notification: webhook channel

internal/notification/webhook.go

@@ -0,0 +1,98 @@
+package notification
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
+)
+
+// WebhookConfig is the per-channel JSON shape stored AEAD-encrypted
+// in notification_channels.config.
+type WebhookConfig struct {
+	URL         string `json:"url"`
+	BearerToken string `json:"bearer_token,omitempty"`
+	HeaderName  string `json:"header_name,omitempty"`
+	HeaderValue string `json:"header_value,omitempty"`
+}
+
+// WebhookChannel is the HTTP-POST channel. One per configured channel
+// row. Reused across sends — the http.Client is goroutine-safe.
+type WebhookChannel struct {
+	cfg    WebhookConfig
+	client *http.Client
+}
+
+// NewWebhookChannel builds a webhook with a 5s overall timeout enforced
+// by the http.Client; ctx in Send is layered on top for caller-driven
+// cancel.
+func NewWebhookChannel(cfg WebhookConfig) *WebhookChannel {
+	return &WebhookChannel{
+		cfg:    cfg,
+		client: &http.Client{Timeout: 5 * time.Second},
+	}
+}
+
+// Kind returns "webhook" for log enrichment and dispatcher routing.
+func (c *WebhookChannel) Kind() string { return "webhook" }
+
+// webhookBody is the wire-stable envelope. Documented in the spec; do
+// not reorder fields freely — operators write switch statements on
+// "event" and "severity".
+type webhookBody struct {
+	Event    string `json:"event"`
+	AlertID  string `json:"alert_id"`
+	Severity string `json:"severity"`
+	Kind     string `json:"kind"`
+	HostID   string `json:"host_id"`
+	HostName string `json:"host_name"`
+	Message  string `json:"message"`
+	RaisedAt string `json:"raised_at"`
+	Link     string `json:"link"`
+}
+
+// Send delivers the payload as a JSON POST. Returns (statusCode, latency, err).
+// 4xx/5xx responses are returned as errors with the status code set.
+func (c *WebhookChannel) Send(ctx context.Context, p Payload) (int, time.Duration, error) {
+	body := webhookBody{
+		Event: string(p.Event), AlertID: p.AlertID,
+		Severity: p.Severity, Kind: p.Kind,
+		HostID: p.HostID, HostName: p.HostName,
+		Message:  p.Message,
+		RaisedAt: p.RaisedAt.UTC().Format(time.RFC3339Nano),
+		Link:     p.Link,
+	}
+	buf, err := json.Marshal(body)
+	if err != nil {
+		return 0, 0, fmt.Errorf("webhook: marshal body: %w", err)
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.cfg.URL, bytes.NewReader(buf))
+	if err != nil {
+		return 0, 0, fmt.Errorf("webhook: build request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+	if c.cfg.BearerToken != "" {
+		req.Header.Set("Authorization", "Bearer "+c.cfg.BearerToken)
+	}
+	if c.cfg.HeaderName != "" {
+		req.Header.Set(c.cfg.HeaderName, c.cfg.HeaderValue)
+	}
+
+	t0 := time.Now()
+	res, err := c.client.Do(req)
+	latency := time.Since(t0)
+	if err != nil {
+		return 0, latency, fmt.Errorf("webhook: do: %w", err)
+	}
+	defer func() { _ = res.Body.Close() }()
+	// Drain body — keep the connection reusable.
+	_, _ = io.Copy(io.Discard, res.Body)
+	if res.StatusCode >= 400 {
+		return res.StatusCode, latency, fmt.Errorf("webhook: http %d", res.StatusCode)
+	}
+	return res.StatusCode, latency, nil
+}