package nfsclient

import (
	"bufio"
	"fmt"
	"os"
	"regexp"
	"strconv"
	"strings"

	"github.com/influxdata/telegraf"
	"github.com/influxdata/telegraf/internal/choice"
	"github.com/influxdata/telegraf/plugins/inputs"
)

type NFSClient struct {
	Fullstat          bool            `toml:"fullstat"`
	IncludeMounts     []string        `toml:"include_mounts"`
	ExcludeMounts     []string        `toml:"exclude_mounts"`
	IncludeOperations []string        `toml:"include_operations"`
	ExcludeOperations []string        `toml:"exclude_operations"`
	Log               telegraf.Logger `toml:"-"`
	nfs3Ops           map[string]bool
	nfs4Ops           map[string]bool
	mountstatsPath    string
}

const sampleConfig = `
  ## Read more low-level metrics (optional, defaults to false)
  # fullstat = false

  ## List of mounts to explictly include or exclude (optional)
  ## The pattern (Go regexp) is matched against the mount point (not the
  ## device being mounted).  If include_mounts is set, all mounts are ignored
  ## unless present in the list. If a mount is listed in both include_mounts
  ## and exclude_mounts, it is excluded.  Go regexp patterns can be used.
  # include_mounts = []
  # exclude_mounts = []

  ## List of operations to include or exclude from collecting.  This applies
  ## only when fullstat=true.  Symantics are similar to {include,exclude}_mounts:
  ## the default is to collect everything; when include_operations is set, only
  ## those OPs are collected; when exclude_operations is set, all are collected
  ## except those listed.  If include and exclude are set, the OP is excluded.
  ## See /proc/self/mountstats for a list of valid operations; note that
  ## NFSv3 and NFSv4 have different lists.  While it is not possible to
  ## have different include/exclude lists for NFSv3/4, unused elements
  ## in the list should be okay.  It is possible to have different lists
  ## for different mountpoints:  use mulitple [[input.nfsclient]] stanzas,
  ## with their own lists.  See "include_mounts" above, and be careful of
  ## duplicate metrics.
  # include_operations = []
  # exclude_operations = []
`

func (n *NFSClient) SampleConfig() string {
	return sampleConfig
}

func (n *NFSClient) Description() string {
	return "Read per-mount NFS client metrics from /proc/self/mountstats"
}

func convertToUint64(line []string) ([]uint64, error) {
	/* A "line" of input data (a pre-split array of strings) is
	   processed one field at a time.  Each field is converted to
	   an uint64 value, and appened to an array of return values.
	   On an error, check for ErrRange, and returns an error
	   if found.  This situation indicates a pretty major issue in
	   the /proc/self/mountstats file, and returning faulty data
	   is worse than no data.  Other errors are ignored, and append
	   whatever we got in the first place (probably 0).
	   Yes, this is ugly. */

	var nline []uint64

	if len(line) < 2 {
		return nline, nil
	}

	// Skip the first field; it's handled specially as the "first" variable
	for _, l := range line[1:] {
		val, err := strconv.ParseUint(l, 10, 64)
		if err != nil {
			if numError, ok := err.(*strconv.NumError); ok {
				if numError.Err == strconv.ErrRange {
					return nil, fmt.Errorf("errrange: line:[%v] raw:[%v] -> parsed:[%v]", line, l, val)
				}
			}
		}
		nline = append(nline, val)
	}
	return nline, nil
}

func (n *NFSClient) parseStat(mountpoint string, export string, version string, line []string, acc telegraf.Accumulator) error {
	tags := map[string]string{"mountpoint": mountpoint, "serverexport": export}
	nline, err := convertToUint64(line)
	if err != nil {
		return err
	}

	if len(nline) == 0 {
		n.Log.Warnf("Parsing Stat line with one field: %s\n", line)
		return nil
	}

	first := strings.Replace(line[0], ":", "", 1)

	var eventsFields = []string{
		"inoderevalidates",
		"dentryrevalidates",
		"datainvalidates",
		"attrinvalidates",
		"vfsopen",
		"vfslookup",
		"vfsaccess",
		"vfsupdatepage",
		"vfsreadpage",
		"vfsreadpages",
		"vfswritepage",
		"vfswritepages",
		"vfsgetdents",
		"vfssetattr",
		"vfsflush",
		"vfsfsync",
		"vfslock",
		"vfsrelease",
		"congestionwait",
		"setattrtrunc",
		"extendwrite",
		"sillyrenames",
		"shortreads",
		"shortwrites",
		"delay",
		"pnfsreads",
		"pnfswrites",
	}

	var bytesFields = []string{
		"normalreadbytes",
		"normalwritebytes",
		"directreadbytes",
		"directwritebytes",
		"serverreadbytes",
		"serverwritebytes",
		"readpages",
		"writepages",
	}

	var xprtudpFields = []string{
		"bind_count",
		"rpcsends",
		"rpcreceives",
		"badxids",
		"inflightsends",
		"backlogutil",
	}

	var xprttcpFields = []string{
		"bind_count",
		"connect_count",
		"connect_time",
		"idle_time",
		"rpcsends",
		"rpcreceives",
		"badxids",
		"inflightsends",
		"backlogutil",
	}

	var nfsopFields = []string{
		"ops",
		"trans",
		"timeouts",
		"bytes_sent",
		"bytes_recv",
		"queue_time",
		"response_time",
		"total_time",
		"errors",
	}

	var fields = make(map[string]interface{})

	switch first {
	case "READ", "WRITE":
		fields["ops"] = nline[0]
		fields["retrans"] = nline[1] - nline[0]
		fields["bytes"] = nline[3] + nline[4]
		fields["rtt"] = nline[6]
		fields["exe"] = nline[7]
		fields["rtt_per_op"] = 0.0
		if nline[0] > 0 {
			fields["rtt_per_op"] = float64(nline[6]) / float64(nline[0])
		}
		tags["operation"] = first
		acc.AddFields("nfsstat", fields, tags)
	}

	if n.Fullstat {
		switch first {
		case "events":
			if len(nline) >= len(eventsFields) {
				for i, t := range eventsFields {
					fields[t] = nline[i]
				}
				acc.AddFields("nfs_events", fields, tags)
			}

		case "bytes":
			if len(nline) >= len(bytesFields) {
				for i, t := range bytesFields {
					fields[t] = nline[i]
				}
				acc.AddFields("nfs_bytes", fields, tags)
			}

		case "xprt":
			if len(line) > 1 {
				switch line[1] {
				case "tcp":
					if len(nline)+2 >= len(xprttcpFields) {
						for i, t := range xprttcpFields {
							fields[t] = nline[i+2]
						}
						acc.AddFields("nfs_xprt_tcp", fields, tags)
					}
				case "udp":
					if len(nline)+2 >= len(xprtudpFields) {
						for i, t := range xprtudpFields {
							fields[t] = nline[i+2]
						}
						acc.AddFields("nfs_xprt_udp", fields, tags)
					}
				}
			}
		}

		if (version == "3" && n.nfs3Ops[first]) || (version == "4" && n.nfs4Ops[first]) {
			tags["operation"] = first
			if len(nline) <= len(nfsopFields) {
				for i, t := range nline {
					fields[nfsopFields[i]] = t
				}
				acc.AddFields("nfs_ops", fields, tags)
			}
		}
	}

	return nil
}

func (n *NFSClient) processText(scanner *bufio.Scanner, acc telegraf.Accumulator) error {
	var mount string
	var version string
	var export string
	var skip bool

	for scanner.Scan() {
		line := strings.Fields(scanner.Text())
		lineLength := len(line)

		if lineLength == 0 {
			continue
		}

		skip = false

		// This denotes a new mount has been found, so set
		// mount and export, and stop skipping (for now)
		if lineLength > 4 && choice.Contains("fstype", line) && (choice.Contains("nfs", line) || choice.Contains("nfs4", line)) {
			mount = line[4]
			export = line[1]
		} else if lineLength > 5 && (choice.Contains("(nfs)", line) || choice.Contains("(nfs4)", line)) {
			version = strings.Split(line[5], "/")[1]
		}

		if mount == "" {
			continue
		}

		if len(n.IncludeMounts) > 0 {
			skip = true
			for _, RE := range n.IncludeMounts {
				matched, _ := regexp.MatchString(RE, mount)
				if matched {
					skip = false
					break
				}
			}
		}

		if !skip && len(n.ExcludeMounts) > 0 {
			for _, RE := range n.ExcludeMounts {
				matched, _ := regexp.MatchString(RE, mount)
				if matched {
					skip = true
					break
				}
			}
		}

		if !skip {
			err := n.parseStat(mount, export, version, line, acc)
			if err != nil {
				return fmt.Errorf("could not parseStat: %w", err)
			}
		}
	}

	return nil
}

func (n *NFSClient) getMountStatsPath() string {
	path := "/proc/self/mountstats"
	if os.Getenv("MOUNT_PROC") != "" {
		path = os.Getenv("MOUNT_PROC")
	}
	n.Log.Debugf("using [%s] for mountstats", path)
	return path
}

func (n *NFSClient) Gather(acc telegraf.Accumulator) error {
	file, err := os.Open(n.mountstatsPath)
	if err != nil {
		n.Log.Errorf("Failed opening the [%s] file: %s ", file, err)
		return err
	}
	defer file.Close()

	scanner := bufio.NewScanner(file)
	if err := n.processText(scanner, acc); err != nil {
		return err
	}

	if err := scanner.Err(); err != nil {
		n.Log.Errorf("%s", err)
		return err
	}

	return nil
}

func (n *NFSClient) Init() error {
	var nfs3Fields = []string{
		"NULL",
		"GETATTR",
		"SETATTR",
		"LOOKUP",
		"ACCESS",
		"READLINK",
		"READ",
		"WRITE",
		"CREATE",
		"MKDIR",
		"SYMLINK",
		"MKNOD",
		"REMOVE",
		"RMDIR",
		"RENAME",
		"LINK",
		"READDIR",
		"READDIRPLUS",
		"FSSTAT",
		"FSINFO",
		"PATHCONF",
		"COMMIT",
	}

	var nfs4Fields = []string{
		"NULL",
		"READ",
		"WRITE",
		"COMMIT",
		"OPEN",
		"OPEN_CONFIRM",
		"OPEN_NOATTR",
		"OPEN_DOWNGRADE",
		"CLOSE",
		"SETATTR",
		"FSINFO",
		"RENEW",
		"SETCLIENTID",
		"SETCLIENTID_CONFIRM",
		"LOCK",
		"LOCKT",
		"LOCKU",
		"ACCESS",
		"GETATTR",
		"LOOKUP",
		"LOOKUP_ROOT",
		"REMOVE",
		"RENAME",
		"LINK",
		"SYMLINK",
		"CREATE",
		"PATHCONF",
		"STATFS",
		"READLINK",
		"READDIR",
		"SERVER_CAPS",
		"DELEGRETURN",
		"GETACL",
		"SETACL",
		"FS_LOCATIONS",
		"RELEASE_LOCKOWNER",
		"SECINFO",
		"FSID_PRESENT",
		"EXCHANGE_ID",
		"CREATE_SESSION",
		"DESTROY_SESSION",
		"SEQUENCE",
		"GET_LEASE_TIME",
		"RECLAIM_COMPLETE",
		"LAYOUTGET",
		"GETDEVICEINFO",
		"LAYOUTCOMMIT",
		"LAYOUTRETURN",
		"SECINFO_NO_NAME",
		"TEST_STATEID",
		"FREE_STATEID",
		"GETDEVICELIST",
		"BIND_CONN_TO_SESSION",
		"DESTROY_CLIENTID",
		"SEEK",
		"ALLOCATE",
		"DEALLOCATE",
		"LAYOUTSTATS",
		"CLONE",
		"COPY",
		"OFFLOAD_CANCEL",
		"LOOKUPP",
		"LAYOUTERROR",
		"COPY_NOTIFY",
		"GETXATTR",
		"SETXATTR",
		"LISTXATTRS",
		"REMOVEXATTR",
	}

	nfs3Ops := make(map[string]bool)
	nfs4Ops := make(map[string]bool)

	n.mountstatsPath = n.getMountStatsPath()

	if len(n.IncludeOperations) == 0 {
		for _, Op := range nfs3Fields {
			nfs3Ops[Op] = true
		}
		for _, Op := range nfs4Fields {
			nfs4Ops[Op] = true
		}
	} else {
		for _, Op := range n.IncludeOperations {
			nfs3Ops[Op] = true
		}
		for _, Op := range n.IncludeOperations {
			nfs4Ops[Op] = true
		}
	}

	if len(n.ExcludeOperations) > 0 {
		for _, Op := range n.ExcludeOperations {
			if nfs3Ops[Op] {
				delete(nfs3Ops, Op)
			}
			if nfs4Ops[Op] {
				delete(nfs4Ops, Op)
			}
		}
	}

	n.nfs3Ops = nfs3Ops
	n.nfs4Ops = nfs4Ops

	if len(n.IncludeMounts) > 0 {
		n.Log.Debugf("Including these mount patterns: %v", n.IncludeMounts)
	} else {
		n.Log.Debugf("Including all mounts.")
	}

	if len(n.ExcludeMounts) > 0 {
		n.Log.Debugf("Excluding these mount patterns: %v", n.ExcludeMounts)
	} else {
		n.Log.Debugf("Not excluding any mounts.")
	}

	if len(n.IncludeOperations) > 0 {
		n.Log.Debugf("Including these operations: %v", n.IncludeOperations)
	} else {
		n.Log.Debugf("Including all operations.")
	}

	if len(n.ExcludeOperations) > 0 {
		n.Log.Debugf("Excluding these mount patterns: %v", n.ExcludeOperations)
	} else {
		n.Log.Debugf("Not excluding any operations.")
	}

	return nil
}

func init() {
	inputs.Add("nfsclient", func() telegraf.Input {
		return &NFSClient{}
	})
}