make docker-credential-wincred work like docker-credential-osxkeychain

* fetch credentials for server with matching hostname if scheme, path, or port are not provided
* if the credential request includes specific scheme, path, or port that does not match entry, don't return
* extract url helpers into a package

Signed-off-by: Emily Casey <ecasey@pivotal.io>
Signed-off-by: Danny Joyce <djoyce@pivotal.io>

wincred/wincred_windows.go

@@ -2,6 +2,8 @@ package wincred
 
 import (
 	"bytes"
+	"github.com/docker/docker-credential-helpers/registryurl"
+	"net/url"
 	"strings"
 
 	winc "github.com/danieljoos/wincred"
@@ -37,10 +39,18 @@ func (h Wincred) Delete(serverURL string) error {
 
 // Get retrieves credentials from the windows credentials manager.
 func (h Wincred) Get(serverURL string) (string, string, error) {
-	g, _ := winc.GetGenericCredential(serverURL)
+	target, err := getTarget(serverURL)
+	if err != nil {
+		return "", "", err
+	} else if target == "" {
+		return "", "", credentials.NewErrCredentialsNotFound()
+	}
+
+	g, _ := winc.GetGenericCredential(target)
 	if g == nil {
 		return "", "", credentials.NewErrCredentialsNotFound()
 	}
+
 	for _, attr := range g.Attributes {
 		if strings.Compare(attr.Keyword, "label") == 0 &&
 			bytes.Compare(attr.Value, []byte(credentials.CredsLabel)) == 0 {
@@ -51,6 +61,72 @@ func (h Wincred) Get(serverURL string) (string, string, error) {
 	return "", "", credentials.NewErrCredentialsNotFound()
 }
 
+func getTarget(serverURL string) (string, error) {
+	s, err := registryurl.Parse(serverURL)
+	if err != nil {
+		return serverURL, nil
+	}
+
+	creds, err := winc.List()
+	if err != nil {
+		return "", err
+	}
+
+	targets := make([]string, 0)
+	for i := range creds {
+		attrs := creds[i].Attributes
+		for _, attr := range attrs {
+			if strings.Compare(attr.Keyword, "label") == 0 &&
+				bytes.Compare(attr.Value, []byte(credentials.CredsLabel)) == 0 {
+				targets = append(targets, creds[i].TargetName)
+			}
+		}
+	}
+
+	if target, found := findMatch(s, targets, exactMatch); found {
+		return target, nil
+	}
+
+	if target, found := findMatch(s, targets, approximateMatch); found {
+		return target, nil
+	}
+
+	return "", nil
+}
+
+func findMatch(serverUrl *url.URL, targets []string, matches func(url.URL, url.URL) bool) (string, bool) {
+	for _, target := range targets {
+		tURL, err := registryurl.Parse(target)
+		if err != nil {
+			continue
+		}
+		if matches(*serverUrl, *tURL) {
+			return target, true
+		}
+	}
+	return "", false
+}
+
+func exactMatch(serverURL, target url.URL) bool {
+	return serverURL.String() == target.String()
+}
+
+func approximateMatch(serverURL, target url.URL) bool {
+	//if scheme is missing assume it is the same as target
+	if serverURL.Scheme == "" {
+		serverURL.Scheme = target.Scheme
+	}
+	//if port is missing assume it is the same as target
+	if serverURL.Port() == "" && target.Port() != "" {
+		serverURL.Host = serverURL.Host + ":" + target.Port()
+	}
+	//if path is missing assume it is the same as target
+	if serverURL.Path == "" {
+		serverURL.Path = target.Path
+	}
+	return serverURL.String() == target.String()
+}
+
 // List returns the stored URLs and corresponding usernames for a given credentials label.
 func (h Wincred) List() (map[string]string, error) {
 	creds, err := winc.List()