package cabana

import (
	"fmt"
	"regexp"
	"strings"

	"git.golem15.com/golem15/summercms/modules/backpack"
)

// DefaultAdminPrefix is the admin mount path when backend.uri is unset.
// It matches WinterCMS's backendUri default.
const DefaultAdminPrefix = "/backend"

// AdminCookieName carries the admin JWT for the embedded SPA (D-19).
const AdminCookieName = "summer_admin"

// adminAPIVersion is appended to the prefix for every admin API route.
const adminAPIVersion = "/api/v1"

var adminPrefixPattern = regexp.MustCompile(`^(/[a-z0-9][a-z0-9_-]*)+$`)

// AdminPrefix reads backend.uri and returns the normalized admin mount path.
// Spaces are trimmed, a leading slash is added and trailing slashes are
// removed; an empty value falls back to DefaultAdminPrefix. Every segment
// must be lowercase letters, digits, '-' or '_' and start with a letter or
// digit, so "/" alone, uppercase, spaces and dot segments are rejected.
func AdminPrefix(app *backpack.App) (string, error) {
	raw := ""
	if app != nil && app.Config != nil {
		raw = app.Config.String("backend.uri")
	}
	return normalizeAdminPrefix(raw)
}

func normalizeAdminPrefix(raw string) (string, error) {
	value := strings.TrimSpace(raw)
	if value == "" {
		return DefaultAdminPrefix, nil
	}
	if !strings.HasPrefix(value, "/") {
		value = "/" + value
	}
	value = strings.TrimRight(value, "/")
	if value == "" || !adminPrefixPattern.MatchString(value) {
		return "", fmt.Errorf("cabana: backend.uri %q is invalid: use one or more lowercase path segments such as /backend (set SUMMER_BACKEND__URI)", raw)
	}
	return value, nil
}