From 7587d8004169429659b865857adeb18ba9e2767a Mon Sep 17 00:00:00 2001
From: Eric Chiang <eric.chiang.m@gmail.com>
Date: Tue, 10 Jan 2017 22:05:37 -0800
Subject: [PATCH] add a discovery client for querying server version and
 resources

---
 client.go         | 10 ++++++++
 discovery.go      | 63 +++++++++++++++++++++++++++++++++++++++++++++++
 discovery_test.go | 28 +++++++++++++++++++++
 3 files changed, 101 insertions(+)
 create mode 100644 discovery.go
 create mode 100644 discovery_test.go

diff --git a/client.go b/client.go
index aae77f8..75718f3 100644
--- a/client.go
+++ b/client.go
@@ -399,6 +399,16 @@ func (c *Client) urlFor(apiGroup, apiVersion, namespace, resource, name string,
 	return endpoint + "?" + v.Encode()
 }
 
+func (c *Client) urlForPath(path string) string {
+	if strings.HasPrefix(path, "/") {
+		path = path[1:]
+	}
+	if strings.HasSuffix(c.Endpoint, "/") {
+		return c.Endpoint + path
+	}
+	return c.Endpoint + "/" + path
+}
+
 func (c *Client) create(ctx context.Context, codec *codec, verb, url string, req, resp interface{}) error {
 	body, err := codec.marshal(req)
 	if err != nil {
diff --git a/discovery.go b/discovery.go
new file mode 100644
index 0000000..b2713cb
--- /dev/null
+++ b/discovery.go
@@ -0,0 +1,63 @@
+package k8s
+
+import (
+	"context"
+	"path"
+
+	"github.com/ericchiang/k8s/api/unversioned"
+)
+
+type Version struct {
+	Major        string `json:"major"`
+	Minor        string `json:"minor"`
+	GitVersion   string `json:"gitVersion"`
+	GitCommit    string `json:"gitCommit"`
+	GitTreeState string `json:"gitTreeState"`
+	BuildDate    string `json:"buildDate"`
+	GoVersion    string `json:"goVersion"`
+	Compiler     string `json:"compiler"`
+	Platform     string `json:"platform"`
+}
+
+func (c *Client) Discovery() *Discovery {
+	return &Discovery{c}
+}
+
+// Discovery is a client used to determine the API version and supported
+// resources of the server.
+type Discovery struct {
+	client *Client
+}
+
+func (d *Discovery) Version(ctx context.Context) (*Version, error) {
+	var v Version
+	if err := d.client.get(ctx, jsonCodec, d.client.urlForPath("version"), &v); err != nil {
+		return nil, err
+	}
+	return &v, nil
+}
+
+func (d *Discovery) APIGroups(ctx context.Context) (*unversioned.APIGroupList, error) {
+	var groups unversioned.APIGroupList
+	if err := d.client.get(ctx, pbCodec, d.client.urlForPath("apis"), &groups); err != nil {
+		return nil, err
+	}
+	return &groups, nil
+}
+
+func (d *Discovery) APIGroup(ctx context.Context, name string) (*unversioned.APIGroup, error) {
+	var group unversioned.APIGroup
+	if err := d.client.get(ctx, pbCodec, d.client.urlForPath(path.Join("apis", name)), &group); err != nil {
+		return nil, err
+	}
+	return &group, nil
+}
+
+func (d *Discovery) APIResources(ctx context.Context, groupName, groupVersion string) (*unversioned.APIResourceList, error) {
+	var list unversioned.APIResourceList
+	if err := d.client.get(ctx, pbCodec, d.client.urlForPath(path.Join("apis", groupName, groupVersion)), &list); err != nil {
+		return nil, err
+	}
+	return &list, nil
+
+}
diff --git a/discovery_test.go b/discovery_test.go
new file mode 100644
index 0000000..562a98f
--- /dev/null
+++ b/discovery_test.go
@@ -0,0 +1,28 @@
+package k8s
+
+import (
+	"context"
+	"testing"
+)
+
+func TestDiscovery(t *testing.T) {
+	client := newTestClient(t).Discovery()
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	if _, err := client.Version(ctx); err != nil {
+		t.Errorf("list version: %v", err)
+	}
+
+	if _, err := client.APIGroups(ctx); err != nil {
+		t.Errorf("list api groups: %v", err)
+	}
+
+	if _, err := client.APIGroup(ctx, "extensions"); err != nil {
+		t.Errorf("list api group: %v", err)
+	}
+
+	if _, err := client.APIResources(ctx, "extensions", "v1beta1"); err != nil {
+		t.Errorf("list api group resources: %v", err)
+	}
+}