core: refine Application interface and add Governance interface (#24)

Add a new Governance interface for interaction with the governance contract.

Also remove the ValidateBlock call in application interface as the application should validate it before putting it into the consensus module.

A new BlockConverter interface is also added. The consensus module should accept the BlockConverter interface in future implementation, and use the Block() function to get the underlying block info.

5 files changed, 77 insertions, 9 deletions

diff --git a/core/application.go b/core/application.go
index 7eca66e..edeb686 100644
--- a/core/application.go
+++ b/core/application.go
@@ -17,11 +17,20 @@
 
 package core
 
-import "github.com/dexon-foundation/dexon-consensus-core/core/types"
+import (
+	"time"
+
+	"github.com/dexon-foundation/dexon-consensus-core/common"
+	"github.com/dexon-foundation/dexon-consensus-core/core/types"
+)
 
 // Application describes the application interface that interacts with DEXON
 // consensus core.
 type Application interface {
-	ValidateBlock(b *types.Block) bool
-	Deliver(blocks []*types.Block, early bool)
+	// TotalOrderingDeliver is called when the total ordering algorithm deliver
+	// a set of block.
+	TotalOrderingDeliver(blocks []*types.Block, early bool)
+
+	// DeliverBlock is called when a block is add to the compaction chain.
+	DeliverBlock(blockHash common.Hash, timestamp time.Time)
 }
diff --git a/core/blocklattice.go b/core/blocklattice.go
index e4a76cc..1f12474 100644
--- a/core/blocklattice.go
+++ b/core/blocklattice.go
@@ -532,7 +532,7 @@ func (l *BlockLattice) totalOrdering(b *types.Block) {
 	sort.Sort(types.ByHash(output))
 
 	if len(output) > 0 {
-		l.app.Deliver(output, earlyDelivery)
+		l.app.TotalOrderingDeliver(output, earlyDelivery)
 	}
 
 	// Rescan pending blocks to add into candidate set.
diff --git a/core/blocklattice_test.go b/core/blocklattice_test.go
index 0f78dc5..835c35e 100644
--- a/core/blocklattice_test.go
+++ b/core/blocklattice_test.go
@@ -20,6 +20,7 @@ package core
 import (
 	"sort"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/suite"
 
@@ -42,15 +43,14 @@ type TestApp struct {
 	Early   bool
 }
 
-func (a *TestApp) ValidateBlock(b *types.Block) bool {
-	return true
-}
-
-func (a *TestApp) Deliver(blocks []*types.Block, early bool) {
+func (a *TestApp) TotalOrderingDeliver(blocks []*types.Block, early bool) {
 	a.Outputs = append(a.Outputs, blocks...)
 	a.Early = early
 }
 
+func (a *TestApp) DeliverBlock(blockHashes common.Hash, timestamp time.Time) {
+}
+
 func (a *TestApp) Clear() {
 	a.Outputs = nil
 	a.Early = false
diff --git a/core/governance.go b/core/governance.go
new file mode 100644
index 0000000..a3bc3af
--- /dev/null
+++ b/core/governance.go
@@ -0,0 +1,53 @@
+// Copyright 2018 The dexon-consensus-core Authors
+// This file is part of the dexon-consensus-core library.
+//
+// The dexon-consensus-core library is free software: you can redistribute it
+// and/or modify it under the terms of the GNU Lesser General Public License as
+// published by the Free Software Foundation, either version 3 of the License,
+// or (at your option) any later version.
+//
+// The dexon-consensus-core library is distributed in the hope that it will be
+// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
+// General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the dexon-consensus-core library. If not, see
+// <http://www.gnu.org/licenses/>.
+
+package core
+
+import (
+	"github.com/cobinhood/decimal"
+
+	"github.com/dexon-foundation/dexon-consensus-core/core/types"
+)
+
+// MembershipActionType specifies the action of a membership event.
+type MembershipActionType int
+
+// Event enums.
+const (
+	MembershipActionAdd    MembershipActionType = 0
+	MembershipActionDelete MembershipActionType = 1
+)
+
+// MembershipEvent specifies the event of membership changes.
+type MembershipEvent struct {
+	Epoch  int
+	Action MembershipActionType
+}
+
+// Governance interface specifies interface to control the governance contract.
+// Note that there are a lot more methods in the governance contract, that this
+// interface only define those that are required to run the consensus algorithm.
+type Governance interface {
+	// Get the current validator set and it's corresponding stake.
+	GetValidatorSet() map[types.ValidatorID]decimal.Decimal
+
+	// Get block proposing interval (in milliseconds).
+	GetBlockProposingInterval() int
+
+	// Get membership events after a certain epoch.
+	GetMembershipEvents(epoch int) []MembershipEvent
+}
diff --git a/core/types/block.go b/core/types/block.go
index 61b6535..c445fd2 100644
--- a/core/types/block.go
+++ b/core/types/block.go
@@ -50,6 +50,12 @@ type Block struct {
 	Status          Status                   `json:"-"`
 }
 
+// BlockConverter interface define the interface for extracting block
+// information from an existing object.
+type BlockConverter interface {
+	Block() *Block
+}
+
 func (b *Block) String() string {
 	return fmt.Sprintf("Block(%v)", b.Hash.String()[:6])
 }