// Package classes holds the menu plugin's link rules and the tree the public
// API serves.
package classes

import "strings"

// AllowedURL reports whether an entry URL may be stored and served: empty, a
// path starting with "/", a fragment starting with "#", or an absolute
// http, https, mailto or tel URL (case-insensitive). Anything else, such as
// javascript: or data:, is refused, and so is a URL with surrounding
// whitespace or control characters, which browsers strip before reading the
// scheme (RESEARCH Pitfall 15).
func AllowedURL(url string) bool {
	if url == "" {
		return true
	}
	for _, r := range url {
		if r < 0x20 || r == 0x7f {
			return false
		}
	}
	if strings.TrimSpace(url) != url {
		return false
	}
	if url[0] == '/' || url[0] == '#' {
		return true
	}
	lower := strings.ToLower(url)
	for _, prefix := range []string{"http://", "https://", "mailto:", "tel:"} {
		if strings.HasPrefix(lower, prefix) {
			return true
		}
	}
	return false
}

// The link targets an entry may open in.
const (
	TargetSelf  = "_self"
	TargetBlank = "_blank"
)

// AllowedTarget reports whether target is _self, _blank or empty.
func AllowedTarget(target string) bool {
	return target == "" || target == TargetSelf || target == TargetBlank
}