// Package notariusref owns Narratio's Notarius CLI reference-selector
// vocabulary without depending on Notarius implementation packages.
package notariusref

import (
	"fmt"
	"strings"
)

// NormalizeSelector validates and normalizes a Notarius v0.6 reference
// selector. It intentionally validates selector structure only; Notarius owns
// target, slot, and media compatibility.
func NormalizeSelector(value string) (string, error) {
	selector := strings.TrimSpace(value)
	if selector == "" {
		return "", fmt.Errorf("reference selector is required")
	}
	if strings.Contains(selector, "=") {
		return "", fmt.Errorf("reference selector must not contain '='")
	}

	parts := strings.Split(selector, ".")
	for index := range parts {
		parts[index] = strings.TrimSpace(parts[index])
		if parts[index] == "" {
			return "", fmt.Errorf("reference selector components must not be empty")
		}
	}

	switch len(parts) {
	case 1, 2:
		return strings.Join(parts, "."), nil
	case 3:
		switch parts[1] {
		case "extract", "merge", "normalize":
			return strings.Join(parts, "."), nil
		default:
			return "", fmt.Errorf("three-component reference selector must use extract, merge, or normalize as its middle component")
		}
	default:
		return "", fmt.Errorf("reference selector must use slot, chunk.slot, lane.slot, or lane.stage.slot")
	}
}