notification: Hub fan-out + log writer

internal/notification/hub.go

@@ -0,0 +1,187 @@
+package notification
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/hex"
+	"encoding/json"
+	"log/slog"
+	"sync"
+	"time"
+
+	"gitea.dcglab.co.uk/steve/restic-manager/internal/crypto"
+	"gitea.dcglab.co.uk/steve/restic-manager/internal/store"
+)
+
+// Hub fans Payload events out to every enabled channel and persists
+// the result to notification_log. One Hub per process; thread-safe.
+type Hub struct {
+	store       *store.Store
+	aead        *crypto.AEAD
+	baseURL     string // e.g. https://restic-manager.example
+	msgIDDomain string // hostname extracted from baseURL for SMTP Message-ID
+}
+
+// NewHub constructs a Hub. baseURL is the public root of the server
+// (used to build /alerts/<id> links and the SMTP Message-ID domain).
+func NewHub(st *store.Store, aead *crypto.AEAD, baseURL string) *Hub {
+	return &Hub{
+		store:       st,
+		aead:        aead,
+		baseURL:     baseURL,
+		msgIDDomain: extractDomain(baseURL),
+	}
+}
+
+// Dispatch fans out to every enabled channel. Best-effort — failures
+// are logged to notification_log but do not propagate to the caller.
+// Each channel runs in its own goroutine; Dispatch returns only when
+// all goroutines have settled, so the caller can block briefly for
+// the test-button case.
+func (h *Hub) Dispatch(ctx context.Context, p Payload) {
+	chans, err := h.store.ListEnabledNotificationChannels(ctx)
+	if err != nil {
+		slog.Error("notification: list channels", "err", err)
+		return
+	}
+	// Stamp the alert link if the caller left it empty.
+	if p.Link == "" {
+		p.Link = h.baseURL + "/alerts/" + p.AlertID
+	}
+
+	var wg sync.WaitGroup
+	for _, c := range chans {
+		wg.Add(1)
+		go func(c store.NotificationChannel) {
+			defer wg.Done()
+			h.send(ctx, c, p)
+		}(c)
+	}
+	wg.Wait()
+}
+
+// DispatchOne fires a single channel — used by the "Send test
+// notification" button. Returns the log entry that was persisted so
+// the handler can render the result inline.
+func (h *Hub) DispatchOne(ctx context.Context, channelID string, p Payload) (store.NotificationLogEntry, error) {
+	c, err := h.store.GetNotificationChannel(ctx, channelID)
+	if err != nil {
+		return store.NotificationLogEntry{}, err
+	}
+	if p.Link == "" {
+		p.Link = h.baseURL + "/alerts/" + p.AlertID
+	}
+	return h.send(ctx, *c, p), nil
+}
+
+// send builds the channel impl, delivers the payload, and persists a
+// notification_log row regardless of success or failure.
+func (h *Hub) send(ctx context.Context, c store.NotificationChannel, p Payload) store.NotificationLogEntry {
+	ch, buildErr := h.buildChannel(c)
+	logEntry := store.NotificationLogEntry{
+		ID:        newID(),
+		ChannelID: c.ID,
+		Event:     string(p.Event),
+		FiredAt:   time.Now().UTC(),
+	}
+	if p.AlertID != "" {
+		aid := p.AlertID
+		logEntry.AlertID = &aid
+	}
+	if buildErr != nil {
+		errStr := buildErr.Error()
+		logEntry.OK = false
+		logEntry.Error = &errStr
+		_ = h.store.AppendNotificationLog(ctx, logEntry)
+		return logEntry
+	}
+
+	code, latency, sendErr := ch.Send(ctx, p)
+	statusCode := code
+	latencyMS := int(latency.Milliseconds())
+	logEntry.StatusCode = &statusCode
+	logEntry.LatencyMS = &latencyMS
+	if sendErr != nil {
+		errStr := sendErr.Error()
+		logEntry.OK = false
+		logEntry.Error = &errStr
+	} else {
+		logEntry.OK = true
+	}
+	if err := h.store.AppendNotificationLog(ctx, logEntry); err != nil {
+		slog.Warn("notification: persist log", "err", err)
+	}
+	return logEntry
+}
+
+// buildChannel decrypts the channel config and returns a concrete
+// Channel implementation for the channel's kind.
+func (h *Hub) buildChannel(row store.NotificationChannel) (Channel, error) {
+	plain, err := h.aead.Decrypt(string(row.Config), []byte("notification-channel:"+row.ID))
+	if err != nil {
+		return nil, err
+	}
+	switch row.Kind {
+	case "webhook":
+		var cfg WebhookConfig
+		if err := json.Unmarshal(plain, &cfg); err != nil {
+			return nil, err
+		}
+		return NewWebhookChannel(cfg), nil
+	case "ntfy":
+		var cfg NtfyConfig
+		if err := json.Unmarshal(plain, &cfg); err != nil {
+			return nil, err
+		}
+		dp := ""
+		if row.DefaultPriority != nil {
+			dp = *row.DefaultPriority
+		}
+		return NewNtfyChannel(cfg, dp), nil
+	case "smtp":
+		var cfg SMTPConfig
+		if err := json.Unmarshal(plain, &cfg); err != nil {
+			return nil, err
+		}
+		return NewSMTPChannel(cfg, h.msgIDDomain), nil
+	}
+	return nil, errUnknownKind(row.Kind)
+}
+
+// newID returns a 32-hex-char random identifier for notification_log rows.
+func newID() string {
+	var b [16]byte
+	_, _ = rand.Read(b[:])
+	return hex.EncodeToString(b[:])
+}
+
+// extractDomain strips the scheme and path from baseURL, leaving only
+// the host[:port] component. Used as the right-hand side of SMTP
+// Message-IDs.
+func extractDomain(baseURL string) string {
+	s := baseURL
+	if i := indexOf(s, "://"); i >= 0 {
+		s = s[i+3:]
+	}
+	if i := indexOf(s, "/"); i >= 0 {
+		s = s[:i]
+	}
+	if s == "" {
+		return "restic-manager.local"
+	}
+	return s
+}
+
+// indexOf returns the index of the first occurrence of sub in s, or -1.
+func indexOf(s, sub string) int {
+	for i := 0; i+len(sub) <= len(s); i++ {
+		if s[i:i+len(sub)] == sub {
+			return i
+		}
+	}
+	return -1
+}
+
+type errUnknownKind string
+
+func (e errUnknownKind) Error() string { return "notification: unknown kind: " + string(e) }