#!/bin/sh

# chezmoi install script
# contains code from and inspired by
# https://github.com/client9/shlib
# https://github.com/goreleaser/godownloader

set -e

BINDIR=${BINDIR:-./bin}
CHEZMOI_USER_REPO=${CHEZMOI_USER_REPO:-twpayne/chezmoi}
TAGARG=latest
LOG_LEVEL=2
EXECARGS=

GITHUB_DOWNLOAD=https://github.com/${CHEZMOI_USER_REPO}/releases/download

tmpdir=$(mktemp -d)
trap 'rm -rf ${tmpdir}' EXIT

usage() {
	this="$1"
	cat <<EOF
${this}: download chezmoi and optionally run chezmoi

Usage: ${this} [-b bindir] [-d] [-t tag] [chezmoi-args]
  -b sets the installation directory, default is ${BINDIR}.
  -d enables debug logging.
  -t sets the tag, default is ${TAG}.
If chezmoi-args are given, after install chezmoi is executed with chezmoi-args.
EOF
	exit 2
}

main() {
	parse_args "$@"

	GOOS=$(get_goos)
	GOARCH=$(get_goarch)
	check_goos_goarch "${GOOS}/${GOARCH}"

	TAG="$(real_tag $TAGARG)"
	VERSION="${TAG#v}"

	log_info "found version ${VERSION} for ${TAGARG}/${GOOS}/${GOARCH}"

	BINSUFFIX=
	FORMAT=tar.gz
	GOOS_EXTRA=
	case "${GOOS}" in
	linux)
		case "${GOARCH}" in
		amd64)
			case "$(get_libc)" in
			glibc)
				GOOS_EXTRA="-glibc"
				;;
			musl)
				GOOS_EXTRA="-musl"
				;;
			esac
		esac
		;;
	windows)
		BINSUFFIX=.exe
		FORMAT=zip
		;;
	esac
	case "${GOARCH}" in
	386) arch=i386 ;;
	*) arch="${GOARCH}" ;;
	esac

	# download tarball
	NAME="chezmoi_${VERSION}_${GOOS}${GOOS_EXTRA}_${arch}"
	TARBALL="${NAME}.${FORMAT}"
	TARBALL_URL="${GITHUB_DOWNLOAD}/${TAG}/${TARBALL}"
	http_download "${tmpdir}/${TARBALL}" "${TARBALL_URL}" || exit 1

	# download checksums
	CHECKSUMS="chezmoi_${VERSION}_checksums.txt"
	CHECKSUMS_URL="${GITHUB_DOWNLOAD}/${TAG}/${CHECKSUMS}"
	http_download "${tmpdir}/${CHECKSUMS}" "${CHECKSUMS_URL}" || exit 1

	# verify checksums
	hash_sha256_verify "${tmpdir}/${TARBALL}" "${tmpdir}/${CHECKSUMS}"

	(cd "${tmpdir}" && untar "${TARBALL}")

	# install binary
	if [ ! -d "${BINDIR}" ]; then
		install -d "${BINDIR}"
	fi
	BINARY="chezmoi${BINSUFFIX}"
	install "${tmpdir}/${BINARY}" "${BINDIR}/"
	log_info "installed ${BINDIR}/${BINARY}"

	if [ -n "${EXECARGS}" ]; then
		# shellcheck disable=SC2086
		exec "${BINDIR}/${BINARY}" $EXECARGS
	fi
}

parse_args() {
	while getopts "b:dh?t:" arg; do
		case "${arg}" in
		b) BINDIR="${OPTARG}" ;;
		d) LOG_LEVEL=3 ;;
		h | \?) usage "$0" ;;
		t) TAGARG="${OPTARG}" ;;
		*) return 1 ;;
		esac
	done
	shift $((OPTIND - 1))
	EXECARGS="$*"
}

get_goos() {
	os=$(uname -s | tr '[:upper:]' '[:lower:]')
	case "${os}" in
	cygwin_nt*) goos="windows" ;;
	mingw*) goos="windows" ;;
	msys_nt*) goos="windows" ;;
	sunos*)
		kernel=$(uname -o | tr '[:upper:]' '[:lower:]')
		case "${kernel}" in
		illumos*) goos="illumos" ;;
		solaris*) goos="solaris" ;;
		*) goos="${os}" ;;
		esac
		;;
	*) goos="${os}" ;;
	esac
	echo "${goos}"
}

get_goarch() {
	arch=$(uname -m)
	case "${arch}" in
	aarch64) goarch="arm64" ;;
	armv*) goarch="arm" ;;
	i386) goarch="386" ;;
	i686) goarch="386" ;;
	i86pc) goarch="amd64" ;;
	x86) goarch="386" ;;
	x86_64) goarch="amd64" ;;
	*) goarch="${arch}" ;;
	esac
	echo "${goarch}"
}

check_goos_goarch() {
	case "$1" in
{{- range .Platforms }}
	{{ .GOOS }}/{{ .GOARCH }}) return 0 ;;
{{- end }}
	*)
		echo "$1: unsupported platform" 1>&2
		return 1
		;;
	esac
}

get_libc() {
	if is_command ldd; then
		case "$(ldd --version 2>&1 | tr '[:upper:]' '[:lower:]')" in
		*glibc*|"*gnu libc*")
			echo glibc
			return
			;;
		*musl*)
			echo musl
			return
			;;
		esac
	fi
	if is_command getconf; then
		case "$(getconf GNU_LIBC_VERSION 2>&1)" in
		*glibc*)
			echo glibc
			return
			;;
		esac
	fi
	log_crit "unable to determine libc" 1>&2
	exit 1
}

real_tag() {
	tag=$1
	log_debug "checking GitHub for tag ${tag}"
	release_url="https://github.com/${CHEZMOI_USER_REPO}/releases/${tag}"
	json=$(http_get "${release_url}" "Accept: application/json")
	if [ -z "${json}" ]; then
		log_err "real_tag error retrieving GitHub release ${tag}"
		return 1
	fi
	real_tag=$(echo "${json}" | tr -s '\n' ' ' | sed 's/.*"tag_name":"//' | sed 's/".*//')
	if [ -z "${real_tag}" ]; then
		log_err "real_tag error determining real tag of GitHub release ${tag}"
		return 1
	fi
	if [ -z "${real_tag}" ]; then
		return 1
	fi
	log_debug "found tag ${real_tag} for ${tag}"
	echo "${real_tag}"
}

http_get() {
	tmpfile=$(mktemp)
	http_download "${tmpfile}" "$1" "$2" || return 1
	body=$(cat "${tmpfile}")
	rm -f "${tmpfile}"
	echo "${body}"
}

http_download_curl() {
	local_file=$1
	source_url=$2
	header=$3
	if [ -z "${header}" ]; then
		code=$(curl -w '%{http_code}' -sL -o "${local_file}" "${source_url}")
	else
		code=$(curl -w '%{http_code}' -sL -H "${header}" -o "${local_file}" "${source_url}")
	fi
	if [ "${code}" != "200" ]; then
		log_debug "http_download_curl received HTTP status ${code}"
		return 1
	fi
	return 0
}

http_download_wget() {
	local_file=$1
	source_url=$2
	header=$3
	if [ -z "${header}" ]; then
		wget -q -O "${local_file}" "${source_url}" || return 1
	else
		wget -q --header "${header}" -O "${local_file}" "${source_url}" || return 1
	fi
}

http_download() {
	log_debug "http_download $2"
	if is_command curl; then
		http_download_curl "$@" || return 1
		return
	elif is_command wget; then
		http_download_wget "$@" || return 1
		return
	fi
	log_crit "http_download unable to find wget or curl"
	return 1
}

hash_sha256() {
	target=$1
	if is_command sha256sum; then
		hash=$(sha256sum "${target}") || return 1
		echo "${hash}" | cut -d ' ' -f 1
	elif is_command shasum; then
		hash=$(shasum -a 256 "${target}" 2>/dev/null) || return 1
		echo "${hash}" | cut -d ' ' -f 1
	elif is_command sha256; then
		hash=$(sha256 -q "${target}" 2>/dev/null) || return 1
		echo "${hash}" | cut -d ' ' -f 1
	elif is_command openssl; then
		hash=$(openssl dgst -sha256 "${target}") || return 1
		echo "${hash}" | cut -d ' ' -f a
	else
		log_crit "hash_sha256 unable to find command to compute SHA256 hash"
		return 1
	fi
}

hash_sha256_verify() {
	target=$1
	checksums=$2
	basename=${target##*/}

	want=$(grep "${basename}" "${checksums}" 2>/dev/null | tr '\t' ' ' | cut -d ' ' -f 1)
	if [ -z "${want}" ]; then
		log_err "hash_sha256_verify unable to find checksum for ${target} in ${checksums}"
		return 1
	fi

	got=$(hash_sha256 "${target}")
	if [ "${want}" != "${got}" ]; then
		log_err "hash_sha256_verify checksum for ${target} did not verify ${want} vs ${got}"
		return 1
	fi
}

untar() {
	tarball=$1
	case "${tarball}" in
	*.tar.gz | *.tgz) tar -xzf "${tarball}" ;;
	*.tar) tar -xf "${tarball}" ;;
	*.zip) unzip "${tarball}" ;;
	*)
		log_err "untar unknown archive format for ${tarball}"
		return 1
		;;
	esac
}

is_command() {
	command -v "$1" >/dev/null
}

log_debug() {
	[ 3 -le "${LOG_LEVEL}" ] || return 0
	echo debug "$@" 1>&2
}

log_info() {
	[ 2 -le "${LOG_LEVEL}" ] || return 0
	echo info "$@" 1>&2
}

log_err() {
	[ 1 -le "${LOG_LEVEL}" ] || return 0
	echo error "$@" 1>&2
}

log_crit() {
	[ 0 -le "${LOG_LEVEL}" ] || return 0
	echo critical "$@" 1>&2
}

main "$@"
