Pass topics along with events (#2563)

* Introduce an IndexedEvent

* Plumb topics through the Ext interface.

* Add topics to ext_deposit_event

* Charging for events.

* Check the number of topics.

* Check for duplicate topics.

* Bump API version.

* Move derive(*Eq) under test.

* Use sorting for finding duplicates.

substrate/srml/contract/src/exec.rs

@@ -29,6 +29,9 @@ pub type CallOf<T> = <T as Trait>::Call;
 pub type MomentOf<T> = <T as timestamp::Trait>::Moment;
 pub type SeedOf<T> = <T as system::Trait>::Hash;
 
+/// A type that represents a topic of an event. At the moment a hash is used.
+pub type TopicOf<T> = <T as system::Trait>::Hash;
+
 #[cfg_attr(test, derive(Debug))]
 pub struct InstantiateReceipt<AccountId> {
 	pub address: AccountId,
@@ -106,8 +109,10 @@ pub trait Ext {
 	/// Returns a reference to the random seed for the current block
 	fn random_seed(&self) -> &SeedOf<Self::T>;
 
-	/// Deposit an event.
-	fn deposit_event(&mut self, data: Vec<u8>);
+	/// Deposit an event with the given topics.
+	///
+	/// There should not be any duplicates in `topics`.
+	fn deposit_event(&mut self, topics: Vec<TopicOf<Self::T>>, data: Vec<u8>);
 
 	/// Set rent allowance of the contract
 	fn set_rent_allowance(&mut self, rent_allowance: BalanceOf<Self::T>);
@@ -189,6 +194,15 @@ impl VmExecResult {
 	}
 }
 
+/// Struct that records a request to deposit an event with a list of topics.
+#[cfg_attr(any(feature = "std", test), derive(Debug, PartialEq, Eq))]
+pub struct IndexedEvent<T: Trait> {
+	/// A list of topics this event will be deposited with.
+	pub topics: Vec<T::Hash>,
+	/// The event to deposit.
+	pub event: Event<T>,
+}
+
 /// A trait that represent a virtual machine.
 ///
 /// You can view a virtual machine as something that takes code, an input data buffer,
@@ -238,7 +252,7 @@ pub struct ExecutionContext<'a, T: Trait + 'a, V, L> {
 	pub self_trie_id: Option<TrieId>,
 	pub overlay: OverlayAccountDb<'a, T>,
 	pub depth: usize,
-	pub events: Vec<Event<T>>,
+	pub events: Vec<IndexedEvent<T>>,
 	pub calls: Vec<(T::AccountId, T::Call)>,
 	pub config: &'a Config<T>,
 	pub vm: &'a V,
@@ -418,7 +432,10 @@ where
 				.into_result()?;
 
 			// Deposit an instantiation event.
-			nested.events.push(RawEvent::Instantiated(self.self_account.clone(), dest.clone()));
+			nested.events.push(IndexedEvent {
+				event: RawEvent::Instantiated(self.self_account.clone(), dest.clone()),
+				topics: Vec::new(),
+			});
 
 			(nested.overlay.into_change_set(), nested.events, nested.calls)
 		};
@@ -545,8 +562,10 @@ fn transfer<'a, T: Trait, V: Vm<T>, L: Loader<T>>(
 	if transactor != dest {
 		ctx.overlay.set_balance(transactor, new_from_balance);
 		ctx.overlay.set_balance(dest, new_to_balance);
-		ctx.events
-			.push(RawEvent::Transfer(transactor.clone(), dest.clone(), value));
+		ctx.events.push(IndexedEvent {
+			event: RawEvent::Transfer(transactor.clone(), dest.clone(), value),
+			topics: Vec::new(),
+		});
 	}
 
 	Ok(())
@@ -631,8 +650,11 @@ where
 		&self.timestamp
 	}
 
-	fn deposit_event(&mut self, data: Vec<u8>) {
-		self.ctx.events.push(RawEvent::Contract(self.ctx.self_account.clone(), data));
+	fn deposit_event(&mut self, topics: Vec<T::Hash>, data: Vec<u8>) {
+		self.ctx.events.push(IndexedEvent {
+			topics,
+			event: RawEvent::Contract(self.ctx.self_account.clone(), data),
+		});
 	}
 
 	fn set_rent_allowance(&mut self, rent_allowance: BalanceOf<T>) {
@@ -659,7 +681,7 @@ where
 mod tests {
 	use super::{
 		BalanceOf, ExecFeeToken, ExecutionContext, Ext, Loader, EmptyOutputBuf, TransferFeeKind, TransferFeeToken,
-		Vm, VmExecResult, InstantiateReceipt, RawEvent,
+		Vm, VmExecResult, InstantiateReceipt, RawEvent, IndexedEvent,
 	};
 	use crate::account_db::AccountDb;
 	use crate::gas::GasMeter;
@@ -1262,8 +1284,14 @@ mod tests {
 				// there are instantiation event.
 				assert_eq!(ctx.overlay.get_code_hash(&created_contract_address).unwrap(), dummy_ch);
 				assert_eq!(&ctx.events, &[
-					RawEvent::Transfer(ALICE, created_contract_address, 100),
-					RawEvent::Instantiated(ALICE, created_contract_address),
+					IndexedEvent {
+						event: RawEvent::Transfer(ALICE, created_contract_address, 100),
+						topics: Vec::new(),
+					},
+					IndexedEvent {
+						event: RawEvent::Instantiated(ALICE, created_contract_address),
+						topics: Vec::new(),
+					}
 				]);
 			}
 		);
@@ -1314,9 +1342,18 @@ mod tests {
 				// there are instantiation event.
 				assert_eq!(ctx.overlay.get_code_hash(&created_contract_address).unwrap(), dummy_ch);
 				assert_eq!(&ctx.events, &[
-					RawEvent::Transfer(ALICE, BOB, 20),
-					RawEvent::Transfer(BOB, created_contract_address, 15),
-					RawEvent::Instantiated(BOB, created_contract_address),
+					IndexedEvent {
+						event: RawEvent::Transfer(ALICE, BOB, 20),
+						topics: Vec::new(),
+					},
+					IndexedEvent {
+						event: RawEvent::Transfer(BOB, created_contract_address, 15),
+						topics: Vec::new(),
+					},
+					IndexedEvent {
+						event: RawEvent::Instantiated(BOB, created_contract_address),
+						topics: Vec::new(),
+					},
 				]);
 			}
 		);
@@ -1362,7 +1399,10 @@ mod tests {
 				// The contract wasn't created so we don't expect to see an instantiation
 				// event here.
 				assert_eq!(&ctx.events, &[
-					RawEvent::Transfer(ALICE, BOB, 20),
+					IndexedEvent {
+						event: RawEvent::Transfer(ALICE, BOB, 20),
+						topics: Vec::new(),
+					},
 				]);
 			}
 		);