// Package controlsock names the root instance-control channel (design
// §5). It is a leaf package with no internal imports so both
// internal/provision and internal/unixdial can depend on it without an
// import cycle: provision already imports internal/release (for the
// store), and internal/release's unix dial sites need
// unixdial.Checked — which must know the control endpoint's path
// without pulling provision (and therefore release) back in.
package controlsock

import (
	"path/filepath"
	"strings"
)

// Dir and Path are the root instance-control channel (design §5).
// Deliberately NOT under provision.SocketDir: an instance's namespace
// replaces /run/carlos with an empty tmpfs, and nothing an instance can
// reach must resolve to this path.
const (
	Dir  = "/run/carlos-control"
	Path = Dir + "/control.sock"
)

// IsEndpoint reports whether path is the control channel or anything
// else under its directory. The edge and the agent refuse to dial such a
// path as an upstream (design §5.4): a registry row pointing at it is
// refused before connect().
func IsEndpoint(path string) bool {
	clean := filepath.Clean(path)
	return clean == Dir || strings.HasPrefix(clean, Dir+"/")
}