// Copyright 2019 PingCAP, Inc.
//
// 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,
// See the License for the specific language governing permissions and
// limitations under the License.

//go:build freebsd

package utils

import (
	"reflect"

	"github.com/pingcap/tiflow/dm/pkg/terror"
	"golang.org/x/sys/unix"
)

// GetStorageSize gets storage's capacity and available size.
func GetStorageSize(dir string) (size StorageSize, err error) {
	var stat unix.Statfs_t

	err = unix.Statfs(dir, &stat)
	if err != nil {
		return size, terror.ErrStatFileSize.Delegate(err)
	}

	// When container is run in MacOS, `bsize` obtained by `statfs` syscall is not the fundamental block size,
	// but the `iosize` (optimal transfer block size) instead, it's usually 1024 times larger than the `bsize`.
	// for example `4096 * 1024`. To get the correct block size, we should use `frsize`. But `frsize` isn't
	// guaranteed to be supported everywhere, so we need to check whether it's supported before use it.
	// For more details, please refer to: https://github.com/docker/for-mac/issues/2136
	bSize := uint64(stat.Bsize)
	field := reflect.ValueOf(&stat).Elem().FieldByName("Frsize")
	if field.IsValid() {
		if field.Kind() == reflect.Uint64 {
			bSize = field.Uint()
		} else {
			bSize = uint64(field.Int())
		}
	}

	// Available blocks * size per block = available space in bytes
	size.Available = uint64(stat.Bavail) * bSize
	size.Capacity = stat.Blocks * bSize

	return
}