func (cli *Client) SendMessageEvent(roomID string, eventType string, contentJSON interface{}) (resp *RespSendEvent, err error) {
	txnID := txnID()
	urlPath := cli.BuildURL("rooms", roomID, "send", eventType, txnID)
	_, err = cli.MakeRequest("PUT", urlPath, contentJSON, &resp)
	return
}
SendMessageEvent sends a message event into a room. See http://matrix.org/docs/spec/client_server/r0.2.0.html#put-matrix-client-r0-rooms-roomid-send-eventtype-txnid
contentJSON should be a pointer to something that can be encoded as JSON using json.Marshal.
package gomatrix
import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"net/url"
	"path"
	"strconv"
	"strings"
	"sync"
	"time"
)
type Client struct {
	HomeserverURL *url.URL      
	Prefix        string        
	UserID        string        
	AccessToken   string        
	Client        *http.Client  
	Syncer        Syncer        
	Store         Storer        
	AppServiceUserID string
	syncingMutex sync.Mutex  
	syncingID    uint32      
}
type HTTPError struct {
	WrappedError error
	Message      string
	Code         int
}
func (e HTTPError) Error() string {
	var wrappedErrMsg string
	if e.WrappedError != nil {
		wrappedErrMsg = e.WrappedError.Error()
	}
	return fmt.Sprintf("msg=%s code=%d wrapped=%s", e.Message, e.Code, wrappedErrMsg)
}
func (cli *Client) BuildURL(urlPath ...string) string {
	ps := []string{cli.Prefix}
	for _, p := range urlPath {
		ps = append(ps, p)
	}
	return cli.BuildBaseURL(ps...)
}
func (cli *Client) BuildBaseURL(urlPath ...string) string {
	hsURL, _ := url.Parse(cli.HomeserverURL.String())
	parts := []string{hsURL.Path}
	parts = append(parts, urlPath...)
	hsURL.Path = path.Join(parts...)
	if strings.HasSuffix(urlPath[len(urlPath)-1], "/") {
		hsURL.Path = hsURL.Path + "/"
	}
	query := hsURL.Query()
	if cli.AccessToken != "" {
		query.Set("access_token", cli.AccessToken)
	}
	if cli.AppServiceUserID != "" {
		query.Set("user_id", cli.AppServiceUserID)
	}
	hsURL.RawQuery = query.Encode()
	return hsURL.String()
}
func (cli *Client) BuildURLWithQuery(urlPath []string, urlQuery map[string]string) string {
	u, _ := url.Parse(cli.BuildURL(urlPath...))
	q := u.Query()
	for k, v := range urlQuery {
		q.Set(k, v)
	}
	u.RawQuery = q.Encode()
	return u.String()
}
func (cli *Client) SetCredentials(userID, accessToken string) {
	cli.AccessToken = accessToken
	cli.UserID = userID
}
func (cli *Client) ClearCredentials() {
	cli.AccessToken = ""
	cli.UserID = ""
}
func (cli *Client) Sync() error {
	syncingID := cli.incrementSyncingID()
	nextBatch := cli.Store.LoadNextBatch(cli.UserID)
	filterID := cli.Store.LoadFilterID(cli.UserID)
	if filterID == "" {
		filterJSON := cli.Syncer.GetFilterJSON(cli.UserID)
		resFilter, err := cli.CreateFilter(filterJSON)
		if err != nil {
			return err
		}
		filterID = resFilter.FilterID
		cli.Store.SaveFilterID(cli.UserID, filterID)
	}
	for {
		resSync, err := cli.SyncRequest(30000, nextBatch, filterID, false, "")
		if err != nil {
			duration, err2 := cli.Syncer.OnFailedSync(resSync, err)
			if err2 != nil {
				return err2
			}
			time.Sleep(duration)
			continue
		}
		if cli.getSyncingID() != syncingID {
			return nil
		}
		cli.Store.SaveNextBatch(cli.UserID, resSync.NextBatch)
		if err = cli.Syncer.ProcessResponse(resSync, nextBatch); err != nil {
			return err
		}
		nextBatch = resSync.NextBatch
	}
}
func (cli *Client) incrementSyncingID() uint32 {
	cli.syncingMutex.Lock()
	defer cli.syncingMutex.Unlock()
	cli.syncingID++
	return cli.syncingID
}
func (cli *Client) getSyncingID() uint32 {
	cli.syncingMutex.Lock()
	defer cli.syncingMutex.Unlock()
	return cli.syncingID
}
func (cli *Client) StopSync() {
	cli.incrementSyncingID()
}
func (cli *Client) MakeRequest(method string, httpURL string, reqBody interface{}, resBody interface{}) ([]byte, error) {
	var req *http.Request
	var err error
	if reqBody != nil {
		var jsonStr []byte
		jsonStr, err = json.Marshal(reqBody)
		if err != nil {
			return nil, err
		}
		req, err = http.NewRequest(method, httpURL, bytes.NewBuffer(jsonStr))
	} else {
		req, err = http.NewRequest(method, httpURL, nil)
	}
	if err != nil {
		return nil, err
	}
	req.Header.Set("Content-Type", "application/json")
	res, err := cli.Client.Do(req)
	if res != nil {
		defer res.Body.Close()
	}
	if err != nil {
		return nil, err
	}
	contents, err := ioutil.ReadAll(res.Body)
	if res.StatusCode/100 != 2 {  
		var wrap error
		var respErr RespError
		if _ = json.Unmarshal(contents, &respErr); respErr.ErrCode != "" {
			wrap = respErr
		}
		msg := "Failed to " + method + " JSON to " + req.URL.Path
		if wrap == nil {
			msg = msg + ": " + string(contents)
		}
		return contents, HTTPError{
			Code:         res.StatusCode,
			Message:      msg,
			WrappedError: wrap,
		}
	}
	if err != nil {
		return nil, err
	}
	if resBody != nil {
		if err = json.Unmarshal(contents, &resBody); err != nil {
			return nil, err
		}
	}
	return contents, nil
}
func (cli *Client) CreateFilter(filter json.RawMessage) (resp *RespCreateFilter, err error) {
	urlPath := cli.BuildURL("user", cli.UserID, "filter")
	_, err = cli.MakeRequest("POST", urlPath, &filter, &resp)
	return
}
func (cli *Client) SyncRequest(timeout int, since, filterID string, fullState bool, setPresence string) (resp *RespSync, err error) {
	query := map[string]string{
		"timeout": strconv.Itoa(timeout),
	}
	if since != "" {
		query["since"] = since
	}
	if filterID != "" {
		query["filter"] = filterID
	}
	if setPresence != "" {
		query["set_presence"] = setPresence
	}
	if fullState {
		query["full_state"] = "true"
	}
	urlPath := cli.BuildURLWithQuery([]string{"sync"}, query)
	_, err = cli.MakeRequest("GET", urlPath, nil, &resp)
	return
}
func (cli *Client) register(u string, req *ReqRegister) (resp *RespRegister, uiaResp *RespUserInteractive, err error) {
	var bodyBytes []byte
	bodyBytes, err = cli.MakeRequest("POST", u, req, nil)
	if err != nil {
		httpErr, ok := err.(HTTPError)
		if !ok {  
			return
		}
		if httpErr.Code == 401 {
			err = json.Unmarshal(bodyBytes, &uiaResp)
			return
		}
		return
	}
	err = json.Unmarshal(bodyBytes, &resp)
	return
}
func (cli *Client) Register(req *ReqRegister) (*RespRegister, *RespUserInteractive, error) {
	u := cli.BuildURL("register")
	return cli.register(u, req)
}
func (cli *Client) RegisterGuest(req *ReqRegister) (*RespRegister, *RespUserInteractive, error) {
	query := map[string]string{
		"kind": "guest",
	}
	u := cli.BuildURLWithQuery([]string{"register"}, query)
	return cli.register(u, req)
}
func (cli *Client) RegisterDummy(req *ReqRegister) (*RespRegister, error) {
	res, uia, err := cli.Register(req)
	if err != nil && uia == nil {
		return nil, err
	}
	if uia != nil && uia.HasSingleStageFlow("m.login.dummy") {
		req.Auth = struct {
			Type    string `json:"type"`
			Session string `json:"session,omitempty"`
		}{"m.login.dummy", uia.Session}
		res, _, err = cli.Register(req)
		if err != nil {
			return nil, err
		}
	}
	if res == nil {
		return nil, fmt.Errorf("registration failed: does this server support m.login.dummy?")
	}
	return res, nil
}
func (cli *Client) Login(req *ReqLogin) (resp *RespLogin, err error) {
	urlPath := cli.BuildURL("login")
	_, err = cli.MakeRequest("POST", urlPath, req, &resp)
	return
}
func (cli *Client) Logout() (resp *RespLogout, err error) {
	urlPath := cli.BuildURL("logout")
	_, err = cli.MakeRequest("POST", urlPath, nil, &resp)
	return
}
func (cli *Client) Versions() (resp *RespVersions, err error) {
	urlPath := cli.BuildBaseURL("_matrix", "client", "versions")
	_, err = cli.MakeRequest("GET", urlPath, nil, &resp)
	return
}
func (cli *Client) JoinRoom(roomIDorAlias, serverName string, content interface{}) (resp *RespJoinRoom, err error) {
	var urlPath string
	if serverName != "" {
		urlPath = cli.BuildURLWithQuery([]string{"join", roomIDorAlias}, map[string]string{
			"server_name": serverName,
		})
	} else {
		urlPath = cli.BuildURL("join", roomIDorAlias)
	}
	_, err = cli.MakeRequest("POST", urlPath, content, &resp)
	return
}
func (cli *Client) GetDisplayName(mxid string) (resp *RespUserDisplayName, err error) {
	urlPath := cli.BuildURL("profile", mxid, "displayname")
	_, err = cli.MakeRequest("GET", urlPath, nil, &resp)
	return
}
func (cli *Client) GetOwnDisplayName() (resp *RespUserDisplayName, err error) {
	urlPath := cli.BuildURL("profile", cli.UserID, "displayname")
	_, err = cli.MakeRequest("GET", urlPath, nil, &resp)
	return
}
func (cli *Client) SetDisplayName(displayName string) (err error) {
	urlPath := cli.BuildURL("profile", cli.UserID, "displayname")
	s := struct {
		DisplayName string `json:"displayname"`
	}{displayName}
	_, err = cli.MakeRequest("PUT", urlPath, &s, nil)
	return
}
func (cli *Client) GetAvatarURL() (url string, err error) {
	urlPath := cli.BuildURL("profile", cli.UserID, "avatar_url")
	s := struct {
		AvatarURL string `json:"avatar_url"`
	}{}
	_, err = cli.MakeRequest("GET", urlPath, nil, &s)
	if err != nil {
		return "", err
	}
	return s.AvatarURL, nil
}
func (cli *Client) SetAvatarURL(url string) (err error) {
	urlPath := cli.BuildURL("profile", cli.UserID, "avatar_url")
	s := struct {
		AvatarURL string `json:"avatar_url"`
	}{url}
	_, err = cli.MakeRequest("PUT", urlPath, &s, nil)
	if err != nil {
		return err
	}
	return nil
}