[Mattermost Integrations] Interactive Message Menu

BODY='{
  "attachments": [{
    "title": "Echo text",
    "actions": [{
	  "id": "echo",
      "name": "Would you like to echo?",
      "integration": {
        "url": "http://localhost:8080/actions/echo",
        "context": {
          "text": "sample text"
		}
	  },
	  "type": "select",
	  "options": [{
		  "text": "Echo",
		  "value": "echo"
	  }, {
		  "text": "Reject",
		  "value": "reject"
	  }]
	}]
  }]
}'

curl \
  -H "Content-Type: application/json" \
  -d "$BODY"  \
  http://localhost:8065/hooks/ucw5qjw86jgeum77o1uw8197jr

BODY='{
  "attachments": [{
    "title": "Echo text",
    "actions": [{
	  "id": "echo",
      "name": "Would you like to echo?",
      "integration": {
        "url": "http://localhost:8080/actions/echo",
        "context": {
          "text": "sample text"
		}
	  },
	  "type": "select",
	  "data_source": "channels"
	}]
  }]
}'

curl \
  -H "Content-Type: application/json" \
  -d "$BODY"  \
  http://localhost:8065/hooks/ucw5qjw86jgeum77o1uw8197jr

package main

import (
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"

	"github.com/mattermost/mattermost-server/v5/model"
)

func main() {
	http.HandleFunc("/command", func(w http.ResponseWriter, r *http.Request) {
		r.ParseForm()

		response := model.CommandResponse{
			ResponseType: model.COMMAND_RESPONSE_TYPE_IN_CHANNEL,
			Attachments: []*model.SlackAttachment{{
				Title: "Echo server",
				Actions: []*model.PostAction{{
					// (1) Echoメニュー
					Name: "Echo",
					Integration: &model.PostActionIntegration{
						URL: "http://localhost:8080/actions/echo",
						Context: map[string]interface{}{
							"text": r.Form.Get("text"),
						},
					},
					Type: model.POST_ACTION_TYPE_SELECT,
					Options: []*model.PostActionOptions{{
						Text:  "Echo",
						Value: "echo",
					}, {
						Text:  "Reject",
						Value: "reject",
					}},
				}},
			}},
		}

		// Need to set header. if not, just json string will be posted.
		w.Header().Add("Content-Type", "application/json")
		io.WriteString(w, response.ToJson())
	})

	// (2) Echo Buttonが押されたときの処理
	http.HandleFunc("/actions/echo", func(w http.ResponseWriter, r *http.Request) {
		defer r.Body.Close()

		// (3) リクエストデータの読み出し
		b, _ := ioutil.ReadAll(r.Body)
		var payload model.PostActionIntegrationRequest
		json.Unmarshal(b, &payload)

		text, ok := payload.Context["text"].(string)
		if !ok {
			resp := &model.PostActionIntegrationResponse{EphemeralText: "invalid request. Context['text'] is not found."}
			fmt.Fprint(w, resp.ToJson())
			return
		}

		selected, ok := payload.Context["selected_option"].(string)
		if !ok {
			resp := &model.PostActionIntegrationResponse{EphemeralText: "invalid request. Context['selected_option'] is not found."}
			fmt.Fprint(w, resp.ToJson())
			return
		}

		// (4) レスポンスの構築
		response := &model.PostActionIntegrationResponse{}
		switch selected {
		case "echo":
			response.Update = &model.Post{
				Message: text,
				Props:   model.StringInterface{},
			}
		case "reject":
			response.Update = &model.Post{Props: model.StringInterface{}}
			response.EphemeralText = "Echoing was rejected"
		default:
			response.EphemeralText = "invalid operation"
		}

		w.Header().Add("Content-Type", "application/json")
		io.WriteString(w, string(response.ToJson()))
	})

	http.ListenAndServe(":8080", nil)
}

type PostActionIntegrationRequest struct {
	UserId      string                 `json:"user_id"`
	UserName    string                 `json:"user_name"`
	ChannelId   string                 `json:"channel_id"`
	ChannelName string                 `json:"channel_name"`
	TeamId      string                 `json:"team_id"`
	TeamName    string                 `json:"team_domain"`
	PostId      string                 `json:"post_id"`
	TriggerId   string                 `json:"trigger_id"`
	Type        string                 `json:"type"`
	DataSource  string                 `json:"data_source"`
	Context     map[string]interface{} `json:"context,omitempty"`
}

type PostActionIntegrationResponse struct {
	Update           *Post  `json:"update"`
	EphemeralText    string `json:"ephemeral_text"`
	SkipSlackParsing bool   `json:"skip_slack_parsing"` // Set to `true` to skip the Slack-compatibility handling of Text.
}