package sarama

import (
	"crypto/tls"
	"encoding/binary"
	"fmt"
	"io"
	"net"
	"strconv"
	"sync"
	"sync/atomic"
	"time"
)

// Broker represents a single Kafka broker connection. All operations on this object are entirely concurrency-safe.
type Broker struct {
	id   int32
	addr string

	conf          *Config
	correlationID int32
	conn          net.Conn
	connErr       error
	lock          sync.Mutex
	opened        int32

	responses chan responsePromise
	done      chan bool
}

type responsePromise struct {
	correlationID int32
	packets       chan []byte
	errors        chan error
}

// NewBroker creates and returns a Broker targetting the given host:port address.
// This does not attempt to actually connect, you have to call Open() for that.
func NewBroker(addr string) *Broker {
	return &Broker{id: -1, addr: addr}
}

// Open tries to connect to the Broker if it is not already connected or connecting, but does not block
// waiting for the connection to complete. This means that any subsequent operations on the broker will
// block waiting for the connection to succeed or fail. To get the effect of a fully synchronous Open call,
// follow it by a call to Connected(). The only errors Open will return directly are ConfigurationError or
// AlreadyConnected. If conf is nil, the result of NewConfig() is used.
func (b *Broker) Open(conf *Config) error {
	if !atomic.CompareAndSwapInt32(&b.opened, 0, 1) {
		return ErrAlreadyConnected
	}

	if conf == nil {
		conf = NewConfig()
	}

	err := conf.Validate()
	if err != nil {
		return err
	}

	b.lock.Lock()

	go withRecover(func() {
		defer b.lock.Unlock()

		dialer := net.Dialer{
			Timeout:   conf.Net.DialTimeout,
			KeepAlive: conf.Net.KeepAlive,
		}

		if conf.Net.TLS.Enable {
			b.conn, b.connErr = tls.DialWithDialer(&dialer, "tcp", b.addr, conf.Net.TLS.Config)
		} else {
			b.conn, b.connErr = dialer.Dial("tcp", b.addr)
		}
		if b.connErr != nil {
			Logger.Printf("Failed to connect to broker %s: %s\n", b.addr, b.connErr)
			b.conn = nil
			atomic.StoreInt32(&b.opened, 0)
			return
		}
		b.conn = newBufConn(b.conn)

		b.conf = conf

		if conf.Net.SASL.Enable {
			b.connErr = b.sendAndReceiveSASLPlainAuth()
			if b.connErr != nil {
				err = b.conn.Close()
				if err == nil {
					Logger.Printf("Closed connection to broker %s\n", b.addr)
				} else {
					Logger.Printf("Error while closing connection to broker %s: %s\n", b.addr, err)
				}
				b.conn = nil
				atomic.StoreInt32(&b.opened, 0)
				return
			}
		}

		b.done = make(chan bool)
		b.responses = make(chan responsePromise, b.conf.Net.MaxOpenRequests-1)

		if b.id >= 0 {
			Logger.Printf("Connected to broker at %s (registered as #%d)\n", b.addr, b.id)
		} else {
			Logger.Printf("Connected to broker at %s (unregistered)\n", b.addr)
		}
		go withRecover(b.responseReceiver)
	})

	return nil
}

// Connected returns true if the broker is connected and false otherwise. If the broker is not
// connected but it had tried to connect, the error from that connection attempt is also returned.
func (b *Broker) Connected() (bool, error) {
	b.lock.Lock()
	defer b.lock.Unlock()

	return b.conn != nil, b.connErr
}

func (b *Broker) Close() error {
	b.lock.Lock()
	defer b.lock.Unlock()

	if b.conn == nil {
		return ErrNotConnected
	}

	close(b.responses)
	<-b.done

	err := b.conn.Close()

	b.conn = nil
	b.connErr = nil
	b.done = nil
	b.responses = nil

	if err == nil {
		Logger.Printf("Closed connection to broker %s\n", b.addr)
	} else {
		Logger.Printf("Error while closing connection to broker %s: %s\n", b.addr, err)
	}

	atomic.StoreInt32(&b.opened, 0)

	return err
}

// ID returns the broker ID retrieved from Kafka's metadata, or -1 if that is not known.
func (b *Broker) ID() int32 {
	return b.id
}

// Addr returns the broker address as either retrieved from Kafka's metadata or passed to NewBroker.
func (b *Broker) Addr() string {
	return b.addr
}

func (b *Broker) GetMetadata(request *MetadataRequest) (*MetadataResponse, error) {
	response := new(MetadataResponse)

	err := b.sendAndReceive(request, response)

	if err != nil {
		return nil, err
	}

	return response, nil
}

func (b *Broker) GetConsumerMetadata(request *ConsumerMetadataRequest) (*ConsumerMetadataResponse, error) {
	response := new(ConsumerMetadataResponse)

	err := b.sendAndReceive(request, response)

	if err != nil {
		return nil, err
	}

	return response, nil
}

func (b *Broker) GetAvailableOffsets(request *OffsetRequest) (*OffsetResponse, error) {
	response := new(OffsetResponse)

	err := b.sendAndReceive(request, response)

	if err != nil {
		return nil, err
	}

	return response, nil
}

func (b *Broker) Produce(request *ProduceRequest) (*ProduceResponse, error) {
	var response *ProduceResponse
	var err error

	if request.RequiredAcks == NoResponse {
		err = b.sendAndReceive(request, nil)
	} else {
		response = new(ProduceResponse)
		err = b.sendAndReceive(request, response)
	}

	if err != nil {
		return nil, err
	}

	return response, nil
}

func (b *Broker) Fetch(request *FetchRequest) (*FetchResponse, error) {
	response := new(FetchResponse)

	err := b.sendAndReceive(request, response)

	if err != nil {
		return nil, err
	}

	return response, nil
}

func (b *Broker) CommitOffset(request *OffsetCommitRequest) (*OffsetCommitResponse, error) {
	response := new(OffsetCommitResponse)

	err := b.sendAndReceive(request, response)

	if err != nil {
		return nil, err
	}

	return response, nil
}

func (b *Broker) FetchOffset(request *OffsetFetchRequest) (*OffsetFetchResponse, error) {
	response := new(OffsetFetchResponse)

	err := b.sendAndReceive(request, response)

	if err != nil {
		return nil, err
	}

	return response, nil
}

func (b *Broker) JoinGroup(request *JoinGroupRequest) (*JoinGroupResponse, error) {
	response := new(JoinGroupResponse)

	err := b.sendAndReceive(request, response)
	if err != nil {
		return nil, err
	}

	return response, nil
}

func (b *Broker) SyncGroup(request *SyncGroupRequest) (*SyncGroupResponse, error) {
	response := new(SyncGroupResponse)

	err := b.sendAndReceive(request, response)
	if err != nil {
		return nil, err
	}

	return response, nil
}

func (b *Broker) LeaveGroup(request *LeaveGroupRequest) (*LeaveGroupResponse, error) {
	response := new(LeaveGroupResponse)

	err := b.sendAndReceive(request, response)
	if err != nil {
		return nil, err
	}

	return response, nil
}

func (b *Broker) Heartbeat(request *HeartbeatRequest) (*HeartbeatResponse, error) {
	response := new(HeartbeatResponse)

	err := b.sendAndReceive(request, response)
	if err != nil {
		return nil, err
	}

	return response, nil
}

func (b *Broker) ListGroups(request *ListGroupsRequest) (*ListGroupsResponse, error) {
	response := new(ListGroupsResponse)

	err := b.sendAndReceive(request, response)
	if err != nil {
		return nil, err
	}

	return response, nil
}

func (b *Broker) DescribeGroups(request *DescribeGroupsRequest) (*DescribeGroupsResponse, error) {
	response := new(DescribeGroupsResponse)

	err := b.sendAndReceive(request, response)
	if err != nil {
		return nil, err
	}

	return response, nil
}

func (b *Broker) send(rb protocolBody, promiseResponse bool) (*responsePromise, error) {
	b.lock.Lock()
	defer b.lock.Unlock()

	if b.conn == nil {
		if b.connErr != nil {
			return nil, b.connErr
		}
		return nil, ErrNotConnected
	}

	if !b.conf.Version.IsAtLeast(rb.requiredVersion()) {
		return nil, ErrUnsupportedVersion
	}

	req := &request{correlationID: b.correlationID, clientID: b.conf.ClientID, body: rb}
	buf, err := encode(req)
	if err != nil {
		return nil, err
	}

	err = b.conn.SetWriteDeadline(time.Now().Add(b.conf.Net.WriteTimeout))
	if err != nil {
		return nil, err
	}

	_, err = b.conn.Write(buf)
	if err != nil {
		return nil, err
	}
	b.correlationID++

	if !promiseResponse {
		return nil, nil
	}

	promise := responsePromise{req.correlationID, make(chan []byte), make(chan error)}
	b.responses <- promise

	return &promise, nil
}

func (b *Broker) sendAndReceive(req protocolBody, res versionedDecoder) error {
	promise, err := b.send(req, res != nil)

	if err != nil {
		return err
	}

	if promise == nil {
		return nil
	}

	select {
	case buf := <-promise.packets:
		return versionedDecode(buf, res, req.version())
	case err = <-promise.errors:
		return err
	}
}

func (b *Broker) decode(pd packetDecoder) (err error) {
	b.id, err = pd.getInt32()
	if err != nil {
		return err
	}

	host, err := pd.getString()
	if err != nil {
		return err
	}

	port, err := pd.getInt32()
	if err != nil {
		return err
	}

	b.addr = net.JoinHostPort(host, fmt.Sprint(port))
	if _, _, err := net.SplitHostPort(b.addr); err != nil {
		return err
	}

	return nil
}

func (b *Broker) encode(pe packetEncoder) (err error) {

	host, portstr, err := net.SplitHostPort(b.addr)
	if err != nil {
		return err
	}
	port, err := strconv.Atoi(portstr)
	if err != nil {
		return err
	}

	pe.putInt32(b.id)

	err = pe.putString(host)
	if err != nil {
		return err
	}

	pe.putInt32(int32(port))

	return nil
}

func (b *Broker) responseReceiver() {
	var dead error
	header := make([]byte, 8)
	for response := range b.responses {
		if dead != nil {
			response.errors <- dead
			continue
		}

		err := b.conn.SetReadDeadline(time.Now().Add(b.conf.Net.ReadTimeout))
		if err != nil {
			dead = err
			response.errors <- err
			continue
		}

		_, err = io.ReadFull(b.conn, header)
		if err != nil {
			dead = err
			response.errors <- err
			continue
		}

		decodedHeader := responseHeader{}
		err = decode(header, &decodedHeader)
		if err != nil {
			dead = err
			response.errors <- err
			continue
		}
		if decodedHeader.correlationID != response.correlationID {
			// TODO if decoded ID < cur ID, discard until we catch up
			// TODO if decoded ID > cur ID, save it so when cur ID catches up we have a response
			dead = PacketDecodingError{fmt.Sprintf("correlation ID didn't match, wanted %d, got %d", response.correlationID, decodedHeader.correlationID)}
			response.errors <- dead
			continue
		}

		buf := make([]byte, decodedHeader.length-4)
		_, err = io.ReadFull(b.conn, buf)
		if err != nil {
			dead = err
			response.errors <- err
			continue
		}

		response.packets <- buf
	}
	close(b.done)
}

// Kafka 0.10.0 plans to support SASL Plain and Kerberos as per PR #812 (KIP-43)/(JIRA KAFKA-3149)
// Some hosted kafka services such as IBM Message Hub already offer SASL/PLAIN auth with Kafka 0.9
//
// In SASL Plain, Kafka expects the auth header to be in the following format
// Message format (from https://tools.ietf.org/html/rfc4616):
//
//   message   = [authzid] UTF8NUL authcid UTF8NUL passwd
//   authcid   = 1*SAFE ; MUST accept up to 255 octets
//   authzid   = 1*SAFE ; MUST accept up to 255 octets
//   passwd    = 1*SAFE ; MUST accept up to 255 octets
//   UTF8NUL   = %x00 ; UTF-8 encoded NUL character
//
//   SAFE      = UTF1 / UTF2 / UTF3 / UTF4
//                  ;; any UTF-8 encoded Unicode character except NUL
//
// When credentials are valid, Kafka returns a 4 byte array of null characters.
// When credentials are invalid, Kafka closes the connection. This does not seem to be the ideal way
// of responding to bad credentials but thats how its being done today.
func (b *Broker) sendAndReceiveSASLPlainAuth() error {
	length := 1 + len(b.conf.Net.SASL.User) + 1 + len(b.conf.Net.SASL.Password)
	authBytes := make([]byte, length+4) //4 byte length header + auth data
	binary.BigEndian.PutUint32(authBytes, uint32(length))
	copy(authBytes[4:], []byte("\x00"+b.conf.Net.SASL.User+"\x00"+b.conf.Net.SASL.Password))

	err := b.conn.SetWriteDeadline(time.Now().Add(b.conf.Net.WriteTimeout))
	if err != nil {
		Logger.Printf("Failed to set write deadline when doing SASL auth with broker %s: %s\n", b.addr, err.Error())
		return err
	}

	_, err = b.conn.Write(authBytes)
	if err != nil {
		Logger.Printf("Failed to write SASL auth header to broker %s: %s\n", b.addr, err.Error())
		return err
	}

	header := make([]byte, 4)
	n, err := io.ReadFull(b.conn, header)
	// If the credentials are valid, we would get a 4 byte response filled with null characters.
	// Otherwise, the broker closes the connection and we get an EOF
	if err != nil {
		Logger.Printf("Failed to read response while authenticating with SASL to broker %s: %s\n", b.addr, err.Error())
		return err
	}

	Logger.Printf("SASL authentication successful with broker %s:%v - %v\n", b.addr, n, header)
	return nil
}
