Better context and connection handling

.idea/workspace.xml

@@ -4,10 +4,8 @@
     <option name="autoReloadType" value="ALL" />
   </component>
   <component name="ChangeListManager">
-    <list default="true" id="b79e8e7a-d892-4ce4-8bf4-f9e45415b803" name="Changes" comment="Progress">
-      <change afterPath="$PROJECT_DIR$/auth.go" afterDir="false" />
+    <list default="true" id="b79e8e7a-d892-4ce4-8bf4-f9e45415b803" name="Changes" comment="Implemented SMTP AUTH">
       <change beforePath="$PROJECT_DIR$/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/workspace.xml" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/README.md" beforeDir="false" afterPath="$PROJECT_DIR$/README.md" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/client.go" beforeDir="false" afterPath="$PROJECT_DIR$/client.go" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/cmd/main.go" beforeDir="false" afterPath="$PROJECT_DIR$/cmd/main.go" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/mailmsg.go" beforeDir="false" afterPath="$PROJECT_DIR$/mailmsg.go" afterDir="false" />
@@ -95,7 +93,8 @@
   </component>
   <component name="VcsManagerConfiguration">
     <MESSAGE value="Progress" />
-    <option name="LAST_COMMIT_MESSAGE" value="Progress" />
+    <MESSAGE value="Implemented SMTP AUTH" />
+    <option name="LAST_COMMIT_MESSAGE" value="Implemented SMTP AUTH" />
   </component>
   <component name="VgoProject">
     <integration-enabled>true</integration-enabled>

client.go

@@ -53,10 +53,13 @@ type Client struct {
 	// satype represents the authentication type for SMTP AUTH
 	satype SMTPAuthType
 
-	// smtpauth is a pointer to smtp.Auth
+	// co is the net.Conn that the smtp.Client is based on
+	co net.Conn
+
+	// sa is a pointer to smtp.Auth
 	sa smtp.Auth
 
-	// The SMTP client that is set up when using the Dial*() methods
+	// sc is the smtp.Client that is set up when using the Dial*() methods
 	sc *smtp.Client
 }
 
@@ -66,6 +69,13 @@ type Option func(*Client)
 var (
 	// ErrNoHostname should be used if a Client has no hostname set
 	ErrNoHostname = errors.New("hostname for client cannot be empty")
+
+	// ErrDeadlineExtendFailed should be used if the extension of the connection deadline fails
+	ErrDeadlineExtendFailed = errors.New("connection deadline extension failed")
+
+	// ErrNoActiveConnection should be used when a method is used that requies a server connection
+	// but is not yet connected
+	ErrNoActiveConnection = errors.New("not connected to SMTP server")
 )
 
 // NewClient returns a new Session client object
@@ -190,9 +200,24 @@ func (c *Client) SetTLSConfig(co *tls.Config) {
 	c.tlsconfig = co
 }
 
-// Send sends out the mail message
-func (c *Client) Send() error {
-	return nil
+// SetUsername overrides the current username string with the given value
+func (c *Client) SetUsername(u string) {
+	c.user = u
+}
+
+// SetPassword overrides the current password string with the given value
+func (c *Client) SetPassword(p string) {
+	c.pass = p
+}
+
+// SetSMTPAuth overrides the current SMTP AUTH type setting with the given value
+func (c *Client) SetSMTPAuth(a SMTPAuthType) {
+	c.satype = a
+}
+
+// SetSMTPAuthCustom overrides the current SMTP AUTH setting with the given custom smtp.Auth
+func (c *Client) SetSMTPAuthCustom(sa smtp.Auth) {
+	c.sa = sa
 }
 
 // Close closes the connection cto the SMTP server
@@ -210,33 +235,26 @@ func (c *Client) setDefaultHelo() error {
 	return nil
 }
 
-// Dial establishes a connection cto the SMTP server with a default context.Background
-func (c *Client) Dial() error {
-	ctx := context.Background()
-	return c.DialWithContext(ctx)
-}
-
 // DialWithContext establishes a connection cto the SMTP server with a given context.Context
-func (c *Client) DialWithContext(uctx context.Context) error {
-	ctx, cfn := context.WithTimeout(uctx, c.cto)
+func (c *Client) DialWithContext(pc context.Context) error {
+	ctx, cfn := context.WithDeadline(pc, time.Now().Add(c.cto))
 	defer cfn()
 
 	nd := net.Dialer{}
 	td := tls.Dialer{}
-	var co net.Conn
 	var err error
 	if c.ssl {
 		c.enc = true
-		co, err = td.DialContext(ctx, "tcp", c.ServerAddr())
+		c.co, err = td.DialContext(ctx, "tcp", c.ServerAddr())
 	}
 	if !c.ssl {
-		co, err = nd.DialContext(ctx, "tcp", c.ServerAddr())
+		c.co, err = nd.DialContext(ctx, "tcp", c.ServerAddr())
 	}
 	if err != nil {
 		return err
 	}
 
-	c.sc, err = smtp.NewClient(co, c.host)
+	c.sc, err = smtp.NewClient(c.co, c.host)
 	if err != nil {
 		return err
 	}
@@ -274,8 +292,45 @@ func (c *Client) DialWithContext(uctx context.Context) error {
 	return nil
 }
 
+// Send sends out the mail message
+func (c *Client) Send() error {
+	if err := c.checkConn(); err != nil {
+		return fmt.Errorf("failed to send mail: %w", err)
+	}
+
+	return nil
+}
+
+// DialAndSend establishes a connection to the SMTP server with a
+// default context.Background and sends the mail
+func (c *Client) DialAndSend() error {
+	ctx := context.Background()
+	if err := c.DialWithContext(ctx); err != nil {
+		return fmt.Errorf("dial failed: %w", err)
+	}
+	if err := c.Send(); err != nil {
+		return fmt.Errorf("send failed: %w", err)
+	}
+	return nil
+}
+
+// checkConn makes sure that a required server connection is available and extends the
+// connection deadline
+func (c *Client) checkConn() error {
+	if c.co == nil {
+		return ErrNoActiveConnection
+	}
+	if err := c.co.SetDeadline(time.Now().Add(c.cto)); err != nil {
+		return ErrDeadlineExtendFailed
+	}
+	return nil
+}
+
 // auth will try to perform SMTP AUTH if requested
 func (c *Client) auth() error {
+	if err := c.checkConn(); err != nil {
+		return fmt.Errorf("failed to authenticate: %w", err)
+	}
 	if c.sa == nil && c.satype != "" {
 		sa, sat := c.sc.Extension("AUTH")
 		if !sa {

cmd/main.go

@@ -1,7 +1,6 @@
 package main
 
 import (
-	"context"
 	"fmt"
 	"github.com/wneessen/go-mail"
 	"os"
@@ -14,24 +13,15 @@ func main() {
 		fmt.Printf("$TEST_HOST env variable cannot be empty\n")
 		os.Exit(1)
 	}
-
 	tu := os.Getenv("TEST_USER")
 	tp := os.Getenv("TEST_PASS")
+
 	c, err := mail.NewClient(th, mail.WithTimeout(time.Millisecond*500), mail.WithTLSPolicy(mail.TLSMandatory),
 		mail.WithSMTPAuth(mail.SMTPAuthDigestMD5), mail.WithUsername(tu), mail.WithPassword(tp))
 	if err != nil {
 		fmt.Printf("failed to create new client: %s\n", err)
 		os.Exit(1)
 	}
-	//c.SetTLSPolicy(mail.TLSMandatory)
-
-	ctx, cfn := context.WithCancel(context.Background())
-	defer cfn()
-
-	if err := c.DialWithContext(ctx); err != nil {
-		fmt.Printf("failed to dial: %s\n", err)
-		os.Exit(1)
-	}
 
 	m := mail.NewMsg()
 	m.From("wn@neessen.net")
@@ -41,4 +31,8 @@ func main() {
 	m.SetBulk()
 	m.Header()
 
+	if err := c.DialAndSend(); err != nil {
+		fmt.Printf("failed to dial: %s\n", err)
+		os.Exit(1)
+	}
 }

mailmsg.go

@@ -73,14 +73,15 @@ func (m *Msg) SetMessageIDWithValue(v string) {
 	m.SetHeader(HeaderMessageID, v)
 }
 
-// SetBulk sets the "Precedense: bulk" header which is recommended for
+// SetBulk sets the "Precedence: bulk" header which is recommended for
 // automated mails like OOO replies
 // See: https://www.rfc-editor.org/rfc/rfc2076#section-3.9
 func (m *Msg) SetBulk() {
 	m.SetHeader(HeaderPrecedence, "bulk")
 }
 
-// Header FixMe
+// Header does something
+// FIXME: This is only here to quickly show the set headers for debugging purpose. Remove me later
 func (m *Msg) Header() {
 	fmt.Printf("%+v\n", m.header)