getzig

#!/usr/bin/env bash
#
# Download the binary archive of the latest Zig toolchain and install it
# if it is not already installed.
#-----------------------------------------------------------------------------
#
# Where the Zig toolchain is installed
BASE_DIR=/opt/zig

: "${GETZIG_DEBUG:=0}"
: "${GETZIG_DRYRUN:=0}"

#-----------------------------------------------------------------------------
main() {
	set -euo pipefail
	declare -A info
	local release="${1-stable}" infovars

	checkdeps

	infovars="$(get_latest_info "${release}")"
	while IFS='=' read -r key value; do
		info["${key}"]="${value}"
	done <<<"${infovars}"

	version="${info[version]}"
	install_dir="${BASE_DIR}/${version}"
	if [[ -e "${install_dir}" ]]; then
		printf '%s version %s is up to date\n' "${release}" "${version}"
		exit 0
	fi

	printf 'Downloading latest %s version %s\n' "${release}" "${version}"
	mkdir "${install_dir}"
	run curl -sL -o - "${info[tarball]}" | run tar -C "${install_dir}" -x -J --strip-components=1
	run mkdir "${install_dir}/bin"
	run mv "${install_dir}/zig" "${install_dir}/bin"
	run ln -nsf "${version}" "${BASE_DIR}/${release}"
}

#-----------------------------------------------------------------------------
checkdeps() {
	if ((BASH_VERSINFO[0] < 4)); then
		echo "This script requires bash 4 or later" >&2
		return 1
	fi

	if ! which jq >/dev/null 2>&1; then
		echo "jq is required" >&2
		return 1
	fi

	if ! which curl >/dev/null 2>&1; then
		echo "curl is required" >&2
		return 1
	fi
}
#-----------------------------------------------------------------------------
get_latest_info() {
	local os arch
	case $(uname) in
	Linux) os=linux ;;
	Darwin) os=macos ;;
	*)
		printf 'Unknown OS name: %s\n' "$(uname)" >&2
		exit 1
		;;
	esac

	case $(uname -m) in
	x86_64) arch=x86_64 ;;
	aarch64 | arm64) arch=aarch64 ;;
	arm*) arch=armv7a ;;
	*)
		printf 'Unknown architecture: %s\n' "$(uname -m)" >&2
		exit 1
		;;
	esac

	local select_release=''
	local select_file=".[\"${arch}-${os}\"] + {version: .version}"
	local to_key_val='to_entries | .[] | .key + "=" + (.value | tostring)'

	case "${1-}" in
	master)
		select_release='.master'
		;;
	stable | '')
		# Note: this relies on jq processing map entries in the order they appear. This
		# may not be the case with gojq
		select_release='to_entries | .[1] | {version: .key} + .value'
		;;
	*)
		printf 'unknown release type. Must be stable (default) or master\n' >&2
		exit 1
		;;
	esac

	alwaysrun curl -sL "https://ziglang.org/download/index.json" |
		alwaysrun jq -r "${select_release} | ${select_file} | ${to_key_val}" |
		debug
}

#-----------------------------------------------------------------------------
# run runs a command if dry run mode is off, and prints that command to
# stderr if debug or dry run mode is on.
run() {
	if ((GETZIG_DEBUG > 0 || GETZIG_DRYRUN > 0)); then
		echo "$@" >&2
	fi
	if ((GETZIG_DRYRUN > 0)); then
		return
	fi
	"$@"
}

# alwaysrun runs a command even if dry run mode is on.
alwaysrun() {
	if ((GETZIG_DEBUG > 0 || GETZIG_DRYRUN > 0)); then
		echo "$@" >&2
	fi
	"$@"
}

# debug sends stdin to stdout, and if debug mode is on, also sends stdin to
# stderr.
debug() {
	if ((GETZIG_DEBUG > 0)); then
		tee /dev/stderr
	else
		cat
	fi
}
#-----------------------------------------------------------------------------
# Only run main if executed as a script and not sourced.
if [[ "${BASH_SOURCE[0]}" == "$0" ]]; then main "$@"; fi