resource_printer.go

package cloudcfg

import (
	"encoding/json"
	"fmt"
	"io"
	"strings"
	"text/tabwriter"

	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
	"gopkg.in/v1/yaml"
)

// ResourcePrinter is an interface that knows how to print API resources
type ResourcePrinter interface {
	// Print receives an arbitrary JSON body, formats it and prints it to a writer
	Print(string, io.Writer) error
}

// Identity printer simply copies the body out to the output stream
type IdentityPrinter struct{}

func (i *IdentityPrinter) Print(data string, w io.Writer) error {
	_, err := fmt.Fprint(w, data)
	return err
}

// YAMLPrinter parses JSON, and re-formats as YAML
type YAMLPrinter struct{}

func (y *YAMLPrinter) Print(data string, w io.Writer) error {
	var obj interface{}
	if err := json.Unmarshal([]byte(data), &obj); err != nil {
		return err
	}
	output, err := yaml.Marshal(obj)
	if err != nil {
		return err
	}
	_, err = fmt.Fprint(w, string(output))
	return err
}

// HumanReadablePrinter attempts to provide more elegant output
type HumanReadablePrinter struct{}

var podColumns = []string{"Name", "Image(s)", "Host", "Labels"}
var replicationControllerColumns = []string{"Name", "Image(s)", "Label Query", "Replicas"}
var serviceColumns = []string{"Name", "Label Query", "Port"}

func (h *HumanReadablePrinter) unknown(data string, w io.Writer) error {
	_, err := fmt.Fprintf(w, "Unknown object: %s", data)
	return err
}

func (h *HumanReadablePrinter) printHeader(columnNames []string, w io.Writer) error {
	if _, err := fmt.Fprintf(w, "%s\n", strings.Join(columnNames, "\t")); err != nil {
		return err
	}
	var lines []string
	for _, _ = range columnNames {
		lines = append(lines, "----------")
	}
	_, err := fmt.Fprintf(w, "%s\n", strings.Join(lines, "\t"))
	return err
}

func (h *HumanReadablePrinter) makeImageList(manifest api.ContainerManifest) string {
	var images []string
	for _, container := range manifest.Containers {
		images = append(images, container.Image)
	}
	return strings.Join(images, ",")
}

func (h *HumanReadablePrinter) makeLabelsList(labels map[string]string) string {
	var vals []string
	for key, value := range labels {
		vals = append(vals, fmt.Sprintf("%s=%s", key, value))
	}
	return strings.Join(vals, ",")
}

func (h *HumanReadablePrinter) printPod(pod api.Pod, w io.Writer) error {
	_, err := fmt.Fprintf(w, "%s\t%s\t%s\t%s\n",
		pod.ID, h.makeImageList(pod.DesiredState.Manifest), pod.CurrentState.Host, h.makeLabelsList(pod.Labels))
	return err
}

func (h *HumanReadablePrinter) printPodList(podList api.PodList, w io.Writer) error {
	for _, pod := range podList.Items {
		if err := h.printPod(pod, w); err != nil {
			return err
		}
	}
	return nil
}

func (h *HumanReadablePrinter) printReplicationController(ctrl api.ReplicationController, w io.Writer) error {
	_, err := fmt.Fprintf(w, "%s\t%s\t%s\t%d\n",
		ctrl.ID, h.makeImageList(ctrl.DesiredState.PodTemplate.DesiredState.Manifest), h.makeLabelsList(ctrl.DesiredState.ReplicasInSet), ctrl.DesiredState.Replicas)
	return err
}

func (h *HumanReadablePrinter) printReplicationControllerList(list api.ReplicationControllerList, w io.Writer) error {
	for _, ctrl := range list.Items {
		if err := h.printReplicationController(ctrl, w); err != nil {
			return err
		}
	}
	return nil
}

func (h *HumanReadablePrinter) printService(svc api.Service, w io.Writer) error {
	_, err := fmt.Fprintf(w, "%s\t%s\t%d\n", svc.ID, h.makeLabelsList(svc.Labels), svc.Port)
	return err
}

func (h *HumanReadablePrinter) printServiceList(list api.ServiceList, w io.Writer) error {
	for _, svc := range list.Items {
		if err := h.printService(svc, w); err != nil {
			return err
		}
	}
	return nil
}

// TODO replace this with something that returns a concrete printer object, rather than
//  having the secondary switch below.
func (h *HumanReadablePrinter) extractObject(data, kind string) (interface{}, error) {
	// TODO: I think this can be replaced with some reflection and a map[string]type
	switch kind {
	case "cluster#pod":
		var obj api.Pod
		if err := json.Unmarshal([]byte(data), &obj); err != nil {
			return nil, err
		}
		return obj, nil
	case "cluster#podList":
		var list api.PodList
		if err := json.Unmarshal([]byte(data), &list); err != nil {
			return nil, err
		}
		return list, nil
	case "cluster#replicationController":
		var ctrl api.ReplicationController
		if err := json.Unmarshal([]byte(data), &ctrl); err != nil {
			return nil, err
		}
		return ctrl, nil
	case "cluster#replicationControllerList":
		var list api.ReplicationControllerList
		if err := json.Unmarshal([]byte(data), &list); err != nil {
			return nil, err
		}
		return list, nil
	case "cluster#service":
		var ctrl api.Service
		if err := json.Unmarshal([]byte(data), &ctrl); err != nil {
			return nil, err
		}
		return ctrl, nil
	case "cluster#serviceList":
		var list api.ServiceList
		if err := json.Unmarshal([]byte(data), &list); err != nil {
			return nil, err
		}
		return list, nil
	default:
		return nil, fmt.Errorf("Unknown kind: %s", kind)
	}
}

func (h *HumanReadablePrinter) Print(data string, output io.Writer) error {
	w := tabwriter.NewWriter(output, 20, 5, 3, ' ', 0)
	defer w.Flush()
	var obj interface{}
	if err := json.Unmarshal([]byte(data), &obj); err != nil {
		return err
	}

	if _, contains := obj.(map[string]interface{})["kind"]; !contains {
		return fmt.Errorf("Unexpected object with no 'kind' field: %s", data)
	}
	kind := (obj.(map[string]interface{})["kind"]).(string)
	obj, err := h.extractObject(data, kind)
	if err != nil {
		return err
	}
	switch obj.(type) {
	case api.Pod:
		h.printHeader(podColumns, w)
		return h.printPod(obj.(api.Pod), w)
	case api.PodList:
		h.printHeader(podColumns, w)
		return h.printPodList(obj.(api.PodList), w)
	case api.ReplicationController:
		h.printHeader(replicationControllerColumns, w)
		return h.printReplicationController(obj.(api.ReplicationController), w)
	case api.ReplicationControllerList:
		h.printHeader(replicationControllerColumns, w)
		return h.printReplicationControllerList(obj.(api.ReplicationControllerList), w)
	case api.Service:
		h.printHeader(serviceColumns, w)
		return h.printService(obj.(api.Service), w)
	case api.ServiceList:
		h.printHeader(serviceColumns, w)
		return h.printServiceList(obj.(api.ServiceList), w)
	default:
		return h.unknown(data, w)
	}
}