#!/usr/bin/env bash
# rename_prefix.sh [-n|--dry-run] [-v] PREFIX REPLACEMENT
set -o errexit -o pipefail
set -o nounset

dry_run=0
verbose=0

# ---- Parse flags
while [[ $# -gt 0 ]]; do
  case "$1" in
    -n|--dry-run) dry_run=1; shift ;;
    -v|--verbose) verbose=1; shift ;;
    --) shift; break ;;
    -*) echo "Unknown option: $1" >&2; exit 2 ;;
    *)  break ;;
  esac
done

if [[ $# -lt 2 ]]; then
  echo "Usage: ${0##*/} [-n|--dry-run] [-v] PREFIX REPLACEMENT" >&2
  exit 2
fi

prefix=$1
replacement=$2

if [[ -z "$prefix" ]]; then
  echo "Refusing to run: PREFIX cannot be empty." >&2
  exit 2
fi

# Match files in current dir whose names start with $prefix
# nullglob: if no matches, the glob expands to nothing (prevents literal)
shopt -s nullglob

# Include dotfiles if the prefix starts with a dot (like .env)
# (Bash already matches dotfiles when the pattern itself starts with a dot.)
# Handle spaces safely by quoting $f everywhere.
for f in -- "$prefix"*; do
  [[ -e "$f" ]] || continue

  dir=$(dirname -- "$f")
  base=$(basename -- "$f")

  # Replace only if $prefix is at the START of the filename
  newbase="${base/#$prefix/$replacement}"
  newpath="$dir/$newbase"

  # Skip if nothing changes
  [[ "$f" == "$newpath" ]] && continue

  if (( dry_run )); then
    printf '[DRY-RUN] mv -- %q %q\n' "$f" "$newpath"
  else
    # -n: don't overwrite existing files accidentally
    # Add -v if requested
    if (( verbose )); then
      mv -vn -- "$f" "$newpath"
    else
      mv -n  -- "$f" "$newpath"
    fi
  fi
done