// Copyright 2020 The gVisor Authors.
//
// 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 tools

import (
	"fmt"
	"net"
	"regexp"
	"strconv"
	"testing"
)

const length = 64 * 1024

// Iperf is for the client side of `iperf`.
type Iperf struct {
	Num int // Number of bytes to send in KB.
}

// MakeCmd returns a iperf client command.
func (i *Iperf) MakeCmd(ip net.IP, port int) []string {
	return []string{
		"iperf",
		"--format", "K", // Output in KBytes.
		"--realtime",                       // Measured in realtime.
		"--num", fmt.Sprintf("%dK", i.Num), // Number of bytes to send in KB.
		"--length", fmt.Sprintf("%d", length),
		"--client", ip.String(),
		"--port", fmt.Sprintf("%d", port),
	}
}

// Report parses output from iperf client and reports metrics.
func (i *Iperf) Report(b *testing.B, output string) {
	b.Helper()
	// Parse bandwidth and report it.
	bW, err := i.bandwidth(output)
	if err != nil {
		b.Fatalf("failed to parse bandwitdth from %s: %v", output, err)
	}
	b.SetBytes(length) // Measure Bytes/sec for b.N, although below is iperf output.
	ReportCustomMetric(b, bW*1024, "bandwidth" /*metric name*/, "bytes_per_second" /*unit*/)
}

// bandwidth parses the Bandwidth number from an iperf report. A sample is below.
func (i *Iperf) bandwidth(data string) (float64, error) {
	re := regexp.MustCompile(`\[\s*\d+\][^\n]+\s+(\d+\.?\d*)\s+KBytes/sec`)
	match := re.FindStringSubmatch(data)
	if len(match) < 1 {
		return 0, fmt.Errorf("failed get bandwidth: %s", data)
	}
	return strconv.ParseFloat(match[1], 64)
}