Merge pull request #39 from moov-io/intro-request-id-generator

add RequestIDGenerator interface to allow custom implementations

Author: alovak

connection.go

@@ -348,7 +348,7 @@ func (c *Connection) Send(message *iso8583.Message) (*iso8583.Message, error) {
 	}
 
 	// prepare request
-	reqID, err := requestID(message)
+	reqID, err := c.Opts.RequestIDGenerator.GenerateRequestID(message)
 	if err != nil {
 		return nil, fmt.Errorf("creating request ID: %w", err)
 	}
@@ -451,26 +451,6 @@ func (c *Connection) Reply(message *iso8583.Message) error {
 	return err
 }
 
-// requestID is a unique identifier for a request.  responses from the server
-// are not guaranteed to return in order so we must have an id to reference the
-// original req. built from stan and datetime
-func requestID(message *iso8583.Message) (string, error) {
-	if message == nil {
-		return "", fmt.Errorf("message required")
-	}
-
-	stan, err := message.GetString(11)
-	if err != nil {
-		return "", fmt.Errorf("getting STAN (field 11) of the message: %w", err)
-	}
-
-	if stan == "" {
-		return "", errors.New("STAN is missing")
-	}
-
-	return stan, nil
-}
-
 const (
 	// position of the MTI specifies the message function which
 	// defines how the message should flow within the system.
@@ -620,7 +600,7 @@ func (c *Connection) handleResponse(rawMessage []byte) {
 	}
 
 	if isResponse(message) {
-		reqID, err := requestID(message)
+		reqID, err := c.Opts.RequestIDGenerator.GenerateRequestID(message)
 		if err != nil {
 			c.handleError(fmt.Errorf("creating request ID:  %w", err))
 			return

options.go

@@ -60,18 +60,23 @@ type Options struct {
 
 	// OnClose is called synchronously before a connection is closed
 	OnClose func(c *Connection) error
+
+	// RequestIDGenerator is used to generate a unique identifier for a request
+	// so that responses from the server can be matched to the original request.
+	RequestIDGenerator RequestIDGenerator
 }
 
 type Option func(*Options) error
 
 func GetDefaultOptions() Options {
 	return Options{
-		ConnectTimeout: 10 * time.Second,
-		SendTimeout:    30 * time.Second,
-		IdleTime:       5 * time.Second,
-		ReadTimeout:    60 * time.Second,
-		PingHandler:    nil,
-		TLSConfig:      nil,
+		ConnectTimeout:     10 * time.Second,
+		SendTimeout:        30 * time.Second,
+		IdleTime:           5 * time.Second,
+		ReadTimeout:        60 * time.Second,
+		PingHandler:        nil,
+		TLSConfig:          nil,
+		RequestIDGenerator: &defaultRequestIDGenerator{},
 	}
 }
 
@@ -231,3 +236,11 @@ func SetTLSConfig(cfg func(*tls.Config)) Option {
 		return nil
 	}
 }
+
+// RequestIDGenerator sets a RequestIDGenerator option
+func SetRequestIDGenerator(g RequestIDGenerator) Option {
+	return func(o *Options) error {
+		o.RequestIDGenerator = g
+		return nil
+	}
+}

request_id_generator.go

@@ -0,0 +1,36 @@
+package connection
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/moov-io/iso8583"
+)
+
+// RequestIDGenerator is an interface that generates a unique identifier for a
+// request so that responses from the server can be matched to the original
+// request.
+type RequestIDGenerator interface {
+	GenerateRequestID(msg *iso8583.Message) (string, error)
+}
+
+// defaultRequestIDGenerator is the default implementation of RequestIDGenerator
+// that uses the STAN (field 11) of the message as the request ID.
+type defaultRequestIDGenerator struct{}
+
+func (d *defaultRequestIDGenerator) GenerateRequestID(message *iso8583.Message) (string, error) {
+	if message == nil {
+		return "", fmt.Errorf("message required")
+	}
+
+	stan, err := message.GetString(11)
+	if err != nil {
+		return "", fmt.Errorf("getting STAN (field 11) of the message: %w", err)
+	}
+
+	if stan == "" {
+		return "", errors.New("STAN is missing")
+	}
+
+	return stan, nil
+}