#!/bin/bash

# query.sh - Set of Bash functions to work with wdef files.
# 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/>.

set -euo pipefail

readonly WIKIDATA_SPARQL_ENDPOINT='https://query.wikidata.org/bigdata/namespace/wdq/sparql'

readonly CACHE_DIR=${CACHE_DIR:-"${HOME}/.cache/wdef_tools/"}
readonly QUERY_CACHE_DIR="${CACHE_DIR}/queries/"

# Send query and return a path to the result into cache dir
# Parameter:
#   $1: Path to file containing query
# Output:
#   Path to the file containing result, in cache dir
function query() {
	local -r query_path="${1}"
	
	if [ ! -s "${query_path}" ]
	then
		echo "Query not found at path ${query_path}. Exiting." >&2
		return 1
	fi
	
	local -r query_checksum=$(md5sum "${query_path}" | cut -d ' ' -f 1)
	local -r result_path="${QUERY_CACHE_DIR}/${query_checksum}"
	
	# Prepare query
	local -r query=$(cat "${query_path}" | jq -sRr @uri)
	
	# Send query, cache result
	mkdir -p "${QUERY_CACHE_DIR}"
	wget -O "${result_path}" "${WIKIDATA_SPARQL_ENDPOINT}?query=${query}"
	
	echo "${result_path}"
}

# Build query from template and a set of variables
# Params:
#   $1: Path to file containing query template
#   $2: Associative array with variables values, indexed on their names
# Output:
#   Path to the file containing result, in cache dir
function queryVariables() {
	local -r template_path="${1}"
	local -nr variables=${2}
	
	# Check parameters
	if [ ! -s "${template_path}" ]
	then
		echo "Query template not found at path ${template_path}. Exiting." >&2
		return 1
	fi
	if [ ${#variables[@]} -eq 0 ]
	then
		echo "Missing query variables. Exiting." >&2
		return 1
	fi
	
	local -r template_checksum=$(md5sum "${template_path}" | cut -d ' ' -f 1)
	local -r variables_checksum=$(echo "$(typeset -p ${2})" | md5sum - | cut -d ' ' -f 1)
	
	# Build query
	local query=$(cat "${template_path}")
	for var_name in ${!variables[@]}
	do
		query=${query//\%${var_name}\%/${variables[${var_name}]}}
	done
	
	# Save query into a temporary file
	local -r query_path="$(mktemp)"
	echo "${query}" > "${query_path}"
	
	# Check at least one variable has been substituted (file name collision otherwise)
	if [ "$(md5sum "${query_path}" | cut -d ' ' -f 1)" == "${template_checksum}" ]
	then
		echo "No variable substituted. Exiting." >&2
		return 1
	fi
	
	# Send query
	local -r query_result_path=$(query "${query_path}")
	
	# Generate query result cache path, create dir if needed
	local -r query_cache_path="${QUERY_CACHE_DIR}/${template_checksum}/${variables_checksum}"
	mkdir -p "$(dirname "${query_cache_path}")"
	
	# Link result
	if [ ! -f "${query_cache_path}" ]
	then
		ln "${query_result_path}" "${query_cache_path}"
	fi
	
	# Remove query
	rm "${query_path}"
	
	# Return result path
	echo "${query_cache_path}"
}