#!/bin/bash

# get_merged_element.sh - Return an element in wdef:knowledge after it's been
#                         merged with a RDF.
# Copyright (C) 2022  Pierre Choffet
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of version 3 of the GNU General Public License as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

readonly SCRIPT_DIR="$(dirname "$0")"

source "${SCRIPT_DIR}/rdf.sh"

set -euo pipefail

# Any rdf cache older than this (in minutes) will be updated
RDFS_MAX_AGE=${RDFS_MAX_AGE:=1440}

readonly CANONICALIZE_XSLT_PATH="${SCRIPT_DIR}/../xslts/canonicalize.xslt"
readonly MERGE_XSLT_PATH="${SCRIPT_DIR}/../xslts/merge_rdf.xslt"

function usage() {
	cat << EOF
USAGE: get_merged_element.sh <wdef_path> <QID>

Merge a RDF into an element inside a wdef file. A wdef file containing this
single element is returned.
EOF
}

if [ "$#" -ne 2 ]
then
	usage >&2
	exit 1
fi

readonly WDEF_PATH="${1}"
readonly ELEMENT_QID="${2}"

# Check wdef exists
if [ ! -s "${WDEF_PATH}" ]
then
	echo "WDEF file doesn't exist. Exiting" >&2
	exit
fi

# Export element from wdef
readonly ELEMENT_PATH="$(mktemp)"
xmlstarlet sel -D -t -e 'wdef:knowledge' -m '/wdef:knowledge' -c "wdef:element[@wdef:id = '${ELEMENT_QID}']" "${WDEF_PATH}" | xmlstarlet fo - > "${ELEMENT_PATH}"

# Check element is in temp file
if [ "$(xmlstarlet sel -t -i "/wdef:knowledge/wdef:element[@wdef:id = '${ELEMENT_QID}']" -v "'true'" "${ELEMENT_PATH}")" != 'true' ]
then
	echo "Element not available in wdef. Exiting." >&2
	exit
fi

# Cache RDF
readonly RDF_PATH=$(cacheRDFMaxAge "${ELEMENT_QID}" "${RDFS_MAX_AGE}")

# Merge and return canonicalized result
xmlstarlet tr "${MERGE_XSLT_PATH}" -s action=reduce \
           -s "rdf-path=${RDF_PATH}" \
           "${WDEF_PATH}" | xmlstarlet tr ${CANONICALIZE_XSLT_PATH} -

rm "${ELEMENT_PATH}"