#!/bin/sh
set -eu

if [ "$#" -lt 2 ] || [ "$#" -gt 3 ]; then
  echo "usage: $0 <source> <destination> [metadata-source]" >&2
  exit 64
fi

src="$1"
dst="$2"
metadata_source=${3:-}
dst_dir=$(dirname "$dst")
dst_name=$(basename "$dst")
dst_ext=""

case "$dst_name" in
  *.*)
    dst_ext=${dst_name##*.}
    ;;
esac

test -f "$src" || {
  echo "source file not found: $src" >&2
  exit 66
}

owner=""
group=""
mode=""
sample=""

if [ -e "$dst" ]; then
  owner=$(stat -f '%Su' "$dst")
  group=$(stat -f '%Sg' "$dst")
  mode=$(stat -f '%Lp' "$dst")
else
  if [ -n "$metadata_source" ]; then
    test -e "$metadata_source" || {
      echo "metadata source not found: $metadata_source" >&2
      exit 66
    }
    sample=$metadata_source
  elif [ -n "$dst_ext" ]; then
    for candidate in "$dst_dir"/*."$dst_ext"; do
      [ -e "$candidate" ] || continue
      sample=$candidate
      break
    done
  fi

  if [ -z "$sample" ]; then
    for candidate in "$dst_dir"/*; do
      [ -f "$candidate" ] || continue
      sample=$candidate
      break
    done
  fi

  if [ -n "$sample" ]; then
    owner=$(stat -f '%Su' "$sample")
    group=$(stat -f '%Sg' "$sample")
    mode=$(stat -f '%Lp' "$sample")
  else
    owner=$(stat -f '%Su' "$dst_dir")
    group=$(stat -f '%Sg' "$dst_dir")
    mode=644
  fi
fi

cp "$src" "$dst"
chown "$owner":"$group" "$dst"
chmod "$mode" "$dst"

printf 'copied %s -> %s\n' "$src" "$dst"
printf 'restored owner=%s group=%s mode=%s\n' "$owner" "$group" "$mode"
if [ -n "$sample" ]; then
  printf 'metadata source=%s\n' "$sample"
fi