package main

import (
	"flag"
	"fmt"
	"io"
	"os"

	"github.com/slackhq/nebula/pkclient"

	"github.com/slackhq/nebula/cert"
)

type keygenFlags struct {
	set        *flag.FlagSet
	outKeyPath *string
	outPubPath *string
	curve      *string
	p11url     *string
}

func newKeygenFlags() *keygenFlags {
	cf := keygenFlags{set: flag.NewFlagSet("keygen", flag.ContinueOnError)}
	cf.set.Usage = func() {}
	cf.outPubPath = cf.set.String("out-pub", "", "Required: path to write the public key to")
	cf.outKeyPath = cf.set.String("out-key", "", "Required: path to write the private key to")
	cf.curve = cf.set.String("curve", "25519", "ECDH Curve (25519, P256)")
	cf.p11url = p11Flag(cf.set)
	return &cf
}

func keygen(args []string, out io.Writer, errOut io.Writer) error {
	cf := newKeygenFlags()
	err := cf.set.Parse(args)
	if err != nil {
		return err
	}

	isP11 := len(*cf.p11url) > 0

	if !isP11 {
		if err = mustFlagString("out-key", cf.outKeyPath); err != nil {
			return err
		}
	}
	if err = mustFlagString("out-pub", cf.outPubPath); err != nil {
		return err
	}

	var pub, rawPriv []byte
	var curve cert.Curve
	if isP11 {
		switch *cf.curve {
		case "P256":
			curve = cert.Curve_P256
		default:
			return fmt.Errorf("invalid curve for PKCS#11: %s", *cf.curve)
		}
	} else {
		switch *cf.curve {
		case "25519", "X25519", "Curve25519", "CURVE25519":
			pub, rawPriv = x25519Keypair()
			curve = cert.Curve_CURVE25519
		case "P256":
			pub, rawPriv = p256Keypair()
			curve = cert.Curve_P256
		default:
			return fmt.Errorf("invalid curve: %s", *cf.curve)
		}
	}

	if isP11 {
		p11Client, err := pkclient.FromUrl(*cf.p11url)
		if err != nil {
			return fmt.Errorf("error while creating PKCS#11 client: %w", err)
		}
		defer func(client *pkclient.PKClient) {
			_ = client.Close()
		}(p11Client)
		pub, err = p11Client.GetPubKey()
		if err != nil {
			return fmt.Errorf("error while getting public key: %w", err)
		}
	} else {
		err = os.WriteFile(*cf.outKeyPath, cert.MarshalPrivateKeyToPEM(curve, rawPriv), 0600)
		if err != nil {
			return fmt.Errorf("error while writing out-key: %s", err)
		}
	}
	err = os.WriteFile(*cf.outPubPath, cert.MarshalPublicKeyToPEM(curve, pub), 0600)
	if err != nil {
		return fmt.Errorf("error while writing out-pub: %s", err)
	}

	return nil
}

func keygenSummary() string {
	return "keygen <flags>: create a public/private key pair. the public key can be passed to `nebula-cert sign`"
}

func keygenHelp(out io.Writer) {
	cf := newKeygenFlags()
	_, _ = out.Write([]byte("Usage of " + os.Args[0] + " " + keygenSummary() + "\n"))
	cf.set.SetOutput(out)
	cf.set.PrintDefaults()
}