From 0262be65ef1c29b7f48befd427ab1cb23c89ca5f Mon Sep 17 00:00:00 2001
From: Maxime Delporte <maxime@civiterra.fr>
Date: Thu, 4 Dec 2025 14:12:55 +0100
Subject: [PATCH] Sending background emails.

---
 cmd/api/helpers.go | 21 +++++++++++++++++++--
 cmd/api/users.go   | 20 ++++++++++++--------
 2 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/cmd/api/helpers.go b/cmd/api/helpers.go
index 52fb1f6..ddfe6da 100644
--- a/cmd/api/helpers.go
+++ b/cmd/api/helpers.go
@@ -4,13 +4,14 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"github.com/julienschmidt/httprouter"
-	"greenlight.craftr.fr/internal/validator"
 	"io"
 	"net/http"
 	"net/url"
 	"strconv"
 	"strings"
+
+	"github.com/julienschmidt/httprouter"
+	"greenlight.craftr.fr/internal/validator"
 )
 
 /*
@@ -204,3 +205,19 @@ func (app *application) readInt(qs url.Values, key string, defaultValue int, v *
 	// Otherwise, return the converted integer value
 	return i
 }
+
+// Background: accepts an arbitrary function as a parameter
+func (app *application) background(fn func()) {
+	// Launch a background goroutine
+	go func() {
+		// recover any panic.
+		defer func() {
+			if err := recover(); err != nil {
+				app.logger.Error("%v", err)
+			}
+		}()
+
+		// Execute the arbitrary function that we passed as the parameter
+		fn()
+	}()
+}
diff --git a/cmd/api/users.go b/cmd/api/users.go
index 1d3fce1..e5102eb 100644
--- a/cmd/api/users.go
+++ b/cmd/api/users.go
@@ -59,15 +59,19 @@ func (app *application) registerUserHandler(w http.ResponseWriter, r *http.Reque
 		return
 	}
 
-	// Call the Send() method on our Mail, passing in the user's email address, name of the template file, and the User struct containing the new user's data.
-	err = app.mailer.Send(user.Email, "user_welcome.tmpl", user)
-	if err != nil {
-		app.serverErrorResponse(w, r, err)
-		return
-	}
+	// Use the background helper to execute an anonymous function that send the welcome email
+	app.background(func() {
+		// Call the Send() method on our Mail, passing in the user's email address, name of the template file, and the User struct containing the new user's data.
+		err = app.mailer.Send(user.Email, "user_welcome.tmpl", user)
+		
+		if err != nil {
+			// Importantly, if there is an error sending the email, then we use the app.logger.Error() helper to manage it, instead of the app.serverErrorResponse() helper like before.
+			app.logger.Error(err.Error())
+		}
+	})
 
-	// Write a JSON response containing the user data along with a 201 Created status code
-	err = app.writeJSON(w, http.StatusCreated, envelope{"user": user}, nil)
+	// Not that we also change this to send the client a 202 Accepted status code. This status code indicates that the request has been accepted for processing, but the processing has not been completed.
+	err = app.writeJSON(w, http.StatusAccepted, envelope{"user": user}, nil)
 	if err != nil {
 		app.serverErrorResponse(w, r, err)
 	}