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client.go
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client.go
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package pubsubsse
import (
"context"
"encoding/json"
"fmt"
"sync"
"time"
"github.com/apex/log"
"github.com/google/uuid"
)
type status int
const (
Waiting status = iota
Receving
)
type OnEventFunc func(string)
// Client represents a subscriber with a channel to send messages.
type Client struct {
id string
status status
stream chan string
stopchan chan struct{}
lock sync.Mutex
sSEPubSubService *SSEPubSubService
privateTopics map[string]*Topic
groups map[string]*Group
}
// Create a new client
func newClient(sSEPubSubService *SSEPubSubService) *Client {
return &Client{
id: uuid.New().String(),
status: Waiting,
stream: make(chan string, 100),
lock: sync.Mutex{},
stopchan: nil,
sSEPubSubService: sSEPubSubService,
privateTopics: make(map[string]*Topic),
groups: make(map[string]*Group),
}
}
// Stop the client from receiving messages over the event stream
func (c *Client) stop() {
// Lock the client
c.lock.Lock()
defer c.lock.Unlock()
if c.status == Waiting {
return
}
// Stop the client
c.status = Waiting
// Close the stream
if c.stream != nil {
close(c.stream)
}
}
// Get ID
func (c *Client) GetID() string {
c.lock.Lock()
defer c.lock.Unlock()
return c.id
}
// Get Status
func (c *Client) GetStatus() status {
c.lock.Lock()
defer c.lock.Unlock()
return c.status
}
// Get public topics
func (c *Client) GetPublicTopics() map[string]*Topic {
return c.sSEPubSubService.GetPublicTopics()
}
// Get public topic by name
func (c *Client) GetPublicTopicByName(name string) (*Topic, bool) {
return c.sSEPubSubService.GetPublicTopicByName(name)
}
// Get private topics
func (c *Client) GetPrivateTopics() map[string]*Topic {
c.lock.Lock()
defer c.lock.Unlock()
// Create a copy of the private topics
newmap := make(map[string]*Topic)
for k, v := range c.privateTopics {
newmap[k] = v
}
return newmap
}
// Get private topic by name
func (c *Client) GetPrivateTopicByName(name string) (*Topic, bool) {
c.lock.Lock()
defer c.lock.Unlock()
t, ok := c.privateTopics[name]
return t, ok
}
// Add group
func (c *Client) addGroup(g *Group) {
c.lock.Lock()
defer c.lock.Unlock()
c.groups[g.GetName()] = g
}
// Remove group
func (c *Client) removeGroup(g *Group) {
c.lock.Lock()
defer c.lock.Unlock()
delete(c.groups, g.GetName())
}
// Get groups
func (c *Client) GetGroups() map[string]*Group {
c.lock.Lock()
defer c.lock.Unlock()
// Create a copy of the groups
newmap := make(map[string]*Group)
for k, v := range c.groups {
newmap[k] = v
}
return newmap
}
// Get group by name
func (c *Client) GetGroupByName(name string) (*Group, bool) {
c.lock.Lock()
defer c.lock.Unlock()
g, ok := c.groups[name]
return g, ok
}
// Get all topics
func (c *Client) GetAllTopics() map[string]*Topic {
c.lock.Lock()
defer c.lock.Unlock()
newmap := make(map[string]*Topic)
for k, v := range c.GetPublicTopics() {
newmap[k] = v
}
for _, v := range c.groups {
for k, v := range v.GetTopics() {
newmap[k] = v
}
}
for k, v := range c.privateTopics {
newmap[k] = v
}
return newmap
}
// Get topic by name
func (c *Client) GetTopicByName(name string) (*Topic, bool) {
topics := c.GetAllTopics()
t, ok := topics[name]
return t, ok
}
// Get subscribed topics
func (c *Client) GetSubscribedTopics() map[string]*Topic {
topics := make(map[string]*Topic)
for k, v := range c.GetAllTopics() {
if v.IsSubscribed(c) {
topics[k] = v
}
}
return topics
}
// New private topic
// 0. Check if topic already exists, return it if it does
// 1. Create a new private topic
// 2. Add the topic to the client
// 3. Inform the client about the new topic
func (c *Client) NewPrivateTopic(name string) *Topic {
// if topic exists, return it
if t, ok := c.GetPrivateTopicByName(name); ok {
return t
}
t := newTopic(name, TPrivate)
c.lock.Lock()
c.privateTopics[t.GetName()] = t
c.lock.Unlock()
// Inform the client about the new topic
if err := c.sendTopicList(); err != nil {
log.Errorf("[C:%s]: Error sending new topic to client: %s", c.GetID(), err)
}
return t
}
// Remove private topic
// 0. Check if topic exists, return error if it does not
// 1. Unsubscribe from the topic
// 2. Remove the topic from the client
// 3. Inform the client about the removed topic by sending the new topic list
func (c *Client) RemovePrivateTopic(t *Topic) {
// if topic does not exist, return
if _, ok := c.GetPrivateTopicByName(t.GetName()); !ok {
log.Errorf("[C:%s]: topic %s does not exist", c.GetID(), t.GetName())
return
}
// Remove this topic from all clients
for _, c := range t.GetClients() {
c.Unsub(t) // Try to unsubscribe from the topic
}
// Remove topic from client
c.lock.Lock()
delete(c.privateTopics, t.GetName())
c.lock.Unlock()
// Inform the client about the removed topic by sending the new topic list
if err := c.sendTopicList(); err != nil {
log.Errorf("[C:%s]: Error sending new topic to client: %s", c.GetID(), err)
}
}
// Subscribe to a topic
// 1. If client can subscribe to this topic, add client to topic and return nil
// 2. Inform the client about the new topic by sending this topic as subscribed
func (c *Client) Sub(topic *Topic) error {
// if topic exists, add client to topic and return nil
if t, ok := c.GetTopicByName(topic.GetName()); ok {
if topic == t {
t.addClient(c)
// Inform the client about the new topic by sending this topic as subscribed
if err := c.sendSubscribedTopic(t); err != nil {
log.Errorf("[C:%s]: Error sending new topic to client: %s", c.GetID(), err)
}
return nil
}
}
return fmt.Errorf("[C:%s]: topic %s does not exist or client can not subscribe to it", c.GetID(), topic.GetName())
}
// Unsubscribe from a topic
// 1. If client is subscribed to this topic, remove client from topic and return nil
// 2. Inform the client about the new topic by sending this topic as unsubscribed
func (c *Client) Unsub(topic *Topic) error {
// if topic exists and client is subscribed to it, remove client from topic and return nil
if t, ok := c.GetTopicByName(topic.GetName()); ok {
if topic == t {
if !t.IsSubscribed(c) {
return fmt.Errorf("[C:%s]: client is not subscribed to topic %s", c.GetID(), topic.GetName())
}
t.removeClient(c)
// Inform the client about the new topic by sending this topic as unsubscribed
if err := c.sendUnsubscribedTopic(t); err != nil {
log.Errorf("[C:%s]: Error sending new topic to client: %s", c.GetID(), err)
}
return nil
}
}
return fmt.Errorf("[C:%s]: topic %s does not exist or client can not unsubscribe from it", c.GetID(), topic.GetName())
}
// send a message to the client
// 1. Marshal the data
// 2. Put the data into the stream to send it to the client
func (c *Client) send(msg interface{}) error {
// Marshal the data
jsonData, err := json.Marshal(msg)
if err != nil {
return err
}
// Send the data
if c.GetStatus() == Receving {
data := "data: " + string(jsonData) + "\n\n"
//Try 10 times with 100ms to send data to the stream
for i := 0; i < 10; i++ {
select {
case c.stream <- data:
// successfully sent
log.Infof("[C:%s]: push data to stream", c.GetID())
return nil
default:
log.Infof("[C:%s]: stream is full: try: %d", c.GetID(), i)
time.Sleep(10 * time.Millisecond)
}
}
// handle the case where the channel is full or the client is not receiving
return fmt.Errorf("[C:%s]: stream is full", c.GetID())
}
return fmt.Errorf("[C:%s]: client is not receiving", c.GetID())
}
// sendTopicList sends a message to the client to inform it about the topics
func (c *Client) sendTopicList() error {
// Get all topics
topics := c.GetAllTopics()
// Build the JSON data
fulldata := &eventData{
Sys: []eventDataSys{
{
Type: "topics",
List: []eventDataSysList{},
},
},
}
// Append topics data
for _, topic := range topics {
t := eventDataSysList{
Name: topic.GetName(),
Type: topic.GetType(),
}
fulldata.Sys[0].List = append(fulldata.Sys[0].List, t)
}
// Send the JSON data to the client
if err := c.send(fulldata); err != nil {
return err
}
return nil
}
// sendSubscribedTopic sends a message to the client to inform it about the subscribed topic
func (c *Client) sendSubscribedTopic(topic *Topic) error {
// Build the JSON data
fulldata := &eventData{
Sys: []eventDataSys{
{
Type: "subscribed",
List: []eventDataSysList{
{
Name: topic.GetName(),
},
},
},
},
}
// Send the JSON data to the client
if err := c.send(fulldata); err != nil {
return err
}
return nil
}
// sendUnsubscribedTopic sends a message to the client to inform it about the unsubscribed topic
func (c *Client) sendUnsubscribedTopic(topic *Topic) error {
// Build the JSON data
fulldata := &eventData{
Sys: []eventDataSys{
{
Type: "unsubscribed",
List: []eventDataSysList{
{
Name: topic.GetName(),
},
},
},
},
}
// Send the JSON data to the client
if err := c.send(fulldata); err != nil {
return err
}
return nil
}
// sendInitMSG generates the initial message to send to the client
// It contains all topics and subscribed topics
func (c *Client) sendInitMSG(onEvent OnEventFunc) error {
// Get all topics and subscribed topics
topics := c.GetAllTopics()
subtopics := c.GetSubscribedTopics()
// Build the JSON data
fulldata := &eventData{
Sys: make([]eventDataSys, 0, 2),
}
// Append topics data
if len(topics) > 0 {
topicData := eventDataSys{Type: "topics"}
for _, topic := range topics {
topicData.List = append(topicData.List, eventDataSysList{
Name: topic.GetName(),
Type: topic.GetType(),
})
}
fulldata.Sys = append(fulldata.Sys, topicData)
}
// Append subscribed topics data
if len(subtopics) > 0 {
subTopicData := eventDataSys{Type: "subscribed"}
for _, topic := range subtopics {
subTopicData.List = append(subTopicData.List, eventDataSysList{Name: topic.GetName()})
}
fulldata.Sys = append(fulldata.Sys, subTopicData)
}
// Marshal the data
jsonData, err := json.Marshal(fulldata)
if err != nil {
return err
}
onEvent("data: " + string(jsonData) + "\n\n")
// Send JSON data to the client
return err
}
// Start the client
// 0. Check if client is already receiving
// 1. Set status to Receving and create stop channel
// 2. Send init message to client
// 3. Keep the connection open
// 4. Send message to client if new data is published over the stream
// 5. Stop the client if the stop channel is closed
func (c *Client) Start(ctx context.Context, onEvent OnEventFunc) error {
// Set status to Receving and create stop channel
if c.GetStatus() == Receving {
return fmt.Errorf("[C:%s]: Client is already receiving", c.GetID())
}
// Set status to Receving and create stop channel
c.lock.Lock()
c.stopchan = make(chan struct{})
c.status = Receving
c.stream = make(chan string)
c.lock.Unlock()
// Stop the client at the end
defer func() {
c.stop()
}()
if err := c.sendInitMSG(onEvent); err != nil {
log.Errorf("[C:%s]: Error sending init message to client: %s", c.GetID(), err)
return err
}
// Keep the connection open until it's closed by the client
loop:
for {
select {
case msg, ok := <-c.stream:
if !ok {
log.Infof("[C:%s] Client stopped receiving", c.GetID())
break loop
}
log.Infof("[C:%s] Sending message to client: %s", c.GetID(), msg)
onEvent(msg)
case <-ctx.Done():
log.Infof("[C:%s] Client stopped receiving", c.GetID())
break loop
case <-c.stopchan:
log.Infof("[C:%s] Client stopped receiving", c.GetID())
break loop
}
}
return nil
}