[Mattermost Integrations] Interactive Message Button

BODY='{
  "attachments": [{
    "title": "Echo text",
    "actions": [{
	  "id": "echo",
      "name": "Echo",
      "integration": {
        "url": "http://localhost:8080/actions/echo",
        "context": {
          "text": "sample text"
		}
	  }
	}, {
      "name": "Reject",
	  "style": "danger",
      "integration": {
        "url": "http://localhost:8080/actions/reject"
	  }
	}]
  }]
}'

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

{
  "id": "echo",
  "name": "Echo",
  "integration": {
    "url": "http://localhost:8080/actions/echo",
    "context": {
      "text": "sample text"
    }
  }
}

package main

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

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

func main() {
	// (1) Interactive Message Button作成用slash command
	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 text",
				Actions: []*model.PostAction{{
					// (2) Echoボタン
					Id:   "echo",
					Name: "Echo",
					Integration: &model.PostActionIntegration{
						URL: "http://localhost:8080/actions/echo",
						Context: map[string]interface{}{
							"text": r.Form.Get("text"),
						},
					},
				}, {
					// (3) Rejectボタン
					Name:  "Reject",
					Style: "danger",
					Integration: &model.PostActionIntegration{
						URL: "http://localhost:8080/actions/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())
	})

	// (4) 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()

		// (5) 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
		}

		// (6) レスポンスの構築
		response := &model.PostActionIntegrationResponse{
			Update: &model.Post{
				Message: text,
				Props:   model.StringInterface{},
			},
		}

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

	// (7) Rejectボタンが押されたときの処理
	http.HandleFunc("/actions/reject", func(w http.ResponseWriter, r *http.Request) {
		// (8) レスポンスの構築
		response := &model.PostActionIntegrationResponse{
			Update: &model.Post{
				Props: model.StringInterface{},
			},
			EphemeralText: "Echoing was rejected.",
		}

		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.
}