#!/bin/bash
# back up a git repository tree
# $Id$

OIFS="$IFS"
IFS=" 	
"

if test -f "$HOME/bin/functions"
then
    . "$HOME/bin/functions"
else
    echo "Cannot open functions library $HOME/bin/functions" 1>&2
    exit 1
fi

abort()
{
    notice "Aborted"
    exit 1
}

cleanup()
{
    if test -f "$dfout"
    then
        info "Cleaning up $dfout"
        run rm -rf -- "$dfout"
    fi

    if test -d "$snapdir"
    then
        info "Cleaning up $snapdir"
        run rm -rf -- "$snapdir"
    fi
}

#
# default configuration
#
debug=
quiet=true
simulate=		# empty means false
dateformat='%-e %B %Y'
timeformat='%H:%M:%S'
srcroot=/home/mikelward/git
tmpdir="${TMPDIR:-$HOME/tmp}"
dstroot=mikelward.homedns.org:/home/mikel/git
logfile=/home/mikelward/log/gitbackup.log

#
# start
#
trap 'abort' INT TERM

#
# ensure required programs are available
#
if ! silent type git
then
    error "Cannot find git in PATH"
    exit 1
fi

usage()
{
    cat <<EOF 1>&2
Usage: gitbackup [-hn]
EOF
}

while getopts ":hn" option
do
    case $option in
        h)
            usage
            exit 0
            ;;
        n)
            simulate=true
            ;;
        ':')
            echo "Missing argument to -$option" 1>&2
            usage
            exit 2
            ;;
        '?')
            echo "Invalid option -$OPTARG" 1>&2
            usage
            exit 2
            ;;
        *)
            echo "Program does not support -$option yet" 1>&2
            usage
            exit 2
            ;;
    esac
done
shift $((OPTIND - 1))

#
# normalize paths
#
dstroot=${dstroot%/}/
srcroot=${srcroot%/}/

info "Starting gitbackup on "$(date +"$dateformat")" at "$(date +"$timeformat")

if is_remote "$dstroot"
then
    debug "Remote destination"
    dsthost=$(get_hostname_part "$dstroot")
    dstbase=$(get_location_part "$dstroot")
    dstbase=${dstbase%/}/
    debug "dsthost=$dsthost, dstbase=$dstbase"
else
    error "Local destinations are currently unsupported"
    exit 1
fi

# assumption: $srcroot contains subdirectiories which are git bare repos
# e.g.
# srcroot=/srv/git
# /srv/git
#   /srv/git/proj1.git
#   /srv/git/proj2/proj2a.git
#   /srv/git/proj2/proj2b.git
for srcdir in $(find "$srcroot" -type d -name "*.git")
do
    info "Starting backup of $srcdir on "$(date +"$dateformat")" at "$(date +"$timeformat")

    # do each repo in a new subshell so we can call cleanup on error and success via trap
    (

    trap cleanup EXIT

    tmpdir=$(get_temporary_directory)
    if test $? -ne 0
    then
        error "Cannot determine temporary directory"
        exit 1
    fi

    # case 1: srcdir is subdir of srcroot - OK
    # case 2: srcdir is / - CAN'T HAPPEN
    # case 3: srcdir = srcroot - NOT SUPPORTED
    reponame=${srcdir#$srcroot}
    reponame=${reponame%/}
    if test "$reponame" = ""
    then
        error "Cannot determine repository name: invalid srcdir?"
        exit 1
    fi

    #
    # check disk space requirements
    #
    size=$(get_size_of_file_or_directory "$srcdir")
    if test $? -ne 0
    then
        error "Cannot determine disk usage of $srcdir"
        exit 1
    fi

    available=$(get_free_space_on_filesystem "$tmpdir")
    if test $? -ne 0
    then
        error "Cannot determine free space on $tmpdir"
        exit 1
    fi

    if test $available -lt $size
    then
        error "Need at least $size kilobytes free on $tmpdir"
        exit 1
    fi

    #
    # take a snapshot of the repository
    #

    # turn the path into a single directory so we don't have to mess around with mkdirs
    dirname=$reponame
    dirname=${dirname//\//.}
    if test -z "$dirname"
    then
        dirname="root"
    fi
    snapdir="$tmpdir"/"$dirname".$$
    if test -d "$snapdir"
    then
        error "Snapshot directory $snapdir already exists"
        exit 1
    fi

    info "Cloning $srcdir to $snapdir"
    run git clone --bare --quiet "$srcdir" "$snapdir"
    if test $? -ne 0
    then
        error "Cannot clone $srcdir"
        exit 1
    fi

    #
    # copy the hot copy to the backup directory
    #
    dstdir=$dstbase$reponame
    dsturl=$dsthost:$dstdir
    debug "dstdir=$dstdir, dsturl=$dsturl"

    # create the destination directory if it doesn't exist
    # (rsync won't create the whole tree because we're only syncing part of the tree on each pass)
    debug "Creating $dstdir on $dsthost"
    run ssh $dsthost 'dstdir="'"$dstdir"'"; test -d "$dstdir" || mkdir -p "$dstdir"'

    flags=
    if test "$debug"
    then
        flags="$flags -v"
    fi
    if test "$quiet"
    then
        flags="$flags -q"
    fi
    #scp -C -r $flags "$snapdir" "$dst"
    # ensure source has a trailing slash so we only copy the directory contents
    # (local:~/svn.12345/ -> remote:~/svn rather than
    #  local:~/svn.12345/ -> remote:~/svn/svn.12345)
    snapdir=${snapdir%/}/
    info "Syncing $snapdir to $dsturl"
    run rsync -a --delete $flags "$snapdir" "$dsturl"
    if test $? -ne 0
    then
        error "Error syncing $snapdir to $dsturl"
        exit 1
    fi

    )

    info "Finished backup of $srcdir on "$(date +"$dateformat")" at "$(date +"$timeformat")
done

info "Finished gitbackup on "$(date +"$dateformat")" at "$(date +"$timeformat")