#! /bin/sh

DRY_RUN=

# Check whether argument is actually a local branch name
# (i.e., names something in refs/heads/).  Return the
# cleaned-up branch name, i.e., HEAD becomes master or
# whatever branch you're on.
check_branch_name()
{
	local full branch fail

	fail=true
	full=$(git rev-parse -q --verify --symbolic-full-name "${1}") &&
	case "$full" in
	refs/heads/*)
		branch=${full#refs/heads/}
		fail=false
		;;
	esac
	$fail && {
		echo "'$1': not a branch name or equivalent" 1>&2
		return 1
	}
	echo "$branch"
	return 0
}

# Compute gerrit name for given branch, with optional error message
# (and nonzero status) if there is none.  Supply remote if known
# with -r, quiet errors with -q.
gerrit_name()
{
	local branch track remote theirref
	local errmsg print_err
	local result

	print_err=true
	while true; do
		case "$1" in
		-q)	print_err=false;;
		-r)	remote="$2"; shift;;
		-r*)	remote=${1#-r};;
		*)	break;;
		esac
		shift
	done

	branch="$1"

	case "$remote" in
	"")	remote=$(git config --get branch."$1".remote);;
	esac

	errmsg=""
	case "$remote" in
	"")	errmsg="branch '$branch' is not tracking anything";;
	".")	errmsg="branch '$branch' is tracking a local branch";;
	*)	theirref=$(git config --get branch."$branch".merge)
		case "$theirref" in
		"") errmsg="branch '$branch' is not tracking anything";;
		refs/heads/*)	;;
		*) errmsg="branch '$branch': don't grok '$theirref'";;
		esac
		;;
	esac

	[ -n "$errmsg" ] && {
		$print_err && echo "$errmsg" 1>&2
		return 1
	}

	echo "refs/for/${theirref#refs/heads/}"
	return 0
}

# Push current branch to gerrit name, or print error
# and return nonzero if there is no such name
review_current()
{
	local branch remote target

	branch=$(git symbolic-ref -q --short HEAD) || {
		echo "you seem to be in detached HEAD mode" 1>&2
		return 1
	}
	remote=$(git config --get branch."$branch".remote)
	target=$(gerrit_name -r "$remote" "$branch") || return 1
	$DRY_RUN git push "$remote" "$branch:$target"
}

# Push all local branches to gerrit names (use with care!)
# Skips non-viable names quietly.
review_all()
{
	local branch remote target

	git for-each-ref --format='%(refname:short)' refs/heads |
	while read branch; do
		remote=$(git config --get branch."$branch".remote) || continue
		target=$(gerrit_name -r "$remote" -q "$branch") || continue
		$DRY_RUN git push "$remote" "$branch:$target"
	done
}

# Push given name(s) to gerrit names.
review_given()
{
	local arg branch remote target

	# Two passes: first check everything, then actually do it.
	for arg do
		branch=$(check_branch_name "$arg") || return 1
		gerrit_name "$branch" > /dev/null || return 1
	done
	for arg do
		branch=$(check_branch_name "$arg") || return 1
		remote=$(git config --get branch."$branch".remote)
		target=$(gerrit_name -r "$remote" "$branch") || return 1
		$DRY_RUN git push "$remote" "$branch:$target"
	done
}

usage()
{
	cat <<- EOF
Usage: $(basename $0) [-h | --help] [--dry-run] [branch ...]

With no arguments, push current branch to gerrit for review.
With branch name arguments, push given branch(es) for review.

Options:
  -n, --dry-run: show what this would do, without actually doing it
  -h, --help: show this usage
EOF
}

main()
{
	while true; do
		case "$1" in
		-h|--help) usage; exit 0;;
		-n|--dry-run) DRY_RUN=echo;;
		--)	break;;
		-*)	usage 1>&2; exit 1;;
		*)	break;;
		esac
		shift
	done

	case $# in
	0)	review_current;;
	*)	review_given "$@";;
	esac
}

main "$@"