#!/usr/bin/env sh

USAGE="ssync-fetch [options] QUEUE_FILE DEST_DIR
    OPTIONS
        -r REMOTE_HOST
           remote host to download from such as user@hostname
           username can be omitted if identical to $USER
           or if set in ssh_config
        -k KEY_FILE
           ssh-key file to use (needs to be non-interactive)
           optional: will use default session key
           or key set in ssh_config for REMOTE_HOST
	-b BACKEND
	   sftp (default) | rsync
        -v verbose logging
        -h print this message"

# HELPER FUNCTIONS

verbose_log() {
    if [ ! -z "$VERBOSE_FLAG" ]; then
        echo "$@"
    fi
}
lines() {
    echo $(wc -l $1 | cut -d' ' -f1)
}

# OPTIONS

KEY_FILE_FLAG=
KEY_FILE_ARG=
REMOTE_HOST_FLAG=
REMOTE_HOST_ARG=
BACKEND_FLAG=
BACKEND_ARG=
VERBOSE_FLAG=

while getopts "hvr:k:b:" opt; do
    case "${opt}" in
        h) echo "$USAGE"
           exit 1
           ;;
        v) VERBOSE_FLAG=1
           ;;
        k) KEY_FILE_FLAG=1
           KEY_FILE_ARG="${OPTARG}"
           ;;
        r) REMOTE_HOST_FLAG=1
           REMOTE_HOST_ARG="${OPTARG}"
           ;;
	b) BACKEND_FLAG=1
	   BACKEND_ARG="${OPTARG}"
	   ;;
    esac
done

shift $(($OPTIND -1))

if [ $# -ne 2 ]; then
    echo "$USAGE"
    exit 1
fi

QUEUE_FILE=$1
DEST_DIR=$2

# VALIDATION

if [ ! -f "$QUEUE_FILE" ]; then
    echo "Queue file '$QUEUE_FILE' does not exist"
    exit 1
elif [ $(lines $QUEUE_FILE) -le 0 ]; then
    echo "Queue file empty. Exiting"
    exit 0
fi

if [ ! -d "$DEST_DIR" ]; then
    echo "Destination directory '$DEST_DIR' does not exist"
    exit 1
fi

if [ -z "$REMOTE_HOST_FLAG" ]; then
    echo "Remote host option -r required"
    exit 1
elif [ -z "$REMOTE_HOST_ARG" ]; then
    echo "Invalid remote host '$REMOTE_HOST_ARG'"
    exit 1
fi

if [ -z "$BACKEND_FLAG" ]; then
    BACKEND="sftp"
else
    BACKEND=$BACKEND_ARG
fi

if [ "$BACKEND" != "sftp" ]; then
    if [ "$BACKEND" != "rsync" ]; then
	echo "Invalid backend $BACKEND"
	exit 1
    fi
fi

# CONFIGURATIONS

ssh_id_param=""
if [ ! -z "${KEY_FILE_FLAG}" ]; then
    if [ ! -f "${KEY_FILE_ARG}" ]; then
        echo "Identity file '${KEY_FILE_ARG}' does not exist"
        exit 1
    fi
    ssh_id_param="-i ${KEY_FILE_ARG}"
fi

real_dest=$(realpath $DEST_DIR)
tmp_dir=$(mktemp -d /tmp/ssync_fetch_run.XXXXXX)
ts=$(date +%s)
verbose_log "Writing temp files to ${tmp_dir} with timestamp ${ts}"

# GENERATE BATCH

if [ "$BACKEND" = "sftp" ]; then
    batch_file=$tmp_dir/batch_${ts}
    verbose_log "Converting the queue file to sftp batch file: ${batch_file}"
    cat $QUEUE_FILE | xargs -I{} echo -e "@reget {} ${real_dest}/" > $batch_file

    verbose_log "Beginning download"
    verbose_log "sftp -N ${ssh_id_param} -b ${batch_file} ${REMOTE_HOST_ARG}"

    sftp -N ${ssh_id_param} -b ${batch_file} ${REMOTE_HOST_ARG}
elif [ "$BACKEND" = "rsync" ]; then
    verbose_log "Fetching files from queue file: $QUEUE_FILE"
    verbose_log "Beginning download"
    verbose_log "rsync --files-from=${QUEUE_FILE} rsync://${REMOTE_HOST_ARG} ${real_dest}"
    rsync -av --no-relative --files-from=${QUEUE_FILE} ${REMOTE_HOST_ARG}:/ ${real_dest}
fi

verbose_log "ssync-fetch finished"