calswap

#!/usr/bin/env bash
# Swaps the active calories database to another path
# If the path doesn't exist, it copies the current database,
# along with all the data

declare script_name
script_name='calswap'

# function to verify an external command is installed
havecmd() {
	local BINARY ERRMSG
	# error if first argument isn't provided
	BINARY="${1:?Must provide command to check}"
	# the commend exists, exit with 0 (success!)
	if command -v "$BINARY" >/dev/null 2>&1; then
		return 0
	else
		# construct error message
		ERRMSG="'$script_name' requires '$BINARY', could not find that on your \$PATH"
		if [[ -n "$2" ]]; then
			ERRMSG="$ERRMSG. $2"
		fi
		printf '%s\n' "$ERRMSG" 1>&2
		return 1
	fi
}

set -e
havecmd realpath
havecmd calories "See https://github.com/zupzup/calories"
havecmd jq "See https://stedolan.github.io/jq/download/"
set +e

conf_path() {
	printf '%s' "${GOBIN:?The GOBIN environment variable must be set}/.caloriesconf"
}

db_path() {
	cat "$(conf_path)"
}

# updates the caloriesconf to the filepath passed as the first argument
update_caloriesconf() {
	local CONF_PATH
	CONF_PATH="$(conf_path)" || return $?
	printf '%s' "${1?:Must pass path to update caloriesconf with}" >"${CONF_PATH}"
}

main() {
	local SWAP_TO CURRENT_DB
	SWAP_TO="${1:?Must provide a path to swap the current database to}"
	SWAP_TO="$(realpath "${SWAP_TO}")"
	CURRENT_DB="$(db_path)" || return $?
	# make sure that isn't already the active database
	if [[ "${SWAP_TO}" == "${CURRENT_DB}" ]]; then
		printf 'Error: "%s" is already the active database...\n' "${SWAP_TO}" >&2
		return 1
	fi
	# if the database doesn't exist, copy the current database
	if [[ ! -e "${SWAP_TO}" ]]; then
		printf "Database doesn't exist, copying current database...\n"
		# cp should error if the files are the same path
		cp -v "${CURRENT_DB}" "${SWAP_TO}" || return $?
	fi
	# update the caloriesconf file to the new database path
	update_caloriesconf "$SWAP_TO" || return $?
	printf 'Successfully swapped the current database to "%s"\n' "${SWAP_TO}"
}

main "$@" || exit $?