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package main

import (
        "crypto/rsa"
        "crypto/x509"
        "encoding/base64"
        "encoding/json"
        "encoding/pem"
        "flag"
        "fmt"
        "golang.org/x/crypto/ssh"
        "io/ioutil"
        "math/big"
)

type Jwks struct {
        Keys []Key `json:"keys"`
}
type Key struct {
        Kid string `json:"kid"`
        Kty string `json:"kty"`
        Use string `json:"use"`
        N   string `json:"n"`
        E   string `json:"e"`
}

var keyFile string
var keyType string

func getKeyFromPrivate(key []byte) (*rsa.PublicKey){
        parsed, err := ssh.ParseRawPrivateKey(key)
        if err != nil {
                fmt.Println(err)
        }

        // Convert back to an *rsa.PrivateKey
        privateKey := parsed.(*rsa.PrivateKey)

        publicKey := &privateKey.PublicKey
        return publicKey
}

func getKeyFromPublic(key []byte) (*rsa.PublicKey){
        pubPem, _ := pem.Decode(key)

        parsed, err := x509.ParsePKIXPublicKey(pubPem.Bytes)
        if err != nil {
                fmt.Println("Unable to parse RSA public key", err)
        }

        // Convert back to an *rsa.PrivateKeyPublicKey
        publicKey := parsed.(*rsa.PublicKey)

        return publicKey
}

func main() {
        flag.StringVar(&keyFile, "keyFile", "/mnt/c/Users/ktimoney/keycloak-certs/client_pub.key", "Location of key file")
        flag.StringVar(&keyType, "keyType", "public", "Type of key file")
        flag.Parse()

        key, err := ioutil.ReadFile(keyFile)
        if err != nil {
                fmt.Println(err)
        }

        var publicKey *rsa.PublicKey

        if keyType == "public" {
           publicKey = getKeyFromPublic(key)
        }else{
           publicKey = getKeyFromPrivate(key)
        }

        jwksKey := Key{
                "something",
                "RSA",
                "sig",
                base64.RawStdEncoding.EncodeToString(publicKey.N.Bytes()),
                base64.RawStdEncoding.EncodeToString(big.NewInt(int64(publicKey.E)).Bytes()),
        }
        jwksKeys := []Key{jwksKey}
        jwks := Jwks{jwksKeys}

        jwksJson, err := json.Marshal(jwks)
        if err != nil {
                fmt.Println(err)
                return
        }
        fmt.Println(string(jwksJson))

}