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package signify

import (
	"bufio"
	"bytes"
	"encoding/base64"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"strings"
)

type EncFile struct {
	Comment string
	Enc     *EncKey
}

func ParseEnc(r io.Reader) (*EncFile, error) {
	comment, raw, _, err := read(r)
	if err != nil {
		return nil, err
	}
	enc := new(EncKey)
	if err := Unmarshal(raw, enc); err != nil {
		return nil, err
	}
	return &EncFile{Comment: comment, Enc: enc}, nil
}

func WriteEnc(w io.Writer, enc *EncFile) error {
	raw, err := Marshal(enc.Enc)
	if err != nil {
		return err
	}
	return write(w, enc.Comment, raw, nil)
}

type PubFile struct {
	Comment string
	Pub     *PubKey
}

func ParsePub(r io.Reader) (*PubFile, error) {
	comment, raw, _, err := read(r)
	if err != nil {
		return nil, err
	}
	pub := new(PubKey)
	if err := Unmarshal(raw, pub); err != nil {
		return nil, err
	}
	return &PubFile{Comment: comment, Pub: pub}, nil
}

type SigFile struct {
	Comment string
	Sig     *Sig
	Message []byte
}

func WritePub(w io.Writer, pub *PubFile) error {
	raw, err := Marshal(pub.Pub)
	if err != nil {
		return err
	}
	return write(w, pub.Comment, raw, nil)
}

func ParseSig(r io.Reader) (*SigFile, error) {
	comment, raw, message, err := read(r)
	if err != nil {
		return nil, err
	}
	sig := new(Sig)
	if err := Unmarshal(raw, sig); err != nil {
		return nil, err
	}
	return &SigFile{Comment: comment, Sig: sig, Message: message}, nil
}

func WriteSig(w io.Writer, sig *SigFile) error {
	raw, err := Marshal(sig.Sig)
	if err != nil {
		return err
	}
	return write(w, sig.Comment, raw, sig.Message)
}

type File struct {
	Comment string
	RawKey  []byte
	Message []byte
}

const (
	commentHdr = "untrusted comment:"
	sigFrom    = "signature from %s"
)

var (
	ErrCommentSize      = errors.New("comment line to long")
	ErrUntrustedComment = errors.New("expected untrusted comment")
)

func checkComment(comment string) error {
	// compatibility with original version
	if len(comment) > 1024 {
		return ErrCommentSize
	}
	if !strings.HasPrefix(comment, commentHdr) {
		return ErrUntrustedComment
	}
	return nil
}

func (f *File) Embedded() bool {
	return len(f.Message) > 0
}

func read(r io.Reader) (string, []byte, []byte, error) {
	buf := bufio.NewReader(r)
	comment, err := buf.ReadString('\n')
	if err != nil {
		return "", nil, nil, err
	}
	if err := checkComment(comment); err != nil {
		return "", nil, nil, err
	}
	comment = strings.TrimSpace(comment[len(commentHdr):])
	raw, err := buf.ReadString('\n')
	if err != nil {
		return "", nil, nil, err
	}
	rawKey, err := base64.StdEncoding.DecodeString(raw)
	if err != nil {
		return "", nil, nil, err
	}
	message, err := ioutil.ReadAll(buf)
	if err != nil {
		return "", nil, nil, err
	}
	return comment, rawKey, message, nil
}

func (f *File) ReadFrom(r io.Reader) (err error) {
	f.Comment, f.RawKey, f.Message, err = read(r)
	if err != nil {
		return err
	}
	return nil
}

func Parse(b []byte) (*File, error) {
	r := bytes.NewReader(b)
	f := new(File)
	return f, f.ReadFrom(r)
}

func ParseFile(fname string) (*File, error) {
	fd, err := os.Open(fname)
	if err != nil {
		return nil, err
	}
	defer fd.Close()
	f := new(File)
	return f, f.ReadFrom(fd)
}

func (f File) Bytes() ([]byte, error) {
	buf := new(bytes.Buffer)
	err := f.WriteTo(buf)
	if err != nil {
		return nil, err
	}
	return buf.Bytes(), nil
}

func write(w io.Writer, comment string, key, message []byte) error {
	fmt.Fprintln(w, commentHdr, comment)
	fmt.Fprintln(w, base64.StdEncoding.EncodeToString(key))
	if message != nil {
		w.Write(message)
	}
	return nil
}

func (f File) WriteTo(w io.Writer) error {
	return write(w, f.Comment, f.RawKey, f.Message)
}

const (
	SecMode os.FileMode = 0600
	PubMode os.FileMode = 0644
)

func (f File) WriteFile(fname string, perm os.FileMode) error {
	fd, err := os.OpenFile(fname, os.O_WRONLY|os.O_CREATE, perm)
	if err != nil {
		return err
	}
	defer fd.Close()
	return f.WriteTo(fd)
}