#!/bin/bash
# Copyright (C) 2016 Ian Kelling
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# usage: mount-latest-subvol

[[ $EUID == 0 ]] || exec sudo -E "$BASH_SOURCE" "$@"

errcatch() {
    set -E; shopt -s extdebug
    _err-trap() {
        err=$?
        exec >&2
        set +x
        echo "${BASH_SOURCE[1]}:${BASH_LINENO[0]}:in \`$BASH_COMMAND' returned $err"
        bash-trace 2
        echo "$0: exiting with code $err"
        exit $err
    }
    trap _err-trap ERR
    set -o pipefail
}
bash-trace() {
    local -i argc_index=0 frame i start=${1:-1} max_indent=8 indent
    local source
    local extdebug=false
    if [[ $(shopt -p extdebug) == *-s* ]]; then
        extdebug=true
    fi

    for ((frame=0; frame < ${#FUNCNAME[@]}-1; frame++)); do
        argc=${BASH_ARGC[frame]}
        argc_index+=$argc
        ((frame < start)) && continue
        if (( ${#BASH_SOURCE[@]} > 1 )); then
            source="${BASH_SOURCE[frame+1]}:${BASH_LINENO[frame]}:"
        fi
        indent=$((frame-start+1))
        indent=$((indent < max_indent ? indent : max_indent))
        printf "%${indent}s↳%sin \`%s" '' "$source" "${FUNCNAME[frame]}"
        if $extdebug; then
            for ((i=argc_index-1; i >= argc_index-argc; i--)); do
                printf " %s" "${BASH_ARGV[i]}"
            done
        fi
        echo \'
    done
}
errcatch

tu() {
    while read -r line; do
        file="$1"
        grep -xFq "$line" "$file" || tee -a "$file"<<<"$line"
    done
}
e() { printf "%s\n" "$*"; "$@"; }
mnt() {
    dir=$1
    if ! mountpoint $dir &>/dev/null; then
        mkdir -p $dir
        e mount $dir
    fi
}
fstab() {
    while read -r start mpoint end; do
        l="$start $mpoint $end"
        # kill off any lines that duplicate the mount point.
        sed --follow-symlinks -ri "\%$l%b;\%^\s*\S+\s+$mpoint\s%d" /etc/fstab
        tu /etc/fstab <<<"$l"
    done
}
kill-dir() {
    found_pids=false
    sig=${1:-TERM}
    if pids=$(timeout 4 lsof -t $dir); then
        found_pids=true
        timeout 4 lsof -w $dir
        kill -$sig $pids
    fi
    # fuser will find open sockets that lsof won't, for example from gpg-agent.
    # note: -v shows kernel processes, which then doesn't return true when we want
    if timeout 4 fuser -m $dir &>/dev/null; then
        found_pids=true
        fuser -$sig -mvk $dir
    fi
    if $found_pids; then
        sleep .5
        return 0
    fi
    return 1
}

force=false
if [[ $1 == -f ]]; then
    force=true
fi

ret=0

##### begin setup fstab for subvols we care about ######
first_root_crypt=$(awk '$2 == "/" {print $1}' /etc/mtab)
fstab <<EOF
$first_root_crypt  /a  btrfs  noatime,subvol=a  0 0
EOF

shopt -s nullglob

f=(/mnt/root/btrbk/q.*)
if [[ -e $f ]]; then
    fstab <<EOF
$first_root_crypt  /q  btrfs  noatime,subvol=q  0 0
/q/p  /p  none  bind  0 0
EOF
fi

f=(/mnt/root/btrbk/o.*)
if [[ -e $f ]]; then
    fstab <<EOF
$first_root_crypt  /o  btrfs  noatime,subvol=o  0 0
/o/m  /m  none  bind  0 0
EOF
fi

if [[ $HOSTNAME == frodo ]]; then
    fstab <<EOF
$first_root_crypt  /i  btrfs  noatime,subvol=i  0 0
EOF
fi
##### end setup fstab for subvols we care about ######

for vol in q a o i; do
    d=/$vol
    if ! awk '{print $2}' /etc/fstab | grep -xF $d &>/dev/null; then
        continue
    fi


    ##### begin building up list of bind mounts  ######
    binds=() # list of bind mounts
    roots=($d) # list of bind mounts, plus the original mount
    while true; do
        new_roots=()
        for r in ${roots[@]}; do
            # eg. when r=/q/p, for lines like
            # /q/p  /p  none  bind  0 0
            # output /p
            new_roots+=($(sed -rn "s#^$r/\S+\s+(\S+)\s+none\s+bind\s.*#\1#p" /etc/fstab))
        done
        (( ${#new_roots} )) || break
        binds+=(${new_roots[@]})
        roots=( ${new_roots[@]} )
    done
    ##### end building up list of bind mounts  ######


    # if latest is already mounted, make sure binds are mounted and move on
    if e check-subvol-stale $d; then
        mnt $d
        for b in ${binds[@]}; do
            mnt $b
        done
        continue
    fi

    fresh_snap=$(</nocow/btrfs-stale/$vol)
    if [[ ! $fresh_snap ]]; then
        echo "$0: error. empty fresh_snap var"
        ret=1
        continue
    fi

    umount_ret=true
    unmounted=()
    for dir in $(echo $d ${binds[*]}\ |tac -s\ ); do
        if mountpoint $dir; then
            if e umount -R $dir; then
                unmounted+=($dir)
            else
                kill-dir || kill-dir INT || kill-dir HUP || ! $force || kill-dir KILL ||:

                if e umount -R $dir; then
                    unmounted+=($dir)
                else
                    echo "$0: failed to umount $dir"
                    umount_ret=false
                    ret=1
                    continue
                fi
            fi
        fi
    done

    if ! $umount_ret; then
        for dir in ${unmounted[@]}; do
            mnt $dir
        done
        continue
    fi

    # todo: decipher /mnt/root, like we do in check-subvol-stale
    cd /mnt/root
    if [[ -e $vol ]]; then
        e mv $vol $vol.leaf.$(date +%Y%m%dT%H%M%S%z)
    fi
    # Note, we make a few assumptions in this script, like
    # $d was not a different subvol id than $vol, and
    # things otherwise didn't get mounted very strangely.
    e btrfs sub snapshot $fresh_snap $vol
    for dir in $d ${binds[@]}; do
        e mnt $dir
    done
    stale_dir=/nocow/btrfs-stale
    rm -f $stale_dir/$d
done

### disabled
if [[ $HOSTNAME == treetowlxxxxxxxxx ]]; then
    # partitioned it with fai partitioner outside of fai,
    # because it\'s worth it to have 1% space reserved for boot and
    # swap partitions in case I ever want to boot off those drives.
    # as root:
    # . /a/bin/fai/fai-wrapper
    # eval-fai-classfile /a/bin/fai/fai/config/class/51-multi-boot
    # fai-setclass ROTATIONAL
    # export LUKS_DIR=/q/root/luks/
    # # because the partition nums existed already
    # fai-setclass REPARTITION
    # /a/bin/fai/fai/config/hooks/partition.DEFAULT

    devs=(
        ata-TOSHIBA_MD04ACA500_84REK6NTFS9A-part1
        ata-TOSHIBA_MD04ACA500_84R2K773FS9A-part1
        ata-TOSHIBA_MD04ACA500_8471K430FS9A-part1
        ata-TOSHIBA_MD04ACA500_8481K493FS9A-part1
    )
    first=true
    for dev in ${devs[@]}; do
        if $first; then
            first=false
            tu /etc/fstab <<EOF
/dev/mapper/crypt_dev_$dev /i btrfs  noatime,subvol=i,noauto  0 0
/dev/mapper/crypt_dev_$dev /mnt/iroot btrfs  noatime,subvolid=0,noauto  0 0
EOF
        fi
        tu /etc/crypttab <<EOF
crypt_dev_$dev  /dev/disk/by-id/$dev  /q/root/luks/host-treetowl  discard,luks
EOF
        if [[ ! -e /dev/mapper/crypt_dev_$dev ]]; then
            cryptdisks_start crypt_dev_$dev
        fi
    done
    # note, could do an else here and have some kind of mount for /i
    # on other hosts.
fi

exit $ret