package main

import (
	"fmt"
	"strings"
)

func ProcUSB(devpath string) (segment string, err error) {
	var (
		bus, conf, iface int
		port_path        []int
		work             string
	)

	res := strings.Split(devpath, ":")
	if len(res) != 2 {
		err = ErrInvalidUSBFormat
		return
	}

	// Bus and ports
	if _, err = fmt.Sscanf(res[0], "%d-%s", &bus, &work); err != nil {
		err = ErrInvalidUSBFormat
		return
	}

	for _, v := range strings.Split(work, ".") {
		var cp int
		if _, err = fmt.Sscanf(v, "%d", &cp); err != nil {
			err = ErrInvalidUSBFormat
			return
		}
		port_path = append(port_path, cp)
	}

	// Configuration and interface
	if _, err = fmt.Sscanf(res[1], "%d.%d", &conf, &iface); err != nil {
		err = ErrInvalidUSBFormat
		return
	}

	var b strings.Builder
	for _, v := range port_path {
		b.WriteString(fmt.Sprintf("u%d", v))
	}
	b.WriteString(fmt.Sprintf("i%d", iface))
	segment = b.String()
	return
}