package main

import (
	"encoding/pem"
	"fmt"
	"io"
	"log"
	"os"

	"github.com/lestrrat-go/jwx/v2/jwk"
)

func main() {
	// Read the JWK from standard input.
	jwkBytes, err := io.ReadAll(os.Stdin)
	if err != nil {
		log.Fatalf("failed to read from stdin: %s", err)
	}

	// Parse the JWK.
	key, err := jwk.ParseKey(jwkBytes)
	if err != nil {
		log.Fatalf("failed to parse JWK: %s", err)
	}

	// Get the public key.
	var rawPublicKey interface{}
	if err := key.Raw(&rawPublicKey); err != nil {
		log.Fatalf("failed to get raw public key: %s", err)
	}

	// Encode the public key to PEM format. [4]
	pemBytes, err := jwk.EncodePEM(key)
	if err != nil {
		log.Fatalf("failed to encode public key to PEM: %s", err)
	}

	// Write the PEM encoded public key to standard output.
	block, _ := pem.Decode(pemBytes)
	if block == nil {
		log.Fatal("failed to decode PEM block")
	}

	if err := pem.Encode(os.Stdout, block); err != nil {
		log.Fatalf("failed to write PEM block to stdout: %s", err)
	}

	fmt.Println()
}