Add functionality to search registries

podman search searches a registry for a matching image
this adds the functionality to support that
some registries respond to the v2 endpoint while others
only respond to the v1 endpoint.
This checks both endpoints for a result, and if none is given
the user is informed.

Signed-off-by: umohnani8 <umohnani@redhat.com>

Author: umohnani8

docker/docker_client.go

@@ -8,7 +8,9 @@ import (
 	"io"
 	"io/ioutil"
 	"net/http"
+	"net/url"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"time"
 
@@ -221,6 +223,84 @@ func CheckAuth(ctx context.Context, sCtx *types.SystemContext, username, passwor
 	}
 }
 
+// SearchResult holds the information of each matching image
+// It matches the output returned by the v1 endpoint
+type SearchResult struct {
+	Name        string `json:"name"`
+	Description string `json:"description"`
+	// StarCount states the number of stars the image has
+	StarCount int  `json:"star_count"`
+	IsTrusted bool `json:"is_trusted"`
+	// IsAutomated states whether the image is an automated build
+	IsAutomated bool `json:"is_automated"`
+	// IsOfficial states whether the image is an official build
+	IsOfficial bool `json:"is_official"`
+}
+
+// SearchRegistry queries a registry for images that contain "image" in their name
+// The limit is the max number of results desired
+// Note: The limit value doesn't work with all registries
+// for example registry.access.redhat.com returns all the results without limiting it to the limit value
+func SearchRegistry(ctx context.Context, sCtx *types.SystemContext, registry, image string, limit int) ([]SearchResult, error) {
+	type V2Results struct {
+		// Repositories holds the results returned by the /v2/_catalog endpoint
+		Repositories []string `json:"repositories"`
+	}
+	type V1Results struct {
+		// Results holds the results returned by the /v1/search endpoint
+		Results []SearchResult `json:"results"`
+	}
+	v2Res := &V2Results{}
+	v1Res := &V1Results{}
+
+	client, err := newDockerClientWithDetails(sCtx, registry, "", "", "", nil, "")
+	if err != nil {
+		return nil, errors.Wrapf(err, "error creating new docker client")
+	}
+
+	logrus.Debugf("trying to talk to v2 search endpoint\n")
+	resp, err := client.makeRequest(ctx, "GET", "/v2/_catalog", nil, nil)
+	if err == nil && resp.StatusCode == http.StatusOK {
+		if err := json.NewDecoder(resp.Body).Decode(v2Res); err != nil {
+			return nil, err
+		}
+		searchRes := []SearchResult{}
+		for _, repo := range v2Res.Repositories {
+			if strings.Contains(repo, image) {
+				res := SearchResult{
+					Name: repo,
+				}
+				searchRes = append(searchRes, res)
+			}
+		}
+		return searchRes, nil
+	}
+	defer resp.Body.Close()
+	logrus.Errorf("error getting search results from v2 endpoint %q, status code %q: %v", registry, resp.StatusCode, err)
+
+	// set up the query values for the v1 endpoint
+	u := url.URL{
+		Path: "/v1/search",
+	}
+	q := u.Query()
+	q.Set("q", image)
+	q.Set("n", strconv.Itoa(limit))
+	u.RawQuery = q.Encode()
+
+	logrus.Debugf("trying to talk to v1 search endpoint\n")
+	resp, err = client.makeRequest(ctx, "GET", u.String(), nil, nil)
+	if err == nil || resp.StatusCode == http.StatusOK {
+		if err := json.NewDecoder(resp.Body).Decode(v1Res); err != nil {
+			return nil, err
+		}
+		return v1Res.Results, nil
+	}
+	defer resp.Body.Close()
+	logrus.Errorf("error getting search results from v2 endpoint %q, status code %q: %v", registry, resp.StatusCode, err)
+
+	return nil, errors.Wrapf(err, "couldn't search registry %q", registry)
+}
+
 // makeRequest creates and executes a http.Request with the specified parameters, adding authentication and TLS options for the Docker client.
 // The host name and schema is taken from the client or autodetected, and the path is relative to it, i.e. the path usually starts with /v2/.
 func (c *dockerClient) makeRequest(ctx context.Context, method, path string, headers map[string][]string, stream io.Reader) (*http.Response, error) {