backend: implement block explorer selection

Add the block explorer prefix url to the configuration that will be used
to open the transaction. The available options to select are statically
defined and the frontend can learn them by calling the
available-explorers endpoint for which a handler was implemented in this
commit.

backend/backend.go

@@ -22,6 +22,7 @@ import (
 	"net/url"
 	"os"
 	"path/filepath"
+	"reflect"
 	"strings"
 	"time"
 
@@ -71,14 +72,7 @@ var fixedURLWhitelist = []string{
 	"https://shiftcrypto.support/",
 	// Exchange rates.
 	"https://www.coingecko.com/",
-	// Block explorers.
-	"https://blockstream.info/tx/",
-	"https://blockstream.info/testnet/tx/",
-	"https://sochain.com/tx/LTCTEST/",
-	"https://blockchair.com/litecoin/transaction/",
-	"https://etherscan.io/tx/",
-	"https://goerli.etherscan.io/tx/",
-	"https://sepolia.etherscan.io/tx/",
+
 	// Moonpay onramp
 	"https://www.moonpay.com/",
 	"https://support.moonpay.com/",
@@ -490,43 +484,51 @@ func (backend *Backend) Coin(code coinpkg.Code) (coinpkg.Coin, error) {
 		servers := backend.defaultElectrumXServers(code)
 		coin = btc.NewCoin(coinpkg.CodeRBTC, "Bitcoin Regtest", "RBTC", coinpkg.BtcUnitDefault, &chaincfg.RegressionNetParams, dbFolder, servers, "", backend.socksProxy)
 	case code == coinpkg.CodeTBTC:
+		blockExplorerPrefix := backend.config.AppConfig().Backend.BlockExplorers.TBTC
 		servers := backend.defaultElectrumXServers(code)
 		coin = btc.NewCoin(coinpkg.CodeTBTC, "Bitcoin Testnet", "TBTC", btcFormatUnit, &chaincfg.TestNet3Params, dbFolder, servers,
-			"https://blockstream.info/testnet/tx/", backend.socksProxy)
+			blockExplorerPrefix, backend.socksProxy)
 	case code == coinpkg.CodeBTC:
+		blockExplorerPrefix := backend.config.AppConfig().Backend.BlockExplorers.BTC
 		servers := backend.defaultElectrumXServers(code)
 		coin = btc.NewCoin(coinpkg.CodeBTC, "Bitcoin", "BTC", btcFormatUnit, &chaincfg.MainNetParams, dbFolder, servers,
-			"https://blockstream.info/tx/", backend.socksProxy)
+			blockExplorerPrefix, backend.socksProxy)
 	case code == coinpkg.CodeTLTC:
+		blockExplorerPrefix := backend.config.AppConfig().Backend.BlockExplorers.TLTC
 		servers := backend.defaultElectrumXServers(code)
 		coin = btc.NewCoin(coinpkg.CodeTLTC, "Litecoin Testnet", "TLTC", coinpkg.BtcUnitDefault, &ltc.TestNet4Params, dbFolder, servers,
-			"https://sochain.com/tx/LTCTEST/", backend.socksProxy)
+			blockExplorerPrefix, backend.socksProxy)
 	case code == coinpkg.CodeLTC:
+		blockExplorerPrefix := backend.config.AppConfig().Backend.BlockExplorers.LTC
 		servers := backend.defaultElectrumXServers(code)
 		coin = btc.NewCoin(coinpkg.CodeLTC, "Litecoin", "LTC", coinpkg.BtcUnitDefault, &ltc.MainNetParams, dbFolder, servers,
-			"https://blockchair.com/litecoin/transaction/", backend.socksProxy)
+			blockExplorerPrefix, backend.socksProxy)
 	case code == coinpkg.CodeETH:
+		blockExplorerPrefix := backend.config.AppConfig().Backend.BlockExplorers.ETH
 		etherScan := etherscan.NewEtherScan("https://api.etherscan.io/api", backend.etherScanHTTPClient)
 		coin = eth.NewCoin(etherScan, code, "Ethereum", "ETH", "ETH", params.MainnetChainConfig,
-			"https://etherscan.io/tx/",
+			blockExplorerPrefix,
 			etherScan,
 			nil)
 	case code == coinpkg.CodeGOETH:
+		blockExplorerPrefix := backend.config.AppConfig().Backend.BlockExplorers.GOETH
 		etherScan := etherscan.NewEtherScan("https://api-goerli.etherscan.io/api", backend.etherScanHTTPClient)
 		coin = eth.NewCoin(etherScan, code, "Ethereum Goerli", "GOETH", "GOETH", params.GoerliChainConfig,
-			"https://goerli.etherscan.io/tx/",
+			blockExplorerPrefix,
 			etherScan,
 			nil)
 	case code == coinpkg.CodeSEPETH:
+		blockExplorerPrefix := backend.config.AppConfig().Backend.BlockExplorers.SEPETH
 		etherScan := etherscan.NewEtherScan("https://api-sepolia.etherscan.io/api", backend.etherScanHTTPClient)
 		coin = eth.NewCoin(etherScan, code, "Ethereum Sepolia", "SEPETH", "SEPETH", params.SepoliaChainConfig,
-			"https://sepolia.etherscan.io/tx/",
+			blockExplorerPrefix,
 			etherScan,
 			nil)
 	case erc20Token != nil:
+		blockExplorerPrefix := backend.config.AppConfig().Backend.BlockExplorers.ETH
 		etherScan := etherscan.NewEtherScan("https://api.etherscan.io/api", backend.etherScanHTTPClient)
 		coin = eth.NewCoin(etherScan, erc20Token.code, erc20Token.name, erc20Token.unit, "ETH", params.MainnetChainConfig,
-			"https://etherscan.io/tx/",
+			blockExplorerPrefix,
 			etherScan,
 			erc20Token.token,
 		)
@@ -827,6 +829,16 @@ func (backend *Backend) SystemOpen(url string) error {
 		}
 	}
 
+	// Block explorers are not defined in the fixedURLWhiteList but in AvailableBlockexplorers.
+	var allAvailableExplorers = reflect.ValueOf(config.AvailableExplorers)
+	for i := 0; i < allAvailableExplorers.NumField(); i++ {
+		coinAvailableExplorers := allAvailableExplorers.Field(i).Interface().([]config.BlockExplorer)
+		for _, explorer := range coinAvailableExplorers {
+			if strings.HasPrefix(url, explorer.Url) {
+				return backend.environment.SystemOpen(url)
+			}
+		}
+	}
 	return errp.Newf("Blocked /open with url: %s", url)
 }
 
@@ -997,4 +1009,10 @@ func (backend *Backend) ExportLogs() error {
 		return err
 	}
 	return nil
+
+}
+
+// AvailableExplorers returns a struct containing all available block explorers for each coin.
+func (backend *Backend) AvailableExplorers() config.AvailableBlockExplorers {
+	return config.AvailableExplorers
 }

backend/config/blockexplorer.go

@@ -0,0 +1,91 @@
+package config
+
+// BlockExplorer defines a selectable block explorer.
+type BlockExplorer struct {
+	// Name of the block explorer used for UI.
+	Name string `json:"name"`
+	// Url of the block explorer that the txid is appended.
+	Url string `json:"url"`
+}
+
+// AvailableBlockExplorers defines all available block explorers for each coin.
+type AvailableBlockExplorers struct {
+	Btc    []BlockExplorer `json:"btc"`
+	Tbtc   []BlockExplorer `json:"tbtc"`
+	Ltc    []BlockExplorer `json:"ltc"`
+	Tltc   []BlockExplorer `json:"tltc"`
+	Eth    []BlockExplorer `json:"eth"`
+	GoEth  []BlockExplorer `json:"goeth"`
+	SepEth []BlockExplorer `json:"sepeth"`
+}
+
+// AvailableExplorers holds all available block explorers for each coin.
+// It is returned from the available-explorers endpoint.
+var AvailableExplorers = AvailableBlockExplorers{
+	Btc: []BlockExplorer{
+		{
+			Name: "blockstream.info",
+			Url:  "https://blockstream.info/tx/",
+		},
+		{
+			Name: "mempool.space",
+			Url:  "https://mempool.space/tx",
+		},
+	},
+	Tbtc: []BlockExplorer{
+		{
+			Name: "mempool.space",
+			Url:  "https://mempool.space/testnet/tx/",
+		},
+		{
+			Name: "blockstream.info",
+			Url:  "https://blockstream.info/testnet/tx/",
+		},
+	},
+	Ltc: []BlockExplorer{
+		{
+			Name: "sochain.com",
+			Url:  "https://sochain.com/tx/",
+		},
+		{
+			Name: "blockchair.com",
+			Url:  "https://blockchair.com/litecoin/transaction",
+		},
+	},
+	Tltc: []BlockExplorer{
+		{
+			Name: "sochain.com",
+			Url:  "https://sochain.com/tx/LTCTEST/",
+		},
+	},
+	Eth: []BlockExplorer{
+		{
+			Name: "etherscan.io",
+			Url:  "https://etherscan.io/tx/",
+		},
+		{
+			Name: "ethplorer.io",
+			Url:  "https://ethplorer.io/tx/",
+		},
+	},
+	GoEth: []BlockExplorer{
+		{
+			Name: "etherscan.io",
+			Url:  "https://goerli.etherscan.io/tx/",
+		},
+		{
+			Name: "ethplorer.io",
+			Url:  "https://goerli.ethplorer.io/tx/",
+		},
+	},
+	SepEth: []BlockExplorer{
+		{
+			Name: "etherscan.io",
+			Url:  "https://sepolia.etherscan.io/tx/",
+		},
+		{
+			Name: "ethplorer.io",
+			Url:  "https://sepolia.ethplorer.io/tx/",
+		},
+	},
+}

backend/config/config.go

@@ -25,6 +25,16 @@ import (
 	"github.com/BitBoxSwiss/bitbox-wallet-app/util/locker"
 )
 
+type blockExplorers struct {
+	BTC    string `json:"btc"`
+	TBTC   string `json:"tbtc"`
+	LTC    string `json:"ltc"`
+	TLTC   string `json:"tltc"`
+	ETH    string `json:"eth"`
+	GOETH  string `json:"goeth"`
+	SEPETH string `json:"sepeth"`
+}
+
 // ServerInfo holds information about the backend server(s).
 type ServerInfo struct {
 	Server  string `json:"server"`
@@ -83,6 +93,8 @@ type Backend struct {
 	TLTC btcCoinConfig `json:"tltc"`
 	ETH  ethCoinConfig `json:"eth"`
 
+	BlockExplorers blockExplorers `json:"blockExplorers"`
+
 	// Removed in v4.35 - don't reuse these two keys.
 	TETH struct{} `json:"teth"`
 	RETH struct{} `json:"reth"`
@@ -228,6 +240,15 @@ func NewDefaultAppConfig() AppConfig {
 			ETH: ethCoinConfig{
 				DeprecatedActiveERC20Tokens: []string{},
 			},
+			BlockExplorers: blockExplorers{
+				BTC:    AvailableExplorers.Btc[0].Url,
+				TBTC:   AvailableExplorers.Tbtc[0].Url,
+				LTC:    AvailableExplorers.Ltc[0].Url,
+				TLTC:   AvailableExplorers.Tltc[0].Url,
+				ETH:    AvailableExplorers.Eth[0].Url,
+				GOETH:  AvailableExplorers.GoEth[0].Url,
+				SEPETH: AvailableExplorers.SepEth[0].Url,
+			},
 			// Copied from frontend/web/src/components/rates/rates.tsx.
 			FiatList: []string{rates.USD.String(), rates.EUR.String(), rates.CHF.String()},
 			MainFiat: rates.USD.String(),

backend/handlers/handlers.go

@@ -107,6 +107,7 @@ type Backend interface {
 	AOPPCancel()
 	AOPPApprove()
 	AOPPChooseAccount(code accountsTypes.Code)
+	AvailableExplorers() config.AvailableBlockExplorers
 	GetAccountFromCode(code accountsTypes.Code) (accounts.Interface, error)
 	HTTPClient() *http.Client
 	LookupInsuredAccounts(accountCode accountsTypes.Code) ([]bitsurance.AccountDetails, error)
@@ -257,6 +258,7 @@ func NewHandlers(
 	getAPIRouterNoError(apiRouter)("/accounts/eth-account-code", handlers.lookupEthAccountCode).Methods("POST")
 	getAPIRouterNoError(apiRouter)("/notes/export", handlers.postExportNotes).Methods("POST")
 	getAPIRouterNoError(apiRouter)("/notes/import", handlers.postImportNotes).Methods("POST")
+	getAPIRouterNoError(apiRouter)("/available-explorers", handlers.getAvailableExplorers).Methods("GET")
 
 	devicesRouter := getAPIRouterNoError(apiRouter.PathPrefix("/devices").Subrouter())
 	devicesRouter("/registered", handlers.getDevicesRegistered).Methods("GET")
@@ -1513,3 +1515,9 @@ func (handlers *Handlers) postImportNotes(r *http.Request) interface{} {
 	}
 	return result{Success: true, Data: data}
 }
+
+// getAvailableExplorers returns a struct containing arrays with block explorers for each
+// individual coin code.
+func (handlers *Handlers) getAvailableExplorers(*http.Request) interface{} {
+	return config.AvailableExplorers
+}