//go:generate ../../../tools/readme_config_includer/generator
package unbound

import (
	"bufio"
	"bytes"
	"context"
	_ "embed"
	"fmt"
	"net"
	"os/exec"
	"strconv"
	"strings"
	"time"

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

//go:embed sample.conf
var sampleConfig string

var (
	defaultBinary  = "/usr/sbin/unbound-control"
	defaultTimeout = config.Duration(time.Second)
)

type Unbound struct {
	Binary      string          `toml:"binary"`
	Timeout     config.Duration `toml:"timeout"`
	UseSudo     bool            `toml:"use_sudo"`
	Server      string          `toml:"server"`
	ThreadAsTag bool            `toml:"thread_as_tag"`
	ConfigFile  string          `toml:"config_file"`
	Histogram   bool            `toml:"histogram"`

	run runner
}

type runner func(unbound Unbound) (*bytes.Buffer, error)

func (*Unbound) SampleConfig() string {
	return sampleConfig
}

// All the dots in stat name will replaced by underscores. Histogram statistics will not be collected.
func (s *Unbound) Gather(acc telegraf.Accumulator) error {
	out, err := s.run(*s)
	if err != nil {
		return fmt.Errorf("error gathering metrics: %w", err)
	}

	// Process values
	fields := make(map[string]interface{})
	fieldsThreads := make(map[string]map[string]interface{})

	scanner := bufio.NewScanner(out)
	for scanner.Scan() {
		cols := strings.Split(scanner.Text(), "=")

		// Check split correctness
		if len(cols) != 2 {
			continue
		}

		stat := cols[0]
		value := cols[1]

		fieldValue, err := strconv.ParseFloat(value, 64)
		if err != nil {
			acc.AddError(fmt.Errorf("expected a numerical value for %s = %v", stat, value))
			continue
		}

		// is this a thread related value?
		if s.ThreadAsTag && strings.HasPrefix(stat, "thread") {
			// split the stat
			statTokens := strings.Split(stat, ".")
			// make sure we split something
			if len(statTokens) > 1 {
				// set the thread identifier
				threadID := strings.TrimPrefix(statTokens[0], "thread")
				// make sure we have a proper thread ID
				if _, err = strconv.Atoi(threadID); err == nil {
					// create new slice without the thread identifier (skip first token)
					threadTokens := statTokens[1:]
					// re-define stat
					field := strings.Join(threadTokens[:], "_")
					if fieldsThreads[threadID] == nil {
						fieldsThreads[threadID] = make(map[string]interface{})
					}
					fieldsThreads[threadID][field] = fieldValue
				}
			}
		} else if suffix, found := strings.CutPrefix(stat, "histogram."); found {
			if s.Histogram {
				suffix, _, _ := strings.Cut(suffix, ".to.")
				suffix = strings.TrimLeft(suffix, "0")
				if strings.HasPrefix(suffix, ".") {
					suffix = "0" + suffix
				}
				fields["histogram_"+suffix] = fieldValue
			}
		} else {
			field := strings.ReplaceAll(stat, ".", "_")
			fields[field] = fieldValue
		}
	}

	acc.AddFields("unbound", fields, nil)

	if s.ThreadAsTag && len(fieldsThreads) > 0 {
		for thisThreadID, thisThreadFields := range fieldsThreads {
			thisThreadTag := map[string]string{"thread": thisThreadID}
			acc.AddFields("unbound_threads", thisThreadFields, thisThreadTag)
		}
	}

	return nil
}

// Shell out to unbound_stat and return the output
func unboundRunner(unbound Unbound) (*bytes.Buffer, error) {
	cmdArgs := []string{"stats_noreset"}

	if unbound.Server != "" {
		host, port, err := net.SplitHostPort(unbound.Server)
		if err != nil { // No port was specified
			host = unbound.Server
			port = ""
		}

		// Unbound control requires an IP address, and we want to be nice to the user
		resolver := net.Resolver{}
		ctx, lookUpCancel := context.WithTimeout(context.Background(), time.Duration(unbound.Timeout))
		defer lookUpCancel()
		serverIps, err := resolver.LookupIPAddr(ctx, host)
		if err != nil {
			return nil, fmt.Errorf("error looking up ip for server %q: %w", unbound.Server, err)
		}
		if len(serverIps) == 0 {
			return nil, fmt.Errorf("error no ip for server %q: %w", unbound.Server, err)
		}
		server := serverIps[0].IP.String()
		if port != "" {
			server = server + "@" + port
		}

		cmdArgs = append([]string{"-s", server}, cmdArgs...)
	}

	if unbound.ConfigFile != "" {
		cmdArgs = append([]string{"-c", unbound.ConfigFile}, cmdArgs...)
	}

	cmd := exec.Command(unbound.Binary, cmdArgs...)

	if unbound.UseSudo {
		cmdArgs = append([]string{unbound.Binary}, cmdArgs...)
		cmd = exec.Command("sudo", cmdArgs...)
	}

	var out bytes.Buffer
	cmd.Stdout = &out
	err := internal.RunTimeout(cmd, time.Duration(unbound.Timeout))
	if err != nil {
		return &out, fmt.Errorf("error running unbound-control %q %q: %w", unbound.Binary, cmdArgs, err)
	}

	return &out, nil
}

func init() {
	inputs.Add("unbound", func() telegraf.Input {
		return &Unbound{
			run:         unboundRunner,
			Binary:      defaultBinary,
			Timeout:     defaultTimeout,
			UseSudo:     false,
			Server:      "",
			ThreadAsTag: false,
			ConfigFile:  "",
			Histogram:   false,
		}
	})
}
