#!/bin/bash
# /usr/local/bin/dos-shell
# 1) reset C: drive contents to only the allowed files
# 2) launch dosemu with /cdrive mounted as C:

set -euo pipefail

ALLOWED_LIST="/etc/dos_allowed"
ALLOWED_REPO="/opt/allowed_repo"   # repository of allowed DOS files stored in container
C_DRIVE="/cdrive"
ENV_DIR="/etc/dos_env"
AUTOEXEC_TEMPLATE="${ENV_DIR}/AUTOEXEC.BAT"
CONFIG_TEMPLATE="${ENV_DIR}/CONFIG.SYS"
SVARDOS_BASE="/opt/svardos/base"
ALLOW_MODE="${DOS_ALLOW_MODE:-all}"   # default to exposing everything from the repo

if [ "$(id -u)" -eq 0 ] && [ ! -d "${ENV_DIR}" ]; then
  mkdir -p "${ENV_DIR}"
fi

# clear C: drive to ensure only allowed programs are present
rm -rf "${C_DRIVE:?}/"*
mkdir -p "${C_DRIVE}"

# Seed the C: drive with the SvarDOS base image
if [ -e "${SVARDOS_BASE}/COMMAND.COM" ] || [ -e "${SVARDOS_BASE}/command.com" ]; then
  cp -a "${SVARDOS_BASE}/." "${C_DRIVE}/"
else
  echo "SvarDOS base not found in ${SVARDOS_BASE}. Aborting." >&2
  exit 1
fi

# Sync additional DOS files into the C: drive
allowed_entries=()
case "${ALLOW_MODE}" in
  all)
    if [ -d "${ALLOWED_REPO}" ] && [ "$(ls -A "${ALLOWED_REPO}")" ]; then
      cp -a "${ALLOWED_REPO}/." "${C_DRIVE}/"
    fi
    ;;
  list|allowlist)
    ;;
  *)
    echo "Unknown DOS_ALLOW_MODE '${ALLOW_MODE}', falling back to allowlist mode." >&2
    ALLOW_MODE="list"
    ;;
esac

if [ "${ALLOW_MODE}" != "all" ]; then
  if [ -f "${ALLOWED_LIST}" ]; then
    while IFS= read -r line || [ -n "$line" ]; do
      # trim whitespace
      line="$(printf '%s' "$line" | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//')"
      # skip blank/comment lines
      case "$line" in
        ''|\#*) continue ;;
      esac
      allowed_entries+=("$line")
    done < "${ALLOWED_LIST}"
  fi

  for entry in "${allowed_entries[@]}"; do
    src="${ALLOWED_REPO}/${entry}"
    if [ -e "$src" ]; then
      dst_dir="$(dirname "${entry}")"
      mkdir -p "${C_DRIVE}/${dst_dir}"
      cp -a "$src" "${C_DRIVE}/${dst_dir}/"
    else
      echo "Warning: allowed file not found: $src" >&2
    fi
  done
fi

# Optional: create an AUTOEXEC.BAT and CONFIG.SYS or other DOS boot files
autoexec_path="${C_DRIVE}/AUTOEXEC.BAT"
config_path="${C_DRIVE}/CONFIG.SYS"

if [ -f "${AUTOEXEC_TEMPLATE}" ]; then
  cp "${AUTOEXEC_TEMPLATE}" "${autoexec_path}"
else
  cat > "${autoexec_path}" <<'EOF'
@echo off
prompt [DOS]$P$G
echo Welcome to the containerized DOS environment.
EOF
fi

if [ "${ALLOW_MODE}" = "all" ]; then
  printf 'echo All repository programs are currently enabled.\r\n' >> "${autoexec_path}"
elif [ ${#allowed_entries[@]} -gt 0 ]; then
  {
    printf 'echo Allowed programs:\r\n'
    for entry in "${allowed_entries[@]}"; do
      dos_entry="${entry//\//\\}"
      printf 'echo   %s\r\n' "${dos_entry}"
    done
  } >> "${autoexec_path}"
else
  {
    printf 'echo No extra programs are currently enabled.\r\n'
  } >> "${autoexec_path}"
fi

if [ -f "${CONFIG_TEMPLATE}" ]; then
  cp "${CONFIG_TEMPLATE}" "${config_path}"
fi

# Drop privileges to dosuser if we were run as root (ssh will run as the user)
# but in case sshd runs ForceCommand as root, we switch.
if [ "$(id -u)" -eq 0 ]; then
  exec runuser -u dosuser -- dosemu -quiet -K "${C_DRIVE}"
else
  # running as the user already
  exec dosemu -quiet -K "${C_DRIVE}"
fi