#!/bin/bash
# /usr/local/bin/dos-shell
# Prepare the SvarDOS environment and launch dosemu.

set -euo pipefail

ALLOWED_LIST="/etc/dos_allowed"
ALLOWED_REPO="/opt/allowed_repo"
ENV_DIR="/etc/dos_env"
AUTOEXEC_TEMPLATE="${ENV_DIR}/AUTOEXEC.BAT"
CONFIG_TEMPLATE="${ENV_DIR}/CONFIG.SYS"
SVARDOS_ROOT="${SVARDOS_ROOT:-/opt/svardos}"
SVARDOS_BASE="${SVARDOS_BASE:-${SVARDOS_ROOT}/base}"
ALLOW_MODE="${DOS_ALLOW_MODE:-all}"
DEFAULT_DOS_USER="dosuser"
INSTALL_SENTINEL=".svardos_installed"

if [ "$(id -u)" -eq 0 ]; then
  DOS_USER="${DEFAULT_DOS_USER}"
  DOS_HOME="$(getent passwd "${DOS_USER}" | cut -d: -f6)"
else
  DOS_USER="$(id -un)"
  DOS_HOME="${HOME}"
fi

if [ -z "${DOS_HOME}" ]; then
  echo "Unable to determine home directory for ${DOS_USER}" >&2
  exit 1
fi

DOSEMU_DIR="${DOS_HOME}/.dosemu"
C_DRIVE="${DOSEMU_DIR}/drive_c"
DOSEMURC_PATH="${DOS_HOME}/.dosemurc"
INSTALL_MARKER="${DOSEMU_DIR}/${INSTALL_SENTINEL}"
DOSEMU_ARGS=(-quiet -t -K "${C_DRIVE}")
allowed_entries=()

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

set_install_marker() {
  touch "${INSTALL_MARKER}"
  if [ "$(id -u)" -eq 0 ]; then
    chown "${DOS_USER}:${DOS_USER}" "${INSTALL_MARKER}"
  fi
}

has_svardos_installation() {
  if [ -f "${C_DRIVE}/KERNEL.SYS" ] || [ -f "${C_DRIVE}/kernel.sys" ]; then
    return 0
  fi
  if [ -f "${C_DRIVE}/BIN/PKG.EXE" ] || [ -f "${C_DRIVE}/bin/pkg.exe" ]; then
    return 0
  fi
  if [ -d "${C_DRIVE}/SVARDOS" ] || [ -d "${C_DRIVE}/svardos" ]; then
    return 0
  fi
  return 1
}

needs_install() {
  if [ "${DOS_FORCE_INSTALL:-0}" = "1" ]; then
    return 0
  fi
  if [ -f "${INSTALL_MARKER}" ]; then
    return 1
  fi
  if has_svardos_installation; then
    set_install_marker
    return 1
  fi
  return 0
}

stage_initial_install() {
  if [ ! -d "${SVARDOS_BASE}" ] || [ -z "$(ls -A "${SVARDOS_BASE}")" ]; then
    echo "SvarDOS base directory ${SVARDOS_BASE} is empty. Aborting." >&2
    exit 1
  fi

  rm -rf "${C_DRIVE:?}/"*

  cp -a "${SVARDOS_BASE}/." "${C_DRIVE}/"
  set_install_marker
  echo "SvarDOS base staged to ${C_DRIVE}"
}

generate_dosemurc() {
  local boot_target="$1"
  {
    printf "%s\n" "\$_hdimage = \"${C_DRIVE}\""
    printf "%s\n" "\$_boot = \"${boot_target}\""
    printf "%s\n" "\$_emusys = \"drdos\""
    printf "%s\n" "\$_fdpp = (off)"
  } > "${DOSEMURC_PATH}"
  if [ -f "${ENV_DIR}/dosemurc" ]; then
    cat "${ENV_DIR}/dosemurc" >> "${DOSEMURC_PATH}"
  fi
  if [ "$(id -u)" -eq 0 ]; then
    chown "${DOS_USER}:${DOS_USER}" "${DOSEMURC_PATH}"
  fi
}

sync_allowed_content() {
  allowed_entries=()
  local mode="${ALLOW_MODE}"
  if [ "${mode}" = "all" ]; then
    if [ -d "${ALLOWED_REPO}" ] && [ "$(ls -A "${ALLOWED_REPO}" 2>/dev/null)" ]; then
      cp -a "${ALLOWED_REPO}/." "${C_DRIVE}/"
      allowed_entries+=("ALL")
    fi
    return
  fi

  if [ "${mode}" != "list" ] && [ "${mode}" != "allowlist" ]; then
    echo "Unknown DOS_ALLOW_MODE '${mode}', defaulting to allowlist mode." >&2
    mode="list"
    ALLOW_MODE="${mode}"
  fi

  if [ -f "${ALLOWED_LIST}" ]; then
    while IFS= read -r line || [ -n "$line" ]; do
      line="$(printf '%s' "$line" | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//')"
      case "$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
}

apply_templates() {
  if [ -f "${AUTOEXEC_TEMPLATE}" ]; then
    cp "${AUTOEXEC_TEMPLATE}" "${C_DRIVE}/AUTOEXEC.BAT"
  fi
  if [ -f "${CONFIG_TEMPLATE}" ]; then
    cp "${CONFIG_TEMPLATE}" "${C_DRIVE}/CONFIG.SYS"
  fi
}

if needs_install; then
  stage_initial_install
fi

generate_dosemurc "c"

sync_allowed_content
apply_templates

if [ "$(id -u)" -eq 0 ]; then
  chown -R "${DOS_USER}:${DOS_USER}" "${DOSEMU_DIR}"
fi

if [ "${ALLOW_MODE}" = "all" ] && [ "${#allowed_entries[@]}" -gt 0 ]; then
  echo "All files in ${ALLOWED_REPO} are available on drive C:."
elif [ "${#allowed_entries[@]}" -gt 0 ]; then
  echo "Allowlisted files copied to C: from ${ALLOWED_REPO}:"
  for entry in "${allowed_entries[@]}"; do
    echo "  ${entry}"
  done
fi

if [ "$(id -u)" -eq 0 ]; then
  exec runuser -u "${DOS_USER}" -- dosemu "${DOSEMU_ARGS[@]}"
else
  exec dosemu "${DOSEMU_ARGS[@]}"
fi