From 57ebb171c54176dd9b3bddfbdf85675b78c5489d Mon Sep 17 00:00:00 2001
From: Winni Neessen <wn@neessen.net>
Date: Thu, 10 Mar 2022 16:19:51 +0100
Subject: [PATCH] Lots of cleanups and refactoring

---
 .idea/workspace.xml |  7 +++-
 README.md           | 29 ++++++++-----
 client.go           | 17 +++++---
 cmd/main.go         | 27 +++++++++----
 header.go           | 40 +++++++++++-------
 mailmsg.go          | 99 ++++++++++++++++++++++++++++++++++++---------
 6 files changed, 163 insertions(+), 56 deletions(-)

diff --git a/.idea/workspace.xml b/.idea/workspace.xml
index c1f67f4..c1f0110 100644
--- a/.idea/workspace.xml
+++ b/.idea/workspace.xml
@@ -4,10 +4,12 @@
     <option name="autoReloadType" value="ALL" />
   </component>
   <component name="ChangeListManager">
-    <list default="true" id="b79e8e7a-d892-4ce4-8bf4-f9e45415b803" name="Changes" comment="Implemented SMTP AUTH">
+    <list default="true" id="b79e8e7a-d892-4ce4-8bf4-f9e45415b803" name="Changes" comment="Better context and connection handling">
       <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="$PROJECT_DIR$/header.go" beforeDir="false" afterPath="$PROJECT_DIR$/header.go" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/mailmsg.go" beforeDir="false" afterPath="$PROJECT_DIR$/mailmsg.go" afterDir="false" />
     </list>
     <option name="SHOW_DIALOG" value="false" />
@@ -94,7 +96,8 @@
   <component name="VcsManagerConfiguration">
     <MESSAGE value="Progress" />
     <MESSAGE value="Implemented SMTP AUTH" />
-    <option name="LAST_COMMIT_MESSAGE" value="Implemented SMTP AUTH" />
+    <MESSAGE value="Better context and connection handling" />
+    <option name="LAST_COMMIT_MESSAGE" value="Better context and connection handling" />
   </component>
   <component name="VgoProject">
     <integration-enabled>true</integration-enabled>
diff --git a/README.md b/README.md
index 1109df4..dd3ff2d 100644
--- a/README.md
+++ b/README.md
@@ -8,7 +8,24 @@ full-fledged mail library.
 
 **This library is "WIP" an should not be considered "production ready", yet.**
 
-go-mail follows idiomatic Go style and best practice.
+go-mail follows idiomatic Go style and best practice. It's only dependency is the Go Standard Library.
+It combines a lot of functionality from the standard library to give easy and convenient access to
+mail and SMTP related tasks.
+
+## Features
+Some of the features of this library:
+* [X] Only Standard Library dependant
+* [X] Modern, idiotmatic Go
+* [X] SSL/TLS support
+* [X] StartTLS support with different policies
+* [X] Makes use of contexts for a better control flow and timeout/cancelation handling
+* [X] SMTP Auth support (LOGIN, PLAIN, CRAM-MD5, DIGEST-MD5)
+* [X] RFC5322 compliant mail address validation
+* [X] Support for common mail header field generation (Message-ID, Date, Bulk-Precedence, etc.)
+* [X] Reusing the same SMTP connection to send multiple mails
+* [ ] Support for different encodings
+* [ ] Support for attachments
+* [ ] Go template support
 
 ## Example
 ```go
@@ -30,17 +47,11 @@ func main() {
 		fmt.Printf("failed to create new client: %s\n", err)
 		os.Exit(1)
 	}
+	defer c.Close()
 
-	ctx, cfn := context.WithCancel(context.Background())
-	defer cfn()
-
-	if err := c.DialWithContext(ctx); err != nil {
+	if err := c.DialAndSend(); err != nil {
 		fmt.Printf("failed to dial: %s\n", err)
 		os.Exit(1)
 	}
-	if err := c.Send(); err != nil {
-		fmt.Printf("failed to send: %s\n", err)
-		os.Exit(1)
-    }
 }
 ```
\ No newline at end of file
diff --git a/client.go b/client.go
index 2b14b6a..bcf23af 100644
--- a/client.go
+++ b/client.go
@@ -220,11 +220,6 @@ func (c *Client) SetSMTPAuthCustom(sa smtp.Auth) {
 	c.sa = sa
 }
 
-// Close closes the connection cto the SMTP server
-func (c *Client) Close() error {
-	return c.sc.Close()
-}
-
 // setDefaultHelo retrieves the current hostname and sets it as HELO/EHLO hostname
 func (c *Client) setDefaultHelo() error {
 	hn, err := os.Hostname()
@@ -301,6 +296,18 @@ func (c *Client) Send() error {
 	return nil
 }
 
+// Close closes the Client connection
+func (c *Client) Close() error {
+	if err := c.checkConn(); err != nil {
+		return err
+	}
+	if err := c.sc.Close(); err != nil {
+		return fmt.Errorf("failed to close SMTP client: %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 {
diff --git a/cmd/main.go b/cmd/main.go
index 9da8ab7..932c549 100644
--- a/cmd/main.go
+++ b/cmd/main.go
@@ -16,20 +16,31 @@ func main() {
 	tu := os.Getenv("TEST_USER")
 	tp := os.Getenv("TEST_PASS")
 
+	m := mail.NewMsg()
+	if err := m.From(`Winni Neessen <wn@neessen.net>`); err != nil {
+		fmt.Printf("failed to set FROM addres: %s", err)
+		os.Exit(1)
+	}
+	m.ToIgnoreInvalid("test@test.de", "foo@bar.de", "blubb@blah.com")
+	m.CcIgnoreInvalid("cc@test.de", "bar.de", "cc@blah.com")
+	m.BccIgnoreInvalid("bcc@test.de", "bcc@blah.com")
+	m.SetMessageID()
+	m.SetDate()
+	m.SetBulk()
+	m.Header()
+
 	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)
 	}
-
-	m := mail.NewMsg()
-	m.From("wn@neessen.net")
-	m.To("test@test.de", "foo@bar.de", "blubb@blah.com")
-	m.Cc("cc@test.de", "cc@bar.de", "cc@blah.com")
-	m.SetMessageID()
-	m.SetBulk()
-	m.Header()
+	defer func() {
+		if err := c.Close(); err != nil {
+			fmt.Printf("failed to close: %s\n", err)
+			os.Exit(1)
+		}
+	}()
 
 	if err := c.DialAndSend(); err != nil {
 		fmt.Printf("failed to dial: %s\n", err)
diff --git a/header.go b/header.go
index b84651b..4a1475d 100644
--- a/header.go
+++ b/header.go
@@ -1,22 +1,13 @@
 package mail
 
-// Header represents a mail header field name
+// Header represents a generic mail header field name
 type Header string
 
-// List of common header field names
+// AddrHeader represents a address related mail Header field name
+type AddrHeader string
+
+// List of common generic header field names
 const (
-	// HeaderFrom is the "From" header field
-	HeaderFrom Header = "From"
-
-	// HeaderTo is the "Receipient" header field
-	HeaderTo Header = "To"
-
-	// HeaderCc is the "Carbon Copy" header field
-	HeaderCc Header = "Cc"
-
-	// HeaderPrecedence is the "Precedence" header field
-	HeaderPrecedence Header = "Precedence"
-
 	// HeaderDate represents the "Date" field
 	// See: https://www.rfc-editor.org/rfc/rfc822#section-5.1
 	HeaderDate Header = "Date"
@@ -24,4 +15,25 @@ const (
 	// HeaderMessageID represents the "Message-ID" field for message identification
 	// See: https://www.rfc-editor.org/rfc/rfc1036#section-2.1.5
 	HeaderMessageID Header = "Message-ID"
+
+	// HeaderPrecedence is the "Precedence" genHeader field
+	HeaderPrecedence Header = "Precedence"
+
+	// HeaderSubject is the "Subject" genHeader field
+	HeaderSubject Header = "Subject"
+)
+
+// List of common generic header field names
+const (
+	// HeaderBcc is the "Blind Carbon Copy" genHeader field
+	HeaderBcc AddrHeader = "Bcc"
+
+	// HeaderCc is the "Carbon Copy" genHeader field
+	HeaderCc AddrHeader = "Cc"
+
+	// HeaderFrom is the "From" genHeader field
+	HeaderFrom AddrHeader = "From"
+
+	// HeaderTo is the "Receipient" genHeader field
+	HeaderTo AddrHeader = "To"
 )
diff --git a/mailmsg.go b/mailmsg.go
index 852ed94..19b7009 100644
--- a/mailmsg.go
+++ b/mailmsg.go
@@ -3,6 +3,7 @@ package mail
 import (
 	"fmt"
 	"math/rand"
+	"net/mail"
 	"os"
 	"time"
 )
@@ -15,42 +16,97 @@ type Msg struct {
 	// encoder represents a mime.WordEncoder from the std lib
 	//encoder mime.WordEncoder
 
-	// header is a slice of strings that the different mail header fields
-	header map[Header][]string
+	// genHeader is a slice of strings that the different generic mail Header fields
+	genHeader map[Header][]string
+
+	// addrHeader is a slice of strings that the different mail AddrHeader fields
+	addrHeader map[AddrHeader][]*mail.Address
 }
 
 // NewMsg returns a new Msg pointer
 func NewMsg() *Msg {
 	m := &Msg{
-		charset: "UTF-8",
-		header:  make(map[Header][]string),
+		charset:    "UTF-8",
+		genHeader:  make(map[Header][]string),
+		addrHeader: make(map[AddrHeader][]*mail.Address),
 	}
 	return m
 }
 
-// SetHeader sets a header field of the Msg
+// SetHeader sets a generic header field of the Msg
 func (m *Msg) SetHeader(h Header, v ...string) {
+	m.genHeader[h] = v
+}
+
+// SetAddrHeader sets an address related header field of the Msg
+func (m *Msg) SetAddrHeader(h AddrHeader, v ...string) error {
+	var al []*mail.Address
+	for _, av := range v {
+		a, err := mail.ParseAddress(av)
+		if err != nil {
+			return fmt.Errorf("failed to parse mail address header %q: %w", av, err)
+		}
+		al = append(al, a)
+	}
 	switch h {
 	case HeaderFrom:
-		m.header[h] = []string{v[0]}
+		m.addrHeader[h] = []*mail.Address{al[0]}
 	default:
-		m.header[h] = v
+		m.addrHeader[h] = al
 	}
+	return nil
 }
 
-// From sets the From: address of the Msg
-func (m *Msg) From(f string) {
-	m.SetHeader(HeaderFrom, f)
+// SetAddrHeaderIgnoreInvalid sets an address related header field of the Msg and ignores invalid address
+// in the validation process
+func (m *Msg) SetAddrHeaderIgnoreInvalid(h AddrHeader, v ...string) {
+	var al []*mail.Address
+	for _, av := range v {
+		a, err := mail.ParseAddress(av)
+		if err != nil {
+			continue
+		}
+		al = append(al, a)
+	}
+	m.addrHeader[h] = al
 }
 
-// To sets the To: addresses of the Msg
-func (m *Msg) To(t ...string) {
-	m.SetHeader(HeaderTo, t...)
+// From takes and validates a given mail address and sets it as "From" genHeader of the Msg
+func (m *Msg) From(f string) error {
+	return m.SetAddrHeader(HeaderFrom, f)
 }
 
-// Cc sets the Cc: addresses of the Msg
-func (m *Msg) Cc(c ...string) {
-	m.SetHeader(HeaderCc, c...)
+// To takes and validates a given mail address list sets the To: addresses of the Msg
+func (m *Msg) To(t ...string) error {
+	return m.SetAddrHeader(HeaderTo, t...)
+}
+
+// ToIgnoreInvalid takes and validates a given mail address list sets the To: addresses of the Msg
+// Any provided address that is not RFC5322 compliant, will be ignored
+func (m *Msg) ToIgnoreInvalid(t ...string) {
+	m.SetAddrHeaderIgnoreInvalid(HeaderTo, t...)
+}
+
+// Cc takes and validates a given mail address list sets the Cc: addresses of the Msg
+func (m *Msg) Cc(c ...string) error {
+	return m.SetAddrHeader(HeaderCc, c...)
+}
+
+// CcIgnoreInvalid takes and validates a given mail address list sets the Cc: addresses of the Msg
+// Any provided address that is not RFC5322 compliant, will be ignored
+func (m *Msg) CcIgnoreInvalid(c ...string) {
+	m.SetAddrHeaderIgnoreInvalid(HeaderCc, c...)
+}
+
+// Bcc takes and validates a given mail address list sets the Bcc: addresses of the Msg
+func (m *Msg) Bcc(b ...string) error {
+	return m.SetAddrHeader(HeaderBcc, b...)
+}
+
+// BccIgnoreInvalid takes and validates a given mail address list sets the Bcc: addresses of the Msg
+// Any provided address that is not RFC5322 compliant, will be ignored
+func (m *Msg) BccIgnoreInvalid(b ...string) {
+	m.SetAddrHeaderIgnoreInvalid(HeaderBcc, b...)
 }
 
 // SetMessageID generates a random message id for the mail
@@ -73,16 +129,23 @@ func (m *Msg) SetMessageIDWithValue(v string) {
 	m.SetHeader(HeaderMessageID, v)
 }
 
-// SetBulk sets the "Precedence: bulk" header which is recommended for
+// SetBulk sets the "Precedence: bulk" genHeader 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")
 }
 
+// SetDate sets the Date genHeader field to the current time in a valid format
+func (m *Msg) SetDate() {
+	ts := time.Now().Format(time.RFC1123Z)
+	m.SetHeader(HeaderDate, ts)
+}
+
 // 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)
+	fmt.Printf("Address header: %+v\n", m.addrHeader)
+	fmt.Printf("Generic header: %+v\n", m.genHeader)
 
 }