#!/bin/bash

# Informational output w/ happy colors
DEBUG=true
debug () {
    [[ $DEBUG ]] && echo -e '\033[1;33mDEBUG ::\033[1;m ' $*
}

info () {
    echo -e '\033[1;34m::\033[1;m ' $*
}

die () {
    echo -e '\033[1;31mERROR ::\033[1;m ' $*
    exit 1
}

CONFIG=/etc/squashfu
source $CONFIG
[[ $? -gt 0 ]] && die "Error in config file. Please check your syntax"

mount_union_ro () {
    # build branch string
    branches="br="
    for i in `seq $1 -1 1`; do
        branches="${branches}${BKUP_ROOT}/bins/${i}=ro:"
    done
    branches="${branches}${BKUP_ROOT}/ro=ro"

    # build and execute mount command
    debug "Mounting union as entirely read only"
    mount -t aufs none $BKUP_ROOT/rw -o udba=reval,$branches
}

mount_union_branch_rw () {
    debug "Remount branch $i as read-write"
    mount -o remount,mod:bins/$1=rw "${BKUP_ROOT}/rw"
}

create_new_seed () {
    # Create a new squashfs based on the contents of the union
    # It's okay if we make an empty squash, we'll tell the user
    # about it at the end and suggest --resquash
    debug "Making new squash seed $(basename $SEED)"
    mksquashfs "${BKUP_ROOT}/rw" "$SEED" -b 65536

    # Delete the rsync source since its now squashed
    #[[ "$1" == "--initial" ]] && rm -rf "${BKUP_ROOT}/rw/*"
}

move_old_tree () {
    storage="${BKUP_ROOT}/bkup-$(date +%Y-%m-%d)"
    mkdir "$storage"
    cd "$BKUP_ROOT" && mv {$SEED,bins/} "$storage"
}

mount_seed () {
    debug "Mounting seed"
    # Mount the squashed seed, failing if we can't
    mount -o loop,ro "${SEED}" "${BKUP_ROOT}/ro" || {
        die FATAL: Error mounting $SEED;
    }
}

mount_aufs_by_day() {
    # convert DoW to a number
    mount_union_ro `date --date=$1 +%u`
}

run_rsync() {
    # Gather includes and excludes from config file
    # No error checking here -- user better not have
    # effed up the config
    INCLUDES=($(grep ^#+ $CONFIG | cut -d+ -f2-))
    EXCLUDES=($(grep ^#- $CONFIG | cut -d- -f2-))

    # rsync source to $BKUP_ROOT/rw
    debug "Rsync executing with:"
    debug "   Options: ${RSYNC_OPTS[@]}"
    debug "   Includes: ${INCLUDES[@]}"
    debug "   Excludes: ${EXCLUDES[@]}"
    rsync ${RSYNC_OPTS[@]} ${INCLUDES[@]} ${EXCLUDES[@]} ${BKUP_ROOT}/rw || return 1
}

# Unmount union and squash
unmount_all () {
    #Union must be unmounted first, or bad things happen
    grep "${BKUP_ROOT}/rw" /proc/mounts && 
        { debug Unmounting union...; umount "$BKUP_ROOT/rw"; }
    grep "${SEED}" /proc/mounts &&
        { debug Unmounting squash...; umount "${SEED}"; }
}

finish_routine () {
    # Do another sanity check -- check sizes of bins versus squash.
    bin_size=$(du -s ${BKUP_ROOT}/bins | awk '{print $1}')
    sfs_size=$(du -s $SEED | awk '{print $1}')
    if [[ $bin_size -gt $sfs_size ]]; then
        info "Your incrementals are larger than your seed! You might consider resquashing your backup with $0 --resquash"
    fi

    unmount_all
}

usage () {
    info "This is what happens when you can't read"
    exit
}

# The meat and potatoes of the script.
do-backup () {
    ################################
    # Sanity checks
    ################################
    #  - Are we root?
    #  - is our BKUP_ROOT valid? (FAIL)
    #  - Check for pre-existing mounts just in case (and unmount them)
    #  - do we have a proper (expected) directory structure in place?
    #       (Use cd to BKUP_ROOT to avoid issues with brace expansion in a quoted path)
    [[ $UID -eq 0 ]] || die Must be root!

    [[ -w "${BKUP_ROOT}" ]] || 
        die "Backup root is not accessible. Please check your setting in /etc/squashfu"

    unmount_all

    cd "$BKUP_ROOT" && mkdir -p {rw,ro,bins/{1,2,3,4,5,6,7}}


    ################################
    # Prep work
    ################################
    #  - does seed exist? (if not, our backup is creating the seed)
    #  - Prepare union mount with proper bins
    [[ -f "$SEED" ]] || {
        debug "No seed found -- creating a new one...";
        create_new_seed;
    }

    mount_union_ro $(( $(date +%u) + $MODIFIER ))

    mount_union_branch_rw $(( $(date +%u) + $MODIFIER ))


    ################################
    # Ready for backup!
    ################################
    run_rsync


    ################################
    # Cleanup 
    ################################
    #  - Is this resquash day? If so, we need a new squash
    #  - If new squash creation fails, we're in trouble. (by default, keep previous week)
    [[ $(date +%u) -eq $RESQUASH_DAY ]] && {
        create_new_seed
        # Set aside last week's tree if user opted to, else delete it all
        if [[ $KEEP_LAST_WEEK -eq 1 ]]; then
            move_old_tree
        else
            find "${BKUP_ROOT}/bins/" -type f -delete
            rm $SEED
        fi
    }

    finish_routine
}

#Option parsing / Decision making
[[ $# -eq 0 ]] && usage

while [[ $# -gt 0 ]]; do
    case $1 in
        "-c")    ;;
        *) usage ;;
    esac
    shift
done