package stat

import (
	"io"
	"bufio"
	"regexp"
	"strings"
	"fmt"
)

type NetDevStat struct {
	iface,
	recvByte,
	recvPacket,
	recvErr,
	recvDrop,
	recvFifo,
	recvFrame,
	recvCompressed,
	recvMulticast,
	transByte,
	transPacket,
	transErr,
	transDrop,
	transFifo,
	transFrame,
	transCompressed,
	transMulticast string
}

func (net *NetDevStat) Command() string {
	return "cat /proc/net/dev"
}

func (net *NetDevStat) Parse(r io.Reader) ([]NetDevStat, error) {
	var (
		scanner            = bufio.NewScanner(r)
		procNetDevFieldSep = regexp.MustCompile("[ :] *")
		netDevStats        = []NetDevStat{}
	)
	scanner.Scan()
	scanner.Scan()
	parts := strings.Split(scanner.Text(), "|")
	if len(parts) != 3 { // interface + receive + transmit
		return nil, fmt.Errorf("invalid header line in net/dev: %s",
			scanner.Text())
	}

	header := strings.Fields(parts[1])
	for scanner.Scan() {
		line := strings.TrimLeft(scanner.Text(), " ")
		parts := procNetDevFieldSep.Split(line, -1)
		if len(parts) != 2*len(header)+1 {
			return nil, fmt.Errorf("invalid line in net/dev: %s", scanner.Text())
		}

		dev := parts[0][:len(parts[0])]
		netDevStats = append(netDevStats, NetDevStat{
			iface:           dev,
			recvByte:        parts[1],
			recvPacket:      parts[2],
			recvErr:         parts[3],
			recvDrop:        parts[4],
			recvFifo:        parts[5],
			recvFrame:       parts[6],
			recvCompressed:  parts[7],
			recvMulticast:   parts[8],
			transByte:       parts[9],
			transPacket:     parts[10],
			transErr:        parts[11],
			transDrop:       parts[12],
			transFifo:       parts[13],
			transFrame:      parts[14],
			transCompressed: parts[15],
			transMulticast:  parts[16],
		})
	}
	return netDevStats, scanner.Err()
}