split larger slack notifications into multiple messages to prevent co…

…de block formatting from breaking (#746)

* refactor slack notification to use interface

pkg/digger/digger.go

@@ -1,8 +1,6 @@
 package digger
 
 import (
-	"bytes"
-	"encoding/json"
 	"errors"
 	"fmt"
 	config "github.com/diggerhq/digger/libs/digger_config"
@@ -17,11 +15,10 @@ import (
 	"github.com/diggerhq/digger/pkg/core/terraform"
 	"github.com/diggerhq/digger/pkg/core/utils"
 	"github.com/diggerhq/digger/pkg/locking"
+	"github.com/diggerhq/digger/pkg/notification"
 	"github.com/diggerhq/digger/pkg/reporting"
 	"github.com/diggerhq/digger/pkg/usage"
-	"io"
 	"log"
-	"net/http"
 	"os"
 	"path"
 	"strings"
@@ -576,54 +573,20 @@ func runDriftDetection(policyChecker policy.Checker, SCMOrganisation string, SCM
 	}
 
 	if planPerformed && nonEmptyPlan {
-		httpClient := &http.Client{}
 		slackNotificationUrl := os.Getenv("INPUT_DRIFT_DETECTION_SLACK_NOTIFICATION_URL")
 
 		if slackNotificationUrl == "" {
 			msg := "no INPUT_DRIFT_DETECTION_SLACK_NOTIFICATION_URL set, not sending notification"
 			log.Printf(msg)
 			return msg, fmt.Errorf(msg)
 		}
-
-		type SlackMessage struct {
-			Text string `json:"text"`
-		}
-		slackMessage := SlackMessage{
-			Text: fmt.Sprintf(":bangbang: Drift detected in digger project %v details below: \n\n```\n%v\n```", projectName, plan),
-		}
-
-		jsonData, err := json.Marshal(slackMessage)
-		if err != nil {
-			msg := fmt.Sprintf("failed to marshal slack message. %v", err)
-			log.Printf(msg)
-			return msg, fmt.Errorf(msg)
-		}
-
-		request, err := http.NewRequest("POST", slackNotificationUrl, bytes.NewBuffer(jsonData))
-		if err != nil {
-			msg := fmt.Sprintf("failed to create slack notification request. %v", err)
-			log.Printf(msg)
-			return msg, fmt.Errorf(msg)
-		}
-
-		request.Header.Set("Content-Type", "application/json")
-		resp, err := httpClient.Do(request)
+		// send notification
+		notificationMessage := fmt.Sprintf(":bangbang: Drift detected in digger project %v details below: \n\n```\n%v\n```", projectName, plan)
+		notification := notification.SlackNotification{Url: slackNotificationUrl}
+		err := notification.Send(notificationMessage)
 		if err != nil {
-			msg := fmt.Sprintf("failed to send slack notification request. %v", err)
-			log.Printf(msg)
-		}
-		if resp.StatusCode != 200 {
-			body, err := io.ReadAll(resp.Body)
-			if err != nil {
-				msg := fmt.Sprintf("failed to read response body. %v", err)
-				log.Printf(msg)
-				return msg, fmt.Errorf(msg)
-			}
-			msg := fmt.Sprintf("failed to send slack notification request. %v. Message: %v", resp.Status, body)
-			log.Printf(msg)
-			return msg, fmt.Errorf(msg)
+			log.Printf("Erorr sending drift notification: %v", err)
 		}
-		defer resp.Body.Close()
 	} else if planPerformed && !nonEmptyPlan {
 		log.Printf("No drift detected")
 	} else {

pkg/notification/slack.go

@@ -0,0 +1,94 @@
+package notification
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"regexp"
+	"strings"
+)
+
+type Notification interface {
+	Send(message string) error
+}
+
+type SlackNotification struct {
+	Url string
+}
+
+func SplitCodeBlocks(message string) []string {
+	var res []string
+
+	if strings.Count(message, "```") < 2 {
+		res = append(res, message)
+		return res
+	}
+
+	regex := regexp.MustCompile("\n")
+	split := regex.Split(message, -1)
+	part := ""
+	for _, line := range split {
+		if len(part+line) > 4000 {
+			res = append(res, part+"\n"+line+"\n```")
+			part = "```\n" + line
+		} else {
+			part = part + "\n" + line
+		}
+	}
+	if len(part) > 0 {
+		res = append(res, part)
+	}
+	return res
+}
+
+func (slack SlackNotification) Send(message string) error {
+	httpClient := &http.Client{}
+	type SlackMessage struct {
+		Text string `json:"text"`
+	}
+	parts := SplitCodeBlocks(message)
+	for _, part := range parts {
+		slackMessage := SlackMessage{
+			Text: part,
+		}
+
+		jsonData, err := json.Marshal(slackMessage)
+		if err != nil {
+			msg := fmt.Sprintf("failed to marshal slack message. %v", err)
+			log.Printf(msg)
+			return fmt.Errorf(msg)
+		}
+
+		request, err := http.NewRequest("POST", slack.Url, bytes.NewBuffer(jsonData))
+		if err != nil {
+			msg := fmt.Sprintf("failed to create slack notification request. %v", err)
+			log.Printf(msg)
+			return fmt.Errorf(msg)
+		}
+
+		request.Header.Set("Content-Type", "application/json")
+		resp, err := httpClient.Do(request)
+		if err != nil {
+			msg := fmt.Sprintf("failed to send slack notification request. %v", err)
+			log.Printf(msg)
+			return fmt.Errorf(msg)
+		}
+		if resp.StatusCode != 200 {
+			body, err := io.ReadAll(resp.Body)
+			if err != nil {
+				msg := fmt.Sprintf("failed to read response body. %v", err)
+				log.Printf(msg)
+				return fmt.Errorf(msg)
+			}
+			msg := fmt.Sprintf("failed to send slack notification request. %v. Message: %v", resp.Status, body)
+			log.Printf(msg)
+			return fmt.Errorf(msg)
+		}
+		resp.Body.Close()
+	}
+
+	return nil
+}