notification: ntfy channel

internal/notification/ntfy.go

@@ -0,0 +1,103 @@
+package notification
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
+)
+
+// NtfyConfig is the per-channel JSON shape stored AEAD-encrypted in
+// notification_channels.config.
+type NtfyConfig struct {
+	ServerURL   string `json:"server_url"`
+	Topic       string `json:"topic"`
+	AccessToken string `json:"access_token,omitempty"`
+}
+
+// NtfyChannel delivers alerts to an ntfy server using POST with
+// ntfy-specific headers (Title, Priority, Tags, Click). One instance
+// per configured channel row. Reused across sends — http.Client is
+// goroutine-safe.
+type NtfyChannel struct {
+	cfg             NtfyConfig
+	defaultPriority string // "min"/"low"/"default"/"high"/"urgent" or ""
+	client          *http.Client
+}
+
+// NewNtfyChannel builds an ntfy channel with a 5s http.Client timeout.
+// defaultPriority is the channel-configured fallback when no
+// severity-specific mapping applies; pass "" to use the built-in
+// fallbacks (4 for warning, 3 for everything else).
+func NewNtfyChannel(cfg NtfyConfig, defaultPriority string) *NtfyChannel {
+	if cfg.ServerURL == "" {
+		cfg.ServerURL = "https://ntfy.sh"
+	}
+	return &NtfyChannel{
+		cfg:             cfg,
+		defaultPriority: defaultPriority,
+		client:          &http.Client{Timeout: 5 * time.Second},
+	}
+}
+
+// Kind returns "ntfy" for log enrichment and dispatcher routing.
+func (c *NtfyChannel) Kind() string { return "ntfy" }
+
+// Send delivers the payload as a plain-text POST to <server>/<topic>
+// with ntfy headers. Returns (statusCode, latency, err). 4xx/5xx
+// responses are returned as errors with the status code set.
+func (c *NtfyChannel) Send(ctx context.Context, p Payload) (int, time.Duration, error) {
+	url := c.cfg.ServerURL + "/" + c.cfg.Topic
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewBufferString(p.Message))
+	if err != nil {
+		return 0, 0, fmt.Errorf("ntfy: build request: %w", err)
+	}
+
+	req.Header.Set("Title", fmt.Sprintf("[%s] %s %s", p.Severity, p.HostName, p.Kind))
+	req.Header.Set("Tags", p.Severity+","+p.Kind)
+	req.Header.Set("Priority", priorityForSeverity(p.Severity, c.defaultPriority))
+	if p.Link != "" {
+		req.Header.Set("Click", p.Link)
+	}
+	if c.cfg.AccessToken != "" {
+		req.Header.Set("Authorization", "Bearer "+c.cfg.AccessToken)
+	}
+
+	t0 := time.Now()
+	res, err := c.client.Do(req)
+	latency := time.Since(t0)
+	if err != nil {
+		return 0, latency, fmt.Errorf("ntfy: do: %w", err)
+	}
+	defer func() { _ = res.Body.Close() }()
+	// Drain body to keep the connection reusable.
+	_, _ = io.Copy(io.Discard, res.Body)
+	if res.StatusCode >= 400 {
+		return res.StatusCode, latency, fmt.Errorf("ntfy: http %d", res.StatusCode)
+	}
+	return res.StatusCode, latency, nil
+}
+
+// priorityForSeverity maps a severity string to an ntfy numeric priority
+// string. critical always returns "5" regardless of defaultPri. For
+// other severities, defaultPri is returned when non-empty, otherwise
+// "4" for warning and "3" for everything else.
+func priorityForSeverity(severity, defaultPri string) string {
+	switch severity {
+	case "critical":
+		return "5"
+	case "warning":
+		if defaultPri != "" {
+			return defaultPri
+		}
+		return "4"
+	default:
+		if defaultPri != "" {
+			return defaultPri
+		}
+		return "3"
+	}
+}