#!/bin/sh
help ()
{
  echo "
  A small utility to easily and quickly rename files in bulk based upon a
  pattern.

  Proper Usage:
      file-rename-pattern "S2 " "episode-" { --dry-run | -d }
      file-rename-pattern "S2 " "episode-" { --exec | -e }

  --dry-run is on by default.
  ";
}

if [[ $# < 2 || $# > 3 ]]; then
  help
fi

PATTERN=$1
REPLACE=$2

if [[ $# == 2 || ($# == 3 && ($3 == "--dry-run" || $3 == "-d" )) ]]; then
  for f in *$PATTERN*; do echo mv -i -- "$f" "${f//$PATTERN/$REPLACE}"; done
elif [[ $# == 3 && ($3 == "--exec" || $3 == "-e" ) ]]; then
  for f in *$PATTERN*; do mv -i -- "$f" "${f//$PATTERN/$REPLACE}"; done
fi