removed intermediate /internal directory

server/api/sse/router.go

@@ -0,0 +1,118 @@
+package sse
+
+import (
+	"context"
+	"sync"
+
+	"github.com/gin-gonic/gin"
+
+	"ruben/inventory2/logging"
+	"ruben/inventory2/server/auth"
+	"ruben/inventory2/server/response"
+	"ruben/inventory2/server/sse"
+)
+
+const (
+	maxNumOpenConnectionsPerUser = 3
+)
+
+type (
+	sseRouter struct {
+		log *logging.Logger
+		sse *sse.Queue
+
+		users map[string][maxNumOpenConnectionsPerUser]context.CancelFunc
+		lock  sync.Mutex
+	}
+)
+
+func Routes(
+	r gin.IRouter,
+	logger *logging.Logger,
+	sq *sse.Queue,
+) {
+	s := &sseRouter{
+		log:   logger,
+		sse:   sq,
+		users: make(map[string][maxNumOpenConnectionsPerUser]context.CancelFunc),
+	}
+
+	r.GET("/", response.Handler(s.serveEvents))
+}
+
+func (r *sseRouter) serveEvents(c *gin.Context) (response.Response, error) {
+	acct := auth.GetIdentity(c).Account
+	acctID := acct.AccountID
+	userID := acct.UserID
+	email := acct.Email
+
+	log := r.log.WithGroup("serveEvents").With(
+		"accountID", acctID,
+		"userID", userID,
+		"email", email,
+		"userAgent", c.Request.UserAgent(),
+	)
+	log.Info("user connected to sse queue")
+
+	ctx := r.closeOutstandingConnectionsForUserAndStoreCancelFuncForUser(c, userID)
+
+	w := c.Writer
+
+	hdr := w.Header()
+	hdr.Set("Access-Control-Allow-Origin", "*")
+	hdr.Set("Access-Control-Expose-Headers", "Content-Type")
+	hdr.Set("Content-Type", "text/event-stream")
+	hdr.Set("Connection", "keep-alive")
+	hdr.Set("Cache-Control", "no-cache")
+	w.Flush()
+
+	err := r.sse.Listen(ctx, acctID, func(ctx context.Context, e *sse.Event) error {
+		log.Debugf("sending event of type %s", e.Type)
+
+		e.Write(w)
+
+		return nil
+	})
+	if err != nil {
+		log.Errorf("no longer connected to sse queue due to error: %v", err)
+		return nil, err
+	}
+
+	// send a 'close' message so the front end doesn't try to reconnect
+	(&sse.Event{Type: "close"}).Write(w)
+
+	log.Info("user disconnecting sse queue")
+	return response.Status(200), nil
+}
+
+func (r *sseRouter) closeOutstandingConnectionsForUserAndStoreCancelFuncForUser(ctx context.Context, userID string) context.Context {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+
+	ctx, cancel := context.WithCancel(ctx)
+
+	closeConnFuncs := r.users[userID]
+	defer func() {
+		r.users[userID] = closeConnFuncs
+	}()
+
+	// close existing connection
+
+	for i := range maxNumOpenConnectionsPerUser {
+		if fn := closeConnFuncs[i]; fn == nil {
+			// not hit limit on connections.
+			// save the cancellation func and done
+			closeConnFuncs[i] = cancel
+			return ctx
+		}
+	}
+
+	// close the oldest connection, shift all cancellation funcs down, and push the new one in
+	closeConnFuncs[0]()
+	for i := range maxNumOpenConnectionsPerUser - 1 {
+		closeConnFuncs[i] = closeConnFuncs[i+1]
+	}
+	closeConnFuncs[maxNumOpenConnectionsPerUser-1] = cancel
+
+	return ctx
+}