#!/usr/bin/env bash
# shellcheck disable=SC2034,SC1090
#
# refresh libgen databases from dump files

version="0.7.0"
release="20210701"

trap "trap_error" TERM
trap "trap_clean" EXIT
export TOP_PID=$$

functions="$(dirname "$0")/books_functions"
if [ -f "$functions" ]; then
        source "$functions"
else
        echo "$functions not found"
        exit 1              
fi

main () {

	exlock now || exit 1

	# PREFERENCES
	config=${XDG_CONFIG_HOME:-$HOME/.config}/books.conf

	# maximum age (in days) of database dump file to use
	max_age=5

	# database server to use
	dbhost="localhost"
	dbport="3306"
	dbuser="libgen"

	# where to get updates. A change here probably necessitates a change in the urls array
	# as dump file names can be site-specific. 
	base="http://libgen.rs/dbdumps/"

	# database names
	declare -A databases=(
		[libgen]=libgen
		[compact]=libgen_compact
		[fiction]=libgen_fiction
	)

	# source config file if it exists
	[[ -f ${config} ]] && source "${config}"

	# (mostly) END OF PREFERENCES

	# urls for dump files (minus datestamp and extension)
	declare -A urls=(
		[libgen]="${base}/libgen"
		[compact]="${base}/libgen_compact"
		[fiction]="${base}/fiction"
	)

	# sql to get time last modified for database
	declare -A lastmodified=(
		[libgen]="select max(timelastmodified) from updated;"
		[compact]="select max(timelastmodified) from updated;"
		[fiction]="select max(timelastmodified) from fiction;"
	)

	# stream filters can be applied during extraction, saving time and storage space
	declare -A stream_filter=(
		[libgen]='s/DEFINER[ ]*=[ ]*[^*]*\*/\*/;s/DEFINER[ ]*=[ ]*[^*]*PROCEDURE/PROCEDURE/;s/DEFINER[ ]*=[ ]*[^*]*FUNCTION/FUNCTION/;s/^INSERT INTO `updated_edited`.*$/-- skip/;s/^INSERT INTO `description_edited`.*$/-- skip/'
		[compact]='s/DEFINER[ ]*=[ ]*[^*]*\*/\*/;s/DEFINER[ ]*=[ ]*[^*]*PROCEDURE/PROCEDURE/;s/DEFINER[ ]*=[ ]*[^*]*FUNCTION/FUNCTION/;s/^INSERT INTO `updated_edited`.*$/-- skip/'
	)

	# file filters are used in case the whole file needs to be extracted before the filter can be applied
	# if both a stream filter as well as a file filter is defined, only the file filter is used
	declare -A file_filter=(
	)

	# sql to run BEFORE update
	declare -A before_update=(
	)

	# sql to run AFTER update
	declare -A after_update=(
		[libgen]="drop trigger libgen_description_update_all"
		[compact]="drop trigger libgen_description_update_all;create table description (id int(11) not null auto_increment, md5 varchar(32) not null default '', descr varchar(20000) not null default '', toc mediumtext not null, TimeLastModified timestamp not null default current_timestamp on update current_timestamp, primary key (id), unique key md5_unique (md5) using btree, key time (timelastmodified) using btree, key md5_hash (md5) using hash);"
	)

	declare -A options=(
		[wget]="-nv"
		[wget_verbose]=""
		[unrar]="-inul"
		[unrar_verbose]=""
	)


	tmpdir=$(mktemp -d /var/tmp/libgen.XXXXXX)

	unrar=$(find_tool "unrar")
	wget=$(find_tool "wget")
	w3m=$(find_tool "w3m")

	while getopts "a:cd:efhH:knP:u:U:v@" OPTION
	do
	case $OPTION in
		n)
			no_action=1
			;;
		f)
			force_refresh=1
			;;
		d)
			max_age=${OPTARG}
			;;
		u)
			if [[ -v "databases[${OPTARG}]" ]]; then
				dbs+=" ${OPTARG}"
			else
				exit_with_error "-u ${OPTARG}: no such database"
			fi
			;;
		v)
			pv=$(find_tool "pv")
			verbose="_verbose"
			;;
		H)
			dbhost="${OPTARG}"
			;;
		P)
			dbport="${OPTARG}"
			;;
		U)
			dbuser="${OPTARG}"
			;;
		c)
			if [[ ! -f "${config}" ]]; then
				cat <<-EOT > "${config}"
				dbhost=${dbhost}
				dbport=${dbport}
				dbuser=${dbuser}
				base=${base}
				EOT
			else
				exit_with_error "-c: config file ${config} exists, either remove it or edit it directly"
			fi
			exit
			;;
		e)
			if [[ -f "$config" ]]; then
				if [[ "$VISUAL" ]]; then "$VISUAL" "$config";
				elif [[ "$EDITOR" ]]; then "$EDITOR" "$config";
				else exit_with_error "-e: no editor configured, can not edit $config"
				fi
			else
				exit_with_error "-e: config file does not exist, create is first (see -c)"
			fi
			exit
			;;
		a)
			if url_available "${OPTARG}"; then
				base="${OPTARG}"
			else
				exit_with_error "-a ${OPTARG}: repository not available"
			fi
			;;
		@)
			torsocks=$(find_tool "torsocks")
			export TORSOCKS_TOR_PORT=$OPTARG
			;;
		k)
			keep_downloaded_files=1
			;;
		h)
			help
			exit
			;;
		*)
			exit_with_error "unknown option: $OPTION"
			;;
	esac
	done

	[[ -z ${dbs} ]] && dbs="${!databases[*]}"

	pushd "$tmpdir" >/dev/null || exit_with_error "can not change directory to $tmpdir"
	for db in ${dbs}; do
		database=${databases[$db]}
		if [[ $(db_exists "$database") ]]; then
			db_dump=$(is_available "${db}" "${max_age}")
			if [[ -n $db_dump ]]; then
				[[ -n $verbose ]] && echo "update available for ${db}: ${db_dump}"
				if [[ -z ${no_action} ]]; then
					$torsocks "$wget" "${options[$wget${verbose}]}" "${db_dump}"
					dbfilename="$(basename "${db_dump}")"
					if [[ -z "${file_filter[$db]}" ]]; then
						if [[ -n "${stream_filter[$db]}" ]]; then
							dumpcmd() { $unrar p -ierr "$dbfilename"|run_filter "${stream_filter[$db]}"; }
						else
							dumpcmd() { $unrar p -ierr "$dbfilename"; }
						fi
					else
						dumpname="$($unrar lb "$dbfilename")"
						$unrar "${options[$unrar${verbose}]}" x "$(basename "${db_dump}")"
						run_filter "${filter[$db]}" "$dumpname"
						dumpcmd() { cat "$dumpname"; }
					fi
					drop_tables=$(drop_table_sql "$database")
					[[ -n $drop_tables ]] && dbx "$database" "$drop_tables"
					[[ -n ${before_update[$db]} ]] && dbx "$database" "${before_update[$db]}"
					if [[ -n $verbose ]]; then
						echo "importing $dbfilename into $database"
						dumpcmd | $pv | dbx "$database"
					else
						dumpcmd | dbx "$database"
					fi
					[[ -n ${after_update[$db]} ]] && dbx "$database" "${after_update[$db]}"
				fi
			else
				[[ -n $verbose ]] && echo "no update available for ${db}"
			fi
		else
			echo "database '$database' does not exist, please create it before attempting to refresh" >&2
		fi
	done
	popd >/dev/null || exit_with_error "popd failed?"
}

# check whether there is a dump file which is more recent than the current database and no older
# than $max_age
is_available () {
        db="$1"
        max_age="$2"

	db_age=$(db_age "$db")

	age=0

	while [[ $age -lt $db_age && $age -lt $max_age ]]; do
		timestamp=$(date -d "@$(($(date +%s) - $((60*60*24*age))))" +%Y-%m-%d)
        	result=$($w3m -dump "${base}" | awk '{ print $1 }'|grep "$(basename "${urls[$db]}_${timestamp}.rar")")
		[[ -n $result ]] && break
		((age++))
	done

    [[ -n $result ]] && echo "$(dirname "${urls[$db]}")"/"${result}"
}

# drop tables to prepare database for refresh
drop_table_sql () {
        database="$1"
	dbx "$database" "SELECT concat('DROP TABLE IF EXISTS ', table_name, ';') FROM information_schema.tables WHERE table_schema = '$database';"
}

# returns database name if it exists, nothing otherwise
db_exists () {
	database="$1"
	dbx "$database" "select schema_name from information_schema.schemata where schema_name='$database';" 2>/dev/null
}

# return database age in days
db_age () {
	db="$1"
	now=$(date +%s)
	age=0
	if [[ "$force_refresh" -gt 0 ]]; then
		age=$max_age
	else
		db_last_modified=$(date -d "$(dbx "$database" "${lastmodified[$db]}")" +%s)
		age=$(((now-db_last_modified)/60/60/24))
	fi
	echo -n $age
}

# run filter on dump
run_filter () {
	flt="$1"
	file="$2"
	if [[ -n "$file" ]]; then
		sed -i -e "$flt" "$file"
	else
		sed -e "$flt"
	fi
}

check_credentials () {
	if [[ ! $(dbx "" "select true;" 2>/dev/null) ]]; then
		exit_with_error "database connection error, bad username or password?"
	fi
}

url_available () {
	url="$1"
	$torsocks "$wget" -q --spider "$url"
}

cleanup () {
        if [[ ! -v keep_downloaded_files ]]; then
            rm -rf "${tmpdir}"
        else
            echo "-k option active, temporary directory ${tmpdir} not removed"
        fi
}

help () {
        echo "$(basename "$(readlink -f "$0")")" "version $version"
        cat <<- EOT

	Usage: refresh_libgen OPTIONS

	Performs a refresh from a database dump file for the chosen libgen databases.

	Make sure the database credentials are configured (in \$HOME/.my.cnf) before
	using this tool.

	    -n		do not refresh database
	 		use together with '-v' to check if recent dumps are available
	    -f		force refresh, use this on first install
	    -v		be verbose about what is being updated
	    -d DAYS	only use database dump files no older than DAYS days (default: ${max_age})
	    -u DBS	refresh DBS databases (default: ${!databases[@]})

	    -H DBHOST	database host (${dbhost})
	    -P DBPORT	database port (${dbport})
	    -U DBUSER	database user (${dbuser})
	    -a REPO	dump repository (${base})
	    -c 		create a config file using current settings (see -H, -P, -U, -R)
	    -e		edit config file

	    -@ TORPORT	use tor (through torsocks) to connect to libgen server
	    -k		keep downloaded files after exit
	    -h		this help message

	EOT
}

exlock prepare || exit 1

main "$@"