build.sh

#!/usr/bin/env sh
# SPDX-License-Identifier: Unlicense
CMD="$0"
SCRIPT_DIR="$(dirname "$(realpath "$0")")"
SCRIPT_NAME="$(basename "$(realpath "$0")")"
is_debug=${BUILD_DEBUG:+1}
case "$BUILD_DEBUG" in *trace*) is_trace=1 ;; esac
case "$BUILD_DEBUG" in *dry-run*) is_dry_run=1 ;; esac

print_help_text() {
	cat <<EOF
$SCRIPT_NAME - Build this project

Usage: $CMD [OPTION...] APP_NAME BUILD_DIR VERSION

Options:
    --dry-run     Only output what would be done, but don't actually do
                  anything
 -v --verbose     Output debug information (-vv very verbose)
 -h --help        Print this help text and exit
EOF
	exit
}

log_error() { printf 'ERROR %s\n' "$*" >&2; }
log_warn() { printf 'WARN %s\n' "$*" >&2; }
log_info() { printf '%s\n' "$*"; }
log_debug() { [ "$is_debug" ] && printf 'DEBUG %s\n' "$*"; }
log_trace() { [ "$is_trace" ] && printf 'TRACE %s\n' "$*"; }
abort() {
	log_error "$*"
	exit 1
}
unknown_option() { abort "Unknown option $*. Run $CMD --help"; }

get_argv() {
	argc=$((argc + 1))
	case "$argc" in
	1) app_name="$1" ;;
	2) build_dir="$1" ;;
	3) version="$1" ;;
	*) abort "Too many arguments. Run $CMD --help" ;;
	esac
}

read_arguments() {
	app_name=
	build_dir=
	version=
	argc=
	for _arg in "$@"; do
		case "$_arg" in
		--dry-run) is_dry_run=1 ;;
		--verbose | -v) is_debug=1 ;;
		-vv) is_trace=1 && is_debug=1 ;;
		--help | -h) print_help_text ;;
		-*) unknown_option "$_arg" ;;
		*) get_argv "$_arg" ;;
		esac
	done

	[ "$app_name" ] || abort "Missing APP_NAME argument. Run $CMD --help"
	[ "$build_dir" ] || abort "Missing BUILD_DIR argument. Run $CMD --help"
	[ "$version" ] || abort "Missing VERSION argument. Run $CMD --help"

	case "$version" in
	*[!.0-9]*) version_is_pre_release=1 ;; # If version has any character that is not a . or a digit, it is a pre-release version
	*) version_is_pre_release= ;;
	esac
	app_template_file="${SCRIPT_DIR}/${app_name}.template.sh"
	entrypoint_file="${SCRIPT_DIR}/entrypoint.sh"
	build_path="${SCRIPT_DIR}/$build_dir"
	target_file="${build_path}/$app_name"

	log_debug "is_dry_run=$is_dry_run"
	log_debug "is_debug=$is_debug"
	log_debug "is_trace=$is_trace"
	log_debug "app_name=$app_name"
	log_debug "build_dir=$build_dir"
	log_debug "version=$version"
	log_debug "version_is_pre_release=$version_is_pre_release"
	log_debug "app_template_file=$app_template_file"
	log_debug "entrypoint_file=$entrypoint_file"
	log_debug "build_path=$build_path"
	log_debug "target_file=$target_file"
}

read_git_state() {
	git_status="$(git --no-optional-locks status --porcelain)" || abort "Failed to read git status"
	git_last_commit_info="$(git --no-optional-locks log -1 --pretty='format:(%h %cs)')" || abort "Failed to read git log"
	git_tree_is_dirty=${git_status:+1}

	log_debug "git_status=$git_status"
	log_debug "git_last_commit_info=$git_last_commit_info"
	log_debug "git_tree_is_dirty='$git_tree_is_dirty'"
}

check_dependencies() {
	missing=
	for _dep in "$@"; do
		if ! command -v "$_dep" >/dev/null; then
			log_error "$_dep is not installed"
			missing=1
		fi
	done

	if [ "$missing" ]; then
		abort "Aborted due to missing dependencies. Make sure all dependencies are available in the PATH"
	fi
}

# Escape text for literal use in a replacement string in sed's 's' command
sed_replacement_escape() {
	printf '%s' "$*" | sed -E -e 's/[\\/&]/\\&/g' -e '$!s/$/\\n/' | tr -d '\n'
}

# Strip single quotes from text for use in a shell script single-quoted string
strip_single_quotes() {
	printf '%s' "$*" | tr -d "'"
}

# Render a template from a file with simple string substitution
render_template() {
	_template_file="$1"
	_version="$2"
	_version="${_version}${git_tree_is_dirty:+'+dirty'}${version_is_pre_release:+ $git_last_commit_info}"
	_version="$(sed_replacement_escape "$(strip_single_quotes "$_version")")"
	log_debug "render_template() escaped _version=$_version"
	_entrypoint_text="$(cat "$3")"
	_entrypoint_text="$(sed_replacement_escape "$_entrypoint_text")"
	log_trace "render_template() escaped _entrypoint_text=$_entrypoint_text"
	_result="$(cat "$_template_file")"
	_result="$(printf '%s' "$_result" | sed -E "s/%%VERSION%%/$_version/g")"
	_result="$(printf '%s' "$_result" | sed -E "s/%%BUILD_ENTRYPOINT_FILE%%/$_entrypoint_text/g")"

	[ "$_result" ] || abort "render_template() _result is null"
	render_template_result="$_result"
}

main() {
	check_dependencies cat chmod date git mkdir sed tr
	read_arguments "$@"
	read_git_state

	log_info "Rendering template from $app_template_file with version=$version to file $target_file"
	render_template "$app_template_file" "$version" "$entrypoint_file"

	log_trace "CMD: printf '%s\n' \"${render_template_result}\" >\"$target_file\""
	if [ "$is_dry_run" ]; then
		log_info "DRY-RUN CMD: mkdir -p \"$build_path\""
		log_info "DRY-RUN CMD: printf '%s' \"\$render_template_result\" >\"$target_file\""
		log_info "DRY-RUN CMD: chmod +x \"$target_file\""
	else
		mkdir -p "$build_path" || abort "Failed to create build dir at $build_path"
		printf '%s\n' "$render_template_result" >"$target_file" || abort "Failed to write file $target_file"
		chmod +x "$target_file" || abort "Failed to chmod file $target_file"
	fi
}

main "$@"