events: Implement event system (#4912)

Co-authored-by: Matt Holt <mholt@users.noreply.github.com>

1 files changed, 88 insertions, 0 deletions

diff --git a/modules/caddyevents/eventsconfig/caddyfile.go b/modules/caddyevents/eventsconfig/caddyfile.go
new file mode 100644
index 0000000..9c3fae7
--- /dev/null
+++ b/modules/caddyevents/eventsconfig/caddyfile.go
@@ -0,0 +1,88 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package eventsconfig is for configuring caddyevents.App with the
+// Caddyfile. This code can't be in the caddyevents package because
+// the httpcaddyfile package imports caddyhttp, which imports
+// caddyevents: hence, it creates an import cycle.
+package eventsconfig
+
+import (
+	"encoding/json"
+
+	"github.com/caddyserver/caddy/v2/caddyconfig"
+	"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
+	"github.com/caddyserver/caddy/v2/caddyconfig/httpcaddyfile"
+	"github.com/caddyserver/caddy/v2/modules/caddyevents"
+)
+
+func init() {
+	httpcaddyfile.RegisterGlobalOption("events", parseApp)
+}
+
+// parseApp configures the "events" global option from Caddyfile to set up the events app.
+// Syntax:
+//
+//	events {
+//		on <event> <handler_module...>
+//	}
+//
+// If <event> is *, then it will bind to all events.
+func parseApp(d *caddyfile.Dispenser, _ any) (any, error) {
+	app := new(caddyevents.App)
+
+	// consume the option name
+	if !d.Next() {
+		return nil, d.ArgErr()
+	}
+
+	// handle the block
+	for d.NextBlock(0) {
+		switch d.Val() {
+		case "on":
+			if !d.NextArg() {
+				return nil, d.ArgErr()
+			}
+			eventName := d.Val()
+			if eventName == "*" {
+				eventName = ""
+			}
+
+			if !d.NextArg() {
+				return nil, d.ArgErr()
+			}
+			handlerName := d.Val()
+			modID := "events.handlers." + handlerName
+			unm, err := caddyfile.UnmarshalModule(d, modID)
+			if err != nil {
+				return nil, err
+			}
+
+			app.Subscriptions = append(app.Subscriptions, &caddyevents.Subscription{
+				Events: []string{eventName},
+				HandlersRaw: []json.RawMessage{
+					caddyconfig.JSONModuleObject(unm, "handler", handlerName, nil),
+				},
+			})
+
+		default:
+			return nil, d.ArgErr()
+		}
+	}
+
+	return httpcaddyfile.App{
+		Name:  "events",
+		Value: caddyconfig.JSON(app, nil),
+	}, nil
+}