milo: Enable Swarming LogDog log loading.

logdog/common/types/streamaddr.go

Index: logdog/common/types/streamaddr.go
diff --git a/logdog/common/types/streamaddr.go b/logdog/common/types/streamaddr.go
new file mode 100644
index 0000000000000000000000000000000000000000..a3e703e5bae4a2b87d115d29933954bfe7e99733
--- /dev/null
+++ b/logdog/common/types/streamaddr.go
@@ -0,0 +1,80 @@
+// Copyright 2017 The LUCI Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package types
+
+import (
+	"net/url"
+	"strings"
+
+	"github.com/luci/luci-go/common/errors"
+	"github.com/luci/luci-go/luci_config/common/cfgtypes"
+)
+
+const logDogURLScheme = "logdog"
+
+// StreamAddr is a fully-qualified LogDog stream address.
+type StreamAddr struct {
+	// Host is the LogDog host.
+	Host string
+
+	// Project is the LUCI project name that this log belongs to.
+	Project cfgtypes.ProjectName
+
+	// Path is the LogDog stream path.
+	Path StreamPath
+}
+
+// URL returns a LogDog URL that represents this Stream.
+func (s *StreamAddr) URL() *url.URL {
+	return &url.URL{
+		Scheme: logDogURLScheme,
+		Host:   s.Host,
+		Path:   strings.Join([]string{"", string(s.Project), string(s.Path)}, "/"),
+	}
+}
+
+// ParseURL parses a LogDog URL into a Stream. If the URL is malformed, or
+// if the host, project, or path is invalid, an error will be returned.
+//
+// A LogDog URL has the form:
+// logdog://<host>/<project>/<prefix>/+/<name>
+func ParseURL(v string) (*StreamAddr, error) {
+	u, err := url.Parse(v)
+	if err != nil {
+		return nil, errors.Annotate(err).Reason("failed to parse URL").Err()
+	}
+
+	// Validate Scheme.
+	if u.Scheme != logDogURLScheme {
+		return nil, errors.Reason("URL scheme %(scheme)q is not "+logDogURLScheme).
+			D("scheme", u.Scheme).
+			Err()
+	}
+	addr := StreamAddr{
+		Host: u.Host,
+	}
+
+	parts := strings.SplitN(u.Path, "/", 3)
+	if len(parts) != 3 || len(parts[0]) != 0 {
+		return nil, errors.Reason("URL path does not include both project and path components: %(path)s").
+			D("path", u.Path).
+			Err()
+	}
+
+	addr.Project, addr.Path = cfgtypes.ProjectName(parts[1]), StreamPath(parts[2])
+	if err := addr.Project.Validate(); err != nil {
+		return nil, errors.Annotate(err).Reason("invalid project name: %(project)q").
+			D("project", addr.Project).
+			Err()
+	}
+
+	if err := addr.Path.Validate(); err != nil {
+		return nil, errors.Annotate(err).Reason("invalid stream path: %(path)q").
+			D("path", addr.Path).
+			Err()
+	}
+
+	return &addr, nil
+}