client: begin omaha client implementation

This first commit just covers the basic data structures.

omaha/client/client.go

@@ -0,0 +1,154 @@
+// Copyright 2017 CoreOS, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package client provides a general purpose Omaha update client implementation.
+package client
+
+import (
+	"errors"
+	"fmt"
+	"net/url"
+
+	"github.com/satori/go.uuid"
+)
+
+// Client supports managing multiple apps using a single server.
+type Client struct {
+	apiEndpoint   string
+	clientVersion string
+	userID        string
+	sessionID     string
+	isMachine     bool
+	apps          map[string]*AppClient
+}
+
+// AppClient supports managing a single application.
+type AppClient struct {
+	*Client
+	appID   string
+	track   string
+	version string
+}
+
+// New creates an omaha client for updating one or more applications.
+// userID must be a persistent unique identifier of this update client.
+func New(serverURL, userID string) (*Client, error) {
+	if userID == "" {
+		return nil, errors.New("omaha: empty user identifier")
+	}
+
+	c := &Client{
+		clientVersion: "go-omaha",
+		userID:        userID,
+		sessionID:     uuid.NewV4().String(),
+		apps:          make(map[string]*AppClient),
+	}
+
+	if err := c.SetServerURL(serverURL); err != nil {
+		return nil, err
+	}
+
+	return c, nil
+}
+
+// SetServerURL changes the Omaha server this client talks to.
+// If the URL does not include a path component /v1/update/ is assumed.
+func (c *Client) SetServerURL(serverURL string) error {
+	u, err := url.Parse(serverURL)
+	if err != nil {
+		return fmt.Errorf("omaha: invalid server URL: %v", err)
+	}
+	if u.Scheme != "http" && u.Scheme != "https" {
+		return fmt.Errorf("omaha: invalid server protocol: %s", u)
+	}
+	if u.Host == "" {
+		return fmt.Errorf("omaha: invalid server host: %s", u)
+	}
+	if u.Path == "" || u.Path == "/" {
+		u.Path = "/v1/update/"
+	}
+
+	c.apiEndpoint = u.String()
+	return nil
+}
+
+// SetClientVersion sets the identifier of this updater application.
+// e.g. "update_engine-0.1.0".  Default is "go-omaha".
+func (c *Client) SetClientVersion(clientVersion string) {
+	c.clientVersion = clientVersion
+}
+
+// AppClient gets the application client for the given application ID.
+func (c *Client) AppClient(appID string) (*AppClient, error) {
+	if app, ok := c.apps[appID]; ok {
+		return app, nil
+	}
+
+	return nil, fmt.Errorf("omaha: missing app client %q", appID)
+}
+
+// NewAppClient creates a new application client.
+func (c *Client) NewAppClient(appID, appVersion string) (*AppClient, error) {
+	if _, ok := c.apps[appID]; ok {
+		return nil, fmt.Errorf("omaha: duplicate app client %q", appID)
+	}
+
+	ac := &AppClient{
+		Client: c,
+		appID:  appID,
+	}
+	c.apps[appID] = ac
+
+	return ac, nil
+}
+
+// NewAppClient creates a single application client.
+// Shorthand for New(serverURL, userID).NewAppClient(appID, appVersion).
+func NewAppClient(serverURL, userID, appID, appVersion string) (*AppClient, error) {
+	c, err := New(serverURL, userID)
+	if err != nil {
+		return nil, err
+	}
+
+	ac, err := c.NewAppClient(appID, appVersion)
+	if err := ac.SetVersion(appVersion); err != nil {
+		return nil, err
+	}
+
+	return ac, nil
+}
+
+// SetVersion changes the application version.
+func (ac *AppClient) SetVersion(version string) error {
+	if version == "" {
+		return errors.New("omaha: empty application version")
+	}
+
+	ac.version = version
+	return nil
+}
+
+// SetTrack sets the application update track or group.
+// This is a update_engine/Core Update protocol extension.
+func (ac *AppClient) SetTrack(track string) error {
+	// Although track is an omaha extension and theoretically not required
+	// our Core Update server requires track to be set to a valid id/name.
+	// TODO: deprecate track and use the standard cohort protocol fields.
+	if track == "" {
+		return errors.New("omaha: empty application update track/group")
+	}
+
+	ac.track = track
+	return nil
+}