package go_pgp

import (
	"crypto"
	"errors"
	"fmt"

	// required in order to use the crypto.SHA256- and -SHA512-Hashes
	_ "crypto/sha256"
	_ "crypto/sha512"

	"github.com/ProtonMail/go-crypto/openpgp"
	"github.com/ProtonMail/go-crypto/openpgp/packet"
)

var (
	defaultConfig = packet.Config{
		RSABits:                4096,
		DefaultHash:            crypto.SHA512,
		DefaultCompressionAlgo: packet.CompressionZIP,
		DefaultCipher:          packet.CipherAES256,
		CompressionConfig: &packet.CompressionConfig{
			Level: 5,
		},
	}

	// ErrUndefinedPGPEntity defines the error for a null-reference to an openpgp.Entity
	ErrUndefinedPGPEntity = errors.New("pgp entity undefined")

	// ErrNoData defines the error for missing processable data
	ErrNoData = errors.New("no data to process")
)

type Entity struct {
	openpgp.Entity
	cfg *packet.Config
}

// SetPassword encrypts all contained unencrypted private keys
// using the given passphrase.
func (e *Entity) SetPassword(passphrase []byte) error {
	return e.Entity.EncryptPrivateKeys(passphrase, e.cfg)
}

// CreatePGPEntity creates an OpenPGP Entity with only a name given
func CreatePGPEntity(name string, options ...createOption) (*Entity, error) {
	return createPGPEntity(name, "", "", options...)
}

// CreatePGPEntityEmail creates an OpenPGP Entity with a name and email given
func CreatePGPEntityEmail(name, email string, options ...createOption) (*Entity, error) {
	return createPGPEntity(name, "", email, options...)
}

// CreateCommentedPGPEntity creates an OpenPGP Entity with a name and comment given
func CreateCommentedPGPEntity(name, comment string, options ...createOption) (entity *Entity, err error) {
	return createPGPEntity(name, comment, "", options...)
}

// CreateCommentedPGPEntity creates an OpenPGP Entity with a name and comment given
func createPGPEntity(name, comment, email string, options ...createOption) (entity *Entity, err error) {
	if name == "" && email == "" {
		return nil, fmt.Errorf("name or email must be specified")
	}

	cfg := defaultConfig
	for _, option := range options {
		if option != nil {
			option(&cfg)
		}
	}

	var e *openpgp.Entity
	e, err = openpgp.NewEntity(name, comment, email, &cfg)
	if nil == err {
		for _, identity := range e.Identities {
			if nil != identity && nil != identity.SelfSignature {
				identity.SelfSignature.PreferredHash = []uint8{8, 9, 10} //cf. "golang.org/x/crypto/openpgp/s2k" -> s2k.HashIdToHash
			}
		}
		entity = &Entity{
			Entity: *e,
			cfg:    &cfg,
		}
	}
	return
}