#ft=bash

bail() (
	echo >&2 "ERROR: $1"
	exit 1
)

must_be_root() (
	if [ "$(id --user)" != 0 ]; then
		bail "must run as root"
	fi
)

set_link() (
	TARGET=${1}
	APP_DIR=${2}
	APP_PATH=${3-}

	pushd "$(dirname "${TARGET}")" >/dev/null || exit 1
	unlink_if_set "${TARGET}"
	REL_PATH=$(relative_path "$(dirname "${TARGET}")" "${APP_DIR}/current/${APP_PATH}")
	ln -s "${REL_PATH}" "$(basename "${TARGET}")"
	popd >/dev/null || exit 1
)

get_os() (
	case $(uname -s) in
	Linux*) echo linux ;;
	Darwin*) echo darwin ;;
	Dragonfly*) echo dragonfly ;;
	FreeBSD*) echo freebsd ;;
	NetBSD*) echo netbsd ;;
	OpenBSD*) echo openbsd ;;
	SunOS*) echo solaris ;;
	Windows_NT*) echo windows ;;
	CYGWIN_NT*) echo windows ;;
	*)
		echo >&2 "unsupported os"
		return
		;;
	esac
)

get_arch() (
	case $(uname -m) in
	x86_64*) echo amd64 ;;
	amd64*) echo amd64 ;;
	i386*) echo 386 ;;
	i686*) echo 386 ;;
	arm) echo arm ;;
	armv7*) echo arm ;;
	armv6*) echo arm ;;
	armv8*) echo arm ;;
	aarch64*) echo arm64 ;;
	*)
		echo >&2 "unsupported architecture: $(uname -m)"
		exit 1
		;;
	esac
)

set_current_link() (
	prefix=${1}
	version=${2}
	sudo=${3-}
	current="${prefix}/current"
	if [ -L "${current}" ]; then
		$sudo unlink "${current}"
	fi
	rel="$(relative_path "${prefix}" "${prefix}/${version}")"
	$sudo ln -s "$rel" "${current}"
)

unlink_if_set() (
	dir=$1
	sudo=${2-}
	if [ -L "${dir}" ]; then
		# shellcheck disable=SC2086
		${sudo} unlink "${dir}"
	fi
)

mkdir_if_missing() (
	dir=${1}
	sudo=${2-}
	if [ ! -d "${dir}" ]; then
		# shellcheck disable=SC2086
		$sudo mkdir -p "${dir}"
	fi
)

extract_zip() (
	url=${1}
	dest=${2}
	args=${3-}
	sudo=${4-}
	if [ -d "${dest}" ]; then
		return
	fi

	mkdir_if_missing "${dest}" "${sudo}"
	tmp_dir="$(mktemp -d)"
	zipfile=${tmp_dir}/release.zip
	curl --silent --location --output "${zipfile}" "${url}"
	# shellcheck disable=SC2086
	$sudo unzip -o "${zipfile}" -d "${dest}" ${args}
	rm -rf "${tmp_dir}"
)

extract_tarball() (
	url=${1}
	dest=${2}
	args=${3-}
	sudo=${4-}
	if [ -d "${dest}" ]; then
		return
	fi

	mkdir_if_missing "${dest}" "${sudo}"
	tmp_dir="$(mktemp -d)"
	tarball=${tmp_dir}/release.tar.gz
	curl --silent --location --output "${tarball}" "${url}"
	# shellcheck disable=SC2086
	$sudo tar xf "${tarball}" --directory "${dest}" ${args}
	rm -rf "${tmp_dir}"
)

extract_binary() (
	url=${1}
	dest=${2}
	sudo=${3-}
	if [ -f "${dest}" ]; then
		return
	fi
	mkdir_if_missing "$(dirname "${dest}")" "${sudo}"
	tmp_file="$(mktemp)"
	curl --silent --location --output "${tmp_file}" "${url}"
	$sudo chmod +x "${tmp_file}"
	$sudo mv "${tmp_file}" "${dest}"
)

relative_path() (
	# both $1 and $2 are absolute paths beginning with /
	# $1 must be a canonical path; that is none of its directory
	# components may be ".", ".." or a symbolic link
	#
	# returns relative path to $2/$target from $1/$src
	src=$1
	target=$2

	common_part=$src
	result=

	while [ "${target#"$common_part"}" = "$target" ]; do
		# no match, means that candidate common part is not correct
		# go up one level (reduce common part)
		common_part=$(dirname "$common_part")
		# and record that we went back, with correct / handling
		if [ -z "$result" ]; then
			result=..
		else
			result=../$result
		fi
	done

	if [ "$common_part" = / ]; then
		# special case for root (no common path)
		result=$result/
	fi

	# since we now have identified the common part,
	# compute the non-common part
	forward_part=${target#"$common_part"}

	# and now stick all parts together
	if [ -n "$result" ] && [ -n "$forward_part" ]; then
		result=$result$forward_part
	elif [ -n "$forward_part" ]; then
		# extra slash removal
		result=${forward_part#?}
	fi

	printf '%s' "$result"
)