#!/bin/sh -e
#
# arc_extract - an extractor for archives created by arc
#
# https://romanzolotarev.com/bin/arc_extract
# Copyright 2018-2019 Roman Zolotarev <hi@romanzolotarev.com>
#

fail() { >&2 echo "$@"; exit 1; }

if test "$1" = '-n'
then dry=1; shift
else dry=0
fi

test -z "$1" && fail "usage: ${0##*/} [-n] <archive>"

f_arch="$(readlink -f "$1")"
f_tree="${f_arch}.tree.gz"
f_dgst="${f_arch}.tree.sha256"

test -f "$f_arch" || fail "$f_arch: no file"
test -f "$f_tree" || fail "$f_tree: no file"
test -f "$f_dgst" || fail "$f_dgst: no file"


# generate the hash from the spec file
# get the hash from sha256 file
# exit if they mismatch
tree=$(gunzip < "$f_tree"|sha256)
dgst=$(cat "$f_dgst")
test "$tree" = "$dgst" ||
fail "$dgst"' (tree.sha256) !=
'"$tree"' (tree.gz|sha256)'


# during "dry run" print out the spec file and
# list all the files from the archive, then exit

if test $dry = 1
then
	gunzip < "$f_tree"
	pax -zvf "$f_arch"
	exit 0
fi


# read (-r) and unzip (-z) the archive from $f_arch and "preserve
# everything" (-pe) (uid, gid, mode, atime, mtime)
pax -pe -rzf "$f_arch"

# unzip the spec file, remove nanoseconds (pax doesn't preserve
# them), check the contents of the current directory with mtree
gunzip < "$f_tree" |
sed 's/time=\([0-9]*\)\.[0-9]*/time=\1.0/' |
mtree