Ajout d'une newsletter basique

La newsletter effectue une collecte des évènements sur une période de
temps donné et envoi un récapitulatif à l'ensemble des utilisateurs de
Daddy.

Actuellement, sont collectés et présentés:

- Les créations de groupes de travail
- Les créations de dossiers d'aide à la décision
- Les dossiers dont le statut à été modifié et prêt à voté

internal/mail/mailer.go

@@ -0,0 +1,52 @@
+package mail
+
+const (
+	ContentTypeHTML = "text/html"
+	ContentTypeText = "text/plain"
+)
+
+type Option struct {
+	Host               string
+	Port               int
+	User               string
+	Password           string
+	InsecureSkipVerify bool
+	UseStartTLS        bool
+}
+
+type OptionFunc func(*Option)
+
+type Mailer struct {
+	opt *Option
+}
+
+func WithTLS(useStartTLS, insecureSkipVerify bool) OptionFunc {
+	return func(opt *Option) {
+		opt.UseStartTLS = useStartTLS
+		opt.InsecureSkipVerify = insecureSkipVerify
+	}
+}
+
+func WithServer(host string, port int) OptionFunc {
+	return func(opt *Option) {
+		opt.Host = host
+		opt.Port = port
+	}
+}
+
+func WithCredentials(user, password string) OptionFunc {
+	return func(opt *Option) {
+		opt.User = user
+		opt.Password = password
+	}
+}
+
+func NewMailer(funcs ...OptionFunc) *Mailer {
+	opt := &Option{}
+
+	for _, fn := range funcs {
+		fn(opt)
+	}
+
+	return &Mailer{opt}
+}

internal/mail/provider.go

@@ -0,0 +1,11 @@
+package mail
+
+import "gitlab.com/wpetit/goweb/service"
+
+func ServiceProvider(opts ...OptionFunc) service.Provider {
+	mailer := NewMailer(opts...)
+
+	return func(ctn *service.Container) (interface{}, error) {
+		return mailer, nil
+	}
+}

internal/mail/send.go

@@ -0,0 +1,207 @@
+package mail
+
+import (
+	"crypto/tls"
+	"fmt"
+	"math/rand"
+	"net/mail"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/pkg/errors"
+	gomail "gopkg.in/mail.v2"
+)
+
+var (
+	ErrUnexpectedEmailAddressFormat = errors.New("unexpected email address format")
+)
+
+type SendFunc func(*SendOption)
+
+type SendOption struct {
+	Charset           string
+	AddressHeaders    []AddressHeader
+	Headers           []Header
+	Body              Body
+	AlternativeBodies []Body
+}
+
+type AddressHeader struct {
+	Field   string
+	Address string
+	Name    string
+}
+
+type Header struct {
+	Field  string
+	Values []string
+}
+
+type Body struct {
+	Type        string
+	Content     string
+	PartSetting gomail.PartSetting
+}
+
+func WithCharset(charset string) func(*SendOption) {
+	return func(opt *SendOption) {
+		opt.Charset = charset
+	}
+}
+
+func WithSender(address string, name string) func(*SendOption) {
+	return WithAddressHeader("From", address, name)
+}
+
+func WithSubject(subject string) func(*SendOption) {
+	return WithHeader("Subject", subject)
+}
+
+func WithAddressHeader(field, address, name string) func(*SendOption) {
+	return func(opt *SendOption) {
+		opt.AddressHeaders = append(opt.AddressHeaders, AddressHeader{field, address, name})
+	}
+}
+
+func WithHeader(field string, values ...string) func(*SendOption) {
+	return func(opt *SendOption) {
+		opt.Headers = append(opt.Headers, Header{field, values})
+	}
+}
+
+func WithRecipients(addresses ...string) func(*SendOption) {
+	return WithHeader("To", addresses...)
+}
+
+func WithCopies(addresses ...string) func(*SendOption) {
+	return WithHeader("Cc", addresses...)
+}
+
+func WithInvisibleCopies(addresses ...string) func(*SendOption) {
+	return WithHeader("Cci", addresses...)
+}
+
+func WithBody(contentType string, content string, setting gomail.PartSetting) func(*SendOption) {
+	return func(opt *SendOption) {
+		if setting == nil {
+			setting = gomail.SetPartEncoding(gomail.Unencoded)
+		}
+		opt.Body = Body{contentType, content, setting}
+	}
+}
+
+func WithAlternativeBody(contentType string, content string, setting gomail.PartSetting) func(*SendOption) {
+	return func(opt *SendOption) {
+		if setting == nil {
+			setting = gomail.SetPartEncoding(gomail.Unencoded)
+		}
+		opt.AlternativeBodies = append(opt.AlternativeBodies, Body{contentType, content, setting})
+	}
+}
+
+func (m *Mailer) Send(funcs ...SendFunc) error {
+	opt := &SendOption{
+		Charset: "UTF-8",
+		Body: Body{
+			Type:        "text/plain",
+			Content:     "",
+			PartSetting: gomail.SetPartEncoding(gomail.Unencoded),
+		},
+		AddressHeaders:    make([]AddressHeader, 0),
+		Headers:           make([]Header, 0),
+		AlternativeBodies: make([]Body, 0),
+	}
+
+	for _, f := range funcs {
+		f(opt)
+	}
+
+	conn, err := m.openConnection()
+	if err != nil {
+		return errors.Wrap(err, "could not open connection")
+	}
+
+	defer conn.Close()
+
+	message := gomail.NewMessage(gomail.SetCharset(opt.Charset))
+
+	for _, h := range opt.AddressHeaders {
+		message.SetAddressHeader(h.Field, h.Address, h.Name)
+	}
+
+	for _, h := range opt.Headers {
+		message.SetHeader(h.Field, h.Values...)
+	}
+
+	froms := message.GetHeader("From")
+
+	var sendDomain string
+
+	if len(froms) > 0 {
+		sendDomain, err = extractEmailDomain(froms[0])
+		if err != nil {
+			return err
+		}
+	}
+
+	messageID := generateMessageID(sendDomain)
+	message.SetHeader("Message-Id", messageID)
+
+	message.SetBody(opt.Body.Type, opt.Body.Content, opt.Body.PartSetting)
+
+	for _, b := range opt.AlternativeBodies {
+		message.AddAlternative(b.Type, b.Content, b.PartSetting)
+	}
+
+	if err := gomail.Send(conn, message); err != nil {
+		return errors.Wrap(err, "could not send message")
+	}
+
+	return nil
+}
+
+func (m *Mailer) openConnection() (gomail.SendCloser, error) {
+	dialer := gomail.NewDialer(
+		m.opt.Host,
+		m.opt.Port,
+		m.opt.User,
+		m.opt.Password,
+	)
+
+	if m.opt.InsecureSkipVerify {
+		dialer.TLSConfig = &tls.Config{
+			InsecureSkipVerify: true,
+		}
+	}
+
+	conn, err := dialer.Dial()
+	if err != nil {
+		return nil, errors.Wrap(err, "could not dial smtp server")
+	}
+
+	return conn, nil
+}
+
+func extractEmailDomain(email string) (string, error) {
+	address, err := mail.ParseAddress(email)
+	if err != nil {
+		return "", errors.Wrapf(err, "could not parse email address '%s'", email)
+	}
+
+	addressParts := strings.SplitN(address.Address, "@", 2)
+	if len(addressParts) != 2 { // nolint: gomnd
+		return "", errors.WithStack(ErrUnexpectedEmailAddressFormat)
+	}
+
+	domain := addressParts[1]
+
+	return domain, nil
+}
+
+func generateMessageID(domain string) string {
+	// Based on https://www.jwz.org/doc/mid.html
+	timestamp := strconv.FormatInt(time.Now().UnixNano(), 36)
+	random := strconv.FormatInt(rand.Int63(), 36)
+	return fmt.Sprintf("<%s.%s@%s>", timestamp, random, domain)
+}

internal/mail/service.go

@@ -0,0 +1,33 @@
+package mail
+
+import (
+	"github.com/pkg/errors"
+	"gitlab.com/wpetit/goweb/service"
+)
+
+const ServiceName service.Name = "mail"
+
+// From retrieves the mail service in the given container
+func From(container *service.Container) (*Mailer, error) {
+	service, err := container.Service(ServiceName)
+	if err != nil {
+		return nil, errors.Wrapf(err, "error while retrieving '%s' service", ServiceName)
+	}
+
+	srv, ok := service.(*Mailer)
+	if !ok {
+		return nil, errors.Errorf("retrieved service is not a valid '%s' service", ServiceName)
+	}
+
+	return srv, nil
+}
+
+// Must retrieves the mail service in the given container or panic otherwise
+func Must(container *service.Container) *Mailer {
+	srv, err := From(container)
+	if err != nil {
+		panic(err)
+	}
+
+	return srv
+}