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server.go
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server.go
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package ctl
import (
"encoding/json"
"fmt"
"io"
"net"
"sync"
)
// Server provides a bi-directional event stream with clients on top of named
// pipes.
type Server struct {
Addr string
OnConnect func(c net.Conn)
OnDisconnect func(c net.Conn)
OnEvent func(c net.Conn, e Event)
// ErrorLog specifies an optional log function for errors. If not set,
// errors are not reported.
ErrorLog func(error)
mu sync.Mutex
cmds map[string]func(data interface{}) interface{}
clients []net.Conn
closer io.Closer
}
// Event represents an event either received from or sent to a client.
type Event struct {
Name string `json:"name"`
Data interface{} `json:"data"`
Reply bool `json:"reply"`
}
func (e Event) Bytes() []byte {
b, err := json.Marshal(e)
if err != nil {
return nil
}
b = append(b, '\n')
return b
}
func (s *Server) Start() error {
ln, err := listen(s.Addr)
if err != nil {
return err
}
s.closer = ln
go s.run(ln)
return nil
}
func (s *Server) Command(cmd string, h func(data interface{}) interface{}) {
s.mu.Lock()
defer s.mu.Unlock()
if s.cmds == nil {
s.cmds = map[string]func(data interface{}) interface{}{}
}
s.cmds[cmd] = h
}
// Broadcast broadcasts e to all connected clients.
func (s *Server) Broadcast(e Event) error {
b := e.Bytes()
s.mu.Lock()
defer s.mu.Unlock()
for _, c := range s.clients {
if _, err := c.Write(b); err != nil {
s.logErr(fmt.Errorf("write event: %v", err))
}
}
return nil
}
func (s *Server) run(l net.Listener) {
for {
c, err := l.Accept()
if err != nil {
s.logErr(err)
continue
}
go s.handleEvents(c)
}
}
func (s *Server) handleEvents(c net.Conn) {
if s.OnConnect != nil {
s.OnConnect(c)
}
s.addClient(c)
defer func() {
s.removeClient(c)
c.Close()
if s.OnDisconnect != nil {
s.OnDisconnect(c)
}
}()
dec := json.NewDecoder(c)
for {
var e Event
err := dec.Decode(&e)
if err != nil {
if err != io.EOF {
s.logErr(fmt.Errorf("decode event: %v", err))
}
break
}
if s.OnEvent != nil {
s.OnEvent(c, e)
}
s.handle(c, e)
}
}
func (s *Server) handle(c net.Conn, e Event) {
s.mu.Lock()
defer s.mu.Unlock()
cmd, found := s.cmds[e.Name]
var data interface{}
if found {
s.mu.Unlock()
data = cmd(e.Data)
s.mu.Lock()
}
re := Event{
Name: e.Name,
Reply: true,
Data: data,
}
if _, err := c.Write(re.Bytes()); err != nil {
s.logErr(err)
}
}
func (s *Server) addClient(c net.Conn) {
s.mu.Lock()
defer s.mu.Unlock()
s.clients = append(s.clients, c)
}
func (s *Server) removeClient(c net.Conn) {
s.mu.Lock()
defer s.mu.Unlock()
clients := make([]net.Conn, 0, len(s.clients))
for _, _c := range s.clients {
if c == _c {
continue
}
clients = append(s.clients, _c)
}
s.clients = clients
}
func (s *Server) logErr(err error) {
if s.ErrorLog != nil {
s.ErrorLog(err)
}
}
// Stop stops listening on the named pipe.
func (s *Server) Stop() (err error) {
s.mu.Lock()
defer s.mu.Unlock()
s.clients = nil
if s.closer != nil {
err = s.closer.Close()
s.closer = nil
}
return
}