/*
goredo -- redo implementation on pure Go
Copyright (C) 2020 Sergey Matveev <stargrave@stargrave.org>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, version 3 of the License.

This program 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 General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

package main

import (
	"bufio"
	"encoding/binary"
	"encoding/hex"
	"errors"
	"io"
	"strings"
	"time"
)

const (
	TAI64NSize     = 12
	TAI64NBase     = 0x400000000000000a
	TAI64NLocalFmt = "2006-01-02 15:04:05.000000000"
)

type TAI64N [TAI64NSize]byte

func tai64nNow(ts *TAI64N) {
	t := time.Now()
	binary.BigEndian.PutUint64(ts[:], uint64(TAI64NBase)+uint64(t.Unix()))
	binary.BigEndian.PutUint32(ts[8:], uint32(t.Nanosecond()))
}

func tai64nLocal(dst io.StringWriter, src io.Reader) error {
	scanner := bufio.NewScanner(src)
	var err error
	var s string
	var sep int
	var ts []byte
	var secs int64
	var nano int64
	var t time.Time
	for {
		if !scanner.Scan() {
			if err = scanner.Err(); err != nil {
				return err
			}
			break
		}
		s = scanner.Text()

		if s[0] != '@' {
			dst.WriteString(s + "\n")
		}
		sep = strings.IndexByte(s, byte(' '))
		if sep == -1 {
			dst.WriteString(s + "\n")
		}
		ts, err = hex.DecodeString(s[1:sep])
		if err != nil {
			return err
		}
		if len(ts) != TAI64NSize {
			return errors.New("invalid ts length")
		}
		secs = int64(binary.BigEndian.Uint64(ts[:8]))
		nano = int64(binary.BigEndian.Uint32(ts[8:]))
		t = time.Unix(secs-TAI64NBase, nano)
		dst.WriteString(t.Format(TAI64NLocalFmt) + s[sep:] + "\n")
	}
	return nil
}