#!/bin/bash
VER="1.0"

CONFIG="/etc/squashfu.conf"
source "$CONFIG"

# Informational output w/ happy colors
debug () {
    if [[ "$DEBUG" == "true" ]]; then
        printf '\033[1;33mDEBUG ::\033[1;m %s\n' "$*"
    fi
}

warn () {
    printf '\033[1;33m::\033[1;m %s\n' "$*"
}

info () {
    printf '\033[1;34m::\033[1;m %s\n' "$*"
}

die () {
    printf '\033[1;31m::\033[1;m %s\n' "$*" >&2
    exit 1
}

create_new_squash () {
# Args: number of bins to be squashed, -1 on initial creation
# Returns: 0 on success, non-zero on failure

    # If making first seed, create it directly from source
    if [[ $1 -eq -1 ]]; then
        info "Creating seed from sources (this may take a while)"
        mksquashfs "${INCLUDES[@]}" "$SEED" -b 65536 -e "${EXCLUDES[@]}" >/dev/null
        if [[ $? -eq 0 ]]; then
            mount_squash
            info "Seed creation finished. It has been mounted at "$SQUASH_MOUNT" if you would like to make sure the proper files are included"
            return 0;
        else
            die "There was an error creating the initial squash."
        fi
    fi

    # Determine oldest $1 bins and mount them with the current squash
    local old_bins=($(sort -n -r -t: -k2 "$BINVENTORY" | tail -$1 | cut -d: -f1))

    mount_union_with_bins ${old_bins[@]}

    info "Merging old incrementals"
    # Create new squash with temp name
    mksquashfs "$UNION_MOUNT" "$SEED.replace" -b 65536 >/dev/null

    # If the squash wasn't made correctly, we don't want to continue
    if [[ $? -ne 0 ]]; then
        return 1
    fi

    unmount_all

    # Replace old squash
    mv "${SEED}.replace" "$SEED"

    info "Cleaning up inventory"
    # Delete old bins, and remove entry from binventory
    for bin in ${old_bins[@]}; do
        rm -rf "${BINS_DIR}/$bin"
        sed -i "/^$bin:/d" "$BINVENTORY"
    done

    # Clean up $binventory
    sweep_bins
}

create_new_bin () {
# Arguments: 1, the number of the bin to create
# Returns: 0 on success, non-zero on error

    debug "Asked to create new bin: $1"
    # Create new directory, fail if it exists (something's wrong)
    mkdir "${BINS_DIR}/$1"
    if [[ $? -ne 0 ]]; then
        return $?
    fi

    # Update binventory with new bin name and timestamp
    echo "${1}:$(date +%s)" >> "$BINVENTORY"

    # If write to bin list fails, remove diretory and exit
    if [[ $? -ne 0 ]]; then
        rmdir "${BINS_DIR}/${1}"
        die "Error writing to '$BINVENTORY'"
    fi

    return
}

# Mounting functions
mount_squash () {
# Arguments: none
# Returns: return code of mount command
    debug "Mounting Squash"
    mount -o loop,ro "$SEED" "$SQUASH_MOUNT"
    return $?
}

mount_union_with_bins () {
# Arguments: numbers of bins to be mounted (variable number)
# Returns: 0 on successful mount, non-zero on failure
    info "Mounting union"
    debug "Requested to mount bins: $*"

    # Mount first as rw, shift, and mount the rest ro
    branches="br=${BINS_DIR}/$1=rw:"; shift
    if [[ -n $1 ]]; then
        for bin in $*; do
            branches="${branches}${BINS_DIR}/$bin=ro:"
        done
    fi
    branches="${branches}${SQUASH_MOUNT}=ro"

    mount -t aufs none "$UNION_MOUNT" -o udba=reval,$branches

    return $?
}

# Unmounting functions
unmount_union () {
# Args: none
# Returns: return code from umount
    info "Unmounting union"

    $(mountpoint -q "$UNION_MOUNT") && umount "$UNION_MOUNT" 2>/dev/null

    return $?
}

unmount_squash () {
# Args: none
# Returns: return code from umount
    info "Unmounting squash"

    $(mountpoint -q "$SQUASH_MOUNT") && umount "$SQUASH_MOUNT" 2>/dev/null

    return $?
}

unmount_all () {
# Args: none
# Returns: none

    if [[ $UID -ne 0 ]]; then
        die "Must be root to unmount."
    fi

    # Union MUST be unmounted first
    unmount_union && unmount_squash || die "Failure during unmounting"
}

check_for_resquash () {
# Args: none
# Returns: number of bins needing to be merged
    local number_of_bins=$(grep -vE "^[ ]*$" "$BINVENTORY" | wc -l)
    debug "Found $number_of_bins bins"

    if [[ $number_of_bins -gt $MAX_BINS ]]; then
        return $(( $number_of_bins - $MIN_BINS ))
    else
        return 0
    fi
}

get_next_available_bin () {
# Arguments: none
# Returns: Numeric value of the next unused bin
    next_bin=$(( $(cut -d: -f1 "$BINVENTORY" | sort -n | tail -1) + 1 ))
    debug "Next available bin = $next_bin"
    return $next_bin
}

sweep_bins () {
# Arguments: none
# Returns: none

    info "Rotating chickens"
    # Make sure bins are numbered in order, clean up if not. In other words,
    # if we have 10 bins, make sure they're ordered 1 through 10.
    count=1
    ls "${BINS_DIR}" | while read bin; do
        if [[ ! -d "${BINS_DIR}/$count" ]]; then
            high_bin=$(ls "${BINS_DIR}" | sort -n | tail -1)
            debug "Sweeping bin $high_bin into bin $count"
            mv "${BINS_DIR}/$high_bin" "${BINS_DIR}/$count"
            sed -i "/^$high_bin:/s/^$high_bin:/$count:/" "$BINVENTORY"
        fi
        count=$(( $count + 1 ))
    done
}

action_backup () {
# Args: options array squashfu was invoked with, shifted 1
# Returns: none

    if [[ $UID -ne 0 ]]; then
        die "Must be root to perform a backup"
    fi

    # Does the binventory exist? If not, prompt to make sure this is an initialization
    if [[ ! -f "$BINVENTORY" || ! -f "$SEED" ]]; then
        read -p "Looks like this is your first time running SquashFu. Is this correct? (y/n) " ans
        while [[ true ]]; do
            case $ans in
                [yY]) break ;;
                [nN]) die "Your bin inventory and/or seed seem to be missing. Please fix this before continuing." ;;
                *) ;;
            esac
        done

        # If we got here, the user answered yes, so initialize a new structure
        mkdir -p "$UNION_MOUNT"
        mkdir -p "$SQUASH_MOUNT"
        mkdir -p "${BINS_DIR}"
        touch "$BINVENTORY"
        create_new_squash -1
        exit 0
    fi

    info "Backup requested at $(date --rfc-3339=seconds)"

    # Cleanup union, in case user was doing a rollback and forgot to unmount (or error on last run)
    mountpoint -q "$UNION_MOUNT" && unmount_union

    info "Creating new bin"
    # Make a new bin for this incremenetal
    get_next_available_bin
    local new_bin=$?
    create_new_bin $new_bin

    # Determine the mount order via binventory
    local bin_order=($(sort -n -r -t: -k2 "$BINVENTORY" | cut -d: -f1))

    mountpoint -q "${SQUASH_MOUNT}" || mount_squash
    mount_union_with_bins ${bin_order[@]}

    # Die with error on mount, else start rsync
    if [[ $? -ne 0 ]]; then
        return 1;
    fi

    # Includes are pulled in directly from config
    EXCLUDES=$(for excl in ${EXCLUDES[@]}; do echo --exclude $excl; done)

    debug "rsync ${RSYNC_OPTS[@]} ${INCLUDES[@]} ${EXCLUDES[@]} "$UNION_MOUNT""
    info "Creating new incremental"
    /usr/bin/rsync ${RSYNC_OPTS[@]} ${INCLUDES[@]} ${EXCLUDES[@]} "$UNION_MOUNT"
    rsync_ret=$?

    for error in ${DEL_BIN_ON_FAIL[@]}; do
        if [[ $rsync_ret == $error ]]; then
            warn "Unexpected hangup by rsync ($error). Deleting backup."
            action_remove_bin $new_bin override
        fi
    done

    check_for_resquash
    if [[ val=$? -gt 0 ]]; then
        create_new_squash $val
    fi

    # TODO: Report if requested

    unmount_all

    info "Backup completed at $(date --rfc-3339=seconds)"
}

action_remove_bin () {
    # check if the bin exists both in the binventory AND in the bins directory
    if [[  $UID -ne 0 ]]; then
        die "Must be root to remove a backup"
    fi

    if [[ ! -w "$BINVENTORY" ]]; then
        die "Error writing to ${BINVENTORY}"
    fi

    if [[ $(grep -E "^$1:" ${BINVENTORY}) && -d "${BINS_DIR}/$1" ]]; then
        if [[ -z $2 ]]; then
            echo "Are you SURE you want to remove this bin?"
            local timestamp=$(sed -n "/^$1:/s/^[0-9]*:\([0-9]*\)/\1/p" "${BINVENTORY}")
            printf "\t%15s %s\n\t%15s %s\n\t%15s %s\n" \
                    "Bin:" "$1" \
                    "Date Created:" "$(date --rfc-3339=seconds --date="@$timestamp")" \
                    "Size:" "$(du -sh "${BINS_DIR}/$1" 2>/dev/null | awk '{print $1}')"

            read -p "Confirm deletion (y/N)" confirm
            if [[ $confirm != "y" ]]; then
                info "Delete operation aborted"
                exit 1
            fi
        fi

        info "Deleting bin $1"
        sed -i "/^$1:[0-9]*/d" "${BINVENTORY}"
        rm -rf ${BINS_DIR}/$1

        # tidy up!
        sweep_bins
    else
        die "Bin $1 not found."
    fi

}

action_rollback () {
# Args: number of backups to roll back
# Returns: none

    if [[ $UID -ne 0 ]]; then
        die "Must be root to perform a rollback"
    fi

    # Validate input with test cases
    if [[ -z $1 ]]; then
        die "The rollback action requires 1 additional argument."
    fi

    # Form a chronologically ordered list of bins, assuming the user didn't give bogus input
    local bin_list=($(grep -vE "^[ \t]*$" "$BINVENTORY" | sort -t: -r -n -k2 | cut -d: -f1))

    if [[ $1 -gt ${#bin_list[@]} ]]; then
        die "Cannot rollback more than ${#bin_list[@]} backups"
    fi

    local num_to_mount=$(( ${#bin_list[@]} - $1 ))

    mountpoint -q "$UNION_MOUNT" && unmount_union
    mountpoint -q "$SQUASH_MOUNT" || mount_squash

    mount_union_with_bins ${bin_list[@]:(-$num_to_mount)}

    local rb_timestamp=$(grep -E "^${bin_list[@]:(-$num_to_mount):1}:" "$BINVENTORY" | cut -d: -f2)

    info "You have rolled back to $(date --rfc-3339=seconds --date="@$rb_timestamp")"
    info "Your files can be found at '${UNION_MOUNT}'"
}

action_report () {
    info "SquashFu Usage Report"
    echo
    # Enumerate bins, sort date order, print human readable create date and size

    cd "$BINS_DIR"
    OLDIFS=$IFS;IFS=${IFS}:
    # Collect all data into an array to 'preload' it. Index 0 is the entire
    # folder. The following indicies correspond to the bin number of that index
    printf "%30s\r" "          .: Loading :." >&2
    DATA=($(du -sh . * 2>/dev/null | sort -n -k2 | awk '{print $1}'))
    printf "%30s\r" "                       " >&2

    printf "%10s\t%25s\t%7s\n" "Bin ID" "Date Created" "Size"
    grep -vE "^[\t ]*$" "$BINVENTORY" | sort -r -t: -k2 -n | while read bin stamp; do
        printf "%10d\t%25s\t%7s\n" "$bin" \
               "$(date --rfc-3339=seconds --date="@$stamp")" \
               "${DATA[$bin]}"
    done
    IFS=$OLDIFS
    printf "%10s\t%25s\t%7s\n" "" "Incremental Total" "${DATA[0]}"

    # Print totals (not efficient -- reruns du on things we already ran it on)
    printf "\n%10s\t%25s\t%7s\n" "" "$(basename $SEED)" "$(du -h "${SEED}" | awk '{print $1}')"
    printf "\n%10s\t%25s\t%7s\n" "" "Grand Total" \
    "$(du -csh "$BINS_DIR" "$SEED" 2>/dev/null | grep -E "total$" | awk '{print $1}')"
}

action_resquash_now () {
# Args: none
# Returns: none

    if [[ $UID -ne 0 ]]; then
        die "Must be root to perform a resquash"
    fi

    info "Voluntary resquash requested"

    local number_of_bins=$(grep -vE "^[ ]*$" "$BINVENTORY" | wc -l)
    if [[ $number_of_bins -le $MIN_BINS ]]; then
        die "Nothing to do. Current backups do not exceed MIN_BINS value."
    else
        create_new_squash $(( $number_of_bins - $MIN_BINS ))
    fi

    exit $?
}

action_unmount () {
    unmount_all
}

usage () {
    info "SquashFu: Super Awesome Backup Express (Professional Edition)"
    echo "version: $VER"
    cat <<HELP

USAGE
    squashfu <action> [options]

ACTIONS
  -B
    Runs a regular backup, using the config file at /etc/squashfu.

  -C
    Create a new squash by merging old bins. This will still leave you
    with $MIN_BINS backups (as per the MIN_BINS setting in your config).

  -D <bin number>
    Delete an incremental backup. This is done interactively and you will have
    a chance to confirm before any files are deleted.

  -Q
    Displays the size of the seed, the incrementals, and totals.

  -R <number of bins>
    Rollback specified number of backups and mount union for browsing. The rolled
    back data will be mounted at $UNION_MOUNT.

  -U
    Unmount squash and union. Although SquashFu will always check and unmount as 
    necessary before an operation, this is provided as a safeguard.

OPTIONS
  -c <path_to_config>
    Specify an alternate config file. Options defined will override options in
    the default config. If you specify alternate locations via a supplmenetal config,
    you will need to provide the config for all actions

HELP
    exit 1
}

while getopts :BCD:QR:Uc: opt; do
    case $opt in
        B)
            action=backup ;;
        C)
            action=resquash_now ;;
        D)
            action="remove_bin $OPTARG" ;;
        Q)
            action=report ;;
        R)
            action="rollback $OPTARG" ;;
        U)
            action=unmount ;;
        c)
            [[ -f $OPTARG ]] && source $OPTARG ;;
        \:)
            die "Argument missing from -$OPTARG"
            usage ;;
        \?)
            die "Unrecognized option -$OPTARG"
            usage ;;
    esac >&2
done

[[ -n $action ]] && action_$action || usage