Add artifact workdir layout and locking

internal/artifacts/store.go

@@ -1,19 +1,27 @@
 package artifacts
 
-import "context"
+import "os"
 
-// Ref identifies a pipeline artifact and optional remote location.
+// Ref identifies a pipeline artifact and its local/remote coordinates.
 type Ref struct {
-	Kind      string
-	LocalPath string
-	RemoteKey string
-	Checksum  string
+	Kind         string
+	Category     string
+	SessionID    string
+	RelativePath string
+	AbsolutePath string
+	RemoteKey    string
+	Checksum     string
 }
 
-// Store is a placeholder artifact storage abstraction.
+// Store is the local artifact/workdir abstraction used by orchestration code.
 type Store interface {
-	WriteLocal(ctx context.Context, ref Ref, data []byte) error
-	ReadLocal(ctx context.Context, ref Ref) ([]byte, error)
-	ExistsLocal(ctx context.Context, ref Ref) (bool, error)
-	Upload(ctx context.Context, ref Ref) (string, error)
+	SessionPaths(sessionID string) SessionPaths
+	EnsureLayout(sessionID string) (SessionPaths, error)
+	CopyInput(sessionID, srcPath, destRelativePath string) (Ref, error)
+	Exists(path string) (bool, error)
+	ExistsRef(ref Ref) (bool, error)
+	WriteFileAtomic(path string, data []byte, perm os.FileMode) error
+	Checksum(path string) (string, error)
+	AcquireSessionLock(sessionID string) (*LockHandle, error)
+	ReleaseSessionLock(lock *LockHandle) error
 }