99-grep.bash

shopt -s extglob

function grep.fail {
	printf '%s\n' "$1" >&2
	exit "${2-1}"
}

function grep.get_opt_and_optarg {
	OPT=$1 OPTARG= OPTSHIFT=0

	if [[ $1 == -[!-]?* ]]; then
		OPT=${1:0:2} OPTARG=${1:2}
	elif [[ $1 == --*=* ]]; then
		OPT=${1%%=*} OPTARG=${1#*=}
	elif [[ ${2+.} ]]; then
		OPTARG=$2 OPTSHIFT=1
	else
		return 1
	fi

	return 0
}

function grep {
	local opts=() args=() regex_specified=false i

	while [[ $# -gt 0 ]]; do
		case $1 in
		-[EFGPiwxzsvVbnHhoqaIrRLlcTZU]|--@(extended-regexp|fixed-strings|basic-regexp|perl-regexp|ignore-case|no-ignore-case|word-regexp|line-regexp|null-data|no-messages|invert-match|version|help|byte-offset|line-number|line-buffered|with-filename|no-filename|only-matching|text|recursive|dereference-recursive|files-without-match|files-with-matches|count|initial-tab|null|no-group-separator|binary)|--@(color|colour)?(=*))
			opts+=("$1")
			;;
		-+([[:digit:]])|-[efmdDBAC]*|--@(regexp|file|max-count|label|binary-files|directories|devices|include|exclude|exclude-from|exclude-dir|before-context|after-context|context|group-separator)?(=*))
			grep.get_opt_and_optarg "${@:1:2}"
			shift "${OPTSHIFT}"
			[[ ${OPTARG} ]] || fail "Argument for '${OPT}' can't be empty."
			[[ ${OPT} == @(-e|--regexp) ]] && regex_specified=true
			opts+=("${OPT}" "${OPTARG}")
			;;
		--)
			args+=("${@:2}")
			break
			;;
		-[!-][!-]*)
			set -- "${1:0:2}" "-${1:2}" "${@:2}"
			continue
			;;
		-?*)
			grep.fail "Unrecognized option: $1"
			;;
		*)
			args+=("$1")
			;;
		esac

		shift
	done

	if [[ ${regex_specified} == false && ${args+.} ]]; then
		opts+=(-e "${args}")
		unset 'args[0]'
	fi

	for i in "${!args[@]}"; do
		if [[ ${args[i]%+(/)} == ?(*/)node_modules ]]; then
			echo "Ignoring node_modules target: ${args[i]}" >&2
			unset 'args[i]'

			if [[ ${#args[@]} -eq 0 ]]; then
				grep.fail "No more targets left. Aborting."
			fi
		fi
	done

	command grep "${opts[@]}" -- "${args[@]}"
}