feat: implement thin vertical slice of system-generated notifications (#13537)

coderd/notifications/dispatch/webhook.go

@@ -0,0 +1,105 @@
+package dispatch
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"io"
+	"net/http"
+
+	"github.com/google/uuid"
+	"golang.org/x/xerrors"
+
+	"cdr.dev/slog"
+
+	"github.com/coder/coder/v2/coderd/notifications/types"
+	markdown "github.com/coder/coder/v2/coderd/render"
+	"github.com/coder/coder/v2/codersdk"
+)
+
+// WebhookHandler dispatches notification messages via an HTTP POST webhook.
+type WebhookHandler struct {
+	cfg codersdk.NotificationsWebhookConfig
+	log slog.Logger
+
+	cl *http.Client
+}
+
+// WebhookPayload describes the JSON payload to be delivered to the configured webhook endpoint.
+type WebhookPayload struct {
+	Version string               `json:"_version"`
+	MsgID   uuid.UUID            `json:"msg_id"`
+	Payload types.MessagePayload `json:"payload"`
+	Title   string               `json:"title"`
+	Body    string               `json:"body"`
+}
+
+func NewWebhookHandler(cfg codersdk.NotificationsWebhookConfig, log slog.Logger) *WebhookHandler {
+	return &WebhookHandler{cfg: cfg, log: log, cl: &http.Client{}}
+}
+
+func (w *WebhookHandler) Dispatcher(payload types.MessagePayload, titleTmpl, bodyTmpl string) (DeliveryFunc, error) {
+	if w.cfg.Endpoint.String() == "" {
+		return nil, xerrors.New("webhook endpoint not defined")
+	}
+
+	title, err := markdown.PlaintextFromMarkdown(titleTmpl)
+	if err != nil {
+		return nil, xerrors.Errorf("render title: %w", err)
+	}
+	body, err := markdown.PlaintextFromMarkdown(bodyTmpl)
+	if err != nil {
+		return nil, xerrors.Errorf("render body: %w", err)
+	}
+
+	return w.dispatch(payload, title, body, w.cfg.Endpoint.String()), nil
+}
+
+func (w *WebhookHandler) dispatch(msgPayload types.MessagePayload, title, body, endpoint string) DeliveryFunc {
+	return func(ctx context.Context, msgID uuid.UUID) (retryable bool, err error) {
+		// Prepare payload.
+		payload := WebhookPayload{
+			Version: "1.0",
+			MsgID:   msgID,
+			Title:   title,
+			Body:    body,
+			Payload: msgPayload,
+		}
+		m, err := json.Marshal(payload)
+		if err != nil {
+			return false, xerrors.Errorf("marshal payload: %v", err)
+		}
+
+		// Prepare request.
+		// Outer context has a deadline (see CODER_NOTIFICATIONS_DISPATCH_TIMEOUT).
+		req, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, bytes.NewBuffer(m))
+		if err != nil {
+			return false, xerrors.Errorf("create HTTP request: %v", err)
+		}
+		req.Header.Set("Content-Type", "application/json")
+
+		// Send request.
+		resp, err := w.cl.Do(req)
+		if err != nil {
+			return true, xerrors.Errorf("failed to send HTTP request: %v", err)
+		}
+		defer resp.Body.Close()
+
+		// Handle response.
+		if resp.StatusCode/100 > 2 {
+			// Body could be quite long here, let's grab the first 512B and hope it contains useful debug info.
+			respBody := make([]byte, 512)
+			lr := io.LimitReader(resp.Body, int64(len(respBody)))
+			n, err := lr.Read(respBody)
+			if err != nil && !errors.Is(err, io.EOF) {
+				return true, xerrors.Errorf("non-200 response (%d), read body: %w", resp.StatusCode, err)
+			}
+			w.log.Warn(ctx, "unsuccessful delivery", slog.F("status_code", resp.StatusCode),
+				slog.F("response", respBody[:n]), slog.F("msg_id", msgID))
+			return true, xerrors.Errorf("non-200 response (%d)", resp.StatusCode)
+		}
+
+		return false, nil
+	}
+}