package mqtt_consumer

import (
	"context"
	"errors"
	"fmt"
	"strconv"
	"strings"
	"sync"
	"time"

	mqtt "github.com/eclipse/paho.mqtt.golang"
	"github.com/influxdata/telegraf"
	"github.com/influxdata/telegraf/config"
	"github.com/influxdata/telegraf/internal"
	"github.com/influxdata/telegraf/plugins/common/tls"
	"github.com/influxdata/telegraf/plugins/inputs"
	"github.com/influxdata/telegraf/plugins/parsers"
)

var (
	// 30 Seconds is the default used by paho.mqtt.golang
	defaultConnectionTimeout      = config.Duration(30 * time.Second)
	defaultMaxUndeliveredMessages = 1000
)

type ConnectionState int
type empty struct{}
type semaphore chan empty

const (
	Disconnected ConnectionState = iota
	Connecting
	Connected
)

type Client interface {
	Connect() mqtt.Token
	SubscribeMultiple(filters map[string]byte, callback mqtt.MessageHandler) mqtt.Token
	AddRoute(topic string, callback mqtt.MessageHandler)
	Disconnect(quiesce uint)
}
type ClientFactory func(o *mqtt.ClientOptions) Client
type TopicParsingConfig struct {
	Topic       string            `toml:"topic"`
	Measurement string            `toml:"measurement"`
	Tags        string            `toml:"tags"`
	Fields      string            `toml:"fields"`
	FieldTypes  map[string]string `toml:"types"`
	// cached split of user given information
	MeasurementIndex int
	SplitTags        []string
	SplitFields      []string
	SplitTopic       []string
}
type MQTTConsumer struct {
	Servers                []string             `toml:"servers"`
	Topics                 []string             `toml:"topics"`
	TopicTag               *string              `toml:"topic_tag"`
	TopicParsing           []TopicParsingConfig `toml:"topic_parsing"`
	Username               string               `toml:"username"`
	Password               string               `toml:"password"`
	QoS                    int                  `toml:"qos"`
	ConnectionTimeout      config.Duration      `toml:"connection_timeout"`
	MaxUndeliveredMessages int                  `toml:"max_undelivered_messages"`
	parser                 parsers.Parser
	// Legacy metric buffer support; deprecated in v0.10.3
	MetricBuffer      int
	PersistentSession bool
	ClientID          string `toml:"client_id"`
	tls.ClientConfig
	Log           telegraf.Logger
	clientFactory ClientFactory
	client        Client
	opts          *mqtt.ClientOptions
	acc           telegraf.TrackingAccumulator
	state         ConnectionState
	sem           semaphore
	messages      map[telegraf.TrackingID]bool
	messagesMutex sync.Mutex
	topicTagParse string
	ctx           context.Context
	cancel        context.CancelFunc
}

var sampleConfig = `
  ## Broker URLs for the MQTT server or cluster.  To connect to multiple
  ## clusters or standalone servers, use a separate plugin instance.
  ##   example: servers = ["tcp://localhost:1883"]
  ##            servers = ["ssl://localhost:1883"]
  ##            servers = ["ws://localhost:1883"]
  servers = ["tcp://127.0.0.1:1883"]
  ## Topics that will be subscribed to.
  topics = [
    "telegraf/host01/cpu",
    "telegraf/+/mem",
    "sensors/#",
  ]
  # topic_fields = "_/_/_/temperature" 
  ## The message topic will be stored in a tag specified by this value.  If set
  ## to the empty string no topic tag will be created.
  # topic_tag = "topic"
  ## QoS policy for messages
  ##   0 = at most once
  ##   1 = at least once
  ##   2 = exactly once
  ##
  ## When using a QoS of 1 or 2, you should enable persistent_session to allow
  ## resuming unacknowledged messages.
  # qos = 0
  ## Connection timeout for initial connection in seconds
  # connection_timeout = "30s"
  ## Maximum messages to read from the broker that have not been written by an
  ## output.  For best throughput set based on the number of metrics within
  ## each message and the size of the output's metric_batch_size.
  ##
  ## For example, if each message from the queue contains 10 metrics and the
  ## output metric_batch_size is 1000, setting this to 100 will ensure that a
  ## full batch is collected and the write is triggered immediately without
  ## waiting until the next flush_interval.
  # max_undelivered_messages = 1000
  ## Persistent session disables clearing of the client session on connection.
  ## In order for this option to work you must also set client_id to identify
  ## the client.  To receive messages that arrived while the client is offline,
  ## also set the qos option to 1 or 2 and don't forget to also set the QoS when
  ## publishing.
  # persistent_session = false
  ## If unset, a random client ID will be generated.
  # client_id = ""
  ## Username and password to connect MQTT server.
  # username = "telegraf"
  # password = "metricsmetricsmetricsmetrics"
  ## Optional TLS Config
  # tls_ca = "/etc/telegraf/ca.pem"
  # tls_cert = "/etc/telegraf/cert.pem"
  # tls_key = "/etc/telegraf/key.pem"
  ## Use TLS but skip chain & host verification
  # insecure_skip_verify = false
  ## Data format to consume.
  ## Each data format has its own unique set of configuration options, read
  ## more about them here:
  ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_INPUT.md
  data_format = "influx"
  ## Enable extracting tag values from MQTT topics
  ## _ denotes an ignored entry in the topic path 
  ## [[inputs.mqtt_consumer.topic_parsing]]
  ##  topic = ""
  ##  measurement = ""
  ##  tags = ""
  ##  fields = ""
  ## [inputs.mqtt_consumer.topic_parsing.types]
  ##    
`

func (m *MQTTConsumer) SampleConfig() string {
	return sampleConfig
}
func (m *MQTTConsumer) Description() string {
	return "Read metrics from MQTT topic(s)"
}
func (m *MQTTConsumer) SetParser(parser parsers.Parser) {
	m.parser = parser
}
func (m *MQTTConsumer) Init() error {
	m.state = Disconnected
	if m.PersistentSession && m.ClientID == "" {
		return errors.New("persistent_session requires client_id")
	}
	if m.QoS > 2 || m.QoS < 0 {
		return fmt.Errorf("qos value must be 0, 1, or 2: %d", m.QoS)
	}
	if time.Duration(m.ConnectionTimeout) < 1*time.Second {
		return fmt.Errorf("connection_timeout must be greater than 1s: %s", time.Duration(m.ConnectionTimeout))
	}
	m.topicTagParse = "topic"
	if m.TopicTag != nil {
		m.topicTagParse = *m.TopicTag
	}
	opts, err := m.createOpts()
	if err != nil {
		return err
	}
	m.opts = opts
	m.messages = map[telegraf.TrackingID]bool{}

	for i, p := range m.TopicParsing {
		splitMeasurement := strings.Split(p.Measurement, "/")
		for j := range splitMeasurement {
			if splitMeasurement[j] != "_" {
				m.TopicParsing[i].MeasurementIndex = j
				break
			}
		}
		m.TopicParsing[i].SplitTags = strings.Split(p.Tags, "/")
		m.TopicParsing[i].SplitFields = strings.Split(p.Fields, "/")
		m.TopicParsing[i].SplitTopic = strings.Split(p.Topic, "/")

		if len(splitMeasurement) != len(m.TopicParsing[i].SplitTopic) && len(splitMeasurement) != 1 {
			return fmt.Errorf("config error topic parsing: measurement length does not equal topic length")
		}

		if len(m.TopicParsing[i].SplitFields) != len(m.TopicParsing[i].SplitTopic) && p.Fields != "" {
			return fmt.Errorf("config error topic parsing: fields length does not equal topic length")
		}

		if len(m.TopicParsing[i].SplitTags) != len(m.TopicParsing[i].SplitTopic) && p.Tags != "" {
			return fmt.Errorf("config error topic parsing: tags length does not equal topic length")
		}
	}

	return nil
}
func (m *MQTTConsumer) Start(acc telegraf.Accumulator) error {
	m.state = Disconnected
	m.acc = acc.WithTracking(m.MaxUndeliveredMessages)
	m.sem = make(semaphore, m.MaxUndeliveredMessages)
	m.ctx, m.cancel = context.WithCancel(context.Background())
	m.client = m.clientFactory(m.opts)
	// AddRoute sets up the function for handling messages.  These need to be
	// added in case we find a persistent session containing subscriptions so we
	// know where to dispatch persisted and new messages to.  In the alternate
	// case that we need to create the subscriptions these will be replaced.
	for _, topic := range m.Topics {
		m.client.AddRoute(topic, m.recvMessage)
	}
	m.state = Connecting
	return m.connect()
}
func (m *MQTTConsumer) connect() error {
	token := m.client.Connect()
	if token.Wait() && token.Error() != nil {
		err := token.Error()
		m.state = Disconnected
		return err
	}
	m.Log.Infof("Connected %v", m.Servers)
	m.state = Connected
	// Persistent sessions should skip subscription if a session is present, as
	// the subscriptions are stored by the server.
	type sessionPresent interface {
		SessionPresent() bool
	}
	if t, ok := token.(sessionPresent); ok && t.SessionPresent() {
		m.Log.Debugf("Session found %v", m.Servers)
		return nil
	}
	topics := make(map[string]byte)
	for _, topic := range m.Topics {
		topics[topic] = byte(m.QoS)
	}
	subscribeToken := m.client.SubscribeMultiple(topics, m.recvMessage)
	subscribeToken.Wait()
	if subscribeToken.Error() != nil {
		m.acc.AddError(fmt.Errorf("subscription error: topics: %s: %v",
			strings.Join(m.Topics[:], ","), subscribeToken.Error()))
	}
	return nil
}
func (m *MQTTConsumer) onConnectionLost(_ mqtt.Client, err error) {
	m.acc.AddError(fmt.Errorf("connection lost: %v", err))
	m.Log.Debugf("Disconnected %v", m.Servers)
	m.state = Disconnected
}
func (m *MQTTConsumer) recvMessage(_ mqtt.Client, msg mqtt.Message) {
	for {
		select {
		case track := <-m.acc.Delivered():
			<-m.sem
			m.messagesMutex.Lock()
			_, ok := m.messages[track.ID()]
			if !ok {
				// Added by a previous connection
				continue
			}
			// No ack, MQTT does not support durable handling
			delete(m.messages, track.ID())
			m.messagesMutex.Unlock()
		case m.sem <- empty{}:
			err := m.onMessage(m.acc, msg)
			if err != nil {
				m.acc.AddError(err)
				<-m.sem
			}
			return
		}
	}
}

// compareTopics is used to support the mqtt wild card `+` which allows for one topic of any value
func compareTopics(expected []string, incoming []string) bool {
	if len(expected) != len(incoming) {
		return false
	}

	for i, expected := range expected {
		if incoming[i] != expected && expected != "+" {
			return false
		}
	}

	return true
}

func (m *MQTTConsumer) onMessage(acc telegraf.TrackingAccumulator, msg mqtt.Message) error {
	metrics, err := m.parser.Parse(msg.Payload())
	if err != nil {
		return err
	}

	for _, metric := range metrics {
		if m.topicTagParse != "" {
			metric.AddTag(m.topicTagParse, msg.Topic())
		}
		for _, p := range m.TopicParsing {
			values := strings.Split(msg.Topic(), "/")
			if !compareTopics(p.SplitTopic, values) {
				continue
			}

			if p.Measurement != "" {
				metric.SetName(values[p.MeasurementIndex])
			}
			if p.Tags != "" {
				err := parseMetric(p.SplitTags, values, p.FieldTypes, true, metric)
				if err != nil {
					return err
				}
			}
			if p.Fields != "" {
				err := parseMetric(p.SplitFields, values, p.FieldTypes, false, metric)
				if err != nil {
					return err
				}
			}
		}
	}
	id := acc.AddTrackingMetricGroup(metrics)
	m.messagesMutex.Lock()
	m.messages[id] = true
	m.messagesMutex.Unlock()
	return nil
}
func (m *MQTTConsumer) Stop() {
	if m.state == Connected {
		m.Log.Debugf("Disconnecting %v", m.Servers)
		m.client.Disconnect(200)
		m.Log.Debugf("Disconnected %v", m.Servers)
		m.state = Disconnected
	}
	m.cancel()
}
func (m *MQTTConsumer) Gather(_ telegraf.Accumulator) error {
	if m.state == Disconnected {
		m.state = Connecting
		m.Log.Debugf("Connecting %v", m.Servers)
		return m.connect()
	}
	return nil
}
func (m *MQTTConsumer) createOpts() (*mqtt.ClientOptions, error) {
	opts := mqtt.NewClientOptions()
	opts.ConnectTimeout = time.Duration(m.ConnectionTimeout)
	if m.ClientID == "" {
		opts.SetClientID("Telegraf-Consumer-" + internal.RandomString(5))
	} else {
		opts.SetClientID(m.ClientID)
	}
	tlsCfg, err := m.ClientConfig.TLSConfig()
	if err != nil {
		return nil, err
	}
	if tlsCfg != nil {
		opts.SetTLSConfig(tlsCfg)
	}
	user := m.Username
	if user != "" {
		opts.SetUsername(user)
	}
	password := m.Password
	if password != "" {
		opts.SetPassword(password)
	}
	if len(m.Servers) == 0 {
		return opts, fmt.Errorf("could not get host informations")
	}
	for _, server := range m.Servers {
		// Preserve support for host:port style servers; deprecated in Telegraf 1.4.4
		if !strings.Contains(server, "://") {
			m.Log.Warnf("Server %q should be updated to use `scheme://host:port` format", server)
			if tlsCfg == nil {
				server = "tcp://" + server
			} else {
				server = "ssl://" + server
			}
		}
		opts.AddBroker(server)
	}
	opts.SetAutoReconnect(false)
	opts.SetKeepAlive(time.Second * 60)
	opts.SetCleanSession(!m.PersistentSession)
	opts.SetConnectionLostHandler(m.onConnectionLost)
	return opts, nil
}

// parseFields gets multiple fields from the topic based on the user configuration (TopicParsing.Fields)
func parseMetric(keys []string, values []string, types map[string]string, isTag bool, metric telegraf.Metric) error {
	for i, k := range keys {
		if k == "_" {
			continue
		}

		if isTag {
			metric.AddTag(k, values[i])
		} else {
			newType, err := typeConvert(types, values[i], k)
			if err != nil {
				return err
			}
			metric.AddField(k, newType)
		}
	}
	return nil
}

func typeConvert(types map[string]string, topicValue string, key string) (interface{}, error) {
	var newType interface{}
	var err error
	// If the user configured inputs.mqtt_consumer.topic.types, check for the desired type
	if desiredType, ok := types[key]; ok {
		switch desiredType {
		case "uint":
			newType, err = strconv.ParseUint(topicValue, 10, 64)
			if err != nil {
				return nil, fmt.Errorf("unable to convert field '%s' to type uint: %v", topicValue, err)
			}
		case "int":
			newType, err = strconv.ParseInt(topicValue, 10, 64)
			if err != nil {
				return nil, fmt.Errorf("unable to convert field '%s' to type int: %v", topicValue, err)
			}
		case "float":
			newType, err = strconv.ParseFloat(topicValue, 64)
			if err != nil {
				return nil, fmt.Errorf("unable to convert field '%s' to type float: %v", topicValue, err)
			}
		default:
			return nil, fmt.Errorf("converting to the type %s is not supported: use int, uint, or float", desiredType)
		}
	} else {
		newType = topicValue
	}

	return newType, nil
}

func New(factory ClientFactory) *MQTTConsumer {
	return &MQTTConsumer{
		Servers:                []string{"tcp://127.0.0.1:1883"},
		ConnectionTimeout:      defaultConnectionTimeout,
		MaxUndeliveredMessages: defaultMaxUndeliveredMessages,
		clientFactory:          factory,
		state:                  Disconnected,
	}
}
func init() {
	inputs.Add("mqtt_consumer", func() telegraf.Input {
		return New(func(o *mqtt.ClientOptions) Client {
			return mqtt.NewClient(o)
		})
	})
}
