/**
# Copyright (c) 2021, NVIDIA CORPORATION.  All rights reserved.
#
# 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 lookup

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

	"github.com/sirupsen/logrus"
)

const (
	devRoot = "/dev"
)

// NewCharDeviceLocator creates a Locator that can be used to find char devices at the specified root. A logger is
// also specified.
func NewCharDeviceLocator(logger *logrus.Logger, root string) Locator {
	l := file{
		logger:   logger,
		prefixes: []string{root, filepath.Join(root, devRoot)},
		filter:   assertCharDevice,
	}

	return &l
}

// assertCharDevice checks whether the specified path is a char device and returns an error if this is not the case.
func assertCharDevice(filename string) error {
	info, err := os.Stat(filename)
	if err != nil {
		return fmt.Errorf("error getting info: %v", err)
	}
	if info.Mode()|os.ModeCharDevice == 0 {
		return fmt.Errorf("%v is not a char device", filename)
	}
	return nil
}