task 407: add client session transport

2 files changed, 108 insertions, 0 deletions

diff --git a/internal/session/spec.go b/internal/session/spec.go
index 2d1b77d..0a6ad4e 100644
--- a/internal/session/spec.go
+++ b/internal/session/spec.go
@@ -1,6 +1,8 @@
 package session
 
 import (
+	"encoding/base64"
+	"encoding/json"
 	"fmt"
 	"strings"
 
@@ -45,6 +47,30 @@ func (s Spec) Commands() ([]string, error) {
 	}
 }
 
+// StartCommand returns the SESSION START command for this specification.
+func (s Spec) StartCommand() (string, error) {
+	payload, err := s.encodedPayload()
+	if err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("SESSION START %s", payload), nil
+}
+
+// UpdateCommand returns the SESSION UPDATE command for this specification.
+func (s Spec) UpdateCommand(generation uint64) (string, error) {
+	payload, err := s.encodedPayload()
+	if err != nil {
+		return "", err
+	}
+
+	if generation == 0 {
+		return fmt.Sprintf("SESSION UPDATE %s", payload), nil
+	}
+
+	return fmt.Sprintf("SESSION UPDATE %d %s", generation, payload), nil
+}
+
 func (s Spec) queryCommands() ([]string, error) {
 	if s.Mode != omode.MapClient && s.Mode != omode.TailClient {
 		return nil, fmt.Errorf("session spec query mode requires map or tail mode, got %s", s.Mode)
@@ -122,3 +148,12 @@ func splitFiles(what string) []string {
 	}
 	return files
 }
+
+func (s Spec) encodedPayload() (string, error) {
+	payload, err := json.Marshal(s)
+	if err != nil {
+		return "", fmt.Errorf("marshal session spec: %w", err)
+	}
+
+	return base64.StdEncoding.EncodeToString(payload), nil
+}
diff --git a/internal/session/spec_test.go b/internal/session/spec_test.go
new file mode 100644
index 0000000..182c517
--- /dev/null
+++ b/internal/session/spec_test.go
@@ -0,0 +1,73 @@
+package session
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"reflect"
+	"strings"
+	"testing"
+
+	"github.com/mimecast/dtail/internal/omode"
+)
+
+func TestSpecStartCommandEncodesPayload(t *testing.T) {
+	t.Parallel()
+
+	spec := Spec{
+		Mode:    omode.TailClient,
+		Files:   []string{"/var/log/app.log"},
+		Options: "plain=true",
+		Regex:   "ERROR",
+		Timeout: 15,
+	}
+
+	command, err := spec.StartCommand()
+	if err != nil {
+		t.Fatalf("StartCommand() error = %v", err)
+	}
+	if !strings.HasPrefix(command, "SESSION START ") {
+		t.Fatalf("unexpected start command prefix: %q", command)
+	}
+
+	var decoded Spec
+	if err := decodeSpecPayload(strings.TrimPrefix(command, "SESSION START "), &decoded); err != nil {
+		t.Fatalf("decode start payload: %v", err)
+	}
+	if !reflect.DeepEqual(decoded, spec) {
+		t.Fatalf("unexpected decoded spec: got %#v want %#v", decoded, spec)
+	}
+}
+
+func TestSpecUpdateCommandIncludesGeneration(t *testing.T) {
+	t.Parallel()
+
+	spec := Spec{
+		Mode:  omode.MapClient,
+		Files: []string{"/var/log/app.log"},
+		Query: "from STATS select count(*)",
+	}
+
+	command, err := spec.UpdateCommand(7)
+	if err != nil {
+		t.Fatalf("UpdateCommand() error = %v", err)
+	}
+	if !strings.HasPrefix(command, "SESSION UPDATE 7 ") {
+		t.Fatalf("unexpected update command prefix: %q", command)
+	}
+
+	var decoded Spec
+	if err := decodeSpecPayload(strings.TrimPrefix(command, "SESSION UPDATE 7 "), &decoded); err != nil {
+		t.Fatalf("decode update payload: %v", err)
+	}
+	if !reflect.DeepEqual(decoded, spec) {
+		t.Fatalf("unexpected decoded spec: got %#v want %#v", decoded, spec)
+	}
+}
+
+func decodeSpecPayload(payload string, out *Spec) error {
+	raw, err := base64.StdEncoding.DecodeString(payload)
+	if err != nil {
+		return err
+	}
+	return json.Unmarshal(raw, out)
+}