moved middleware event publisher to sse package

internal/server/sse/publisher.go

@@ -0,0 +1,130 @@
+package sse
+
+import (
+	"context"
+	"fmt"
+	"path"
+	"strings"
+	"time"
+
+	"github.com/gin-gonic/gin"
+
+	"ruben/inventory2/internal/logging"
+)
+
+type (
+	UpdateNotificationPublisher struct {
+		log             *logging.Logger
+		queue           sender
+		getAccountID    func(*gin.Context) int64
+		trimBasePath    string
+		basePathPattern string
+	}
+
+	// sender is satisfied by *Queue
+	sender interface {
+		Send(ctx context.Context, e Event) error
+	}
+)
+
+func (q *Queue) NewUpdateNotificationPublisher(
+	log *logging.Logger,
+	getAccountID func(*gin.Context) int64,
+) *UpdateNotificationPublisher {
+	return &UpdateNotificationPublisher{
+		log:          log,
+		queue:        q,
+		getAccountID: getAccountID,
+	}
+}
+
+// Trim produces an *UpdateNotificationPublisher with the pathPattern
+// trimmed from events otherwise published by p.
+func (p *UpdateNotificationPublisher) Trim(pathPattern string) *UpdateNotificationPublisher {
+	p2 := *p
+	p2.trimBasePath = path.Join(p2.trimBasePath, pathPattern)
+	return &p2
+}
+
+// Group produces an *UpdateNotificationPublisher with the pathPattern
+// appended to the base path used by p, if any, in publishing events.
+// If no base path was set to p, then pathPattern becomes the base path.
+func (p *UpdateNotificationPublisher) Group(pathPattern string) *UpdateNotificationPublisher {
+	p2 := *p
+	p2.basePathPattern = path.Join(p2.basePathPattern, pathPattern)
+	return &p2
+}
+
+// Publish constructs a gin middleware.
+// It must used with and after middleware puts in the Identity into the gin.Context.
+func (p *UpdateNotificationPublisher) Publish(pathPattern string) gin.HandlerFunc {
+	trimBasePathSegs := getPathSegments(p.trimBasePath)
+	trimmedBasePathPattern := path.Join(p.basePathPattern, pathPattern)
+	trimmedBasePathPatternSegs := getPathSegments(trimmedBasePathPattern)
+	fullBasePathPatternSegs := append(trimBasePathSegs, trimmedBasePathPatternSegs...)
+
+	return func(c *gin.Context) {
+		reqPathSegs := getPathSegments(c.Request.URL.Path)
+
+		c.Next()
+		if len(c.Errors) > 0 {
+			return
+		}
+		if len(reqPathSegs) < len(fullBasePathPatternSegs) {
+			p.log.Errorf("req path is less that the full path: %v, %v", c.Request.URL.Path, path.Join(p.trimBasePath, p.basePathPattern, pathPattern))
+			return
+		}
+
+		// if the path is a subpath, then emit events along the subpath.
+
+		for i, s := range trimmedBasePathPatternSegs {
+			if isWildcard := s[0] == ':'; isWildcard {
+				continue
+			}
+
+			rs := reqPathSegs[i]
+			if isSubpath := s != rs; isSubpath {
+				continue
+			}
+
+			return
+		}
+
+		topEventParts := reqPathSegs[len(trimBasePathSegs):len(fullBasePathPatternSegs)]
+		topEvent := strings.Join(topEventParts, "_")
+
+		events := make([]string, len(reqPathSegs)-len(fullBasePathPatternSegs)+1)
+		events[0] = topEvent
+		parentEvent := topEvent
+		for i, s := range reqPathSegs[len(fullBasePathPatternSegs):] {
+			e := parentEvent + "_" + s
+			events[i+1] = e
+			parentEvent = e
+		}
+
+		acctID := p.getAccountID(c)
+		for _, e := range events {
+			go func() {
+				ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
+				defer cancel()
+
+				if err := p.queue.Send(ctx, Event{
+					AccountID: acctID,
+					Type:      e,
+					Data:      []byte(fmt.Sprintf(`{"eventType": %q}`, e)),
+				}); err != nil {
+					p.log.Errorf("failed to send sse event to listener: %v", err)
+				}
+			}()
+		}
+	}
+}
+
+func getPathSegments(p string) []string {
+	p = path.Clean(p)
+	if p == "" || p == "." || p == "/" {
+		return nil
+	}
+
+	return strings.Split(strings.Trim(p, "/"), "/")
+}