Move rollback out of cmd

cli/cloud/cloudcmd/rollback.go

@@ -0,0 +1,60 @@
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"io"
+
+	"go.uber.org/multierr"
+)
+
+// rollbacker does a rollback.
+type rollbacker interface {
+	rollback(ctx context.Context) error
+}
+
+// rollbackOnError calls rollback on the rollbacker if the handed error is not nil,
+// and writes logs to the writer w.
+func rollbackOnError(ctx context.Context, w io.Writer, onErr *error, roll rollbacker) {
+	if *onErr == nil {
+		return
+	}
+	fmt.Fprintf(w, "An error occurred: %s\n", *onErr)
+	fmt.Fprintln(w, "Attempting to roll back.")
+	if err := roll.rollback(ctx); err != nil {
+		*onErr = multierr.Append(*onErr, fmt.Errorf("on rollback: %w", err)) // TODO: print the error, or retrun it?
+		return
+	}
+	fmt.Fprintln(w, "Rollback succeeded.")
+}
+
+type rollbackerGCP struct {
+	client gcpclient
+}
+
+func (r *rollbackerGCP) rollback(ctx context.Context) error {
+	var err error
+	err = multierr.Append(err, r.client.TerminateInstances(ctx))
+	err = multierr.Append(err, r.client.TerminateFirewall(ctx))
+	err = multierr.Append(err, r.client.TerminateVPCs(ctx))
+	return err
+}
+
+type rollbackerAzure struct {
+	client azureclient
+}
+
+func (r *rollbackerAzure) rollback(ctx context.Context) error {
+	return r.client.TerminateResourceGroup(ctx)
+}
+
+type rollbackerAWS struct {
+	client ec2client
+}
+
+func (r *rollbackerAWS) rollback(ctx context.Context) error {
+	var err error
+	err = multierr.Append(err, r.client.TerminateInstances(ctx))
+	err = multierr.Append(err, r.client.DeleteSecurityGroup(ctx))
+	return err
+}