/*
glocate -- ZFS-diff-friendly locate-like utility
Copyright (C) 2022-2023 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"
	"io"
	"log"

	"github.com/klauspost/compress/zstd"
)

func mustReadFull(r io.Reader, buf []byte) {
	if _, err := io.ReadFull(r, buf); err != nil {
		log.Fatalln(err)
	}
}

func reader(src io.Reader, sink chan Ent) {
	comp, err := zstd.NewReader(src)
	if err != nil {
		log.Fatalln(err)
	}
	br := bufio.NewReaderSize(comp, 1<<17)

	num := make([]byte, 8)
	var cols []string
	var namePrev string
	var nameLen uint16
	var depth, depthPrev uint8
	for {
		_, err = io.ReadFull(br, num[:2])
		if err != nil {
			if err == io.EOF {
				break
			}
			log.Fatalln(err)
		}
		nameLen = binary.BigEndian.Uint16(num[:2])
		nameRaw := make([]byte, nameLen)
		mustReadFull(br, nameRaw)
		name := string(nameRaw)
		mustReadFull(br, num[:1])
		depth = uint8(num[0])
		mustReadFull(br, num)
		ent := Ent{mtime: int64(binary.BigEndian.Uint64(num))}
		mustReadFull(br, num)
		ent.size = int64(binary.BigEndian.Uint64(num))
		if depth > depthPrev {
			cols = append(cols, namePrev[:len(namePrev)-1])
		} else if depth < depthPrev {
			cols = cols[:len(cols)-int(depthPrev-depth)]
		}
		ent.name = append([]string{}, append(cols, name)...)
		sink <- ent
		namePrev = name
		depthPrev = depth
	}
	close(sink)
	comp.Close()
}