package site

import "strings"

// splitTilde splits a site URL path into its project and the rest.
//
//	"/~proj"        -> ("proj", "",     true)
//	"/~proj/"       -> ("proj", "/",    true)
//	"/~proj/a/b"    -> ("proj", "/a/b", true)
//	"/", "/x", "/~" -> ("", "", false)
//
// The remainder keeps its leading slash, because its absence is what
// distinguishes "/~proj" — which has to be redirected before relative links
// inside the page can resolve — from "/~proj/".
//
// This is hand-parsed rather than expressed as a ServeMux pattern because
// net/http rejects "/~{project}/{path...}": its wildcards must start a path
// segment. Registering "/" instead also keeps the mux's built-in ".." and "//"
// redirects, though those are a convenience and not a defence — a
// percent-encoded traversal arrives here already decoded and unredirected, so
// Resolve does its own normalisation.
func splitTilde(urlPath string) (project, rest string, ok bool) {
	if !strings.HasPrefix(urlPath, "/~") {
		return "", "", false
	}
	rest = urlPath[len("/~"):]
	if i := strings.IndexByte(rest, '/'); i >= 0 {
		project, rest = rest[:i], rest[i:]
	} else {
		project, rest = rest, ""
	}
	if project == "" {
		return "", "", false
	}
	return project, rest, true
}