Improve follow command output (#43)

arc/cmd/follow.go

@@ -1,8 +1,10 @@
 package cmd
 
 import (
+	"encoding/json"
+	"errors"
 	"fmt"
-	"io"
+	"io/ioutil"
 	"net/http"
 	"os"
 	"os/exec"
@@ -32,14 +34,47 @@ var followCmd = &cobra.Command{
 
 		reqURL := fmt.Sprintf("https://circleci.com/api/v1.1/project/gh/%s/%s/follow?circle-token=%s", org, repo, os.Getenv("CIRCLECI_TOKEN"))
 
-		resp, err := http.Post(reqURL, "application/json", nil)
+		req, err := http.NewRequest("POST", reqURL, nil)
+		if err != nil {
+			return err
+		}
+		req.Header.Set("Accept", "application/json")
+
+		resp, err := http.DefaultClient.Do(req)
 		if err != nil {
 			return err
 		}
 		defer resp.Body.Close()
 
-		body, err := io.ReadAll(resp.Body)
-		fmt.Printf("%s", body)
+		body, err := ioutil.ReadAll(resp.Body)
+		if err != nil {
+			return err
+		}
+
+		var followResp map[string]interface{}
+
+		err = json.Unmarshal(body, &followResp)
+		if err != nil {
+			return errors.New("Failed to unmarshal CircleCI's API reponse.")
+		}
+
+		if followResp["message"] != nil {
+
+			msg := followResp["message"].(string)
+
+			if strings.Contains(msg, "Not Found") {
+				fmt.Println("Error: Failed to follow project as it wasn't found.")
+			} else if strings.Contains(msg, "For security purposes") {
+				fmt.Println("Error: You don't have permission to follow project.")
+			} else {
+				fmt.Printf("Error: Failed to follow project. Here's what CircleCI's API returns: %s", msg)
+			}
+
+			return nil
+
+		}
+
+		fmt.Println("The project has been followed successfully.")
 
 		return nil
 	},