#! /bin/sh -e

badp=nil
myarch=$(dpkg-architecture -qDEB_HOST_ARCH)
while getopts "a:" opt; do
  case $opt in
    a) myarch=$OPTARG ;;
    *) badp=t ;;
  esac
done
shift $(( $OPTIND - 1 ))
case $# in 0) badp=t ;; esac
case $badp in
  t)
    cat >&2 <<EOF
usage: $0 [-a MYARCH] DIST ...
EOF
    exit 1
    ;;
esac
for arg in "$@"; do
  case $arg in *-*) echo >&2 "$0: bad arch name \`$arg'"; exit 1 ;; esac
done
mymulti=$(dpkg-architecture -a$myarch -qDEB_HOST_MULTIARCH)

cross_archs="arm-linux-gnueabi arm-linux-gnueabihf aarch64-linux-gnu"
cross_pkgs="
	apt bash ccache coreutils dash eatmydata fakeroot findutils
	gnupg gpgv gzip m4 make mawk qemu-user-static sed tar xz-utils"
for a in $cross_archs; do
  for i in gcc g++ binutils; do
    cross_pkgs="$cross_pkgs $i-$a"
  done
done
cross_pkgs=$(echo $cross_pkgs)

wanted="
	/usr/bin/ apt apt-cache apt-config apt-get apt-key apt-mark
	/usr/lib/apt/ methods/ solvers/

	/bin/ cat chgrp chown cp date dd df dir echo false ln ls mkdir
		mknod mktemp mv pwd readlink rm rmdir sleep stty sync touch
		true uname vdir
	/usr/bin/ [ arch b2sum base32 base64 basename chcon cksum comm
		csplit cut dircolors dirname du env expand expr factor fmt
		fold groups head hostid id install join link logname md5sum
		mkfifo nice nl nohup nproc numfmt od paste pathchk pinky pr
		printenv printf ptx realpath runcon seq sha1sum sha224sum
		sha256sum sha384sum sha512sum shred shuf sort split stat
		stdbuf sum tac tail tee test timeout tr truncate tsort tty
		unexpand uniq unlink users wc who whoami yes
	/usr/lib/$mymulti/ coreutils/

	/lib/$mymulti/ libnss_*.so.*

	/usr/bin/ gpg gpgv gpgconf kbxutil watchgnupg

	/usr/bin/ qemu-*-static

	/bin/ bash dash gzip sed tar
	/usr/bin/ ccache find m4 make mawk xargs xz
	/usr/lib/$mymulti/ libeatmydata.so* libfakeroot/

	/etc/ld.so.conf.d/ $mymulti.conf fakeroot*.conf"

for a in $cross_archs; do
  wanted="$wanted

	/usr/bin/$a- addr2line ar as c++filt dwp elfedit gprof ld ld.*
		nm objcopy objdump ranlib readelf size strings strip

	/usr/bin/$a- cpp gcc g++ gcov gcov-dump gcov-tool gprof
		gcc-ar gcc-nm gcc-ranlib
	/usr/lib/gcc-cross/$a/ ..."
done
wanted=$(echo $wanted)

case $myarch in
  i386) elfsig=7f454c46010101??0000000000000000????0300 ;;
  amd64) elfsig=7f454c46020101??0000000000000000????3e00 ;;
  *) echo >&2 "$0: unsupported local arch \`$myarch'"; exit 1 ;;
esac

chase_link () {
  p=$1 d=
  while :; do
    case $p in
      "") break ;;
      "/"*) p=${p#/} ;;
      "./"*) p=${p#./} ;;
      "../"*)
	p=${p#../}
	case $d in */*) d=${d%/*} ;; *) d= ;; esac
	;;
      *)
	case $p in */*) f=${p%%/*} p=${p#*/} ;; *) f=$p p="" ;; esac
	d=${d:+$d/}$f
	;;
    esac
    if ! [ -e "$crossnew$d" ] && ! [ -L "$crossnew$d" ]; then
      if [ -d "$root/$d" ] &&  ! [ -L "$root/$d" ]; then
	mkdir "$crossnew$d"
      else
	echo >&2 "$0: copy /$d to satisfy symlinks"
	rsync -aHR $root/./$d $crossnew
      fi
    fi
    if [ -L "$crossnew$d" ]; then
      t=$(readlink "$crossnew$d")
      case $t in /*) t=${t#/} d= ;; esac
      case $d in */*) d=${d%/*} ;; *) d= ;; esac
      p=$t${p:+/$p}
    fi
  done
}

exec 3>&1
for d in "$@"; do
  echo >&2 "$0: create $d snapshot"
  sess=$(schroot -bc$d-$myarch 3>&-)
  schroot -uroot -rc$sess -- eatmydata sh -ec "
	apt-get update
	apt-get -y upgrade
	apt-get -y install $cross_pkgs"
  crossdir=/usr/local.schroot/cross/$d-$myarch/
  crossold=${crossdir%/}.old/ crossnew=${crossdir%/}.new/
  rm -rf $crossnew; mkdir -p $crossnew

  root=/schroot/$sess/fs; dir=/
  for i in $wanted; do
    case $i in
      /*)
	dir=$i
	;;
      *)
	case $i in ...) f=$dir ;; *) f=$dir$i ;; esac
	echo >&2 "$0: copy $f"
	rsync -aHR $root/.$f $crossnew
	;;
    esac
  done

  find $crossnew -xtype l -print | while read i; do
    chase_link ${i#$crossnew}
  done

  find $crossnew -type f -print | while read i; do
    sig=$(head -c20 "$i" | bincode -e -m0 -flowerc hex)
    case $sig in $elfsig) echo "$i" ;; esac
  done >$root/private/QUEUE.in

  counter=0
  cp $root/private/QUEUE.in /tmp/mdw/queue.in.$counter

  while [ -s $root/private/QUEUE.in ]; do
    schroot -uroot -rc$sess -- eatmydata sh -ec '
	prog=$1
	while read i; do
	echo >&2 "$prog: scanning binary $i"
	  ldd "$i" | while read a b c d; do
	    case $a:$b:$c:$d in
	      not:a:dynamic:executable) ;;
	      statically:linked::) ;;
	      /*) echo "$a" ;;
	      *:=\>:/*) echo "$c" ;;
	      linux-*) ;;
	      *) echo >&2 "$i: unable to find $a"; exit 2 ;;
	    esac
	  done
	done </private/QUEUE.in >/private/QUEUE.out' - "$0"

    cp $root/private/QUEUE.out /tmp/mdw/queue.out.$counter
    counter=$(( $counter + 1 ))

    while read i; do
      if [ -e "$crossnew$i" ] || [ -L "$crossnew$i" ]
      then continue; fi
      if [ -d "$root$i" ]; then continue; fi
      echo >&2 "$0: copy $i"
      rsync -aHR $root/.$i $crossnew >&3
      chase_link $i >&3
      sig=$(head -c20 $crossnew$i | bincode -e -m0 -flowerc hex)
      case $sig in $elfsig) echo "$i" ;; esac
    done <$root/private/QUEUE.out >$root/private/QUEUE.in

    cp $root/private/QUEUE.in /tmp/mdw/queue.in.$counter

  done

  echo >&2 "$0: establish TOOLCHAIN"
  for a in $cross_archs; do
    tooldir=$crossnew/TOOLCHAIN/$a
    mkdir -p $tooldir
    for i in $crossnew/usr/bin/$a-*; do
      t=${i#$crossnew/usr/bin/}
      mv $i $tooldir/$t
      ln -s $t $tooldir/${t#$a-}
    done
  done
  mkdir $crossnew/TOOLCHAIN/lib
  ln -s ../../usr/lib/gcc-cross $crossnew/TOOLCHAIN/lib/

  echo >&2 "$0: establish QEMU"
  mkdir $crossnew/QEMU
  mv $crossnew/usr/bin/qemu-*-static $crossnew/QEMU/

  echo >&2 "$0: remove snapshot"
  schroot -ec$sess 3>&-
  if [ -d $crossdir ]; then mv $crossdir $crossold; fi
  mv $crossnew $crossdir; rm -rf $crossold
  echo >&2 "$0: committed $crossdir"
done