Send mailing list emails

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

pkg/mailman/token.go

@@ -0,0 +1,86 @@
+// Copyright (c) 2025 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package mailman
+
+import (
+	"fmt"
+	"time"
+
+	"go.probo.inc/probo/pkg/gid"
+	"go.probo.inc/probo/pkg/mail"
+	"go.probo.inc/probo/pkg/statelesstoken"
+)
+
+const (
+	TokenTypeUnsubscribe = "mailing_list_unsubscribe"
+	TokenTypeConfirm     = "mailing_list_confirm_subscription"
+
+	unsubscribeTokenExpiry = 365 * 24 * time.Hour
+	confirmTokenExpiry     = 15 * 24 * time.Hour
+)
+
+type UnsubscribeTokenData struct {
+	MailingListID gid.GID   `json:"m"`
+	Email         mail.Addr `json:"e"`
+}
+
+func newUnsubscribeToken(secret string, mailingListID gid.GID, recipientEmail mail.Addr) (string, error) {
+	return statelesstoken.NewToken(
+		secret,
+		TokenTypeUnsubscribe,
+		unsubscribeTokenExpiry,
+		UnsubscribeTokenData{
+			MailingListID: mailingListID,
+			Email:         recipientEmail,
+		},
+	)
+}
+
+func ValidateUnsubscribeToken(secret, tokenString string) (*UnsubscribeTokenData, error) {
+	payload, err := statelesstoken.ValidateToken[UnsubscribeTokenData](secret, TokenTypeUnsubscribe, tokenString)
+	if err != nil {
+		return nil, fmt.Errorf("cannot validate unsubscribe token: %w", err)
+	}
+
+	return &payload.Data, nil
+}
+
+type ConfirmTokenData struct {
+	MailingListID gid.GID   `json:"m"`
+	Email         mail.Addr `json:"e"`
+}
+
+func newConfirmToken(secret string, mailingListID gid.GID, recipientEmail mail.Addr) (string, error) {
+	return statelesstoken.NewToken(
+		secret,
+		TokenTypeConfirm,
+		confirmTokenExpiry,
+		ConfirmTokenData{
+			MailingListID: mailingListID,
+			Email:         recipientEmail,
+		},
+	)
+}
+
+// ValidateConfirmToken validates a subscription confirmation token and returns
+// the embedded payload. Exported so the HTTP handler can use it.
+func ValidateConfirmToken(secret, tokenString string) (*ConfirmTokenData, error) {
+	payload, err := statelesstoken.ValidateToken[ConfirmTokenData](secret, TokenTypeConfirm, tokenString)
+	if err != nil {
+		return nil, fmt.Errorf("cannot validate confirm token: %w", err)
+	}
+
+	return &payload.Data, nil
+}