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eventbus.go
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eventbus.go
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// Copyright (c) 2014 - The Event Horizon 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 local
import (
"context"
"sync"
eh "github.com/looplab/eventhorizon"
)
// EventBus is a local event bus that delegates handling of published events
// to all matching registered handlers, in order of registration.
type EventBus struct {
handlers []handler
handlerMu sync.RWMutex
}
type handler struct {
m eh.EventMatcher
h eh.EventHandler
}
// NewEventBus creates a EventBus.
func NewEventBus() *EventBus {
return &EventBus{}
}
// PublishEvent implements the PublishEvent method of the eventhorizon.EventBus interface.
func (b *EventBus) PublishEvent(ctx context.Context, event eh.Event) error {
b.handlerMu.RLock()
defer b.handlerMu.RUnlock()
for _, h := range b.handlers {
if !h.m(event) {
// Ignore events that does not match.
continue
}
if err := h.h.HandleEvent(ctx, event); err != nil {
return err
}
}
return nil
}
// AddHandler implements the AddHandler method of the eventhorizon.EventBus interface.
func (b *EventBus) AddHandler(m eh.EventMatcher, h eh.EventHandler) {
if m == nil {
panic("eventhorizon: matcher can't be nil")
}
if h == nil {
panic("eventhorizon: handler can't be nil")
}
b.handlerMu.Lock()
defer b.handlerMu.Unlock()
b.handlers = append(b.handlers, handler{m, h})
}