feat: email linking

1 files changed, 281 insertions, 0 deletions

diff --git a/internal/mailer/mailer.go b/internal/mailer/mailer.go
new file mode 100644
index 0000000..450b818
--- /dev/null
+++ b/internal/mailer/mailer.go
@@ -0,0 +1,281 @@
+package mailer
+
+import (
+	"crypto/rand"
+	"database/sql"
+	"encoding/base64"
+	"encoding/binary"
+	"fmt"
+	"log/slog"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/SayaAndy/saya-today-web/internal/templatemanager"
+	"github.com/SayaAndy/saya-today-web/locale"
+	"github.com/dgraph-io/ristretto/v2"
+	"github.com/gofiber/fiber/v2"
+	"github.com/wneessen/go-mail"
+	"golang.org/x/crypto/argon2"
+)
+
+type Mailer struct {
+	verificationCodes *ristretto.Cache[uint64, string]
+	db                *sql.DB
+	tm                *templatemanager.TemplateManager
+	mailClient        *mail.Client
+	clientHost        string
+	mailAddress       string
+	publicName        string
+	salt              []byte
+
+	lostMailMap map[string]struct {
+		Dur        time.Duration
+		End        time.Time
+		CodeExpiry time.Time
+	}
+	lostMailMapMutex sync.RWMutex
+
+	hashMap      map[string][]byte
+	hashMapMutex sync.RWMutex
+
+	l map[string]*locale.LocaleConfig
+}
+
+func NewMailer(db *sql.DB, clientHost string, mailHost string, publicName string, mailAddress string, username string, password string, salt []byte, localization map[string]*locale.LocaleConfig) (*Mailer, error) {
+	verificationCodes, err := ristretto.NewCache(&ristretto.Config[uint64, string]{
+		NumCounters:            10000,
+		MaxCost:                1 << 20, // 1 MB
+		BufferItems:            64,
+		TtlTickerDurationInSec: 3600,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("fail to initialize cache for verification codes: %w", err)
+	}
+
+	tm, err := templatemanager.NewTemplateManager(templatemanager.TemplateManagerTemplates{
+		Name:  "new-post",
+		Files: []string{"views/layouts/general-mail.html", "views/messages/new-post.html"},
+	}, templatemanager.TemplateManagerTemplates{
+		Name:  "verify-email",
+		Files: []string{"views/layouts/general-mail.html", "views/messages/verify-email.html"},
+	})
+	if err != nil {
+		return nil, fmt.Errorf("fail to initialize template manager for message templating: %w", err)
+	}
+
+	mailClient, err := mail.NewClient(mailHost,
+		mail.WithSMTPAuth(mail.SMTPAuthAutoDiscover), mail.WithTLSPortPolicy(mail.TLSMandatory),
+		mail.WithUsername(username), mail.WithPassword(password),
+	)
+	if err != nil {
+		return nil, fmt.Errorf("fail to initialize mail client: %w", err)
+	}
+
+	return &Mailer{
+		verificationCodes: verificationCodes,
+		db:                db,
+		clientHost:        clientHost,
+		tm:                tm,
+		mailClient:        mailClient,
+		mailAddress:       mailAddress,
+		publicName:        publicName,
+		salt:              salt,
+		hashMap:           make(map[string][]byte),
+		lostMailMap: make(map[string]struct {
+			Dur        time.Duration
+			End        time.Time
+			CodeExpiry time.Time
+		}, 0),
+		l: localization}, nil
+}
+
+func (m *Mailer) GetHash(id string) []byte {
+	m.hashMapMutex.RLock()
+	if val, ok := m.hashMap[id]; ok {
+		m.hashMapMutex.RUnlock()
+		slog.Debug("gave an old hash", slog.String("hash", base64.RawStdEncoding.EncodeToString(val)))
+		return val
+	}
+	m.hashMapMutex.RUnlock()
+
+	m.hashMapMutex.Lock()
+	defer m.hashMapMutex.Unlock()
+
+	if val, ok := m.hashMap[id]; ok {
+		slog.Debug("gave a newly generated hash", slog.String("hash", base64.RawStdEncoding.EncodeToString(val)))
+		return val
+	}
+
+	m.hashMap[id] = argon2.IDKey([]byte(id), m.salt, 1, 64*1024, 4, 32)
+	slog.Debug("generated hash", slog.String("hash", base64.RawStdEncoding.EncodeToString(m.hashMap[id])))
+	return m.hashMap[id]
+}
+
+func (m *Mailer) IsAllowedToRetryVerification(userId string) (retryAllowed bool, whenAllowed time.Time, codeExpiry time.Time) {
+	m.lostMailMapMutex.RLock()
+	defer m.lostMailMapMutex.RUnlock()
+	previous, ok := m.lostMailMap[userId]
+	if ok && previous.End.After(time.Now()) {
+		return false, previous.End, previous.CodeExpiry
+	}
+	return true, time.Time{}, previous.CodeExpiry
+}
+
+func (m *Mailer) MailIsTaken(email string) (bool, error) {
+	tx, err := m.db.Begin()
+	if err != nil {
+		return false, fmt.Errorf("failed to initialize transaction with db: %s", err)
+	}
+
+	var rows *sql.Rows
+	if rows, err = tx.Query(`SELECT email FROM user_email_table WHERE email=? LIMIT 1;`, email); err != nil {
+		tx.Rollback()
+		return false, fmt.Errorf("failed to query user-email settings in db: %s", err)
+	}
+	defer tx.Commit()
+	defer rows.Close()
+
+	return rows.Next(), nil
+}
+
+func (m *Mailer) GetInfo(userId string) (email string, lang string, err error) {
+	hash := m.GetHash(userId)
+
+	tx, err := m.db.Begin()
+	if err != nil {
+		return "", "", fmt.Errorf("failed to initialize transaction with db: %s", err)
+	}
+
+	var rows *sql.Rows
+	if rows, err = tx.Query(`SELECT email, lang FROM user_email_table WHERE user_id=? LIMIT 1;`, hash); err != nil {
+		tx.Rollback()
+		return "", "", fmt.Errorf("failed to query user-email settings in db: %s", err)
+	}
+	defer tx.Commit()
+	defer rows.Close()
+
+	if !rows.Next() {
+		return "", "", nil
+	}
+
+	if err = rows.Scan(&email, &lang); err != nil {
+		return "", "", fmt.Errorf("failed to scan the result from user-email settings query: %s", err)
+	}
+	return
+}
+
+func (m *Mailer) SendVerificationCode(userId string, address string, lang string) error {
+	message := mail.NewMsg()
+
+	if err := message.EnvelopeFrom(m.mailAddress); err != nil {
+		return fmt.Errorf("failed to set ENVELOPE FROM address: %w", err)
+	}
+	if err := message.FromFormat(m.publicName, m.mailAddress); err != nil {
+		return fmt.Errorf("failed to set formatted FROM address: %w", err)
+	}
+	if err := message.To(address); err != nil {
+		return fmt.Errorf("failed to set TO address: %w", err)
+	}
+
+	message.SetMessageID()
+	message.SetDate()
+	message.SetBulk()
+
+	dur := 1 * time.Minute
+	m.lostMailMapMutex.Lock()
+	if previous, ok := m.lostMailMap[userId]; ok {
+		if time.Now().Before(previous.End) {
+			m.lostMailMapMutex.Unlock()
+			return fmt.Errorf("user is not allowed to send another verification code until %s", previous.End)
+		}
+		dur = 2 * m.lostMailMap[userId].Dur
+	}
+	m.lostMailMap[userId] = struct {
+		Dur        time.Duration
+		End        time.Time
+		CodeExpiry time.Time
+	}{Dur: dur, End: time.Now().Add(dur), CodeExpiry: time.Now().Add(time.Hour)}
+	m.lostMailMapMutex.Unlock()
+
+	verificationCodeBytes := make([]byte, 8)
+	rand.Read(verificationCodeBytes)
+	verificationCode := binary.LittleEndian.Uint64(verificationCodeBytes)
+
+	verificationInfo := fmt.Sprintf("%s.%s", base64.RawStdEncoding.EncodeToString([]byte(userId)), base64.RawStdEncoding.EncodeToString([]byte(address)))
+	m.verificationCodes.Set(verificationCode, verificationInfo, int64(len(verificationInfo)+8))
+
+	message.Subject(m.l[lang].Mail.VerifyEmail.Subject)
+
+	msg, err := m.tm.Render("verify-email", fiber.Map{
+		"L":                m.l[lang],
+		"Lang":             lang,
+		"VerificationCode": fmt.Sprintf("%X", verificationCode),
+		"ClientHost":       m.clientHost,
+	})
+	if err != nil {
+		return fmt.Errorf("failed to render message body: %w", err)
+	}
+
+	message.SetBodyString(mail.TypeTextHTML, string(msg))
+	if err := m.mailClient.DialAndSend(message); err != nil {
+		return fmt.Errorf("failed to send verification code message: %w", err)
+	}
+	slog.Debug("verification code message successfully delivered", slog.String("address", address), slog.String("user_id", userId))
+	return nil
+}
+
+func (m *Mailer) Verify(verificationCodeEncoded string, lang string) error {
+	verificationCode, err := strconv.ParseUint(verificationCodeEncoded, 16, 64)
+	if err != nil {
+		return fmt.Errorf("failed to decode verification code from 8-byte hex: %w", err)
+	}
+
+	verificationInfo, _ := m.verificationCodes.Get(verificationCode)
+	if verificationInfo == "" {
+		return fmt.Errorf("failed to get verification info by its code (might be absent, might be empty)")
+	}
+
+	verificationSegments := strings.Split(verificationInfo, ".")
+	if len(verificationSegments) != 2 {
+		m.verificationCodes.Del(verificationCode)
+		return fmt.Errorf("invalid format of verification info: expected %d segments, got %d", 2, len(verificationSegments))
+	}
+
+	userId, err := base64.RawStdEncoding.DecodeString(verificationSegments[0])
+	if err != nil {
+		m.verificationCodes.Del(verificationCode)
+		delete(m.lostMailMap, verificationSegments[0])
+		return fmt.Errorf("could not decode user id: %s", err)
+	}
+
+	address, err := base64.RawStdEncoding.DecodeString(verificationSegments[1])
+	if err != nil {
+		m.verificationCodes.Del(verificationCode)
+		delete(m.lostMailMap, verificationSegments[0])
+		return fmt.Errorf("could not decode address: %s", err)
+	}
+
+	tx, err := m.db.Begin()
+	if err != nil {
+		return fmt.Errorf("failed to initialize transaction with db: %s", err)
+	}
+
+	if _, err = tx.Exec(`INSERT INTO user_email_table(user_id, email, lang) VALUES(?, ?, ?)
+  ON CONFLICT(user_id) DO UPDATE SET
+  	email=excluded.email,
+	lang=excluded.lang;`, m.GetHash(string(userId)), address, lang); err != nil {
+		tx.Rollback()
+		return fmt.Errorf("failed to configure user-email settings in db: %s", err)
+	}
+
+	if err = tx.Commit(); err != nil {
+		tx.Rollback()
+		return fmt.Errorf("failed to commit transaction to db: %s", err)
+	}
+
+	m.verificationCodes.Del(verificationCode)
+	delete(m.lostMailMap, verificationSegments[0])
+	return nil
+}