test(agentcompat): add integration scenarios

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

integration/agentcompat/internal/scenario/transfer_observation.go

@@ -0,0 +1,86 @@
+//go:build linux
+
+package scenario
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"time"
+)
+
+type transferResidueScope struct {
+	AgentRoot    string
+	DashboardPID int
+}
+
+func confirmTransferQuiescence(ctx context.Context, scope transferResidueScope) (time.Duration, error) {
+	deadline, bounded := ctx.Deadline()
+	if !bounded {
+		return 0, errors.New("transfer quiescence requires a context deadline")
+	}
+	select {
+	case <-ctx.Done():
+		return 0, ctx.Err()
+	default:
+	}
+	residue, err := transferResidue(scope)
+	if err != nil {
+		return 0, err
+	}
+	if len(residue) > 0 {
+		return 0, fmt.Errorf("transfer completion left residue: %s", strings.Join(residue, ", "))
+	}
+	remaining := time.Until(deadline)
+	if remaining <= 0 {
+		return 0, context.DeadlineExceeded
+	}
+	return remaining, nil
+}
+
+func transferResidue(scope transferResidueScope) ([]string, error) {
+	var residue []string
+	err := filepath.WalkDir(scope.AgentRoot, func(path string, entry os.DirEntry, walkErr error) error {
+		if walkErr != nil {
+			return walkErr
+		}
+		if !entry.IsDir() && strings.HasPrefix(entry.Name(), ".mcp-xfer-") {
+			residue = append(residue, path)
+		}
+		return nil
+	})
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		return nil, err
+	}
+	fdDirectory := filepath.Join("/proc", strconv.Itoa(scope.DashboardPID), "fd")
+	entries, err := os.ReadDir(fdDirectory)
+	if err != nil {
+		return nil, fmt.Errorf("read dashboard descriptors: %w", err)
+	}
+	for _, entry := range entries {
+		target, readErr := os.Readlink(filepath.Join(fdDirectory, entry.Name()))
+		if readErr != nil {
+			continue
+		}
+		if strings.Contains(target, "nz-mcp-xfer-") {
+			residue = append(residue, target)
+		}
+	}
+	return residue, nil
+}
+
+func countTransferResidue(residue []string) (agentTemp, dashboardSpool int) {
+	for _, path := range residue {
+		if strings.Contains(filepath.Base(path), ".mcp-xfer-") {
+			agentTemp++
+		}
+		if strings.Contains(path, "nz-mcp-xfer-") {
+			dashboardSpool++
+		}
+	}
+	return agentTemp, dashboardSpool
+}