1 files changed, 185 insertions, 0 deletions
diff --git a/monitor/backend.go b/monitor/backend.go
new file mode 100644
index 0000000..194ed84
--- /dev/null
+++ b/monitor/backend.go
@@ -0,0 +1,185 @@
+package monitor
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"math/big"
+	"strings"
+	"time"
+
+	ethereum "github.com/ethereum/go-ethereum"
+	"github.com/ethereum/go-ethereum/accounts/abi"
+	"github.com/ethereum/go-ethereum/accounts/abi/bind"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/ethclient"
+)
+
+type backendIntf interface {
+	FetchFinedNodes(chan node)
+	NodeSet() []node
+	BalanceFromAddress(*ethclient.Client, common.Address) *big.Int
+}
+
+// BlockchainBackend is the blockchain backend object for fetching blockchain info.
+type BlockchainBackend struct {
+	networkID int
+}
+
+// NodeSet returns the registered nodes.
+func (b *BlockchainBackend) NodeSet() []node {
+	nc := NetworkConfigMap[int64(b.networkID)]
+	conn, err := ethclient.Dial(nc.HTTPEndpoint)
+	if err != nil {
+		log.Println("EthClient Dial failed: ", err)
+		return []node{}
+	}
+	g, err := NewGovernance(GovAddress, conn)
+	if err != nil {
+		panic(err)
+	}
+	txOps := &bind.CallOpts{}
+	nodeLen, err := g.NodesLength(txOps)
+	if err != nil {
+		panic(err)
+	}
+	minStake, err := g.MinStake(txOps)
+	if err != nil {
+		panic(err)
+	}
+	nodes := []node{}
+	for i := uint64(0); i < nodeLen.Uint64(); i++ {
+		n, err := g.Nodes(txOps, big.NewInt(int64(i)))
+		if n.Staked.Cmp(minStake) < 0 {
+			continue
+		}
+		if err != nil {
+			panic(err)
+		}
+		publicKey, err := crypto.UnmarshalPubkey(n.PublicKey)
+		if err != nil {
+			log.Println("Unmarshal publicKey fail: ", err)
+			continue
+		}
+		address := crypto.PubkeyToAddress(*publicKey)
+		nodes = append(nodes, node{
+			owner:          n.Owner,
+			email:          n.Email,
+			fined:          n.Fined,
+			name:           n.Name,
+			publicKey:      n.PublicKey,
+			nodeKeyAddress: address,
+		})
+	}
+	return nodes
+}
+
+// BalanceFromAddress return address's balance.
+func (b *BlockchainBackend) BalanceFromAddress(conn *ethclient.Client,
+	address common.Address) *big.Int {
+	balance, err := conn.BalanceAt(context.Background(),
+		address, nil)
+	if err != nil {
+		log.Println("Get balance fail: ", err)
+		return big.NewInt(0)
+	}
+	return balance
+}
+
+func (b *BlockchainBackend) subscribe(
+	logs chan types.Log,
+	headers chan *types.Header,
+) (ethereum.Subscription, *ethclient.Client, error) {
+
+	nc := NetworkConfigMap[int64(b.networkID)]
+	conn, err := ethclient.Dial(nc.WSEndpoint)
+	if err != nil {
+		log.Println("EthClient Dial failed: ", err)
+		return nil, conn, err
+	}
+	abiObject, err := abi.JSON(strings.NewReader(GovernanceABI))
+	query := ethereum.FilterQuery{
+		Addresses: []common.Address{GovAddress},
+		Topics: [][]common.Hash{
+			[]common.Hash{
+				abiObject.Events["Fined"].Id(),
+			},
+		},
+	}
+	sub, err := conn.SubscribeFilterLogs(context.Background(), query, logs)
+	if err != nil {
+		log.Println("Subscribe logs failed: ", err)
+		return nil, conn, err
+	}
+
+	// Subscribe chain head to keep ws from timeout
+	_, err = conn.SubscribeNewHead(context.Background(), headers)
+	if err != nil {
+		log.Println("Subscribe chain head failed: ", err)
+	}
+	return sub, conn, nil
+}
+
+// FetchFinedNodes fetches nodes' information from blockchain.
+func (b *BlockchainBackend) FetchFinedNodes(nodeChan chan node) {
+	logs := make(chan types.Log)
+	headers := make(chan *types.Header)
+	sub, conn, err := b.subscribe(logs, headers)
+	if err != nil {
+		panic(err)
+	}
+	for {
+		select {
+		case err := <-sub.Err():
+			log.Println("sub.Err()", err)
+			// retry
+			for err != nil {
+				sub, conn, err = b.subscribe(logs, headers)
+				time.Sleep(30000)
+			}
+		case vLog := <-logs:
+			nodeAddress := common.BytesToAddress(vLog.Topics[1].Bytes())
+			log.Println("Notify node: ", nodeAddress.Hex())
+			nodeChan <- b.getNodeByAddress(nodeAddress, conn)
+		}
+	}
+}
+
+func (b *BlockchainBackend) getNodeByAddress(
+	nodeAddress common.Address, conn *ethclient.Client) node {
+
+	g, err := NewGovernance(GovAddress, conn)
+	if err != nil {
+		panic(err)
+	}
+	txOps := &bind.CallOpts{}
+	offset, err := g.NodesOffsetByAddress(txOps, nodeAddress)
+	if err != nil {
+		panic(err)
+	}
+	n, err := g.Nodes(txOps, offset)
+	if err != nil {
+		panic(err)
+	}
+	return node{
+		owner: n.Owner,
+		email: n.Email,
+		fined: n.Fined,
+		name:  n.Name,
+	}
+}
+
+func printNodes(nodes []node) {
+	for i := range nodes {
+		fmt.Println("Owner", nodes[i].owner.Hex())
+		fmt.Println("Email", nodes[i].email)
+		fmt.Println("Fined", nodes[i].fined.Uint64())
+	}
+}
+
+// NewBlockchainBackend is the blockchain backend constructor.
+func NewBlockchainBackend(networkID int) *BlockchainBackend {
+	return &BlockchainBackend{networkID: networkID}
+}