test(agentcompat): add integration scenarios

Co-authored-by: naiba/CloudCode <hi+cloudcode@nai.ba>

integration/agentcompat/internal/scenario/nat_http.go

@@ -0,0 +1,117 @@
+//go:build linux
+
+package scenario
+
+import (
+	"bufio"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/nezhahq/nezha/integration/agentcompat/internal/fixture"
+)
+
+type natRawResponse struct {
+	Status            int
+	Body              string
+	LegacyCloseMarker string
+	PeerWriteClosed   bool
+}
+
+type natHTTPRequestSpec struct {
+	Endpoint string
+	Host     string
+	Method   string
+	Path     string
+	Body     string
+}
+
+const natEchoHeaderValue = "fixture"
+
+func natHTTPStatus(ctx context.Context, endpoint, host string) (natRawResponse, error) {
+	return natHTTPRequest(ctx, natHTTPRequestSpec{Endpoint: endpoint, Host: host, Method: http.MethodGet, Path: "/"})
+}
+
+func natHTTPRoundTrip(ctx context.Context, request natHTTPRequestSpec) (natRawResponse, fixture.NATEchoRecord, error) {
+	response, err := natHTTPRequest(ctx, request)
+	if err != nil {
+		return natRawResponse{}, fixture.NATEchoRecord{}, err
+	}
+	record, err := parseNATResponse(response.Body)
+	return response, record, err
+}
+
+func natHTTPRequest(ctx context.Context, request natHTTPRequestSpec) (natRawResponse, error) {
+	connection, err := (&net.Dialer{}).DialContext(ctx, "tcp", request.Endpoint)
+	if err != nil {
+		return natRawResponse{}, err
+	}
+	defer connection.Close()
+	if deadline, ok := ctx.Deadline(); ok {
+		if err := connection.SetDeadline(deadline); err != nil {
+			return natRawResponse{}, err
+		}
+	}
+	wireRequest := fmt.Sprintf("%s %s HTTP/1.1\r\nHost: %s\r\nX-AgentCompat-Echo: %s\r\nContent-Length: %d\r\nConnection: close\r\n\r\n%s", request.Method, request.Path, request.Host, natEchoHeaderValue, len(request.Body), request.Body)
+	if _, err := io.WriteString(connection, wireRequest); err != nil {
+		return natRawResponse{}, err
+	}
+	reader := bufio.NewReader(connection)
+	response, err := http.ReadResponse(reader, nil)
+	if err != nil {
+		return natRawResponse{}, err
+	}
+	responseBody, err := io.ReadAll(response.Body)
+	if closeErr := response.Body.Close(); err == nil {
+		err = closeErr
+	}
+	if err != nil {
+		return natRawResponse{}, err
+	}
+	// Agent preserves its legacy wire contract by forwarding the local read
+	// result after the HTTP body. Reading through that marker to EOF proves the
+	// backend write-close reached Agent and the stream then terminated.
+	closeMarker, peerCloseErr := io.ReadAll(reader)
+	if peerCloseErr != nil {
+		return natRawResponse{}, fmt.Errorf("observe NAT peer write close: %w", peerCloseErr)
+	}
+	return natRawResponse{Status: response.StatusCode, Body: string(responseBody), LegacyCloseMarker: string(closeMarker), PeerWriteClosed: true}, nil
+}
+
+func natAssertNoBackendConnection(ctx context.Context, backend *fixture.NATEchoBackend) error {
+	deadline, cancel := context.WithTimeout(ctx, 300*time.Millisecond)
+	defer cancel()
+	err := backend.WaitConnection(deadline)
+	if errors.Is(err, context.DeadlineExceeded) {
+		return nil
+	}
+	if err == nil {
+		return errors.New("NAT backend received an unexpected connection")
+	}
+	return err
+}
+
+func parseNATResponse(body string) (fixture.NATEchoRecord, error) {
+	values := make(map[string]string)
+	for _, line := range strings.Split(strings.TrimSuffix(body, "\n"), "\n") {
+		key, value, ok := strings.Cut(line, "=")
+		if ok {
+			values[key] = value
+		}
+	}
+	for _, key := range []string{"method", "path", "host", "x-agentcompat-echo", "body"} {
+		if _, ok := values[key]; !ok {
+			return fixture.NATEchoRecord{}, fmt.Errorf("NAT response missing %s", key)
+		}
+	}
+	return fixture.NATEchoRecord{Method: values["method"], Path: values["path"], Host: values["host"], HeaderValue: values["x-agentcompat-echo"], Body: []byte(values["body"])}, nil
+}
+
+func natExpectedBody(request natHTTPRequestSpec) string {
+	return fmt.Sprintf("method=%s\npath=%s\nhost=%s\nx-agentcompat-echo=%s\nbody=%s\n", request.Method, request.Path, request.Host, natEchoHeaderValue, request.Body)
+}