package broker

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"math/rand"
	"net"
	"net/http"
	"strconv"
	"strings"
	"sync"
	"time"

	log "github.com/golang/glog"
	"github.com/micro/go-micro/errors"
	"github.com/micro/go-micro/registry"
	"github.com/pborman/uuid"
)

// HTTP Broker is a placeholder for actual message brokers.
// This should not really be used in production but useful
// in developer where you want zero dependencies.

type httpBroker struct {
	id          string
	address     string
	unsubscribe chan *httpSubscriber
	opts        Options

	sync.RWMutex
	subscribers map[string][]*httpSubscriber
	running     bool
	exit        chan chan error
}

type httpSubscriber struct {
	opts  SubscribeOptions
	id    string
	topic string
	ch    chan *httpSubscriber
	fn    Handler
	svc   *registry.Service
}

type httpPublication struct {
	m *Message
	t string
}

var (
	DefaultSubPath   = "/_sub"
	broadcastVersion = "ff.http.broadcast"
)

func init() {
	rand.Seed(time.Now().Unix())
}

func newHttpBroker(addrs []string, opt ...Option) Broker {
	addr := ":0"
	if len(addrs) > 0 && len(addrs[0]) > 0 {
		addr = addrs[0]
	}

	return &httpBroker{
		id:          "broker-" + uuid.NewUUID().String(),
		address:     addr,
		subscribers: make(map[string][]*httpSubscriber),
		unsubscribe: make(chan *httpSubscriber),
		exit:        make(chan chan error),
	}
}

func (h *httpPublication) Ack() error {
	return nil
}

func (h *httpPublication) Message() *Message {
	return h.m
}

func (h *httpPublication) Topic() string {
	return h.t
}

func (h *httpSubscriber) Options() SubscribeOptions {
	return h.opts
}

func (h *httpSubscriber) Topic() string {
	return h.topic
}

func (h *httpSubscriber) Unsubscribe() error {
	h.ch <- h
	return nil
}

func (h *httpBroker) start() error {
	h.Lock()
	defer h.Unlock()

	if h.running {
		return nil
	}

	l, err := net.Listen("tcp", h.address)
	if err != nil {
		return err
	}

	log.Infof("Broker Listening on %s", l.Addr().String())
	h.address = l.Addr().String()

	go http.Serve(l, h)

	go func() {
		for {
			select {
			case ch := <-h.exit:
				ch <- l.Close()
				h.Lock()
				h.running = false
				h.Unlock()
				return
			case subscriber := <-h.unsubscribe:
				h.Lock()
				var subscribers []*httpSubscriber
				for _, sub := range h.subscribers[subscriber.topic] {
					if sub.id == subscriber.id {
						registry.Deregister(sub.svc)
					}
					subscribers = append(subscribers, sub)
				}
				h.subscribers[subscriber.topic] = subscribers
				h.Unlock()
			}
		}
	}()

	h.running = true
	return nil
}

func (h *httpBroker) stop() error {
	ch := make(chan error)
	h.exit <- ch
	return <-ch
}

func (h *httpBroker) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	if req.Method != "POST" {
		err := errors.BadRequest("go.micro.broker", "Method not allowed")
		http.Error(w, err.Error(), http.StatusMethodNotAllowed)
		return
	}
	defer req.Body.Close()

	b, err := ioutil.ReadAll(req.Body)
	if err != nil {
		errr := errors.InternalServerError("go.micro.broker", fmt.Sprintf("Error reading request body: %v", err))
		w.WriteHeader(500)
		w.Write([]byte(errr.Error()))
		return
	}

	var m *Message
	if err = json.Unmarshal(b, &m); err != nil {
		errr := errors.InternalServerError("go.micro.broker", fmt.Sprintf("Error parsing request body: %v", err))
		w.WriteHeader(500)
		w.Write([]byte(errr.Error()))
		return
	}

	topic := m.Header[":topic"]
	delete(m.Header, ":topic")

	if len(topic) == 0 {
		errr := errors.InternalServerError("go.micro.broker", "Topic not found")
		w.WriteHeader(500)
		w.Write([]byte(errr.Error()))
		return
	}

	p := &httpPublication{m: m, t: topic}
	h.RLock()
	for _, subscriber := range h.subscribers[topic] {
		subscriber.fn(p)
	}
	h.RUnlock()
}

func (h *httpBroker) Address() string {
	return h.address
}

func (h *httpBroker) Connect() error {
	return h.start()
}

func (h *httpBroker) Disconnect() error {
	return h.stop()
}

func (h *httpBroker) Init(opts ...Option) error {
	if len(h.id) == 0 {
		h.id = "broker-" + uuid.NewUUID().String()
	}

	http.Handle(DefaultSubPath, h)
	return nil
}

func (h *httpBroker) Options() Options {
	return h.opts
}

func (h *httpBroker) Publish(topic string, msg *Message, opts ...PublishOption) error {
	s, err := registry.GetService("topic:" + topic)
	if err != nil {
		return err
	}

	msg.Header[":topic"] = topic
	b, err := json.Marshal(msg)
	if err != nil {
		return err
	}

	fn := func(node *registry.Node, b io.Reader) {
		r, err := http.Post(fmt.Sprintf("http://%s:%d%s", node.Address, node.Port, DefaultSubPath), "application/json", b)
		if err == nil {
			r.Body.Close()
		}
	}

	buf := bytes.NewBuffer(nil)

	for _, service := range s {
		// broadcast version means broadcast to all nodes
		if service.Version == broadcastVersion {
			for _, node := range service.Nodes {
				buf.Reset()
				buf.Write(b)
				fn(node, buf)
			}
			return nil
		}

		node := service.Nodes[rand.Int()%len(service.Nodes)]
		buf.Reset()
		buf.Write(b)
		fn(node, buf)
		return nil
	}

	buf.Reset()
	buf = nil

	return nil
}

func (h *httpBroker) Subscribe(topic string, handler Handler, opts ...SubscribeOption) (Subscriber, error) {
	opt := newSubscribeOptions(opts...)

	// parse address for host, port
	parts := strings.Split(h.Address(), ":")
	host := strings.Join(parts[:len(parts)-1], ":")
	port, _ := strconv.Atoi(parts[len(parts)-1])

	id := uuid.NewUUID().String()

	// register service
	node := &registry.Node{
		Id:      topic + "." + h.id + "." + id,
		Address: host,
		Port:    port,
	}

	version := opt.Queue
	if len(version) == 0 {
		version = broadcastVersion
	}

	service := &registry.Service{
		Name:    "topic:" + topic,
		Version: version,
		Nodes:   []*registry.Node{node},
	}

	subscriber := &httpSubscriber{
		opts:  opt,
		id:    id,
		topic: topic,
		ch:    h.unsubscribe,
		fn:    handler,
		svc:   service,
	}

	if err := registry.Register(service); err != nil {
		return nil, err
	}

	h.Lock()
	h.subscribers[topic] = append(h.subscribers[topic], subscriber)
	h.Unlock()
	return subscriber, nil
}

func (h *httpBroker) String() string {
	return "http"
}