itest+lntest: migrate lntemp to lntest

This commit performs the takeover that `lntemp` is now promoted to be
`lntest`, and the scaffolding is now removed as all the refactoring is
finished!

lntest/fee_service.go

@@ -0,0 +1,140 @@
+package lntest
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"sync"
+	"testing"
+
+	"github.com/lightningnetwork/lnd/lntest/node"
+	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
+	"github.com/stretchr/testify/require"
+)
+
+// WebFeeService defines an interface that's used to provide fee estimation
+// service used in the integration tests. It must provide an URL so that a lnd
+// node can be started with the flag `--feeurl` and uses the customized fee
+// estimator.
+type WebFeeService interface {
+	// Start starts the service.
+	Start() error
+
+	// Stop stops the service.
+	Stop() error
+
+	// URL returns the service's endpoint.
+	URL() string
+
+	// SetFeeRate sets the estimated fee rate for a given confirmation
+	// target.
+	SetFeeRate(feeRate chainfee.SatPerKWeight, conf uint32)
+}
+
+const (
+	// feeServiceTarget is the confirmation target for which a fee estimate
+	// is returned. Requests for higher confirmation targets will fall back
+	// to this.
+	feeServiceTarget = 1
+
+	// DefaultFeeRateSatPerKw specifies the default fee rate used in the
+	// tests.
+	DefaultFeeRateSatPerKw = 12500
+)
+
+// FeeService runs a web service that provides fee estimation information.
+type FeeService struct {
+	*testing.T
+
+	feeRateMap map[uint32]uint32
+	url        string
+
+	srv  *http.Server
+	wg   sync.WaitGroup
+	lock sync.Mutex
+}
+
+// Compile-time check for the WebFeeService interface.
+var _ WebFeeService = (*FeeService)(nil)
+
+// Start spins up a go-routine to serve fee estimates.
+func NewFeeService(t *testing.T) *FeeService {
+	port := node.NextAvailablePort()
+	f := FeeService{
+		T: t,
+		url: fmt.Sprintf(
+			"http://localhost:%v/fee-estimates.json", port,
+		),
+	}
+
+	// Initialize default fee estimate.
+	f.feeRateMap = map[uint32]uint32{
+		feeServiceTarget: DefaultFeeRateSatPerKw,
+	}
+
+	listenAddr := fmt.Sprintf(":%v", port)
+	mux := http.NewServeMux()
+	mux.HandleFunc("/fee-estimates.json", f.handleRequest)
+
+	f.srv = &http.Server{
+		Addr:    listenAddr,
+		Handler: mux,
+	}
+	return &f
+}
+
+// Start starts the web server.
+func (f *FeeService) Start() error {
+	f.wg.Add(1)
+	go func() {
+		defer f.wg.Done()
+
+		if err := f.srv.ListenAndServe(); err != http.ErrServerClosed {
+			require.NoErrorf(f, err, "cannot start fee api")
+		}
+	}()
+
+	return nil
+}
+
+// handleRequest handles a client request for fee estimates.
+func (f *FeeService) handleRequest(w http.ResponseWriter, r *http.Request) {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+
+	bytes, err := json.Marshal(
+		struct {
+			Fees map[uint32]uint32 `json:"fee_by_block_target"`
+		}{
+			Fees: f.feeRateMap,
+		},
+	)
+	require.NoErrorf(f, err, "cannot serialize estimates")
+
+	_, err = io.WriteString(w, string(bytes))
+	require.NoError(f, err, "cannot send estimates")
+}
+
+// Stop stops the web server.
+func (f *FeeService) Stop() error {
+	err := f.srv.Shutdown(context.Background())
+	require.NoError(f, err, "cannot stop fee api")
+
+	f.wg.Wait()
+	return nil
+}
+
+// SetFeeRate sets a fee for the given confirmation target.
+func (f *FeeService) SetFeeRate(fee chainfee.SatPerKWeight, conf uint32) {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+
+	f.feeRateMap[conf] = uint32(fee.FeePerKVByte())
+}
+
+// URL returns the service endpoint.
+func (f *FeeService) URL() string {
+	return f.url
+}