#!/usr/bin/env sh
set -eu

if [ "$#" -ne 4 ]; then
  printf '%s\n' 'Usage: replace-plugin-directory.sh ARCHIVE TARGET INSTALL_DIR BACKUP_DIR' >&2
  exit 2
fi

ARCHIVE=$1
TARGET_DIR=$2
INSTALL_DIR=$3
BACKUP_DIR=$4

for directory in "$TARGET_DIR" "$INSTALL_DIR" "$BACKUP_DIR"; do
  case "$directory" in
    /*) ;;
    *)
      printf '%s\n' 'Plugin replacement directories must be absolute paths' >&2
      exit 2
      ;;
  esac
  if [ "$directory" = / ]; then
    printf '%s\n' 'Plugin replacement directories cannot be the filesystem root' >&2
    exit 2
  fi
done

TARGET_PARENT=$(dirname -- "$TARGET_DIR")
if [ "$(dirname -- "$INSTALL_DIR")" != "$TARGET_PARENT" ] || [ "$(dirname -- "$BACKUP_DIR")" != "$TARGET_PARENT" ]; then
  printf '%s\n' 'Plugin staging and backup directories must share the target parent' >&2
  exit 2
fi
if [ "$TARGET_DIR" = "$INSTALL_DIR" ] || [ "$TARGET_DIR" = "$BACKUP_DIR" ] || [ "$INSTALL_DIR" = "$BACKUP_DIR" ]; then
  printf '%s\n' 'Plugin replacement directories must be distinct' >&2
  exit 2
fi
if [ ! -f "$ARCHIVE" ]; then
  printf '%s\n' "Plugin archive does not exist: $ARCHIVE" >&2
  exit 2
fi

had_target=0

cleanup() {
  status=$?
  trap - EXIT HUP INT TERM
  if [ "$status" -ne 0 ] && [ "$had_target" -eq 1 ] && [ ! -e "$TARGET_DIR" ] && [ -e "$BACKUP_DIR" ]; then
    mv "$BACKUP_DIR" "$TARGET_DIR" || true
  fi
  rm -rf "$INSTALL_DIR"
  if [ "$status" -eq 0 ]; then
    rm -rf "$BACKUP_DIR"
  fi
  exit "$status"
}

trap cleanup EXIT
trap 'exit 1' HUP INT TERM

rm -rf "$INSTALL_DIR"
if [ -e "$BACKUP_DIR" ]; then
  printf '%s\n' "Plugin backup directory already exists: $BACKUP_DIR" >&2
  exit 1
fi

mkdir -p "$INSTALL_DIR"
unzip -q "$ARCHIVE" -d "$INSTALL_DIR"

if [ -e "$TARGET_DIR" ]; then
  mv "$TARGET_DIR" "$BACKUP_DIR"
  had_target=1
fi

mv "$INSTALL_DIR" "$TARGET_DIR"
rm -rf "$BACKUP_DIR"
had_target=0