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newCode.go
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newCode.go
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package code
import (
"math"
"math/bits"
"strings"
"time"
"github.com/Mobilpadde/moths/v5/token/emojies"
)
const EmojiBytes = 4
func NewCode(token string, amount int, em emojies.Emojies, createdAt time.Time, expiresAt time.Time) (Code, error) {
code, err := generateCode(token, amount, em)
if err != nil {
return Code{}, err
}
return Code{
token: token,
emojies: code,
createdAt: createdAt,
expiresAt: expiresAt,
}, nil
}
func generateCode(token string, amount int, em emojies.Emojies) (emojies.Emojies, error) {
emojiAmount := len(em)
size := EmojiBytes * amount
code := strings.Builder{}
code.Grow(size)
buffer := bufferFromToken(token)
// https://github.com/tilaklodha/google-authenticator
mask := 2<<uint32(31-bits.LeadingZeros32(uint32(emojiAmount-1|1))) - 1
step := int(math.Ceil(1.6 * float64(mask*size) / float64(emojiAmount)))
loop:
for {
randomBuffer, err := buffer(step)
if err != nil {
return emojies.EMPTY, err
}
for i := 0; i < step; i++ {
currentIndex := int(randomBuffer[i]) & mask
if currentIndex < emojiAmount {
if _, err := code.WriteRune(em[currentIndex]); err != nil {
return emojies.EMPTY, err
} else if code.Len() == size {
break loop
}
if code.Len() > size {
code.Reset()
}
}
}
}
split := strings.Split(code.String(), "")
return emojies.ToEmojies(split), nil
}