Facebook Messenger for Go

Facebook Messenger API for Go, essential API used for Facebook chat bots

It can send and receive messages from Facebook Messenger.

Use AS IS. It works, but perhapse it needs touch or two and more unit tests.

Example:

package main

import (
    "log"
    "net/http"

    "github.com/mileusna/facebook-messenger"
)

func main() {
    msng := &messenger.Messenger{
        AccessToken:     "YOUR_ACCESS_TOKEN_THAT_YOU_WILL_GENERATE_FOR_YOUR_PAGE_ON_FACEBOOK",
        VerifyToken:     "YOUR_SECRET_TOKEN_FOR_VERIFYING_WEBHOOK_PUT_THE_SAME_VALUE_HERE_AND_ON_FB",
        PageID:          "YOUR_PAGE_ID",
        MessageReceived: messageReceived, // your function for handling received messages, defined below
    }

    // in init or afterwards, you can also specify events when receiving postbacks and message delivery reports from Facebook
    // if you don't want to manage this events, just comment/don't use this receivers
    msng.PostbackReceived = postbackReceived // comment/delete if not used
    // msng.DeliveryReceived = deliveryReceived // comment/delete if not used

    // set URL for your webhook and directly use msng as http Handler
    http.Handle("/mychatbot", msng)
    http.ListenAndServe(":8008", nil)
}

// messageReceived is called when you receive message on you webhook i.e. when someone sends message to your chat bot
// params: messenger that received the message, then the user id that sent us message and message data itself
func messageReceived(msng *messenger.Messenger, userID int64, m messenger.FacebookMessage) {

    // message received, now lets check what user has sent to us
    switch m.Text {
    case "hello", "hi":
        // someone sent hello or hi, reply with simple text message
        msng.SendTextMessage(userID, "Hello there")

    case "send me website":
        // now lets send him some structured message with image and link
        gm := msng.NewGenericMessage(userID)
        gm.AddNewElement("Title", "Subtitle", "http://mysite.com", "http://mysite.com/some-photo.jpeg", nil)

        // GenericMessage can contain up to 10 elements, they are represented as cards and can be scoreled horicontally in messenger
        // So lets add one more element, this time with buttons
        btn1 := msng.NewWebURLButton("Contact US", "http://mysite.com/contact")
        btn2 := msng.NewPostbackButton("Ok", "THIS_DATA_YOU_WILL_RECEIVE_AS_POSTBACK_WHEN_USER_CLICK_THE_BUTTON")
        gm.AddNewElement("Site title", "Subtitle", "http://mysite.com", "http://mysite.com/some-photo.jpeg", []messenger.Button{btn1, btn2})

        // ok, message is ready, lets send
        msng.SendMessage(gm)

    default:
        // upthere we haven't check for errors and responses for cleaner example code
        // but keep in mind that SendMessage returns FacebookResponse struct and error
        // errors are received from Facebook if sometnihg went wrong with message sending
        resp, err := msng.SendTextMessage(userID, m.Text) // echo, send back to user the same text he sent to us
        if err != nil {
            log.Println(err)
            return // if there is an error, resp is empty struct, useless
        }
        log.Println("Message ID", resp.MessageID, "sent to user", resp.RecipientID)
        // store resp.MessageID if you want to track delivery reports that will be sent later from Facebook
    }
}

// postbackReceived is called when you reiceive postback event from Facebook server
func postbackReceived(msng *messenger.Messenger, userID int64, p messenger.FacebookPostback) {
    if p.Payload == "THIS_DATA_YOU_WILL_RECEIVE_AS_POSTBACK_WHEN_USER_CLICK_THE_BUTTON" {
        // user just clicked Ok button from previouse example, lets just send him a message
        msng.SendTextMessage(userID, "Ok, I'm always online, chat with me anytime :)")
    }
}

// deliveryReceived is used if you want to track delivery reports for sent messages
func deliveryReceived(msng *messenger.Messenger, userID int64, d messenger.FacebookDelivery) {
    for _, mid := range d.Mids {
        log.Println("Message delivered, msgID:", mid)
    }
}