Fix malformed URL query

fix-url.go

// Fix (some kinds of) malformed URLs

package main

import (
	"fmt"
	"log"
	"net/url"
)

func main() {
	s := "https://boulanger.scene7.com/is/image/Boulanger/bfr_overlay?layer=comp&$t1=&$product_id=Boulanger/6901443378982_h_f_l_0&$i3=playstore non installé&wid=170&hei=170&fmt=jpg&qlt=85,0&resMode=sharp2&op_usm=1.75,0.3,2,0"
	u, err := url.Parse(s)
	if err != nil {
		log.Fatal(err)
	}

	if u.RawQuery != "" {
		i := 0
		var b []byte
		for j := 0; j < len(u.RawQuery); j++ {
			c := u.RawQuery[j]
			switch {
			case c >= 127 || c <= ' ':
				fmt.Println(c)
				if j > i {
					if i == 0 {
						b = make([]byte, 0, len(u.RawQuery)+2)
					}
					b = append(b, u.RawQuery[i:j]...)
					i = j
				}
				if c == ' ' {
					b = append(b, '+')
				} else {
					b = append(b, '%')
					const upperhex = "0123456789ABCDEF"
					b = append(b, upperhex[c>>4])
					b = append(b, upperhex[c&15])
				}
				i++
			default:
			}
		}
		if i > 0 {
			u.RawQuery = string(append(b, u.RawQuery[i:]...))
		}

	}
	u.Opaque = ""

	fmt.Println("Original:", s)
	fmt.Println("Fix:     ", u.String())
}