//go:build linux

/**
# SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: Apache-2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
**/

package disabledevicenodemodification

import (
	"fmt"
	"os"
	"path/filepath"

	"github.com/opencontainers/runc/libcontainer/utils"
	"golang.org/x/sys/unix"
)

func createParamsFileInContainer(containerRootDirPath string, contents []byte) error {
	tmpRoot, err := os.MkdirTemp("", "nvct-empty-dir*")
	if err != nil {
		return fmt.Errorf("failed to create temp root: %w", err)
	}

	if err := createTmpFs(tmpRoot, len(contents)); err != nil {
		return fmt.Errorf("failed to create tmpfs mount for params file: %w", err)
	}

	modifiedParamsFile, err := os.OpenFile(filepath.Join(tmpRoot, "nvct-params"), os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0444)
	if err != nil {
		return fmt.Errorf("failed to open modified params file: %w", err)
	}
	defer modifiedParamsFile.Close()

	if _, err := modifiedParamsFile.Write(contents); err != nil {
		return fmt.Errorf("failed to write temporary params file: %w", err)
	}

	err = utils.WithProcfd(containerRootDirPath, nvidiaDriverParamsPath, func(nvidiaDriverParamsFdPath string) error {
		return unix.Mount(modifiedParamsFile.Name(), nvidiaDriverParamsFdPath, "", unix.MS_BIND|unix.MS_RDONLY|unix.MS_NODEV|unix.MS_PRIVATE|unix.MS_NOSYMFOLLOW, "")
	})
	if err != nil {
		return fmt.Errorf("failed to mount modified params file: %w", err)
	}

	return nil
}

func createTmpFs(target string, size int) error {
	return unix.Mount("tmpfs", target, "tmpfs", 0, fmt.Sprintf("size=%d", size))
}