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clienthints.go
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/
clienthints.go
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package mimic
import (
"fmt"
"strings"
)
type Brand string
var (
legacyGreasyChars = []string{" ", " ", ";"}
greasyChars = []string{" ", "(", ":", "-", ".", "/", ")", ";", "=", "?", "_"}
greasyVersion = []string{"8", "99", "24"}
greasyOrders = [][]int{
{0, 1, 2}, {0, 2, 1}, {1, 0, 2},
{1, 2, 0}, {2, 0, 1}, {2, 1, 0},
}
BrandChrome Brand = "Google Chrome"
)
func formatBrand(brand Brand, majorVersion string) string {
return fmt.Sprintf(`"%s";v="%s"`, brand, majorVersion)
}
func greasedBrand(seed int, majorVersionNumber int, permutedOrder []int) string {
var brand, version string
switch {
case majorVersionNumber <= 102, majorVersionNumber == 104:
brand = fmt.Sprintf("%sNot%sA%sBrand", legacyGreasyChars[permutedOrder[0]], legacyGreasyChars[permutedOrder[1]], legacyGreasyChars[permutedOrder[2]])
version = "99"
case majorVersionNumber == 103:
brand = fmt.Sprintf("%sNot%sA%sBrand", greasyChars[(seed%(len(greasyChars)-1))+1], greasyChars[(seed+1)%len(greasyChars)], greasyChars[(seed+2)%len(greasyChars)])
version = greasyVersion[seed%len(greasyVersion)]
default: // >=105
// https://github.com/WICG/ua-client-hints/pull/310
brand = fmt.Sprintf("Not%sA%sBrand", greasyChars[seed%len(greasyChars)], greasyChars[(seed+1)%len(greasyChars)])
version = greasyVersion[seed%len(greasyVersion)]
}
return formatBrand(Brand(brand), version)
}
func clientHintUA(brand Brand, majorVersion string, majorVersionNumber int) string {
seed := majorVersionNumber
if majorVersionNumber <= 102 {
// legacy behavior (maybe a bug?)
seed = 0
}
order := greasyOrders[seed%len(greasyOrders)]
greased := make([]string, 3)
greased[order[0]] = greasedBrand(seed, majorVersionNumber, order)
greased[order[1]] = formatBrand("Chromium", majorVersion)
greased[order[2]] = formatBrand(brand, majorVersion)
return strings.Join(greased, ", ")
}