Add printer driver for debug purposes (#15)

cmd/relay/main.go

@@ -6,13 +6,18 @@ import (
 	"time"
 
 	smtp "github.com/emersion/go-smtp"
+	validation "github.com/go-ozzo/ozzo-validation/v4"
+	"github.com/go-ozzo/ozzo-validation/v4/is"
 	"github.com/kelseyhightower/envconfig"
 	mg "github.com/mailgun/mailgun-go/v4"
+	"github.com/pkg/errors"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	log "github.com/sirupsen/logrus"
 	"golang.org/x/sync/errgroup"
 
+	"github.com/teran/relay/driver"
 	"github.com/teran/relay/driver/mailgun"
+	"github.com/teran/relay/driver/printer"
 	smtpWrapper "github.com/teran/relay/smtp"
 )
 
@@ -24,20 +29,34 @@ var (
 type config struct {
 	LogLevel          log.Level `envconfig:"LOG_LEVEL" default:"INFO"`
 	Addr              string    `envconfig:"ADDR" default:":25"`
+	Driver            string    `envconfig:"DRIVER" required:"true"`
 	AllowInsecureAuth bool      `envconfig:"ALLOW_INSECURE_AUTH"`
 	AuthDisabled      bool      `envconfig:"AUTH_DISABLED"`
 	Domain            string    `envconfig:"DOMAIN" required:"true"`
-	MailgunAPIKey     string    `envconfig:"MAILGUN_API_KEY" required:"true"`
-	MailgunURL        string    `envconfig:"MAILGUN_URL" required:"true"`
+	MailgunAPIKey     string    `envconfig:"MAILGUN_API_KEY"`
+	MailgunURL        string    `envconfig:"MAILGUN_URL"`
 	MaxMessageBytes   int64     `default:"1048576" envconfig:"MAX_MESSAGE_BYTES"`
 	MaxRecipients     int       `default:"50" envconfig:"MAX_RECIPIENTS"`
 	MetricsAddr       string    `envconfig:"METRICS_ADDR" default:":8081" `
 }
 
+func (c config) Validate() error {
+	return validation.ValidateStruct(&c,
+		validation.Field(&c.Driver, validation.Required, validation.In("mailgun", "printer")),
+		validation.Field(&c.Domain, validation.Required, is.Domain),
+		validation.Field(&c.MailgunAPIKey, validation.When(c.Driver == "mailgun", validation.Required)),
+		validation.Field(&c.MailgunURL, validation.When(c.Driver == "mailgun", validation.Required, is.URL)),
+	)
+}
+
 func main() {
 	var cfg config
 	envconfig.MustProcess("RELAY", &cfg)
 
+	if err := cfg.Validate(); err != nil {
+		panic(err)
+	}
+
 	ctx := context.Background()
 
 	log.SetLevel(cfg.LogLevel)
@@ -51,10 +70,11 @@ func main() {
 		"build_timestamp": buildTimestamp,
 	}).Infof("initializing application")
 
-	mgCli := mg.NewMailgun(cfg.Domain, cfg.MailgunAPIKey)
-	mgCli.SetAPIBase(cfg.MailgunURL)
+	dr, err := newDriver(cfg)
+	if err != nil {
+		panic(err)
+	}
 
-	dr := mailgun.New(mgCli)
 	be := smtpWrapper.NewBackend(ctx, dr)
 
 	s := smtp.NewServer(be)
@@ -82,3 +102,19 @@ func main() {
 		panic(err)
 	}
 }
+
+func newDriver(cfg config) (driver.Driver, error) {
+	log.Tracef("mailing driver `%s` requested ...", cfg.Driver)
+
+	switch cfg.Driver {
+	case "mailgun":
+		mgCli := mg.NewMailgun(cfg.Domain, cfg.MailgunAPIKey)
+		mgCli.SetAPIBase(cfg.MailgunURL)
+
+		return mailgun.New(mgCli), nil
+	case "printer":
+		return printer.New(), nil
+	default:
+		return nil, errors.Errorf("unexpected driver: `%s`", cfg.Driver)
+	}
+}

driver/mailgun/mailgun.go

@@ -11,6 +11,8 @@ import (
 	"github.com/teran/relay/driver"
 )
 
+var _ driver.Driver = (*mailgun)(nil)
+
 type MailgunImpl interface {
 	NewMIMEMessage(body io.ReadCloser, to ...string) *mg.Message
 	Send(ctx context.Context, m *mg.Message) (string, string, error)

driver/printer/printer.go

@@ -0,0 +1,33 @@
+package printer
+
+import (
+	"context"
+	"io"
+
+	log "github.com/sirupsen/logrus"
+	"github.com/teran/relay/driver"
+)
+
+var _ driver.Driver = (*printer)(nil)
+
+type printer struct{}
+
+func New() driver.Driver {
+	return &printer{}
+}
+
+func (u *printer) Send(ctx context.Context, from string, to []string, r io.Reader) error {
+	message, err := io.ReadAll(r)
+	if err != nil {
+		return err
+	}
+
+	log.WithFields(log.Fields{
+		"driver":  "printer",
+		"from":    from,
+		"to":      to,
+		"message": string(message),
+	}).Infof("Fake sending email")
+
+	return nil
+}

go.mod

@@ -4,6 +4,7 @@ go 1.22.4
 
 require (
 	github.com/emersion/go-smtp v0.21.2
+	github.com/go-ozzo/ozzo-validation/v4 v4.3.0
 	github.com/kelseyhightower/envconfig v1.4.0
 	github.com/mailgun/mailgun-go/v4 v4.12.0
 	github.com/pkg/errors v0.9.1
@@ -14,6 +15,7 @@ require (
 )
 
 require (
+	github.com/asaskevich/govalidator v0.0.0-20200108200545-475eaeb16496 // indirect
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cespare/xxhash/v2 v2.2.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect

go.sum

@@ -1,3 +1,5 @@
+github.com/asaskevich/govalidator v0.0.0-20200108200545-475eaeb16496 h1:zV3ejI06GQ59hwDQAvmK1qxOQGB3WuVTRoY0okPTAv0=
+github.com/asaskevich/govalidator v0.0.0-20200108200545-475eaeb16496/go.mod h1:oGkLhpf+kjZl6xBf758TQhh5XrAeiJv/7FRz/2spLIg=
 github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/cespare/xxhash/v2 v2.2.0 h1:DC2CZ1Ep5Y4k3ZQ899DldepgrayRUGE6BBZ/cd9Cj44=
@@ -20,6 +22,8 @@ github.com/facebookgo/subset v0.0.0-20200203212716-c811ad88dec4 h1:7HZCaLC5+BZpm
 github.com/facebookgo/subset v0.0.0-20200203212716-c811ad88dec4/go.mod h1:5tD+neXqOorC30/tWg0LCSkrqj/AR6gu8yY8/fpw1q0=
 github.com/go-chi/chi/v5 v5.0.8 h1:lD+NLqFcAi1ovnVZpsnObHGW4xb4J8lNmoYVfECH1Y0=
 github.com/go-chi/chi/v5 v5.0.8/go.mod h1:DslCQbL2OYiznFReuXYUmQ2hGd1aDpCnlMNITLSKoi8=
+github.com/go-ozzo/ozzo-validation/v4 v4.3.0 h1:byhDUpfEwjsVQb1vBunvIjh2BHQ9ead57VkAEY4V+Es=
+github.com/go-ozzo/ozzo-validation/v4 v4.3.0/go.mod h1:2NKgrcHl3z6cJs+3Oo940FPRiTzuqKbvfrL2RxCj6Ew=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
@@ -61,6 +65,7 @@ github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+
 github.com/stretchr/objx v0.5.2 h1:xuMeJ0Sdp5ZMRXx/aWO6RZxdr3beISkG5/G/aIRr3pY=
 github.com/stretchr/objx v0.5.2/go.mod h1:FRsXN1f5AsAjCGJKqEizvkpNtU+EGNCLh3NxZ/8L+MA=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
@@ -74,6 +79,7 @@ google.golang.org/protobuf v1.33.0/go.mod h1:c6P6GXX6sHbq/GpV6MGZEdwhWPcYBgnhAHh
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=