event.go

package eventhub

//	MIT License
//
//	Copyright (c) Microsoft Corporation. All rights reserved.
//
//	Permission is hereby granted, free of charge, to any person obtaining a copy
//	of this software and associated documentation files (the "Software"), to deal
//	in the Software without restriction, including without limitation the rights
//	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//	copies of the Software, and to permit persons to whom the Software is
//	furnished to do so, subject to the following conditions:
//
//	The above copyright notice and this permission notice shall be included in all
//	copies or substantial portions of the Software.
//
//	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
//	SOFTWARE

import (
	"time"

	"github.com/Azure/azure-amqp-common-go/persist"
	"pack.ag/amqp"
)

const (
	batchMessageFormat         uint32 = 0x80013700
	partitionKeyAnnotationName string = "x-opt-partition-key"
	sequenceNumberName         string = "x-opt-sequence-number"
	enqueueTimeName            string = "x-opt-enqueued-time"
)

type (
	// Event is an Event Hubs message to be sent or received
	Event struct {
		Data         []byte
		PartitionKey *string
		Properties   map[string]interface{}
		ID           string
		message      *amqp.Message
	}

	// EventBatch is a batch of Event Hubs messages to be sent
	EventBatch struct {
		Events       []*Event
		PartitionKey *string
		Properties   map[string]interface{}
		ID           string
	}
)

// NewEventFromString builds an Event from a string message
func NewEventFromString(message string) *Event {
	return NewEvent([]byte(message))
}

// NewEvent builds an Event from a slice of data
func NewEvent(data []byte) *Event {
	return &Event{
		Data: data,
	}
}

// NewEventBatch builds an EventBatch from an array of Events
func NewEventBatch(events []*Event) *EventBatch {
	return &EventBatch{
		Events: events,
	}
}

// GetCheckpoint returns the checkpoint information on the Event
func (e *Event) GetCheckpoint() persist.Checkpoint {
	var offset string
	var enqueueTime time.Time
	var sequenceNumber int64
	if val, ok := e.message.Annotations[offsetAnnotationName]; ok {
		offset = val.(string)
	}

	if val, ok := e.message.Annotations[enqueueTimeName]; ok {
		enqueueTime = val.(time.Time)
	}

	if val, ok := e.message.Annotations[sequenceNumberName]; ok {
		sequenceNumber = val.(int64)
	}

	return persist.NewCheckpoint(offset, sequenceNumber, enqueueTime)
}

// Set implements opentracing.TextMapWriter and sets properties on the event to be propagated to the message broker
func (e *Event) Set(key, value string) {
	if e.Properties == nil {
		e.Properties = make(map[string]interface{})
	}
	e.Properties[key] = value
}

// ForeachKey implements the opentracing.TextMapReader and gets properties on the event to be propagated from the message broker
func (e *Event) ForeachKey(handler func(key string, val interface{}) error) error {
	for key, value := range e.Properties {
		err := handler(key, value)
		if err != nil {
			return err
		}
	}
	return nil
}

func (e *Event) toMsg() *amqp.Message {
	msg := e.message
	if msg == nil {
		msg = amqp.NewMessage(e.Data)
	}

	msg.Properties = &amqp.MessageProperties{
		MessageID: e.ID,
	}

	if len(e.Properties) > 0 {
		msg.ApplicationProperties = make(map[string]interface{})
		for key, value := range e.Properties {
			msg.ApplicationProperties[key] = value
		}
	}

	if e.PartitionKey != nil {
		msg.Annotations = make(amqp.Annotations)
		msg.Annotations[partitionKeyAnnotationName] = e.PartitionKey
	}
	return msg
}

func (b *EventBatch) toEvent() (*Event, error) {
	msg := &amqp.Message{
		Data: make([][]byte, len(b.Events)),
		Properties: &amqp.MessageProperties{
			MessageID: b.ID,
		},
		Format: batchMessageFormat,
	}

	for idx, event := range b.Events {
		innerMsg := amqp.NewMessage(event.Data)
		bin, err := innerMsg.MarshalBinary()
		if err != nil {
			return nil, err
		}
		msg.Data[idx] = bin
	}

	return eventFromMsg(msg), nil
}

func eventFromMsg(msg *amqp.Message) *Event {
	return newEvent(msg.Data[0], msg)
}

func newEvent(data []byte, msg *amqp.Message) *Event {
	event := &Event{
		Data:    data,
		message: msg,
	}

	if msg.Properties != nil {
		if id, ok := msg.Properties.MessageID.(string); ok {
			event.ID = id
		}
	}

	if msg != nil {
		event.Properties = msg.ApplicationProperties
	}
	return event
}