtime::traits::{Header, Block};
 use sp_api::{BlockId, TransactionFor};
@@ -19,13 +19,13 @@ use sc_client_api::Backend;
 
 use substrate_prometheus_endpoint::Registry;
 
-use frame_support::traits::ValidatorSet;
-
 use tendermint_machine::{
   ext::{BlockNumber, Commit},
   TendermintMachine,
 };
 
+use sp_tendermint::TendermintApi;
+
 use crate::{
   CONSENSUS_ID,
   validators::TendermintValidators,
@@ -100,7 +100,7 @@ where
   TransactionFor<C, B>: Send + Sync + 'static,
   Arc<C>: BlockImport<B, Transaction = TransactionFor<C, B>>,
   <Arc<C> as BlockImport<B>>::Error: Into<Error>,
-  C::Api: ValidatorSet<Public>,
+  C::Api: TendermintApi<B>,
 {
   let import = TendermintImport::new(client, announce, providers, env);
 
@@ -119,7 +119,7 @@ where
             Ok(best) => BlockNumber(best),
             Err(_) => panic!("BlockNumber exceeded u64"),
           },
-          Commit::<TendermintValidators<B, C>>::decode(
+          Commit::<TendermintValidators<B, Be, C>>::decode(
             &mut import_clone
               .client
               .justifications(&BlockId::Number(best))

substrate/tendermint/client/src/tendermint.rs

@@ -10,10 +10,7 @@ use log::warn;
 
 use tokio::sync::RwLock as AsyncRwLock;
 
-use sp_core::{
-  Encode, Decode,
-  sr25519::{Public, Signature},
-};
+use sp_core::{Encode, Decode, sr25519::Signature};
 use sp_inherents::{InherentData, InherentDataProvider, CreateInherentDataProviders};
 use sp_runtime::{
   traits::{Header, Block},
@@ -28,13 +25,13 @@ use sc_consensus::{ForkChoiceStrategy, BlockImportParams, BlockImport, import_qu
 use sc_service::ImportQueue;
 use sc_client_api::{BlockBackend, Backend, Finalizer};
 
-use frame_support::traits::ValidatorSet;
-
 use tendermint_machine::{
   ext::{BlockError, Commit, Network},
   SignedMessage, TendermintHandle,
 };
 
+use sp_tendermint::TendermintApi;
+
 use crate::{
   CONSENSUS_ID,
   validators::TendermintValidators,
@@ -53,7 +50,7 @@ pub trait TendermintClient<B: Block, Be: Backend<B> + 'static>:
   + 'static
 where
   TransactionFor<Self, B>: Send + Sync + 'static,
-  Self::Api: ValidatorSet<Public>,
+  Self::Api: TendermintApi<B>,
 {
 }
 impl<
@@ -70,7 +67,7 @@ impl<
   > TendermintClient<B, Be> for C
 where
   TransactionFor<C, B>: Send + Sync + 'static,
-  C::Api: ValidatorSet<Public>,
+  C::Api: TendermintApi<B>,
 {
 }
 
@@ -83,12 +80,12 @@ pub(crate) struct TendermintImport<
   A: Announce<B>,
 > where
   TransactionFor<C, B>: Send + Sync + 'static,
-  C::Api: ValidatorSet<Public>,
+  C::Api: TendermintApi<B>,
 {
   _block: PhantomData<B>,
   _backend: PhantomData<Be>,
 
-  validators: Arc<TendermintValidators<B, C>>,
+  validators: Arc<TendermintValidators<B, Be, C>>,
 
   importing_block: Arc<RwLock<Option<B::Hash>>>,
   pub(crate) machine: Arc<RwLock<Option<TendermintHandle<Self>>>>,
@@ -111,7 +108,7 @@ impl<
   > Clone for TendermintImport<B, Be, C, CIDP, E, A>
 where
   TransactionFor<C, B>: Send + Sync + 'static,
-  C::Api: ValidatorSet<Public>,
+  C::Api: TendermintApi<B>,
 {
   fn clone(&self) -> Self {
     TendermintImport {
@@ -143,7 +140,7 @@ impl<
   > TendermintImport<B, Be, C, CIDP, E, A>
 where
   TransactionFor<C, B>: Send + Sync + 'static,
-  C::Api: ValidatorSet<Public>,
+  C::Api: TendermintApi<B>,
 {
   pub(crate) fn new(
     client: Arc<C>,
@@ -155,7 +152,7 @@ where
       _block: PhantomData,
       _backend: PhantomData,
 
-      validators: TendermintValidators::new(client),
+      validators: Arc::new(TendermintValidators::new(client.clone())),
 
       importing_block: Arc::new(RwLock::new(None)),
       machine: Arc::new(RwLock::new(None)),
@@ -215,7 +212,7 @@ where
       Err(Error::InvalidJustification)?;
     }
 
-    let commit: Commit<TendermintValidators<B, C>> =
+    let commit: Commit<TendermintValidators<B, Be, C>> =
       Commit::decode(&mut justification.1.as_ref()).map_err(|_| Error::InvalidJustification)?;
     if !self.verify_commit(hash, &commit) {
       Err(Error::InvalidJustification)?;
@@ -328,20 +325,20 @@ impl<
   > Network for TendermintImport<B, Be, C, CIDP, E, A>
 where
   TransactionFor<C, B>: Send + Sync + 'static,
-  C::Api: ValidatorSet<Public>,
+  C::Api: TendermintApi<B>,
 {
   type ValidatorId = u16;
-  type SignatureScheme = TendermintValidators<B, C>;
-  type Weights = TendermintValidators<B, C>;
+  type SignatureScheme = TendermintValidators<B, Be, C>;
+  type Weights = TendermintValidators<B, Be, C>;
   type Block = B;
 
   const BLOCK_TIME: u32 = { (serai_runtime::MILLISECS_PER_BLOCK / 1000) as u32 };
 
-  fn signature_scheme(&self) -> Arc<TendermintValidators<B, C>> {
+  fn signature_scheme(&self) -> Arc<TendermintValidators<B, Be, C>> {
     self.validators.clone()
   }
 
-  fn weights(&self) -> Arc<TendermintValidators<B, C>> {
+  fn weights(&self) -> Arc<TendermintValidators<B, Be, C>> {
     self.validators.clone()
   }
 
@@ -410,7 +407,7 @@ where
     Ok(())
   }
 
-  async fn add_block(&mut self, block: B, commit: Commit<TendermintValidators<B, C>>) -> B {
+  async fn add_block(&mut self, block: B, commit: Commit<TendermintValidators<B, Be, C>>) -> B {
     let hash = block.hash();
     let justification = (CONSENSUS_ID, commit.encode());
     debug_assert!(self.verify_justification(hash, &justification).is_ok());

substrate/tendermint/client/src/validators.rs

@@ -8,12 +8,16 @@ use sp_application_crypto::{
 
 use sp_runtime::traits::Block;
 use sp_staking::SessionIndex;
-use sp_api::ProvideRuntimeApi;
+use sp_api::{BlockId, TransactionFor};
 
-use frame_support::traits::ValidatorSet;
+use sc_client_api::Backend;
 
 use tendermint_machine::ext::{BlockNumber, Round, Weights, SignatureScheme};
 
+use sp_tendermint::TendermintApi;
+
+use crate::tendermint::TendermintClient;
+
 struct TendermintValidatorsStruct {
   session: SessionIndex,
 
@@ -25,17 +29,21 @@ struct TendermintValidatorsStruct {
 }
 
 impl TendermintValidatorsStruct {
-  fn from_module<B: Block, C: Send + Sync + ProvideRuntimeApi<B>>(
-    client: C,
+  fn from_module<B: Block, Be: Backend<B> + 'static, C: TendermintClient<B, Be>>(
+    client: &Arc<C>,
   ) -> TendermintValidatorsStruct
   where
-    C::Api: ValidatorSet<Public>,
+    TransactionFor<C, B>: Send + Sync + 'static,
+    C::Api: TendermintApi<B>,
   {
-    let validators = client.runtime_api().validators();
+    let last = client.info().best_hash;
+    let api = client.runtime_api();
+    let session = api.current_session(&BlockId::Hash(last)).unwrap();
+    let validators = api.validators(&BlockId::Hash(last)).unwrap();
     assert_eq!(validators.len(), 1);
     let keys = Pair::from_string("//Alice", None).unwrap();
     TendermintValidatorsStruct {
-      session: client.runtime_api().session_index(),
+      session,
 
       // TODO
       total_weight: validators.len().try_into().unwrap(),
@@ -48,27 +56,42 @@ impl TendermintValidatorsStruct {
 }
 
 // Wrap every access of the validators struct in something which forces calling refresh
-struct Refresh<B: Block, C: Send + Sync + ProvideRuntimeApi<B>> {
+struct Refresh<B: Block, Be: Backend<B> + 'static, C: TendermintClient<B, Be>>
+where
+  TransactionFor<C, B>: Send + Sync + 'static,
+  C::Api: TendermintApi<B>,
+{
   _block: PhantomData<B>,
-  client: C,
+  _backend: PhantomData<Be>,
+
+  client: Arc<C>,
   _refresh: Arc<RwLock<TendermintValidatorsStruct>>,
 }
-impl<B: Block, C: Send + Sync + ProvideRuntimeApi<B>> Refresh<B, C>
+
+impl<B: Block, Be: Backend<B> + 'static, C: TendermintClient<B, Be>> Refresh<B, Be, C>
 where
-  C::Api: ValidatorSet<Public>,
+  TransactionFor<C, B>: Send + Sync + 'static,
+  C::Api: TendermintApi<B>,
 {
   // If the session has changed, re-create the struct with the data on it
   fn refresh(&self) {
     let session = self._refresh.read().unwrap().session;
-    if session != self.client.runtime_api().session_index() {
-      *self._refresh.write().unwrap() = TendermintValidatorsStruct::from_module(self.client);
+    if session !=
+      self
+        .client
+        .runtime_api()
+        .current_session(&BlockId::Hash(self.client.info().best_hash))
+        .unwrap()
+    {
+      *self._refresh.write().unwrap() = TendermintValidatorsStruct::from_module(&self.client);
     }
   }
 }
 
-impl<B: Block, C: Send + Sync + ProvideRuntimeApi<B>> Deref for Refresh<B, C>
+impl<B: Block, Be: Backend<B> + 'static, C: TendermintClient<B, Be>> Deref for Refresh<B, Be, C>
 where
-  C::Api: ValidatorSet<Public>,
+  TransactionFor<C, B>: Send + Sync + 'static,
+  C::Api: TendermintApi<B>,
 {
   type Target = RwLock<TendermintValidatorsStruct>;
   fn deref(&self) -> &RwLock<TendermintValidatorsStruct> {
@@ -77,25 +100,36 @@ where
   }
 }
 
-pub(crate) struct TendermintValidators<B: Block, C: Send + Sync + ProvideRuntimeApi<B>>(
-  Refresh<B, C>,
-);
-impl<B: Block, C: Send + Sync + ProvideRuntimeApi<B>> TendermintValidators<B, C>
+pub(crate) struct TendermintValidators<
+  B: Block,
+  Be: Backend<B> + 'static,
+  C: TendermintClient<B, Be>,
+>(Refresh<B, Be, C>)
 where
-  C::Api: ValidatorSet<Public>,
+  TransactionFor<C, B>: Send + Sync + 'static,
+  C::Api: TendermintApi<B>;
+
+impl<B: Block, Be: Backend<B> + 'static, C: TendermintClient<B, Be>> TendermintValidators<B, Be, C>
+where
+  TransactionFor<C, B>: Send + Sync + 'static,
+  C::Api: TendermintApi<B>,
 {
-  pub(crate) fn new(client: C) -> TendermintValidators<B, C> {
+  pub(crate) fn new(client: Arc<C>) -> TendermintValidators<B, Be, C> {
     TendermintValidators(Refresh {
       _block: PhantomData,
+      _backend: PhantomData,
+
+      _refresh: Arc::new(RwLock::new(TendermintValidatorsStruct::from_module(&client))),
       client,
-      _refresh: Arc::new(RwLock::new(TendermintValidatorsStruct::from_module())),
     })
   }
 }
 
-impl<B: Block, C: Send + Sync + ProvideRuntimeApi<B>> SignatureScheme for TendermintValidators<B, C>
+impl<B: Block, Be: Backend<B> + 'static, C: TendermintClient<B, Be>> SignatureScheme
+  for TendermintValidators<B, Be, C>
 where
-  C::Api: ValidatorSet<Public>,
+  TransactionFor<C, B>: Send + Sync + 'static,
+  C::Api: TendermintApi<B>,
 {
   type ValidatorId = u16;
   type Signature = Signature;
@@ -126,9 +160,11 @@ where
   }
 }
 
-impl<B: Block, C: Send + Sync + ProvideRuntimeApi<B>> Weights for TendermintValidators<B, C>
+impl<B: Block, Be: Backend<B> + 'static, C: TendermintClient<B, Be>> Weights
+  for TendermintValidators<B, Be, C>
 where
-  C::Api: ValidatorSet<Public>,
+  TransactionFor<C, B>: Send + Sync + 'static,
+  C::Api: TendermintApi<B>,
 {
   type ValidatorId = u16;
 

substrate/tendermint/client/src/verifier.rs

@@ -2,7 +2,6 @@ use std::sync::Arc;
 
 use async_trait::async_trait;
 
-use sp_core::sr25519::Public;
 use sp_inherents::CreateInherentDataProviders;
 use sp_runtime::traits::Block;
 use sp_api::TransactionFor;
@@ -12,7 +11,7 @@ use sc_consensus::{BlockImportParams, BlockImport, Verifier};
 
 use sc_client_api::Backend;
 
-use frame_support::traits::ValidatorSet;
+use sp_tendermint::TendermintApi;
 
 use crate::{
   tendermint::{TendermintClient, TendermintImport},
@@ -32,7 +31,7 @@ where
   TransactionFor<C, B>: Send + Sync + 'static,
   Arc<C>: BlockImport<B, Transaction = TransactionFor<C, B>>,
   <Arc<C> as BlockImport<B>>::Error: Into<Error>,
-  C::Api: ValidatorSet<Public>,
+  C::Api: TendermintApi<B>,
 {
   async fn verify(
     &mut self,

substrate/tendermint/pallet/Cargo.toml

@@ -15,6 +15,8 @@ rustdoc-args = ["--cfg", "docsrs"]
 parity-scale-codec = { version = "3", default-features = false, features = ["derive"] }
 scale-info = { version = "2", default-features = false, features = ["derive"] }
 
+sp-core = { git = "https://github.com/serai-dex/substrate", default-features = false }
+sp-std = { git = "https://github.com/serai-dex/substrate", default-features = false }
 sp-application-crypto = { git = "https://github.com/serai-dex/substrate", default-features = false }
 
 frame-system = { git = "https://github.com/serai-dex/substrate", default-features = false }

substrate/tendermint/pallet/src/lib.rs

@@ -1,25 +1,35 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
-use frame_support::traits::OneSessionHandler;
-
 #[frame_support::pallet]
 pub mod pallet {
+  use sp_std::vec::Vec;
+  use sp_core::sr25519::Public;
+
   use frame_support::pallet_prelude::*;
+  use frame_support::traits::{ConstU32, OneSessionHandler};
+
+  type MaxValidators = ConstU32<{ u16::MAX as u32 }>;
 
   #[pallet::config]
   pub trait Config: frame_system::Config {}
 
   #[pallet::pallet]
+  #[pallet::generate_store(pub(super) trait Store)]
   pub struct Pallet<T>(PhantomData<T>);
-}
 
-pub use pallet::*;
+  #[pallet::storage]
+  #[pallet::getter(fn session)]
+  pub type Session<T: Config> = StorageValue<_, u32, ValueQuery>;
 
-pub mod crypto {
+  #[pallet::storage]
+  #[pallet::getter(fn validators)]
+  pub type Validators<T: Config> = StorageValue<_, BoundedVec<Public, MaxValidators>, ValueQuery>;
+
+  pub mod crypto {
     use sp_application_crypto::{KeyTypeId, app_crypto, sr25519};
     app_crypto!(sr25519, KeyTypeId(*b"tend"));
 
-  impl<C> sp_application_crypto::BoundToRuntimeAppPublic for crate::Pallet<C> {
+    impl<T> sp_application_crypto::BoundToRuntimeAppPublic for crate::Pallet<T> {
       type Public = Public;
     }
 
@@ -28,9 +38,9 @@ pub mod crypto {
     }
     pub type AuthoritySignature = Signature;
     pub type AuthorityId = Public;
-}
+  }
 
-impl<C, V> OneSessionHandler<V> for Pallet<C> {
+  impl<T: Config, V> OneSessionHandler<V> for Pallet<T> {
     type Key = crypto::Public;
 
     fn on_genesis_session<'a, I: 'a>(_validators: I)
@@ -40,21 +50,24 @@ impl<C, V> OneSessionHandler<V> for Pallet<C> {
     {
     }
 
-  fn on_new_session<'a, I: 'a>(_changed: bool, _validators: I, _queued: I)
+    fn on_new_session<'a, I: 'a>(changed: bool, validators: I, _queued: I)
     where
       I: Iterator<Item = (&'a V, Self::Key)>,
       V: 'a,
     {
-    /*
       if !changed {
         return;
       }
 
-    for validator in validators {
-      ...
-    }
-    */
+      Session::<T>::put(Self::session() + 1);
+      Validators::<T>::put(
+        BoundedVec::try_from(validators.map(|(_, key)| key.into()).collect::<Vec<Public>>())
+          .unwrap(),
+      );
     }
 
     fn on_disabled(_validator_index: u32) {}
+  }
 }
+
+pub use pallet::*;

substrate/tendermint/primitives/Cargo.toml

@@ -10,3 +10,12 @@ edition = "2021"
 [package.metadata.docs.rs]
 all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
+
+[dependencies]
+sp-core = { git = "https://github.com/serai-dex/substrate", default-features = false }
+sp-std = { git = "https://github.com/serai-dex/substrate", default-features = false }
+sp-api = { git = "https://github.com/serai-dex/substrate", default-features = false }
+
+[features]
+std = ["sp-core/std", "sp-std/std", "sp-api/std"]
+default = ["std"]

substrate/tendermint/primitives/src/lib.rs

@@ -1,7 +1,15 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use sp_core::sr25519::Public;
+use sp_std::vec::Vec;
 
-trait TendermintApi {
+sp_api::decl_runtime_apis! {
+  pub trait TendermintApi {
+    /// Current session number. A session is NOT a fixed length of blocks, yet rather a continuous
+    /// set of validators.
+    fn current_session() -> u32;
+
+    /// Current validators.
     fn validators() -> Vec<Public>;
+  }
 }