#! /usr/bin/env bash

# Commit and push a new note.
#
# -c
#   Commit only, don't push.
#
usage="usage: $0 [-c]"

owd=`pwd`
trap "{ cd $owd; exit 1; }" ERR
set -o errtrace # Trap in functions.

function info () { echo "$*" 1>&2; }
function error () { info "$*"; exit 1; }

push="y"

while [ $# -gt 0 ]; do
  case $1 in
    -c)
      push="n"
      shift
      ;;
    *)
      error "$usage"
      ;;
  esac
done

if git status --porcelain | grep -q '^M '; then
  error "error: repository already has staged changes"
fi

untracked="$(git status --porcelain | sed -n -e 's/^?? \(.*\)/\1/p')"
modified="$(git status --porcelain  | sed -n -e 's/^ M \(.*\)/\1/p')"

uc="$(echo "$untracked" | wc -w)"
mc="$(echo "$modified" | wc -w)"

if [ "$uc" -eq 0 -a "$mc" -eq 0 ]; then
  error "error: nothing untracked/modified"
fi

if [ "$uc" -gt 0 -a "$mc" -gt 0 ]; then
  error "error: multiple untracked/modified files"
fi

# Add the tracked file to index with --intent-to-add so that we can diff it
# the same way as modified. The not so nice thing about this approach is that
# we have to remember to reset it if things go badly.
#
if [ "$uc" -gt 0 ]; then
  git add --intent-to-add "$untracked"
  modified="$untracked"
fi

# Get the diff output skipping the header (the first four lines until the
# first changeset).
#
diff="$(git diff -U0 | sed -n -e '/^@@/,$p')"
dc="$(echo "$diff" | wc -l)"

# Get the changeset. While we don't care for leading or trailing empty lines
# down the line, we do want them in the count. And preserving them in program
# substitution is more difficult than one would think.
#
cset="$(echo "$diff" | sed -n -e 's/^+\(.*\)/\1/p')"
cc="$(echo "$diff" | sed -n -e 's/^+\(.*\)/\1/p' | wc -l)"

# We should only have one changeset and it should only have added lines. Note
# that this is always the case for a new file.
#
if [ "$dc" -ne "$(($cc + 1))" ]; then
  info "error: multiple changesets or non-add changes"
  git diff -U0
  exit 1
fi

# Get the first non-empty line which should be the header.
#
l=
while read l || [ -n "$l" ]; do
  if [ -n "$l" ]; then
    break
  fi
done < <(echo "$cset")

# Should start with one of [-?!].
#
sum="$(echo "$l" | sed -n -re 's/^[-?!] ([^[]*)( \[.*\])?$/\1/p')"

if [ -z "$sum" ]; then
  info "error: first line does not appear to be a note header"
  info "info: first line is '$l'"
  exit 1
fi

# By convention the first label is a note type (bug, feature, etc).
#
type="$(echo "$l" | sed -n -re 's/^[^[]*\[([^ ]*).*\]$/\1/p')"

if [ -z "$type" ]; then
  error "error: note header does not include note type as first label"
fi

#@@ Maybe check known note types and warn if not one of them?
#

# Ok, all looks good so add, commit and push the change.
#
git add "$modified"
git ci -m "Add $type: $sum"

if [ "$push" = "y" ]; then
  git push
fi