LINE BOT Echo Server

linebot.go

package main

import (
	"bytes"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"os"
	"strconv"

	"github.com/line/line-bot-sdk-go/linebot"

	"google.golang.org/appengine"
	"google.golang.org/appengine/log"
	"google.golang.org/appengine/taskqueue"
	"google.golang.org/appengine/urlfetch"
)

var (
	channelID     int64
	channelSecret string
	channelMID    string
)

func init() {
	var err error

	channelID, err = strconv.ParseInt(os.Getenv("CHANNEL_ID"), 10, 64)
	if err != nil {
		panic(fmt.Sprintf("not set environment variable (CHANNEL_ID). %v", err))
	}

	channelSecret = os.Getenv("CHANNEL_SECRET")
	if channelSecret == "" {
		panic("not set environment variable (CHANNEL_SECRET).")
	}

	channelMID = os.Getenv("CHANNEL_MID")
	if channelMID == "" {
		panic("not set environment variable (CHANNEL_MID).")
	}

	http.HandleFunc("/messages/receive", receiveMessagesHandleFunc)
	http.HandleFunc("/messages/send", sendMessagesHandleFunc)
}

func receiveMessagesHandleFunc(w http.ResponseWriter, r *http.Request) {
	ctx := appengine.NewContext(r)
	client := urlfetch.Client(ctx)
	bot, err := linebot.NewClient(channelID, channelSecret, channelMID, linebot.WithHTTPClient(client))
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	received, err := bot.ParseRequest(r)
	if err != nil {
		if err == linebot.ErrInvalidSignature {
			http.Error(w, err.Error(), http.StatusBadRequest)
		} else {
			http.Error(w, err.Error(), http.StatusInternalServerError)
		}
		return
	}

	for _, result := range received.Results {
		v, err := json.Marshal(&result)
		if err != nil {
			log.Errorf(ctx, "result marshal error: %v", err)
			continue
		}

		t := taskqueue.NewPOSTTask("/messages/send", url.Values{
			"message": {string(v)},
		})
		if _, err := taskqueue.Add(ctx, t, ""); err != nil {
			log.Errorf(ctx, "add task error: %v", err)
		}
	}
}

func sendMessagesHandleFunc(w http.ResponseWriter, r *http.Request) {
	ctx := appengine.NewContext(r)
	client := urlfetch.Client(ctx)
	bot, err := linebot.NewClient(channelID, channelSecret, channelMID, linebot.WithHTTPClient(client))
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	var message linebot.ReceivedResult
	v := r.FormValue("message")
	if err := json.Unmarshal([]byte(v), &message); err != nil {
		log.Errorf(ctx, "message unmarshal error: %v", err)
		return
	}

	content := message.Content()
	if content == nil {
		log.Errorf(ctx, "message content nil. id = %s", message.ID)
		return
	}
	if !content.IsMessage {
		log.Errorf(ctx, "message content is not message. id = %s", message.ID)
		return
	}

	switch content.ContentType {
	case linebot.ContentTypeText:
		text, err := content.TextContent()
		if err != nil {
			log.Errorf(ctx, "get text content error: %v. id = %s", err, message.ID)
			return
		}
		_, err = bot.SendText([]string{content.From}, text.Text)
		if err != nil {
			log.Errorf(ctx, "send message error: %v. id = %s", err, message.ID)
			return
		}
	case linebot.ContentTypeImage:
		log.Errorf(ctx, "not implemented error(image). id = %s", message.ID)
	case linebot.ContentTypeVideo:
		log.Errorf(ctx, "not implemented error(video). id = %s", message.ID)
	case linebot.ContentTypeAudio:
		log.Errorf(ctx, "not implemented error(audio). id = %s", message.ID)
	case linebot.ContentTypeLocation:
		log.Errorf(ctx, "not implemented error(location). id = %s", message.ID)
	case linebot.ContentTypeSticker:
		log.Errorf(ctx, "not implemented error(sticker). id = %s", message.ID)
	case linebot.ContentTypeContact:
		log.Errorf(ctx, "not implemented error(contact). id = %s", message.ID)
	case linebot.ContentTypeRichMessage:
		log.Errorf(ctx, "not implemented error(rich message). id = %s", message.ID)
	}
}