package procfs

import (
	"bufio"
	"fmt"
	"io"
	"strconv"
	"strings"
	"time"
)

const (
	deviceEntryLen = 8

	fieldBytesLen  = 8
	fieldEventsLen = 27

	statVersion10 = "1.0"
	statVersion11 = "1.1"

	fieldTransport10TCPLen = 10
	fieldTransport10UDPLen = 7

	fieldTransport11TCPLen = 13
	fieldTransport11UDPLen = 10
)

	Stats MountStats
}

type MountStats interface {
	mountStats()
}

	Transport NFSTransportStats
}

func (m MountStatsNFS) mountStats() {}

	WritePages uint64
}

	PNFSWrite uint64
}

	CumulativeTotalRequestMilliseconds uint64
}

	CumulativeBacklog uint64

	CumulativePendingQueue uint64
}

func parseMountStats(r io.Reader) ([]*Mount, error) {
	const (
		device            = "device"
		statVersionPrefix = "statvers="

		nfs3Type = "nfs"
		nfs4Type = "nfs4"
	)

	var mounts []*Mount

	s := bufio.NewScanner(r)

		ss := strings.Fields(string(s.Bytes()))
		if len(ss) == 0 || ss[0] != device {
			continue
		}

		m, err := parseMount(ss)
		if err != nil {
			return nil, err
		}

			if m.Type != nfs3Type && m.Type != nfs4Type {
				return nil, fmt.Errorf("cannot parse MountStats for fstype %q", m.Type)
			}

			statVersion := strings.TrimPrefix(ss[8], statVersionPrefix)

			stats, err := parseMountStatsNFS(s, statVersion)
			if err != nil {
				return nil, err
			}

			m.Stats = stats
		}

		mounts = append(mounts, m)
	}

	return mounts, s.Err()
}

func parseMount(ss []string) (*Mount, error) {
	if len(ss) < deviceEntryLen {
		return nil, fmt.Errorf("invalid device entry: %v", ss)
	}

	format := []struct {
		i int
		s string
	}{
		{i: 0, s: "device"},
		{i: 2, s: "mounted"},
		{i: 3, s: "on"},
		{i: 5, s: "with"},
		{i: 6, s: "fstype"},
	}

	for _, f := range format {
		if ss[f.i] != f.s {
			return nil, fmt.Errorf("invalid device entry: %v", ss)
		}
	}

	return &Mount{
		Device: ss[1],
		Mount:  ss[4],
		Type:   ss[7],
	}, nil
}

	const (
		fieldOpts       = "opts:"
		fieldAge        = "age:"
		fieldBytes      = "bytes:"
		fieldEvents     = "events:"
		fieldPerOpStats = "per-op"
		fieldTransport  = "xprt:"
	)

	stats := &MountStatsNFS{
		StatVersion: statVersion,
	}

	for s.Scan() {
		ss := strings.Fields(string(s.Bytes()))
		if len(ss) == 0 {
			break
		}
		if len(ss) < 2 {
			return nil, fmt.Errorf("not enough information for NFS stats: %v", ss)
		}

		switch ss[0] {
		case fieldOpts:
			if stats.Opts == nil {
				stats.Opts = map[string]string{}
			}
			for _, opt := range strings.Split(ss[1], ",") {
				split := strings.Split(opt, "=")
				if len(split) == 2 {
					stats.Opts[split[0]] = split[1]
				} else {
					stats.Opts[opt] = ""
				}
			}

			d, err := time.ParseDuration(ss[1] + "s")
			if err != nil {
				return nil, err
			}

			stats.Age = d
		case fieldBytes:
			bstats, err := parseNFSBytesStats(ss[1:])
			if err != nil {
				return nil, err
			}

			stats.Bytes = *bstats
		case fieldEvents:
			estats, err := parseNFSEventsStats(ss[1:])
			if err != nil {
				return nil, err
			}

			stats.Events = *estats
		case fieldTransport:
			if len(ss) < 3 {
				return nil, fmt.Errorf("not enough information for NFS transport stats: %v", ss)
			}

			tstats, err := parseNFSTransportStats(ss[1:], statVersion)
			if err != nil {
				return nil, err
			}

			stats.Transport = *tstats
		}

		if ss[0] == fieldPerOpStats {
			break
		}
	}

	if err := s.Err(); err != nil {
		return nil, err
	}

	perOpStats, err := parseNFSOperationStats(s)
	if err != nil {
		return nil, err
	}

	stats.Operations = perOpStats

	return stats, nil
}

func parseNFSBytesStats(ss []string) (*NFSBytesStats, error) {
	if len(ss) != fieldBytesLen {
		return nil, fmt.Errorf("invalid NFS bytes stats: %v", ss)
	}

	ns := make([]uint64, 0, fieldBytesLen)
	for _, s := range ss {
		n, err := strconv.ParseUint(s, 10, 64)
		if err != nil {
			return nil, err
		}

		ns = append(ns, n)
	}

	return &NFSBytesStats{
		Read:        ns[0],
		Write:       ns[1],
		DirectRead:  ns[2],
		DirectWrite: ns[3],
		ReadTotal:   ns[4],
		WriteTotal:  ns[5],
		ReadPages:   ns[6],
		WritePages:  ns[7],
	}, nil
}

func parseNFSEventsStats(ss []string) (*NFSEventsStats, error) {
	if len(ss) != fieldEventsLen {
		return nil, fmt.Errorf("invalid NFS events stats: %v", ss)
	}

	ns := make([]uint64, 0, fieldEventsLen)
	for _, s := range ss {
		n, err := strconv.ParseUint(s, 10, 64)
		if err != nil {
			return nil, err
		}

		ns = append(ns, n)
	}

	return &NFSEventsStats{
		InodeRevalidate:     ns[0],
		DnodeRevalidate:     ns[1],
		DataInvalidate:      ns[2],
		AttributeInvalidate: ns[3],
		VFSOpen:             ns[4],
		VFSLookup:           ns[5],
		VFSAccess:           ns[6],
		VFSUpdatePage:       ns[7],
		VFSReadPage:         ns[8],
		VFSReadPages:        ns[9],
		VFSWritePage:        ns[10],
		VFSWritePages:       ns[11],
		VFSGetdents:         ns[12],
		VFSSetattr:          ns[13],
		VFSFlush:            ns[14],
		VFSFsync:            ns[15],
		VFSLock:             ns[16],
		VFSFileRelease:      ns[17],
		CongestionWait:      ns[18],
		Truncation:          ns[19],
		WriteExtension:      ns[20],
		SillyRename:         ns[21],
		ShortRead:           ns[22],
		ShortWrite:          ns[23],
		JukeboxDelay:        ns[24],
		PNFSRead:            ns[25],
		PNFSWrite:           ns[26],
	}, nil
}

func parseNFSOperationStats(s *bufio.Scanner) ([]NFSOperationStats, error) {

		numFields = 9
	)

	var ops []NFSOperationStats

	for s.Scan() {
		ss := strings.Fields(string(s.Bytes()))

			break
		}

		if len(ss) != numFields {
			return nil, fmt.Errorf("invalid NFS per-operations stats: %v", ss)
		}

		ns := make([]uint64, 0, numFields-1)
		for _, st := range ss[1:] {
			n, err := strconv.ParseUint(st, 10, 64)
			if err != nil {
				return nil, err
			}

			ns = append(ns, n)
		}

		ops = append(ops, NFSOperationStats{
			Operation:                           strings.TrimSuffix(ss[0], ":"),
			Requests:                            ns[0],
			Transmissions:                       ns[1],
			MajorTimeouts:                       ns[2],
			BytesSent:                           ns[3],
			BytesReceived:                       ns[4],
			CumulativeQueueMilliseconds:         ns[5],
			CumulativeTotalResponseMilliseconds: ns[6],
			CumulativeTotalRequestMilliseconds:  ns[7],
		})
	}

	return ops, s.Err()
}

	protocol := ss[0]
	ss = ss[1:]

	switch statVersion {
	case statVersion10:
		var expectedLength int
		if protocol == "tcp" {
			expectedLength = fieldTransport10TCPLen
		} else if protocol == "udp" {
			expectedLength = fieldTransport10UDPLen
		} else {
			return nil, fmt.Errorf("invalid NFS protocol \"%s\" in stats 1.0 statement: %v", protocol, ss)
		}
		if len(ss) != expectedLength {
			return nil, fmt.Errorf("invalid NFS transport stats 1.0 statement: %v", ss)
		}
	case statVersion11:
		var expectedLength int
		if protocol == "tcp" {
			expectedLength = fieldTransport11TCPLen
		} else if protocol == "udp" {
			expectedLength = fieldTransport11UDPLen
		} else {
			return nil, fmt.Errorf("invalid NFS protocol \"%s\" in stats 1.1 statement: %v", protocol, ss)
		}
		if len(ss) != expectedLength {
			return nil, fmt.Errorf("invalid NFS transport stats 1.1 statement: %v", ss)
		}
	default:
		return nil, fmt.Errorf("unrecognized NFS transport stats version: %q", statVersion)
	}

	ns := make([]uint64, fieldTransport11TCPLen)
	for i, s := range ss {
		n, err := strconv.ParseUint(s, 10, 64)
		if err != nil {
			return nil, err
		}

		ns[i] = n
	}

	if protocol == "udp" {
		ns = append(ns[:2], append(make([]uint64, 3), ns[2:]...)...)
	}

	return &NFSTransportStats{
		Protocol:                 protocol,
		Port:                     ns[0],
		Bind:                     ns[1],
		Connect:                  ns[2],
		ConnectIdleTime:          ns[3],
		IdleTimeSeconds:          ns[4],
		Sends:                    ns[5],
		Receives:                 ns[6],
		BadTransactionIDs:        ns[7],
		CumulativeActiveRequests: ns[8],
		CumulativeBacklog:        ns[9],
		MaximumRPCSlotsUsed:      ns[10],
		CumulativeSendingQueue:   ns[11],
		CumulativePendingQueue:   ns[12],
	}, nil