feat(agent): job runner, compose override executor and swarm executor (#7)

internal/agent/updater/dispatch.go

@@ -0,0 +1,28 @@
+package updater
+
+import (
+	"context"
+	"fmt"
+	"io"
+
+	"github.com/shcizo/package-updater/internal/protocol"
+)
+
+type dispatch struct{ compose, swarm Executor }
+
+// NewDispatch returns an Executor that picks compose or swarm by job.Kind.
+// KindContainer and unknown kinds fail.
+func NewDispatch(compose, swarm Executor) Executor {
+	return dispatch{compose: compose, swarm: swarm}
+}
+
+func (d dispatch) Execute(ctx context.Context, job protocol.JobStart, out io.Writer) (string, error) {
+	switch job.Kind {
+	case protocol.KindCompose:
+		return d.compose.Execute(ctx, job, out)
+	case protocol.KindSwarm:
+		return d.swarm.Execute(ctx, job, out)
+	default:
+		return "", fmt.Errorf("cannot update a service of kind %q", job.Kind)
+	}
+}