v0.2.0 (#50)

Co-authored-by: Tasnim Kabir Sadik <tksadik@omukk.dev>

Reviewed-on: wrenn/wrenn#50

internal/layout/layout.go

@@ -6,26 +6,28 @@ import (
 	"path/filepath"
 	"sort"
 	"strings"
+	"time"
 
 	"github.com/jackc/pgx/v5/pgtype"
 
 	"git.omukk.dev/wrenn/wrenn/pkg/id"
 )
 
-// IsMinimal reports whether the given team and template IDs represent the
-// built-in "minimal" template (both all-zeros).
-func IsMinimal(teamID, templateID pgtype.UUID) bool {
-	return teamID.Bytes == id.PlatformTeamID.Bytes && templateID.Bytes == id.MinimalTemplateID.Bytes
+func timeNowNano() int64 { return time.Now().UnixNano() }
+
+// IsSystemTemplate reports whether the given team and template IDs represent a
+// built-in system base template (minimal-ubuntu / -alpine / -arch / -fedora):
+// platform-owned with a template ID in the reserved range. System templates are
+// protected from deletion.
+func IsSystemTemplate(teamID, templateID pgtype.UUID) bool {
+	return teamID.Bytes == id.PlatformTeamID.Bytes && id.IsReservedTemplateID(templateID)
 }
 
-// TemplateDir returns the on-disk directory for a template.
+// TemplateDir returns the on-disk directory for a template. Every template —
+// including the built-in system base templates — lives under the teams tree:
 //
-//	minimal (zeros, zeros): {wrennDir}/images/minimal
-//	all others:             {wrennDir}/images/teams/{base36(teamID)}/{base36(templateID)}
+//	{wrennDir}/images/teams/{base36(teamID)}/{base36(templateID)}
 func TemplateDir(wrennDir string, teamID, templateID pgtype.UUID) string {
-	if IsMinimal(teamID, templateID) {
-		return filepath.Join(wrennDir, "images", "minimal")
-	}
 	return filepath.Join(wrennDir, "images", "teams",
 		id.UUIDToBase36(teamID.Bytes),
 		id.UUIDToBase36(templateID.Bytes))
@@ -36,17 +38,64 @@ func TemplateRootfs(wrennDir string, teamID, templateID pgtype.UUID) string {
 	return filepath.Join(TemplateDir(wrennDir, teamID, templateID), "rootfs.ext4")
 }
 
-// PauseSnapshotDir returns the directory for a paused sandbox's snapshot files.
-func PauseSnapshotDir(wrennDir, sandboxID string) string {
-	return filepath.Join(wrennDir, "snapshots", sandboxID)
+// IsSnapshotTemplate reports whether dir contains a Cloud Hypervisor memory
+// snapshot (state.json + config.json + memory-ranges) alongside the flattened
+// rootfs.ext4. Used to distinguish snapshot templates (launch via CH restore)
+// from base/disk-only templates (launch via fresh boot).
+//
+// state.json is CH-authoritative — its presence indicates a complete snapshot.
+func IsSnapshotTemplate(dir string) bool {
+	for _, name := range []string{"state.json", "config.json", "rootfs.ext4"} {
+		if _, err := os.Stat(filepath.Join(dir, name)); err != nil {
+			return false
+		}
+	}
+	return true
 }
 
-// SandboxesDir returns the directory for running sandbox CoW files.
+// SandboxCowName is the filename for a sandbox's CoW rootfs diff, kept inside
+// the per-sandbox directory alongside any pause snapshot files.
+const SandboxCowName = "rootfs.cow"
+
+// SandboxDir returns the per-sandbox directory under sandboxes/. It holds
+// the CoW file and, if the sandbox is paused, the snapshot files.
+//
+// Layout:
+//
+//	{wrennDir}/sandboxes/{id}/rootfs.cow   CoW file (persistent across pause/resume)
+//	{wrennDir}/sandboxes/{id}/             paused snapshot (config.json, state.json, memory-ranges, wrenn-snapshot.json)
+//	{wrennDir}/sandboxes/{id}.staging-*/   in-flight Pause writes (cleaned up by swapDir or startup GC)
+//	{wrennDir}/sandboxes/{id}.trash-*/     mid-swap previous generation (cleaned up by swapDir or startup GC)
+func SandboxDir(wrennDir, sandboxID string) string {
+	return filepath.Join(wrennDir, "sandboxes", sandboxID)
+}
+
+// SandboxCowPath returns the path to a sandbox's CoW rootfs diff file.
+func SandboxCowPath(wrennDir, sandboxID string) string {
+	return filepath.Join(SandboxDir(wrennDir, sandboxID), SandboxCowName)
+}
+
+// PauseSnapshotDir returns the directory for a paused sandbox's snapshot files.
+// Same path as SandboxDir — pause snapshot files live alongside the CoW.
+func PauseSnapshotDir(wrennDir, sandboxID string) string {
+	return SandboxDir(wrennDir, sandboxID)
+}
+
+// PauseStagingDir returns a fresh staging directory for an in-flight Pause.
+// Each call returns a unique path (timestamped) so concurrent retries do not
+// collide.
+func PauseStagingDir(wrennDir, sandboxID string) string {
+	return filepath.Join(wrennDir, "sandboxes",
+		fmt.Sprintf("%s.staging-%d", sandboxID, timeNowNano()))
+}
+
+// SandboxesDir returns the directory for running sandbox CoW files and paused
+// snapshot directories.
 func SandboxesDir(wrennDir string) string {
 	return filepath.Join(wrennDir, "sandboxes")
 }
 
-// KernelPath returns the path to the Firecracker kernel.
+// KernelPath returns the path to the VM kernel.
 func KernelPath(wrennDir string) string {
 	return filepath.Join(wrennDir, "kernels", "vmlinux")
 }