package proxy

import (
	"net/url"
	"strings"
)

// JoinPathPrefix builds the upstream URL the same way as aggregate FetchTelemtGET:
// base URL + path_prefix (e.g. /v1) + rest (e.g. health, stats/users) via url.JoinPath.
func JoinPathPrefix(base *url.URL, pathPrefix, rest string) *url.URL {
	rel := strings.Trim(pathPrefix, "/")
	if rest != "" {
		if rel != "" {
			rel = rel + "/" + rest
		} else {
			rel = rest
		}
	}
	var parts []string
	for _, seg := range strings.Split(rel, "/") {
		if seg != "" {
			parts = append(parts, seg)
		}
	}
	if len(parts) == 0 {
		out := *base
		return &out
	}
	return base.JoinPath(parts...)
}