#!/bin/bash

name="mkbak"
version="1.0"
read -r -d '' help_message <<-EOF
	Create a backup of a target file
	Usage: mkbak TARGET [OPTIONS]
	Options:
	 -d, --diff            diff files before asking to overwrite
	 -f, --force           overwrite without asking
	 -h, --help            print this message and exit
	 -n FILE, --name FILE  name of backup file (Default: TARGET.bak)
	 -q, --quiet           suppress error messages and prompts
	 -v, --verbose         show additional messages
	 -V, --version         print version number and exit
EOF

source /usr/local/lib/mylib.bash

positional=()
quiet=0
verbose=0
force=0
backup_fn=""
while [[ $# -gt 0 ]]; do
  case $1 in

  -d|--diff)
    debug_msg "Setting diff option to 1 (was ${diff})"
    diff=1
    shift
    ;;

  -f|--force)
    debug_msg "Setting force option to 1 (was ${force})"
    force=1
    shift
    ;;

  -h|--help)
    help_msg
    shift
    ;;

  -n|--name)
    debug_msg "Setting output filename to ${2} (was ${backup_fn})"
    backup_fn="$2"
    shift; shift
    ;;

  -q|--quiet)
    debug_msg "Setting quiet option to 1 (was ${quiet})"
    quiet=1
    shift
    ;;

  -v|--verbose)
    debug_msg "Setting verbose option to 1 (was ${verbose})"
    verbose=1
    shift
    ;;

  -V|--version)
    version_msg
    ;;

  *)
    debug_msg "Argument '${1}' added to positional array"
    positional+=("$1")
    shift
    ;;
  esac
done

# error if no filenames given
if [[ "${#positional[@]}" -lt 1 ]]; then
  debug_msg "No input filename was given"
  usage_msg
fi
original_fn="${positional[0]}"

# output filename
if [[ -z "$backup_fn" ]]; then
  debug_msg "No output filename was given, so defaulting to 'TARGET.bak'"
  backup_fn="${original_fn}.bak"
fi

# check files
if [[ ! -f "$original_fn" ]]; then
  error_msg "No such file '${original_fn}'"
elif [[ "$force" -eq 0 && -f "$backup_fn" ]]; then
  if /usr/bin/cmp "$backup_fn" "$original_fn" >/dev/null 2>&1; then
    msg "File '${backup_fn}' already exists and is a copy of '${original_fn}'"
  elif [[ $quiet -eq 0 ]]; then
    if [[ "$diff" -eq 1 ]]; then
      /usr/bin/diff --color "$backup_fn" "$original_fn"
    fi
    if ! prompt_overwrite "$backup_fn"; then
      exit 1
    fi
  fi
fi

# main routine
/usr/bin/cp "$original_fn" "$backup_fn"
exit "$?"