parse-opts.sh

parse-opts.sh

#!/usr/bin/env bash
#
# MIT Licensensed
# Amit Bakshi Jan 2021

# Generic option parser.
# Usage:
#   parse_opts --valid-args 'foo bar link' -- --with-foo=yes --bar=fizz --no-link
#
#  Yields:
#     O_foo=true
#     O_bar=fizz
#     O_link=false
#
#  TODO: Add help generation, maybe from a heredoc that can also serve to
#        provide the valid options.
#
parse_opts() {
    local valid_args="debug verbose quiet"
    while [ $# -gt 0 ]; do
        local cmd="$1"
        shift
        case "$cmd" in
            --) break;;
            --valid-args=*) valid_args+=' '"${cmd#--valid-args=}";;
            --valid-args) valid_args+=" $1"; shift;;
            *) echo >&2 "Invalid option for this section"; return 144;;
        esac
    done
    while [ $# -gt 0 ]; do
        local cmd key value prefix
        cmd="${1#--}"
        if [ -n "$cmd" ] && [[ "$cmd" =~ ^([a-zA-Z][a-zA-Z0-9_-]*) ]]; then
            cmd="${cmd#--}"
            if [[ "$cmd" =~ ^(without|disable|enable|with) ]]; then
                prefix=${BASH_REMATCH[1]}
                cmd="${cmd#$prefix}"
                cmd="${cmd#-}"
            fi
            key="${cmd%%=*}"
            value="${cmd#$key=}"
            sep="${cmd%$value}"
            sep="${sep#$key}"
            if  [ -z "$sep" ]; then
              value=true
            elif [ "$sep" = '=' ]; then
               value="${cmd#$key=}"
            else
               echo >&2 "ERROR: Invalid argument. Should be --foo=bar: $1"
               return 1
            fi

            if [[ "$prefix" =~ ^(without|disable)$ ]]; then
                if [[ "$value" =~ ^(false|disabled|no|0)$ ]]; then
                    value=true
                elif [[ "$value" =~ ^(true|enabled|on|1)$ ]]; then
                    value=false
                fi
            elif [[ "$prefix" =~ ^(with|enable)$ ]]; then
                if [[ "$value" =~ ^(false|disabled|no|0)$ ]]; then
                    value=false
                elif [[ "$value" =~ ^(true|enabled|on|1)$ ]]; then
                    value=true
                fi
            elif [ -z "$prefix" ]; then
                value="${value:-true}"
            else
                echo >&2 "ERROR: Invalid option $1"
                return 1
            fi
            key="${key//-/_}"
            if [[ "$valid_args" =~ $key ]]; then
                eval "O_${key}=$value"
            else
                echo >&2 "Invalid option: $key"
                return 145
            fi
        else
            shift
            echo "$@"
            return $#
        fi
        shift
    done
}