#!/bin/bash
set -e

SCRIPT_NAME=$(basename "$(realpath "$0")")
DB_PATH="/data/data/com.termux/files/usr/var/lib/whatprovides/whatprovides.db"
DB_UPDATES_URL="https://dl.bintray.com/termux/metadata/whatprovides-db/whatprovides.db.gz"

show_usage () {
	{
		echo
		echo "Usage: $SCRIPT_NAME [-u] path/to/file"
		echo "       $SCRIPT_NAME -p [-u] package"
		echo
		echo "Find out packages using specific files."
		echo
		echo "Options:"
		echo
		echo "  -h   Show this help."
		echo
		echo "  -p   Reverse mode. List all files owned by specified"
		echo "       package."
		echo
		echo "  -u   Update the database."
		echo
		echo "  -q   Quiet mode. Suppress informational messages."
		echo
	} >&2
}

update_database() {
	if [ -e "${DB_PATH}.gz" ]; then
		if ! ${QUIET}; then
			echo "[*] Cleaning up the remaining temporary files..." >&2
		fi
		rm -f "${DB_PATH}.gz"
	fi

	if ! ${QUIET}; then
		echo "[*] Downloading the new database..." >&2
		echo >&2

		curl --fail --retry 3 --retry-connrefused --retry-delay 1 --location \
			--output "${DB_PATH}.gz" "${DB_UPDATES_URL}"

		echo >&2
		echo "[*] Installing..." >&2
	else
		curl --silent --fail --retry 3 --retry-connrefused --retry-delay 1 \
			--location --output "${DB_PATH}.gz" "${DB_UPDATES_URL}"
	fi

	rm -f "${DB_PATH}"
	zcat "${DB_PATH}.gz" > "${DB_PATH}"
	rm -f "${DB_PATH}.gz"

	if ! ${QUIET}; then
		echo "[*] Finished." >&2
	fi
}

check_database() {
	if [ ! -e "${DB_PATH}" ]; then
		{
			echo "Error: database is not available."
			echo "Please run '${SCRIPT_NAME} -u' to create it."
		} >&2
		return 1
	fi
}

REVERSE_MODE=false
DO_UPDATE=false
QUIET=false
while (($# > 0)); do
	case "$1" in
		-h) show_usage; exit 0;;
		-p) REVERSE_MODE=true;;
		-q) QUIET=true;;
		-u) DO_UPDATE=true;;
		-*)
			echo >&2
			echo "Unknown option '$1'." >&2
			show_usage
			exit 1
			;;
		*)
			break
			;;
	esac
	shift 1
done

if ${DO_UPDATE}; then
	update_database
	[ $# -lt 1 ] && exit 0
else
	check_database
fi

if [ $# -lt 1 ]; then
	{
		echo
		echo "Error: you have not specified the file or package."
		echo
	} >&2
	exit 1
fi

if ${REVERSE_MODE}; then
	if ! grep -qx '[a-z0-9_+-]\+' <<< "$1"; then
		{
			echo
			echo "Error: package name '${1}' is not valid."
			echo
		} >&2
		exit 1
	fi

	if ! sqlite3 "${DB_PATH}" \
		"SELECT owned_file FROM 'whatprovides' WHERE package_name == '${1}' ORDER BY owned_file" \
		| awk "{ if (substr(\$0, 1, 1) == \"/\") print \"${1}: \"\$0; else print \"${1}: ${PREFIX}/\"\$0 } END { if (NR == 0) exit 1 }"
	then
		{
			echo
			echo "Error: package '$1' is not found."
			echo
		} >&2
		exit 1
	fi
else
	NEWPREFIX=
	FILE="$(realpath -sm "$1")"

	if [[ "${PREFIX}/" = "${FILE}/"* || "${FILE}" = / ]]; then
		# FILE is (((great...)grand)parent of) PREFIX, including root
		if [ "${FILE}" = / ]; then
			FILE=/.
		fi

		sqlite3 "${DB_PATH}" \
			"SELECT DISTINCT package_name FROM 'whatprovides' ORDER BY package_name" \
			| awk "{ print \$0\": ${FILE}\" }"
		exit 0
	fi

	if [[ "${FILE}" = "${PREFIX}/"* ]]; then
		# FILE is in PREFIX
		FILE="${FILE##${PREFIX}/}"
		NEWPREFIX="${PREFIX}/"
	fi # else FILE is entirely separate from PREFIX (unlikely to be in DB)

	FILE_ESC="${FILE//\'/\'\'}"
	if ! sqlite3 "${DB_PATH}" \
		"SELECT DISTINCT package_name FROM 'whatprovides' WHERE owned_file == '${FILE_ESC}' OR substr(owned_file, 1, ${#FILE} +1) == '${FILE_ESC}/' ORDER BY package_name" \
		| awk "{ print \$0\": ${NEWPREFIX}${FILE}\" } END { if (NR == 0) exit 1 }"
	then
		{
			echo
			echo "Error: file '$1' is not found."
			echo
		} >&2
		exit 1
	fi
fi

exit 0