Integrate email notifications into signup and login (#38)

backend/product/notifications/client.go

@@ -0,0 +1,88 @@
+// Package notifications adapts the internal notification wire contract to product models.
+package notifications
+
+import (
+	"context"
+	"crypto/tls"
+	"crypto/x509"
+	"os"
+	"time"
+
+	pb "git.sendico.io/tech/sxchnge/notifications/interface/notifications/v1"
+	merrors "git.sendico.io/tech/sxchnge/shared/errors"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/protobuf/types/known/timestamppb"
+)
+
+type Config struct {
+	Address       string `yaml:"address"`
+	TokenEnv      string `yaml:"token_env"`
+	CAFile        string `yaml:"ca_file"`
+	ServerName    string `yaml:"server_name"`
+	ActivationURL string `yaml:"activation_url"`
+}
+type Message struct {
+	Key, UserID, Email, Locale, Template string
+	Parameters                           map[string]string
+	ExpiresAt                            time.Time
+}
+type Sender interface {
+	Send(context.Context, Message) error
+}
+type Client struct {
+	conn  *grpc.ClientConn
+	rpc   pb.NotificationsServiceClient
+	token string
+}
+
+func Open(c Config) (*Client, error) {
+	token := os.Getenv(c.TokenEnv)
+	if c.Address == "" || len(token) < 32 {
+		return nil, merrors.InvalidArgument("notification address and caller token of at least 32 bytes are required")
+	}
+	tlsConfig := &tls.Config{MinVersion: tls.VersionTLS12, ServerName: c.ServerName}
+	if c.CAFile != "" {
+		pem, err := os.ReadFile(c.CAFile)
+		if err != nil {
+			return nil, merrors.InternalWrap(err, "read notification CA")
+		}
+		pool, err := x509.SystemCertPool()
+		if err != nil {
+			pool = x509.NewCertPool()
+		}
+		if !pool.AppendCertsFromPEM(pem) {
+			return nil, merrors.InvalidArgument("invalid notification CA")
+		}
+		tlsConfig.RootCAs = pool
+	}
+	conn, err := grpc.NewClient(c.Address, grpc.WithTransportCredentials(credentials.NewTLS(tlsConfig)))
+	if err != nil {
+		return nil, merrors.InternalWrap(err, "create notification client")
+	}
+	return &Client{conn: conn, rpc: pb.NewNotificationsServiceClient(conn), token: token}, nil
+}
+func (c *Client) Close() error { return c.conn.Close() }
+func (c *Client) Send(ctx context.Context, m Message) error {
+	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
+	defer cancel()
+	ctx = metadata.AppendToOutgoingContext(ctx, "authorization", "Bearer "+c.token)
+	res, err := c.rpc.Send(ctx, request(m))
+	if err != nil {
+		return merrors.ServiceUnavailableWrap(err, "notification queue unavailable")
+	}
+	if res.GetNotification().GetId() == "" || len(res.GetNotification().GetDeliveries()) != 1 {
+		return merrors.ServiceUnavailable("notification queue returned no receipt")
+	}
+	for _, d := range res.Notification.Deliveries {
+		switch d.State {
+		case pb.DeliveryState_DELIVERY_STATE_FAILED, pb.DeliveryState_DELIVERY_STATE_EXPIRED, pb.DeliveryState_DELIVERY_STATE_UNKNOWN:
+			return merrors.ServiceUnavailable("notification could not be delivered")
+		}
+	}
+	return nil
+}
+func request(m Message) *pb.SendRequest {
+	return &pb.SendRequest{IdempotencyKey: m.Key, UserId: m.UserID, TemplateId: m.Template, TemplateVersion: "1", Locale: m.Locale, Parameters: m.Parameters, ExpiresAt: timestamppb.New(m.ExpiresAt), Targets: []*pb.Target{{Destination: &pb.Target_Email{Email: &pb.EmailTarget{Address: m.Email}}}}}
+}