#!/bin/sh
set -eu


usage() {
	cat <<-'EOF'
		Usage:
		  repos [-e DIR...] [-v] [DIRECTORY]
		  repos -h
	EOF
}

help() {
	cat <<-'EOF'


		Options:
		  -e DIR        exclude the given directory from traversing
		  -v            enable verbose mode
		  -h, --help    show this message

		  DIRECTORY     the folder to traverse


		Traverse DIRECTORY looking for VCS repositores.  As soon as
		one is found, stop recursing, and emit its name alongside its
		type.

		On verbose mode, print the directories being visited.


		Examples:

		  Show all repositories under ~/dev/, excluding a few directories:

		    $ repos -e ~/dev/go/ -e ~/dev/quicklisp/ ~/dev/
		    # ...
	EOF
}


for flag in "$@"; do
	case "$flag" in
		(--)
			break
			;;
		(--help)
			usage
			help
			exit
			;;
		(*)
			;;
	esac
done


# Similar to urlencode but only for % and \n (and not \0).
array_encode() {
	sed 's/%/%25/g' | sed -e :a -e '$!N; s/\n/%0A/; ta'
}

array_decode() {
	sed -e 's/%0A/\
/g' -e 's/%25/%/g'
}


#
# CAVEAT:
# To avoid needing to keep decoding the array elements on every call to
# `arr_includes`, assume directory names don't contain newlines.  This makes the
# current code scanning ~/dev/ from 8 seconds go to 1 second.
#

arr_push() {
	ARR="$1"
	ELT="$2"
	if [ -n "$ARR" ]; then
		printf '%s\n' "$ARR"
	fi
	printf '%s\n' "$ELT" # | array_encode (see CAVEAT)
}

arr_includes() {
	ARR="$1"
	ELT="$2"
	printf '%s\n' "$ARR" | while read -r el; do
		# if [ "$(printf '%s\n' "$el" | array_decode)" = "$ELT" ]; then (see CAVEAT)
		if [ "$el" = "$ELT" ]; then
			return 2
		fi
	done
	if [ $? = 2 ]; then
		return 0
	else
		return 1
	fi
}

EXCLUDE=
VERBOSE=false
while getopts 'e:vh' flag; do
	case "$flag" in
		(e)
			case "$OPTARG" in
				*/)
					ARG="$OPTARG"
					;;
				*)
					ARG="$OPTARG/"
					;;
			esac
			EXCLUDE="$(arr_push "$EXCLUDE" "$ARG")"
			;;
		(v)
			VERBOSE=true
			;;
		(h)
			usage
			help
			exit
			;;
		(*)
			usage >&2
			exit 2
			;;
	esac
done
shift $((OPTIND - 1))


is_repository() {
	TYPE="$(vcs -C "$1" -t 2>/dev/null)"
	if [ -n "$TYPE" ]; then
		printf '%s\n' "$1"
	else
		return 1
	fi
}


traverse_directory() {
	if [ "$VERBOSE" = true ]; then
		printf 'cur: %s\n' "$1" >&2
	fi
	if arr_includes "$EXCLUDE" "$1"; then
		return
	fi
	if is_repository "$1"; then
		return
	fi
	for d in "$1"/*; do
		if [ "$VERBOSE" = true ]; then
			printf 'cur: %s\n' "$d" >&2
		fi
		if [ ! -d "$d" ]; then
			continue
		fi
		if arr_includes "$EXCLUDE" "$d/"; then
			continue
		fi
		if ! is_repository "$d"; then
			traverse_directory "$d"
		fi
	done
}

if [ -z "${1:-}" ]; then
	set -- "$PWD"
fi

for dir in "$@"; do
	traverse_directory "${dir%%/}"
done