Windows: Minimal docker top implementation

Signed-off-by: John Howard <jhoward@microsoft.com>

daemon/top_windows.go

@@ -1,12 +1,32 @@
 package daemon
 
 import (
-	"fmt"
+	"errors"
+	"strconv"
 
 	"github.com/docker/engine-api/types"
 )
 
-// ContainerTop is not supported on Windows and returns an error.
-func (daemon *Daemon) ContainerTop(name string, psArgs string) (*types.ContainerProcessList, error) {
-	return nil, fmt.Errorf("Top is not supported on Windows")
+// ContainerTop is a minimal implementation on Windows currently.
+// TODO Windows: This needs more work, but needs platform API support.
+// All we can currently return (particularly in the case of Hyper-V containers)
+// is a PID and the command.
+func (daemon *Daemon) ContainerTop(containerID string, psArgs string) (*types.ContainerProcessList, error) {
+
+	// It's really not an equivalent to linux 'ps' on Windows
+	if psArgs != "" {
+		return nil, errors.New("Windows does not support arguments to top")
+	}
+
+	s, err := daemon.containerd.Summary(containerID)
+	if err != nil {
+		return nil, err
+	}
+
+	procList := &types.ContainerProcessList{}
+
+	for _, v := range s {
+		procList.Titles = append(procList.Titles, strconv.Itoa(int(v.Pid))+" "+v.Command)
+	}
+	return procList, nil
 }