notification: add channel senders for email, webhook, and UnifiedPush

Implement ChannelSender interface with three backends:
- EmailSender: reuses existing Mailer, sends Markdown-formatted alerts
- WebhookSender: HTTP POST with JSON payload and optional HMAC signature
- UnifiedPushSender: HTTP POST following the UnifiedPush protocol

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/notification/email_sender.go

@@ -0,0 +1,80 @@
+// This file is part of the happyDomain (R) project.
+// Copyright (c) 2020-2026 happyDomain
+// Authors: Pierre-Olivier Mercier, et al.
+//
+// This program is offered under a commercial and under the AGPL license.
+// For commercial licensing, contact us at <contact@happydomain.org>.
+//
+// For AGPL licensing:
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package notification
+
+import (
+	"fmt"
+	"net/mail"
+	"strings"
+
+	"git.happydns.org/happyDomain/model"
+)
+
+// EmailSender sends notifications via email using the existing Mailer.
+type EmailSender struct {
+	mailer happydns.Mailer
+}
+
+// NewEmailSender creates a new EmailSender.
+func NewEmailSender(mailer happydns.Mailer) *EmailSender {
+	return &EmailSender{mailer: mailer}
+}
+
+func (s *EmailSender) Send(channel *happydns.NotificationChannel, payload *NotificationPayload) error {
+	addr := channel.Config.EmailAddress
+	if addr == "" && payload.User != nil {
+		addr = payload.User.Email
+	}
+	if addr == "" {
+		return fmt.Errorf("no email address configured for channel %s", channel.Id)
+	}
+
+	to := &mail.Address{Address: addr}
+	if payload.User != nil {
+		to.Name = payload.User.Email
+	}
+
+	subject := fmt.Sprintf("[happyDomain] %s: %s", payload.DomainName, payload.NewStatus)
+
+	var body strings.Builder
+	fmt.Fprintf(&body, "## Status Change: %s -> %s\n\n", payload.OldStatus, payload.NewStatus)
+	fmt.Fprintf(&body, "**Domain:** %s\n\n", payload.DomainName)
+	fmt.Fprintf(&body, "**Checker:** %s\n\n", payload.CheckerID)
+
+	if len(payload.States) > 0 {
+		body.WriteString("### Rule Results\n\n")
+		for _, state := range payload.States {
+			fmt.Fprintf(&body, "- **%s** (%s): %s\n", state.Code, state.Status, state.Message)
+		}
+		body.WriteString("\n")
+	}
+
+	if payload.Annotation != "" {
+		fmt.Fprintf(&body, "**Note:** %s\n\n", payload.Annotation)
+	}
+
+	if payload.BaseURL != "" {
+		fmt.Fprintf(&body, "[View in happyDomain](%s)\n", payload.BaseURL)
+	}
+
+	return s.mailer.SendMail(to, subject, body.String())
+}

internal/notification/sender.go

@@ -0,0 +1,44 @@
+// This file is part of the happyDomain (R) project.
+// Copyright (c) 2020-2026 happyDomain
+// Authors: Pierre-Olivier Mercier, et al.
+//
+// This program is offered under a commercial and under the AGPL license.
+// For commercial licensing, contact us at <contact@happydomain.org>.
+//
+// For AGPL licensing:
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package notification
+
+import (
+	"git.happydns.org/happyDomain/model"
+)
+
+// NotificationPayload holds the data passed to channel senders.
+type NotificationPayload struct {
+	User       *happydns.User
+	CheckerID  string
+	Target     happydns.CheckTarget
+	DomainName string
+	OldStatus  happydns.Status
+	NewStatus  happydns.Status
+	States     []happydns.CheckState
+	Annotation string
+	BaseURL    string
+}
+
+// ChannelSender sends a notification through a specific channel type.
+type ChannelSender interface {
+	Send(channel *happydns.NotificationChannel, payload *NotificationPayload) error
+}

internal/notification/unifiedpush_sender.go

@@ -0,0 +1,90 @@
+// This file is part of the happyDomain (R) project.
+// Copyright (c) 2020-2026 happyDomain
+// Authors: Pierre-Olivier Mercier, et al.
+//
+// This program is offered under a commercial and under the AGPL license.
+// For commercial licensing, contact us at <contact@happydomain.org>.
+//
+// For AGPL licensing:
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package notification
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
+
+	"git.happydns.org/happyDomain/model"
+)
+
+// UnifiedPushSender sends notifications via the UnifiedPush protocol.
+type UnifiedPushSender struct {
+	client *http.Client
+}
+
+// NewUnifiedPushSender creates a new UnifiedPushSender.
+func NewUnifiedPushSender() *UnifiedPushSender {
+	return &UnifiedPushSender{
+		client: &http.Client{Timeout: 10 * time.Second},
+	}
+}
+
+func (s *UnifiedPushSender) Send(channel *happydns.NotificationChannel, payload *NotificationPayload) error {
+	if channel.Config.UnifiedPushEndpoint == "" {
+		return fmt.Errorf("no UnifiedPush endpoint configured for channel %s", channel.Id)
+	}
+
+	msg := WebhookPayload{
+		Event:     "status_change",
+		Checker:   payload.CheckerID,
+		Domain:    payload.DomainName,
+		Target:    payload.Target,
+		OldStatus: payload.OldStatus,
+		NewStatus: payload.NewStatus,
+		States:    payload.States,
+		Timestamp: time.Now(),
+	}
+	if payload.BaseURL != "" {
+		msg.DashboardURL = payload.BaseURL
+	}
+
+	body, err := json.Marshal(msg)
+	if err != nil {
+		return fmt.Errorf("marshaling UnifiedPush payload: %w", err)
+	}
+
+	req, err := http.NewRequest(http.MethodPost, channel.Config.UnifiedPushEndpoint, bytes.NewReader(body))
+	if err != nil {
+		return fmt.Errorf("creating UnifiedPush request: %w", err)
+	}
+
+	req.Header.Set("Content-Type", "application/json")
+
+	resp, err := s.client.Do(req)
+	if err != nil {
+		return fmt.Errorf("sending UnifiedPush notification: %w", err)
+	}
+	defer resp.Body.Close()
+	io.Copy(io.Discard, resp.Body)
+
+	if resp.StatusCode >= 300 {
+		return fmt.Errorf("UnifiedPush endpoint returned status %d", resp.StatusCode)
+	}
+
+	return nil
+}

internal/notification/webhook_sender.go

@@ -0,0 +1,118 @@
+// This file is part of the happyDomain (R) project.
+// Copyright (c) 2020-2026 happyDomain
+// Authors: Pierre-Olivier Mercier, et al.
+//
+// This program is offered under a commercial and under the AGPL license.
+// For commercial licensing, contact us at <contact@happydomain.org>.
+//
+// For AGPL licensing:
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package notification
+
+import (
+	"bytes"
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
+
+	"git.happydns.org/happyDomain/model"
+)
+
+// WebhookPayload is the JSON body sent to webhook endpoints.
+type WebhookPayload struct {
+	Event        string              `json:"event"`
+	Checker      string              `json:"checker"`
+	Domain       string              `json:"domain"`
+	Target       happydns.CheckTarget `json:"target"`
+	OldStatus    happydns.Status     `json:"oldStatus"`
+	NewStatus    happydns.Status     `json:"newStatus"`
+	States       []happydns.CheckState `json:"states,omitempty"`
+	Timestamp    time.Time           `json:"timestamp"`
+	DashboardURL string              `json:"dashboardUrl,omitempty"`
+}
+
+// WebhookSender sends notifications via HTTP POST to a configured URL.
+type WebhookSender struct {
+	client *http.Client
+}
+
+// NewWebhookSender creates a new WebhookSender.
+func NewWebhookSender() *WebhookSender {
+	return &WebhookSender{
+		client: &http.Client{Timeout: 10 * time.Second},
+	}
+}
+
+func (s *WebhookSender) Send(channel *happydns.NotificationChannel, payload *NotificationPayload) error {
+	if channel.Config.WebhookURL == "" {
+		return fmt.Errorf("no webhook URL configured for channel %s", channel.Id)
+	}
+
+	whPayload := WebhookPayload{
+		Event:     "status_change",
+		Checker:   payload.CheckerID,
+		Domain:    payload.DomainName,
+		Target:    payload.Target,
+		OldStatus: payload.OldStatus,
+		NewStatus: payload.NewStatus,
+		States:    payload.States,
+		Timestamp: time.Now(),
+	}
+	if payload.BaseURL != "" {
+		whPayload.DashboardURL = payload.BaseURL
+	}
+
+	body, err := json.Marshal(whPayload)
+	if err != nil {
+		return fmt.Errorf("marshaling webhook payload: %w", err)
+	}
+
+	req, err := http.NewRequest(http.MethodPost, channel.Config.WebhookURL, bytes.NewReader(body))
+	if err != nil {
+		return fmt.Errorf("creating webhook request: %w", err)
+	}
+
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("User-Agent", "happyDomain-Notification/1.0")
+
+	for k, v := range channel.Config.WebhookHeaders {
+		req.Header.Set(k, v)
+	}
+
+	if channel.Config.WebhookSecret != "" {
+		mac := hmac.New(sha256.New, []byte(channel.Config.WebhookSecret))
+		mac.Write(body)
+		sig := hex.EncodeToString(mac.Sum(nil))
+		req.Header.Set("X-Happydomain-Signature", "sha256="+sig)
+	}
+
+	resp, err := s.client.Do(req)
+	if err != nil {
+		return fmt.Errorf("sending webhook: %w", err)
+	}
+	defer resp.Body.Close()
+	io.Copy(io.Discard, resp.Body)
+
+	if resp.StatusCode >= 300 {
+		return fmt.Errorf("webhook returned status %d", resp.StatusCode)
+	}
+
+	return nil
+}