From db18632dd211238fadcdec0fab643698be534b62 Mon Sep 17 00:00:00 2001
From: Sonic <sonic@dexon.org>
Date: Fri, 9 Nov 2018 17:24:54 +0800
Subject: core: support extracting governance state from state trie

---
 core/blockchain.go     | 27 +++++++++++++++++++++++++++
 core/state/gov.go      | 31 +++++++++++++++++++++++++++++++
 core/types/govstate.go | 15 +++++++++++++++
 3 files changed, 73 insertions(+)
 create mode 100644 core/state/gov.go
 create mode 100644 core/types/govstate.go

diff --git a/core/blockchain.go b/core/blockchain.go
index e7b1c846f..8bf680c38 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -1740,6 +1740,33 @@ func (bc *BlockChain) GetPending() (*types.Block, *state.StateDB) {
 	return block, s
 }
 
+// GetGovStateByHash extracts the governance contract's state from state trie
+// (the merkle proof of governance contract address and the whole storage)
+// at the given block hash.
+func (bc *BlockChain) GetGovStateByHash(hash common.Hash) (*types.GovState, error) {
+	header := bc.GetHeaderByHash(hash)
+	if header == nil {
+		return nil, fmt.Errorf("header not found")
+	}
+	statedb, err := bc.StateAt(header.Root)
+	if err != nil {
+		return nil, err
+	}
+	return state.GetGovState(statedb, header, vm.GovernanceContractAddress)
+}
+
+func (bc *BlockChain) GetGovStateByNumber(number uint64) (*types.GovState, error) {
+	header := bc.GetHeaderByNumber(number)
+	if header == nil {
+		return nil, fmt.Errorf("header not found")
+	}
+	statedb, err := bc.StateAt(header.Root)
+	if err != nil {
+		return nil, err
+	}
+	return state.GetGovState(statedb, header, vm.GovernanceContractAddress)
+}
+
 // reorg takes two blocks, an old chain and a new chain and will reconstruct the
 // blocks and inserts them to be part of the new canonical chain and accumulates
 // potential missing transactions and post an event about them.
diff --git a/core/state/gov.go b/core/state/gov.go
new file mode 100644
index 000000000..8b94cfab2
--- /dev/null
+++ b/core/state/gov.go
@@ -0,0 +1,31 @@
+package state
+
+import (
+	"github.com/dexon-foundation/dexon/common"
+	"github.com/dexon-foundation/dexon/core/types"
+	"github.com/dexon-foundation/dexon/trie"
+)
+
+func GetGovState(statedb *StateDB, header *types.Header,
+	addr common.Address) (*types.GovState, error) {
+	proof, err := statedb.GetProof(addr)
+	if err != nil {
+		return nil, err
+	}
+
+	govState := &types.GovState{
+		BlockHash: header.Hash(),
+		Number:    header.Number,
+		Root:      header.Root,
+		Proof:     proof,
+	}
+
+	if t := statedb.StorageTrie(addr); t != nil {
+		it := trie.NewIterator(t.NodeIterator(nil))
+		for it.Next() {
+			govState.Storage = append(govState.Storage,
+				[2][]byte{it.Key, it.Value})
+		}
+	}
+	return govState, nil
+}
diff --git a/core/types/govstate.go b/core/types/govstate.go
new file mode 100644
index 000000000..75f77cb0d
--- /dev/null
+++ b/core/types/govstate.go
@@ -0,0 +1,15 @@
+package types
+
+import (
+	"math/big"
+
+	"github.com/dexon-foundation/dexon/common"
+)
+
+type GovState struct {
+	BlockHash common.Hash
+	Number    *big.Int
+	Root      common.Hash
+	Proof     [][]byte
+	Storage   [][2][]byte
+}
-- 
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