#!/usr/bin/env bash
set -euo pipefail

usage() {
  cat <<'USAGE'
Copy files via scp or rsync with consistent options.

Usage:
  ssh_copy.sh [options] push HOST LOCAL_PATH REMOTE_PATH
  ssh_copy.sh [options] pull HOST REMOTE_PATH LOCAL_PATH

Options:
  -u, --user USER     Override SSH user (or set REMOTE_USER)
  -p, --port PORT     SSH port (default: REMOTE_PORT or 22)
  -i, --key PATH      Identity file (default: REMOTE_KEY)
  -r, --recursive     Copy directories recursively (scp mode only; rsync always recurses)
      --rsync         Use rsync instead of scp (incremental, shows progress)
      --delete        With --rsync push: delete remote files not present in source
      --accept-new    Set StrictHostKeyChecking=accept-new
      --dry-run       Print the command that would run
  -h, --help          Show help

Environment defaults:
  REMOTE_USER, REMOTE_PORT, REMOTE_KEY

Examples:
  ssh_copy.sh push my-server ./app.tar.gz /tmp/app.tar.gz
  ssh_copy.sh --rsync push my-server ./dist/ /var/www/html/
  ssh_copy.sh --rsync --delete push my-server ./dist/ /var/www/html/
  ssh_copy.sh --user ubuntu pull 10.0.0.1 /var/log/syslog ./syslog
USAGE
}

port="${REMOTE_PORT:-22}"
user="${REMOTE_USER:-}"
key="${REMOTE_KEY:-}"

recursive=false
use_rsync=false
delete_mode=false
accept_new=false
dry_run=false

while [[ $# -gt 0 ]]; do
  case "$1" in
    -u|--user)      user="${2:-}"; shift 2 ;;
    -p|--port)      port="${2:-}"; shift 2 ;;
    -i|--key)       key="${2:-}"; shift 2 ;;
    -r|--recursive) recursive=true; shift ;;
    --rsync)        use_rsync=true; shift ;;
    --delete)       delete_mode=true; shift ;;
    --accept-new)   accept_new=true; shift ;;
    --dry-run)      dry_run=true; shift ;;
    -h|--help)      usage; exit 0 ;;
    -*)
      echo "Unknown option: $1" >&2
      usage >&2
      exit 2
      ;;
    *) break ;;
  esac
done

if [[ $# -lt 4 ]]; then
  usage >&2
  exit 2
fi

direction="$1"; shift
host="$1"; shift

dest_host="$host"
if [[ -n "$user" ]]; then
  host_no_user="${host#*@}"
  dest_host="${user}@${host_no_user}"
fi

if $use_rsync; then
  if ! command -v rsync >/dev/null 2>&1; then
    echo "rsync is required but not installed." >&2
    exit 1
  fi
  ssh_parts=("ssh" "-p" "$port")
  if [[ -n "$key" ]]; then
    ssh_parts+=("-i" "$key" "-o" "IdentitiesOnly=yes")
  fi
  if $accept_new; then
    ssh_parts+=("-o" "StrictHostKeyChecking=accept-new")
  fi
  rsync_opts=(-avz --progress -e "${ssh_parts[*]}")

  case "$direction" in
    push)
      local_path="$1"
      remote_path="$2"
      if $delete_mode; then
        rsync_opts+=(--delete)
      fi
      full_cmd=(rsync "${rsync_opts[@]}" "$local_path" "${dest_host}:${remote_path}")
      ;;
    pull)
      remote_path="$1"
      local_path="$2"
      full_cmd=(rsync "${rsync_opts[@]}" "${dest_host}:${remote_path}" "$local_path")
      ;;
    *)
      echo "Unknown direction: $direction (expected: push|pull)" >&2
      usage >&2
      exit 2
      ;;
  esac
else
  scp_opts=(-P "$port" -p)
  if [[ -n "$key" ]]; then
    scp_opts+=(-i "$key" -o "IdentitiesOnly=yes")
  fi
  if $recursive; then
    scp_opts+=(-r)
  fi
  if $accept_new; then
    scp_opts+=(-o "StrictHostKeyChecking=accept-new")
  fi

  case "$direction" in
    push)
      local_path="$1"
      remote_path="$2"
      full_cmd=(scp "${scp_opts[@]}" "$local_path" "${dest_host}:${remote_path}")
      ;;
    pull)
      remote_path="$1"
      local_path="$2"
      full_cmd=(scp "${scp_opts[@]}" "${dest_host}:${remote_path}" "$local_path")
      ;;
    *)
      echo "Unknown direction: $direction (expected: push|pull)" >&2
      usage >&2
      exit 2
      ;;
  esac
fi

if $dry_run; then
  printf '%q ' "${full_cmd[@]}"
  printf '\n'
  exit 0
fi

"${full_cmd[@]}"