feat: welcome erida

Author: fadyat

.gitignore

@@ -1,3 +1,3 @@
-.env
+*.env
 .idea
 .DS_Store

Makefile

@@ -4,4 +4,9 @@ ifneq (,$(wildcard ./.env))
 endif
 
 run:
-	@go run main.go
+	@go run cmd/main.go
+
+integration:
+	@go test -v ./... -tags=integration
+
+

README.md

@@ -0,0 +1,49 @@
+### Erida: Simplifying Internal Cluster Communication
+
+**Erida** is a straightforward SMTP relay server designed for sending internal cluster emails to an authenticated SMTP
+server with seamless Slack integration.
+
+### Email Address Flexibility
+
+Erida supports a variety of email addresses, including common ones like `fadyat@icloud.com` and those associated with
+messaging services, particularly Slack.
+
+For Slack integration, you can use addresses following this syntax:
+
+- User-specific Slack address: `personal.<username>@slack`
+- Channel-specific Slack address: `channel.<channelname>@slack`
+
+It's important to note that both the `username` and `channelname` are case-insensitive, and the bot must have the
+necessary
+permissions to access the specified Slack channels.
+
+### Configuration Made Easy
+
+Configuring Erida is a breeze. All you need to do is set the following environment variables:
+
+- `SMTP_HOST`: SMTP server host
+- `SMTP_PORT`: SMTP server port
+- `SMTP_USER`: SMTP server username
+- `SMTP_PASSWORD`: SMTP server password
+- `SLACK_TOKEN`: Slack bot token
+- `SMTP_TLS` (Optional, default: true): Enable or disable Start TLS usage
+
+For additional variables, refer to the [configuration file](internal/config.go).
+
+### Getting Started
+
+If you're new to configuring the bot, check out the step-by-step guide
+at [Slack Quickstart](https://api.slack.com/start/quickstart).
+
+Ensure that the bot has the necessary permissions, specifically `chat:write`.
+
+### Example Usage
+
+Let's walk through an example. Assume that an external SMTP server is configured to send emails to **Erida** with the
+following addresses: `personal.fadyat@slack`, `channel.general@slack`, and `fadyat@icloud.com`.
+
+The message will be seamlessly delivered to the Slack channel `#general` and the Slack user `@fadyat`, as well as to the
+email address `fadyat@icloud.com`.
+
+**Erida** simplifies internal communication, bridging the gap between email and Slack effortlessly.
+

cmd/main.go

@@ -1,9 +1,9 @@
 package main
 
 import (
+	"github.com/fadyat/erida/internal"
 	"github.com/ilyakaznacheev/cleanenv"
 	"log/slog"
-	"smpt-relay/internal"
 )
 
 func readConfig() (*internal.Config, error) {

cmd/main_test.go

@@ -0,0 +1,77 @@
+//go:build integration
+
+package main
+
+import (
+	"bytes"
+	"context"
+	"github.com/emersion/go-smtp"
+	"github.com/fadyat/erida/internal"
+	"github.com/ilyakaznacheev/cleanenv"
+	"github.com/stretchr/testify/require"
+	"log/slog"
+	"testing"
+	"time"
+)
+
+const (
+	testConfigPath = "../test.env"
+)
+
+func readTestConfig() (*internal.Config, error) {
+	var cfg internal.Config
+	if err := cleanenv.ReadConfig(testConfigPath, &cfg); err != nil {
+		return nil, err
+	}
+
+	return &cfg, nil
+}
+
+// TestRelayFlow is an integration test, that will start a server and send a
+// message to it.
+//
+// Need to run it with `go test -tags=integration ./...`
+//
+// Real Google GMail SMTP server and Slack API are used.
+// Current test doesn't check the correctness of the message, that was sent.
+// It only checks, that the server is able to send a message to the real services.
+func TestRelayFlow(t *testing.T) {
+	cfg, err := readTestConfig()
+	require.NoError(t, err)
+
+	srv := internal.NewServer(cfg)
+	go func() {
+		if err = srv.ListenAndServe(); err != nil {
+			slog.Error("failed to start server: ", err)
+		}
+	}()
+
+	c, err := smtp.Dial(srv.Addr)
+	require.NoError(t, err)
+
+	var (
+		from = "erida@erida.com"
+		to   = []string{
+			"fadyat@icloud.com",
+			"personal.fadyat@slack",
+			"channel.empty@slack",
+		}
+		body = []byte(`Subject: Integration test
+Content-Type: text/plain; charset=UTF-8
+
+Hello, this Erida!
+We are testing the process of sending messages to Slack and GMail,
+using this SMTP server as a relay.
+
+Best regards, Erida
+`)
+	)
+
+	require.NoError(t, c.SendMail(from, to, bytes.NewReader(body)))
+
+	// sleeping for 3 seconds to let the server process the message
+	time.Sleep(3 * time.Second)
+
+	require.NoError(t, c.Quit())
+	require.NoError(t, srv.Shutdown(context.Background()))
+}

go.mod

@@ -1,4 +1,4 @@
-module smpt-relay
+module github.com/fadyat/erida
 
 go 1.21
 
@@ -7,14 +7,18 @@ require (
 	github.com/emersion/go-smtp v0.19.0
 	github.com/ilyakaznacheev/cleanenv v1.5.0
 	github.com/mocktools/go-smtp-mock/v2 v2.1.0
+	github.com/slack-go/slack v0.12.3
 	github.com/stretchr/testify v1.8.4
 )
 
 require (
 	github.com/BurntSushi/toml v1.3.2 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/gorilla/websocket v1.5.1 // indirect
 	github.com/joho/godotenv v1.5.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/stretchr/objx v0.5.0 // indirect
+	golang.org/x/net v0.18.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 	olympos.io/encoding/edn v0.0.0-20201019073823-d3554ca0b0a3 // indirect
 )

go.sum

@@ -8,6 +8,13 @@ github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21 h1:OJyUGMJTzHTd1X
 github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21/go.mod h1:iL2twTeMvZnrg54ZoPDNfJaJaqy0xIQFuBdrLsmspwQ=
 github.com/emersion/go-smtp v0.19.0 h1:iVCDtR2/JY3RpKoaZ7u6I/sb52S3EzfNHO1fAWVHgng=
 github.com/emersion/go-smtp v0.19.0/go.mod h1:qm27SGYgoIPRot6ubfQ/GpiPy/g3PaZAVRxiO/sDUgQ=
+github.com/go-test/deep v1.0.4 h1:u2CU3YKy9I2pmu9pX0eq50wCgjfGIt539SqR7FbHiho=
+github.com/go-test/deep v1.0.4/go.mod h1:wGDj63lr65AM2AQyKZd/NYHGb0R+1RLqB8NKt3aSFNA=
+github.com/google/go-cmp v0.5.7 h1:81/ik6ipDQS2aGcBfIN5dHDB36BwrStyeAQquSYCV4o=
+github.com/google/go-cmp v0.5.7/go.mod h1:n+brtR0CgQNWTVd5ZUFpTBC8YFBDLK/h/bpaJ8/DtOE=
+github.com/gorilla/websocket v1.4.2/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
+github.com/gorilla/websocket v1.5.1 h1:gmztn0JnHVt9JZquRuzLw3g4wouNVzKL15iLr/zn/QY=
+github.com/gorilla/websocket v1.5.1/go.mod h1:x3kM2JMyaluk02fnUJpQuwD2dCS5NDG2ZHL0uE0tcaY=
 github.com/ilyakaznacheev/cleanenv v1.5.0 h1:0VNZXggJE2OYdXE87bfSSwGxeiGt9moSR2lOrsHHvr4=
 github.com/ilyakaznacheev/cleanenv v1.5.0/go.mod h1:a5aDzaJrLCQZsazHol1w8InnDcOX0OColm64SlIi6gk=
 github.com/joho/godotenv v1.5.1 h1:7eLL/+HRGLY0ldzfGMeQkb7vMd0as4CfYvUVzLqw0N0=
@@ -16,14 +23,20 @@ github.com/mocktools/go-smtp-mock/v2 v2.1.0 h1:gGiWqlaMTExk7Id38G2+sWfOelsE+OAqJ
 github.com/mocktools/go-smtp-mock/v2 v2.1.0/go.mod h1:n8aNpDYncZHH/cZHtJKzQyeYT/Dut00RghVM+J1Ed94=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/slack-go/slack v0.12.3 h1:92/dfFU8Q5XP6Wp5rr5/T5JHLM5c5Smtn53fhToAP88=
+github.com/slack-go/slack v0.12.3/go.mod h1:hlGi5oXA+Gt+yWTPP0plCdRKmjsDxecdHxYQdlMQKOw=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
 github.com/stretchr/objx v0.5.0 h1:1zr/of2m5FGMsad5YfcqgdqdWrIhu+EBEJRhR1U7z/c=
 github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
+github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+golang.org/x/net v0.18.0 h1:mIYleuAkSbHh0tCv7RvjL3F6ZVbLjq4+R7zbOn3Kokg=
+golang.org/x/net v0.18.0/go.mod h1:/czyP5RqHAH4odGYxBJ1qz0+CE5WZ+2j1YgoEo8F2jQ=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

internal/client.go

@@ -0,0 +1,106 @@
+package internal
+
+import (
+	"fmt"
+	"github.com/slack-go/slack"
+	"strings"
+)
+
+const (
+	emailRecipient = "email"
+	slackRecipient = "slack"
+
+	personalMessage = "personal."
+	channelMessage  = "channel."
+)
+
+var (
+	operators = map[string]map[string]string{
+		slackRecipient: {
+			personalMessage: "@",
+			channelMessage:  "#",
+		},
+	}
+)
+
+type client interface {
+
+	// proxify is a function, that will be used as a proxy for the data.
+	proxify(from string, to []string, body string) error
+}
+
+func takeUsernames(recipients []string, recipientType string) []string {
+	var usernames = make([]string, 0, len(recipients))
+
+	for _, r := range recipients {
+		at := strings.Split(r, "@")
+		if len(at) != 2 {
+			continue
+		}
+
+		if at[1] != recipientType {
+			continue
+		}
+
+		usernames = append(usernames, convertToRecipientWay(at[0], recipientType))
+	}
+
+	return usernames
+}
+
+func convertToRecipientWay(username string, recipientType string) string {
+	if _, ok := operators[recipientType]; !ok {
+		return username
+	}
+
+	var msgType string
+	switch {
+	case strings.HasPrefix(username, personalMessage):
+		msgType = personalMessage
+	case strings.HasPrefix(username, channelMessage):
+		msgType = channelMessage
+	}
+
+	operator := operators[recipientType][msgType]
+	return operator + strings.TrimPrefix(username, msgType)
+}
+
+func selectClientType(recipient string) (string, error) {
+	at := strings.Split(recipient, "@")
+	if len(at) != 2 {
+		return "", fmt.Errorf("invalid recipient: %s", recipient)
+	}
+
+	domain := at[1]
+	if domain == slackRecipient {
+		return slackRecipient, nil
+	}
+
+	return emailRecipient, nil
+}
+
+func selectClient(clientType string, cfg *Config) (client, error) {
+	switch clientType {
+	case emailRecipient:
+		return newMailClient(cfg)
+	case slackRecipient:
+		return newSlackClient(slack.New(cfg.SlackToken)), nil
+	default:
+		return nil, fmt.Errorf("unknown client type: %s", clientType)
+	}
+}
+
+func groupByClientType(recipients []string) (map[string][]string, error) {
+	groups := make(map[string][]string)
+
+	for _, recipient := range recipients {
+		clientType, err := selectClientType(recipient)
+		if err != nil {
+			return nil, fmt.Errorf("failed to select client type: %w", err)
+		}
+
+		groups[clientType] = append(groups[clientType], recipient)
+	}
+
+	return groups, nil
+}