#!/bin/sh

# This is a handly little script that accepts a file path and automatically
# generates a github permalink for it (including line numbers, if given). If no
# github remote could be found, then it exits with an error.
#
# The clipboard functionality is handy. For example,
#
#   github-link --clip foo.rs 20 30
#
# will automatically put the URL on your clipboard. (You'll need 'xcp' from
# this repo as well.)

usage() {
  echo "Usage: $(basename "$0") <path> [<lineno1> [<lineno2>]]"
}

clip=
while true; do
  case "$1" in
    -c|--clip) clip=1; shift; ;;
    -h|--help) usage; exit 0 ;;
    -*) usage >&2; exit 1 ;;
    *) break
  esac
done
path="$1"
lineno1="$2"
lineno2="$3"
if [ -z "$path" ] || [ $# -gt 3 ]; then
  echo "Usage: $(basename "$0") <path> [<lineno1> [<lineno2>]]" >&2
  exit 1
fi

dir="$(dirname "$path")"
gitroot="$(cd "$dir" && git rev-parse --show-toplevel)"
if ! git -C "$gitroot" remote -v | grep -q -F 'github.com'; then
  echo "git repo at '$gitroot' has no github remote" >&2
  exit 1
fi
commit="$(cd "$gitroot" && git rev-parse HEAD)"
urlbase="$(
  cd "$gitroot" && git remote -v \
    | grep -F github.com \
    | grep fetch \
    | grep origin \
    | awk '{print $2}' \
    | sed 's/^git@//g' \
    | sed 's/^.*github\.com/github.com/g' \
    | sed 's/^github\.com:/github.com\//g'
)"
urlpath="$(realpath --relative-to "$gitroot" "$path")"

url="$(printf "https://%s/blob/%s/%s" "$urlbase" "$commit" "$urlpath")"
if [ -n "$lineno1" ]; then
  url="$(printf "%s#L%s" "$url" "$lineno1")"
fi
if [ -n "$lineno2" ]; then
  url="$(printf "%s-L%s" "$url" "$lineno2")"
fi
if [ -n "$clip" ]; then
  printf "%s" "$url" | xcp
else
  printf "%s\n" "$url"
fi