core: modify interface (#194)

* Add a new method to notify full node about round cutting.
* Modify interface to return error when preparing block

9 files changed, 38 insertions, 20 deletions

diff --git a/core/interfaces.go b/core/interfaces.go
index 7a5859e..4a20354 100644
--- a/core/interfaces.go
+++ b/core/interfaces.go
@@ -29,10 +29,10 @@ import (
 // consensus core.
 type Application interface {
 	// PreparePayload is called when consensus core is preparing a block.
-	PreparePayload(position types.Position) []byte
+	PreparePayload(position types.Position) ([]byte, error)
 
 	// PrepareWitness will return the witness data no lower than consensusHeight.
-	PrepareWitness(consensusHeight uint64) types.Witness
+	PrepareWitness(consensusHeight uint64) (types.Witness, error)
 
 	// VerifyBlock verifies if the block is valid.
 	VerifyBlock(block *types.Block) bool
@@ -103,6 +103,10 @@ type Governance interface {
 	// Return the genesis node set if round == 0.
 	NodeSet(round uint64) []crypto.PublicKey
 
+	// NotifyRoundHeight notifies governance contract to generate configuration
+	// for that round with the block on that consensus height.
+	NotifyRoundHeight(targetRound, consensusHeight uint64)
+
 	//// DKG-related methods.
 
 	// AddDKGComplaint adds a DKGComplaint.
diff --git a/core/lattice.go b/core/lattice.go
index d634650..ab8aaec 100644
--- a/core/lattice.go
+++ b/core/lattice.go
@@ -79,8 +79,12 @@ func (s *Lattice) PrepareBlock(
 	if err = s.data.prepareBlock(b); err != nil {
 		return
 	}
-	b.Payload = s.app.PreparePayload(b.Position)
-	b.Witness = s.app.PrepareWitness(b.Witness.Height)
+	if b.Payload, err = s.app.PreparePayload(b.Position); err != nil {
+		return
+	}
+	if b.Witness, err = s.app.PrepareWitness(b.Witness.Height); err != nil {
+		return
+	}
 	if err = s.authModule.SignBlock(b); err != nil {
 		return
 	}
diff --git a/core/nodeset-cache_test.go b/core/nodeset-cache_test.go
index 6324421..73f0dee 100644
--- a/core/nodeset-cache_test.go
+++ b/core/nodeset-cache_test.go
@@ -40,8 +40,9 @@ func (g *testGov) Configuration(round uint64) (cfg *types.Config) {
 		NumChains:     4,
 	}
 }
-func (g *testGov) CRS(round uint64) (b common.Hash) { return g.crs }
-func (g *testGov) ProposeCRS([]byte)                {}
+func (g *testGov) CRS(round uint64) (b common.Hash)       { return g.crs }
+func (g *testGov) ProposeCRS([]byte)                      {}
+func (g *testGov) NotifyRoundHeight(round, height uint64) {}
 func (g *testGov) NodeSet(round uint64) []crypto.PublicKey {
 	// Randomly generating keys, and check them for verification.
 	g.curKeys = []crypto.PublicKey{}
diff --git a/core/nonblocking.go b/core/nonblocking.go
index 9bedb4b..532bcb9 100644
--- a/core/nonblocking.go
+++ b/core/nonblocking.go
@@ -119,12 +119,12 @@ func (nb *nonBlocking) wait() {
 }
 
 // PreparePayload cannot be non-blocking.
-func (nb *nonBlocking) PreparePayload(position types.Position) []byte {
+func (nb *nonBlocking) PreparePayload(position types.Position) ([]byte, error) {
 	return nb.app.PreparePayload(position)
 }
 
 // PrepareWitness cannot be non-blocking.
-func (nb *nonBlocking) PrepareWitness(height uint64) types.Witness {
+func (nb *nonBlocking) PrepareWitness(height uint64) (types.Witness, error) {
 	return nb.app.PrepareWitness(height)
 }
 
diff --git a/core/nonblocking_test.go b/core/nonblocking_test.go
index 8cd42d0..50f580a 100644
--- a/core/nonblocking_test.go
+++ b/core/nonblocking_test.go
@@ -45,12 +45,12 @@ func newSlowApp(sleep time.Duration) *slowApp {
 	}
 }
 
-func (app *slowApp) PreparePayload(_ types.Position) []byte {
-	return []byte{}
+func (app *slowApp) PreparePayload(_ types.Position) ([]byte, error) {
+	return []byte{}, nil
 }
 
-func (app *slowApp) PrepareWitness(_ uint64) types.Witness {
-	return types.Witness{}
+func (app *slowApp) PrepareWitness(_ uint64) (types.Witness, error) {
+	return types.Witness{}, nil
 }
 
 func (app *slowApp) VerifyBlock(_ *types.Block) bool {
diff --git a/core/test/app.go b/core/test/app.go
index 60bc26f..d9582c9 100644
--- a/core/test/app.go
+++ b/core/test/app.go
@@ -97,15 +97,15 @@ func NewApp() *App {
 }
 
 // PreparePayload implements Application interface.
-func (app *App) PreparePayload(position types.Position) []byte {
-	return []byte{}
+func (app *App) PreparePayload(position types.Position) ([]byte, error) {
+	return []byte{}, nil
 }
 
 // PrepareWitness implements Application interface.
-func (app *App) PrepareWitness(height uint64) types.Witness {
+func (app *App) PrepareWitness(height uint64) (types.Witness, error) {
 	return types.Witness{
 		Height: height,
-	}
+	}, nil
 }
 
 // VerifyBlock implements Application.
diff --git a/core/test/governance.go b/core/test/governance.go
index de0ec21..88aab37 100644
--- a/core/test/governance.go
+++ b/core/test/governance.go
@@ -115,6 +115,10 @@ func (g *Governance) CRS(round uint64) common.Hash {
 	return g.crs[round]
 }
 
+// NotifyRoundHeight notifies governace contract to snapshot config.
+func (g *Governance) NotifyRoundHeight(round, height uint64) {
+}
+
 // ProposeCRS propose a CRS.
 func (g *Governance) ProposeCRS(signedCRS []byte) {
 	g.lock.Lock()
diff --git a/simulation/app.go b/simulation/app.go
index 0e3e184..0ca65c9 100644
--- a/simulation/app.go
+++ b/simulation/app.go
@@ -98,18 +98,18 @@ func (a *simApp) getAckedBlocks(ackHash common.Hash) (output common.Hashes) {
 }
 
 // PreparePayload implements core.Application.
-func (a *simApp) PreparePayload(position types.Position) []byte {
-	return []byte{}
+func (a *simApp) PreparePayload(position types.Position) ([]byte, error) {
+	return []byte{}, nil
 }
 
 // PrepareWitness implements core.Application.
-func (a *simApp) PrepareWitness(height uint64) types.Witness {
+func (a *simApp) PrepareWitness(height uint64) (types.Witness, error) {
 	a.latestWitnessReady.L.Lock()
 	defer a.latestWitnessReady.L.Unlock()
 	for a.latestWitness.Height < height {
 		a.latestWitnessReady.Wait()
 	}
-	return a.latestWitness
+	return a.latestWitness, nil
 }
 
 // StronglyAcked is called when a block is strongly acked by DEXON
diff --git a/simulation/governance.go b/simulation/governance.go
index 2b0f56b..0a2c886 100644
--- a/simulation/governance.go
+++ b/simulation/governance.go
@@ -114,6 +114,11 @@ func (g *simGovernance) CRS(round uint64) common.Hash {
 	return g.crs[round]
 }
 
+// NotifyRoundHeight notifies governance contract to snapshot configuration
+// for that round with the block on that consensus height.
+func (g *simGovernance) NotifyRoundHeight(round, height uint64) {
+}
+
 // ProposeCRS proposes a CRS of round.
 func (g *simGovernance) ProposeCRS(signedCRS []byte) {
 	crs := crypto.Keccak256Hash(signedCRS)