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

import (
	_ "embed"
	"encoding/csv"
	"errors"
	"fmt"
	"io"
	"net"
	"net/http"
	"net/url"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/influxdata/telegraf"
	"github.com/influxdata/telegraf/plugins/common/tls"
	"github.com/influxdata/telegraf/plugins/inputs"
)

//go:embed sample.conf
var sampleConfig string

var (
	typeNames    = []string{"frontend", "backend", "server", "listener"}
	fieldRenames = map[string]string{
		"pxname":     "proxy",
		"svname":     "sv",
		"act":        "active_servers",
		"bck":        "backup_servers",
		"cli_abrt":   "cli_abort",
		"srv_abrt":   "srv_abort",
		"hrsp_1xx":   "http_response.1xx",
		"hrsp_2xx":   "http_response.2xx",
		"hrsp_3xx":   "http_response.3xx",
		"hrsp_4xx":   "http_response.4xx",
		"hrsp_5xx":   "http_response.5xx",
		"hrsp_other": "http_response.other",
	}
)

// CSV format: https://cbonte.github.io/haproxy-dconv/1.5/configuration.html#9.1

type HAProxy struct {
	Servers        []string `toml:"servers"`
	KeepFieldNames bool     `toml:"keep_field_names"`
	Username       string   `toml:"username"`
	Password       string   `toml:"password"`
	tls.ClientConfig

	client *http.Client
}

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

func (h *HAProxy) Gather(acc telegraf.Accumulator) error {
	if len(h.Servers) == 0 {
		return h.gatherServer("http://127.0.0.1:1936/haproxy?stats", acc)
	}

	endpoints := make([]string, 0, len(h.Servers))

	for _, endpoint := range h.Servers {
		if strings.HasPrefix(endpoint, "http://") || strings.HasPrefix(endpoint, "https://") || strings.HasPrefix(endpoint, "tcp://") {
			endpoints = append(endpoints, endpoint)
			continue
		}

		socketPath := getSocketAddr(endpoint)

		matches, err := filepath.Glob(socketPath)

		if err != nil {
			return err
		}

		if len(matches) == 0 {
			endpoints = append(endpoints, socketPath)
		} else {
			endpoints = append(endpoints, matches...)
		}
	}

	var wg sync.WaitGroup
	wg.Add(len(endpoints))
	for _, server := range endpoints {
		go func(serv string) {
			defer wg.Done()
			if err := h.gatherServer(serv, acc); err != nil {
				acc.AddError(err)
			}
		}(server)
	}

	wg.Wait()
	return nil
}

func (h *HAProxy) gatherServerSocket(addr string, acc telegraf.Accumulator) error {
	var network, address string
	if strings.HasPrefix(addr, "tcp://") {
		network = "tcp"
		address = strings.TrimPrefix(addr, "tcp://")
	} else {
		network = "unix"
		address = getSocketAddr(addr)
	}

	c, err := net.Dial(network, address)
	if err != nil {
		return fmt.Errorf("could not connect to '%s://%s': %w", network, address, err)
	}

	_, errw := c.Write([]byte("show stat\n"))
	if errw != nil {
		return fmt.Errorf("could not write to socket '%s://%s': %w", network, address, errw)
	}

	return h.importCsvResult(c, acc, address)
}

func (h *HAProxy) gatherServer(addr string, acc telegraf.Accumulator) error {
	if !strings.HasPrefix(addr, "http") {
		return h.gatherServerSocket(addr, acc)
	}

	if h.client == nil {
		tlsCfg, err := h.ClientConfig.TLSConfig()
		if err != nil {
			return err
		}
		tr := &http.Transport{
			ResponseHeaderTimeout: 3 * time.Second,
			TLSClientConfig:       tlsCfg,
		}
		client := &http.Client{
			Transport: tr,
			Timeout:   4 * time.Second,
		}
		h.client = client
	}

	if !strings.HasSuffix(addr, ";csv") {
		addr += "/;csv"
	}

	u, err := url.Parse(addr)
	if err != nil {
		return fmt.Errorf("unable parse server address %q: %w", addr, err)
	}

	req, err := http.NewRequest("GET", addr, nil)
	if err != nil {
		return fmt.Errorf("unable to create new request %q: %w", addr, err)
	}
	if u.User != nil {
		p, _ := u.User.Password()
		req.SetBasicAuth(u.User.Username(), p)
		u.User = &url.Userinfo{}
		addr = u.String()
	}

	if h.Username != "" || h.Password != "" {
		req.SetBasicAuth(h.Username, h.Password)
	}

	res, err := h.client.Do(req)
	if err != nil {
		return fmt.Errorf("unable to connect to haproxy server %q: %w", addr, err)
	}
	defer res.Body.Close()

	if res.StatusCode != 200 {
		return fmt.Errorf("unable to get valid stat result from %q, http response code : %d", addr, res.StatusCode)
	}

	if err := h.importCsvResult(res.Body, acc, u.Host); err != nil {
		return fmt.Errorf("unable to parse stat result from %q: %w", addr, err)
	}

	return nil
}

func getSocketAddr(sock string) string {
	socketAddr := strings.Split(sock, ":")

	if len(socketAddr) >= 2 {
		return socketAddr[1]
	}
	return socketAddr[0]
}

func (h *HAProxy) importCsvResult(r io.Reader, acc telegraf.Accumulator, host string) error {
	csvr := csv.NewReader(r)
	now := time.Now()

	headers, err := csvr.Read()
	if err != nil {
		return err
	}
	if len(headers[0]) <= 2 || headers[0][:2] != "# " {
		return errors.New("did not receive standard haproxy headers")
	}
	headers[0] = headers[0][2:]

	for {
		row, err := csvr.Read()
		if errors.Is(err, io.EOF) {
			break
		}
		if err != nil {
			return err
		}

		fields := make(map[string]interface{})
		tags := map[string]string{
			"server": host,
		}

		if len(row) != len(headers) {
			return fmt.Errorf("number of columns does not match number of headers. headers=%d columns=%d", len(headers), len(row))
		}
		for i, v := range row {
			if v == "" {
				continue
			}

			colName := headers[i]
			fieldName := colName
			if !h.KeepFieldNames {
				if fieldRename, ok := fieldRenames[colName]; ok {
					fieldName = fieldRename
				}
			}

			switch colName {
			case "pxname", "svname":
				tags[fieldName] = v
			case "type":
				vi, err := strconv.ParseInt(v, 10, 64)
				if err != nil {
					return fmt.Errorf("unable to parse type value %q", v)
				}
				if vi >= int64(len(typeNames)) {
					return fmt.Errorf("received unknown type value: %d", vi)
				}
				tags[fieldName] = typeNames[vi]
			case "check_desc", "agent_desc":
				// do nothing. These fields are just a more verbose description of the check_status & agent_status fields
			case "status", "check_status", "last_chk", "mode", "tracked", "agent_status", "last_agt", "addr", "cookie":
				// these are string fields
				fields[fieldName] = v
			case "lastsess":
				vi, err := strconv.ParseInt(v, 10, 64)
				if err != nil {
					// TODO log the error. And just once (per column) so we don't spam the log
					continue
				}
				fields[fieldName] = vi
			default:
				vi, err := strconv.ParseUint(v, 10, 64)
				if err != nil {
					// TODO log the error. And just once (per column) so we don't spam the log
					continue
				}
				fields[fieldName] = vi
			}
		}
		acc.AddFields("haproxy", fields, tags, now)
	}
	return err
}

func init() {
	inputs.Add("haproxy", func() telegraf.Input {
		return &HAProxy{}
	})
}
