// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

// signFile reads the contents of an input file and signs it (in armored format)
// with the key provided, placing the signature into the output file.

package build

import (
	"bytes"
	"fmt"
	"os"

	"golang.org/x/crypto/openpgp"
)

// PGPSignFile parses a PGP private key from the specified string and creates a
// signature file into the output parameter of the input file.
//
// Note, this method assumes a single key will be container in the pgpkey arg,
// furthermore that it is in armored format.
func PGPSignFile(input string, output string, pgpkey string) error {
	// Parse the keyring and make sure we only have a single private key in it
	keys, err := openpgp.ReadArmoredKeyRing(bytes.NewBufferString(pgpkey))
	if err != nil {
		return err
	}
	if len(keys) != 1 {
		return fmt.Errorf("key count mismatch: have %d, want %d", len(keys), 1)
	}
	// Create the input and output streams for signing
	in, err := os.Open(input)
	if err != nil {
		return err
	}
	defer in.Close()

	out, err := os.Create(output)
	if err != nil {
		return err
	}
	defer out.Close()

	// Generate the signature and return
	return openpgp.ArmoredDetachSign(out, keys[0], in, nil)
}

// PGPKeyID parses an armored key and returns the key ID.
func PGPKeyID(pgpkey string) (string, error) {
	keys, err := openpgp.ReadArmoredKeyRing(bytes.NewBufferString(pgpkey))
	if err != nil {
		return "", err
	}
	if len(keys) != 1 {
		return "", fmt.Errorf("key count mismatch: have %d, want %d", len(keys), 1)
	}
	return keys[0].PrimaryKey.KeyIdString(), nil
}