chore: import upstream snapshot with attribution

internal/parser/virtual_source_path.go

@@ -0,0 +1,38 @@
+package parser
+
+import (
+	"path/filepath"
+	"strings"
+)
+
+// VirtualSourcePath identifies one logical source inside a shared physical
+// container path, for example one conversation row inside a SQLite database.
+func VirtualSourcePath(containerPath, sourceID string) string {
+	return containerPath + "#" + sourceID
+}
+
+// ParseVirtualSourcePath splits a path created by VirtualSourcePath.
+func ParseVirtualSourcePath(path string) (string, string, bool) {
+	idx := strings.LastIndex(path, "#")
+	if idx < 0 {
+		return "", "", false
+	}
+	containerPath, sourceID := path[:idx], path[idx+1:]
+	if containerPath == "" || sourceID == "" {
+		return "", "", false
+	}
+	return containerPath, sourceID, true
+}
+
+// ParseVirtualSourcePathForBase splits a virtual source path and verifies that
+// the physical container has the expected base filename.
+func ParseVirtualSourcePathForBase(
+	path string,
+	baseName string,
+) (string, string, bool) {
+	containerPath, sourceID, ok := ParseVirtualSourcePath(path)
+	if !ok || filepath.Base(containerPath) != baseName {
+		return "", "", false
+	}
+	return containerPath, sourceID, true
+}