client.go

/*
Package innkeeper implements a DataClient for reading skipper route
definitions from an Innkeeper service.

(See the DataClient interface in the skipper/routing package.)

Innkeeper is a service to maintain large sets of routes in a multi-user
environment with OAuth2 authentication and permission scopes.

See: https://github.com/zalando/innkeeper
*/
package innkeeper

import (
	"bytes"
	"crypto/tls"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"

	log "github.com/sirupsen/logrus"
	"github.com/zalando/skipper/eskip"
)

const (
	allRoutesPath = "/current-routes"
	updatePathFmt = "/updated-routes/%s"
	bearerPrefix  = "Bearer "
)

type (
	authErrorType string
	actionType    string
)

const (
	authHeaderName = "Authorization"

	authErrorAuthorization      = authErrorType("AUTH1")
	authErrorMissingCredentials = authErrorType("AUTH2")
	authErrorAuthentication     = authErrorType("AUTH3")

	createAction   = actionType("create")
	updateAction   = actionType("update")
	activateAction = actionType("activate")
	deleteAction   = actionType("delete")
)

// json serialization object for innkeeper route definitions
type routeData struct {
	Action    actionType `json:"type"`
	Timestamp string     `json:"timestamp"`
	Name      string     `json:"name"`
	Eskip     string     `json:"eskip"`
}

// json serialization object for innkeeper error messages
type apiError struct {
	ErrorType string `json:"type"`
	Status    int32  `json:"status"`
	Title     string `json:"title"`
	Detail    string `json:"detail"`
}

// Initialization options for the Innkeeper client.
type Options struct {

	// The network address where the Innkeeper API is accessible.
	Address string

	// When true, TLS certificate verification is skipped.
	Insecure bool

	// Authentication to be used when connecting to Innkeeper.
	Authentication Authentication

	// An eskip filter chain expression to prepend to each route loaded
	// from Innkeeper. (E.g. "filter1() -> filter2() -> filter3()")
	PreRouteFilters string

	// An eskip filter chain expression to append to each route loaded
	// from Innkeeper. (E.g. "filter1() -> filter2() -> filter3()")
	PostRouteFilters string
}

// A Client is used to load the whole set of routes and the updates from an
// Innkeeper service.
type Client struct {
	opts           Options
	prependFilters []*eskip.Filter
	appendFilters  []*eskip.Filter
	authToken      string
	httpClient     *http.Client
	lastChanged    string
}

func (a actionType) Delete() bool {
	return a == deleteAction
}

// Returns a new Client.
func New(o Options) (*Client, error) {
	preFilters, err := eskip.ParseFilters(o.PreRouteFilters)
	if err != nil {
		return nil, err
	}

	postFilters, err := eskip.ParseFilters(o.PostRouteFilters)
	if err != nil {
		return nil, err
	}

	return &Client{
		opts:           o,
		prependFilters: preFilters,
		appendFilters:  postFilters,
		httpClient: &http.Client{Transport: &http.Transport{
			TLSClientConfig:   &tls.Config{InsecureSkipVerify: o.Insecure},
			DisableKeepAlives: true}}}, nil
}

// Converts a set of Innkeeper route definitions to their eskip representation.
func convertJsonToEskip(data []*routeData, prependFilters, appendFilters []*eskip.Filter) ([]*eskip.Route, []string, string) {
	var (
		routes      []*eskip.Route
		deleted     []string
		lastChanged string
	)

	for _, d := range data {
		if d.Timestamp > lastChanged {
			lastChanged = d.Timestamp
		}

		if d.Action.Delete() {
			deleted = append(deleted, d.Name)
		} else {
			r, err := eskip.Parse(d.Eskip)
			if err == nil {
				for _, ri := range r {
					ri.Filters = append(prependFilters, append(ri.Filters, appendFilters...)...)
				}

				routes = append(routes, r...)
			} else {
				log.Error("error while parsing routes, innkeeper ", d.Name, err)
			}
		}
	}

	return routes, deleted, lastChanged
}

// Parses an Innkeeper API error message and returns its type.
func parseApiError(r io.Reader) (string, error) {
	message, err := ioutil.ReadAll(r)

	if err != nil {
		return "", err
	}

	ae := apiError{}
	if err := json.Unmarshal(message, &ae); err != nil {
		return "", err
	}

	return ae.ErrorType, nil
}

// Checks whether an API error is authentication/authorization related.
func isApiAuthError(error string) bool {
	aerr := authErrorType(error)
	return aerr == authErrorAuthorization || aerr == authErrorMissingCredentials || aerr == authErrorAuthentication
}

// Authenticates a client and stores the authentication token.
func (c *Client) authenticate() error {
	if c.opts.Authentication == nil {
		c.authToken = ""
		return nil
	}

	t, err := c.opts.Authentication.GetToken()
	if err != nil {
		return err
	}

	c.authToken = t
	return nil
}

// Checks if an http response status indicates an error, and returns an error
// object if it does.
func getHttpError(r *http.Response) (error, bool) {
	switch {
	case r.StatusCode < http.StatusBadRequest:
		return nil, false
	case r.StatusCode < http.StatusInternalServerError:
		return fmt.Errorf("innkeeper request failed: %s", r.Status), true
	case r.StatusCode < 600:
		return fmt.Errorf("innkeeper error: %s", r.Status), true
	default:
		return fmt.Errorf("unexpected error: %d - %s", r.StatusCode, r.Status), true
	}
}

func setAuthToken(h http.Header, value string) {
	h.Set(authHeaderName, bearerPrefix+value)
}

func (c *Client) writeRoute(url string, route *jsonRoute) error {

	res, err := json.Marshal(route)

	req, err := http.NewRequest("POST", url, bytes.NewReader(res))

	if err != nil {
		return err
	}

	authToken, err := c.opts.Authentication.GetToken()

	if err != nil {
		return err
	}

	setAuthToken(req.Header, authToken)
	req.Header.Set("Content-Type", "application/json")
	response, err := c.httpClient.Do(req)
	if err != nil {
		return err
	}

	defer response.Body.Close()

	if response.StatusCode == http.StatusUnauthorized || response.StatusCode == http.StatusForbidden ||
		response.StatusCode == http.StatusBadRequest {

		apiError, err := parseApiError(response.Body)
		if err != nil {
			return err
		}

		return fmt.Errorf("unknown error: %s", apiError)
	}

	return nil
}

// Calls an http request to an Innkeeper URL for route definitions.
// If authRetry is true, and the request fails due to an
// authentication/authorization related problem, it retries the request with
// reauthenticating first.
func (c *Client) requestData(authRetry bool, url string) ([]*routeData, error) {
	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return nil, err
	}

	setAuthToken(req.Header, c.authToken)
	response, err := c.httpClient.Do(req)
	if err != nil {
		return nil, err
	}

	defer response.Body.Close()

	if response.StatusCode == http.StatusUnauthorized || response.StatusCode == http.StatusForbidden {
		apiError, err := parseApiError(response.Body)
		if err != nil {
			return nil, err
		}

		if !isApiAuthError(apiError) {
			return nil, fmt.Errorf("unknown authentication error: %s", apiError)
		}

		if !authRetry {
			return nil, errors.New("authentication failed")
		}

		err = c.authenticate()
		if err != nil {
			return nil, err
		}

		return c.requestData(false, url)
	}

	if err, hasErr := getHttpError(response); hasErr {
		return nil, err
	}

	routesData, err := ioutil.ReadAll(response.Body)
	if err != nil {
		return nil, err
	}

	result := []*routeData{}
	err = json.Unmarshal(routesData, &result)
	return result, err
}

func (c *Client) LoadAndParseAll() ([]*eskip.RouteInfo, error) {
	routeList, err := c.LoadAll()
	if err != nil {
		return nil, err
	}

	routeInfos := []*eskip.RouteInfo{}

	for _, route := range routeList {
		routeInfos = append(routeInfos, &eskip.RouteInfo{
			Route:      *route,
			ParseError: nil,
		})
	}

	return routeInfos, nil
}

// Returns all active routes from Innkeeper.
func (c *Client) LoadAll() ([]*eskip.Route, error) {
	d, err := c.requestData(true, c.opts.Address+allRoutesPath)
	if err != nil {
		return nil, err
	}

	routes, _, lastChanged := convertJsonToEskip(d, c.prependFilters, c.appendFilters)
	if lastChanged > c.lastChanged {
		c.lastChanged = lastChanged
	}

	return routes, nil
}

// Returns all new and deleted routes from Innkeeper since the last LoadAll request.
func (c *Client) LoadUpdate() ([]*eskip.Route, []string, error) {
	d, err := c.requestData(true, c.opts.Address+fmt.Sprintf(updatePathFmt, c.lastChanged))
	if err != nil {
		return nil, nil, err
	}

	routes, deleted, lastChanged := convertJsonToEskip(d, c.prependFilters, c.appendFilters)
	if lastChanged > c.lastChanged {
		c.lastChanged = lastChanged
	}

	return routes, deleted, nil
}

func (c *Client) UpsertAll(routes []*eskip.Route) error {
	// convert the routes to the innkeeper json structs
	data := convertEskipToInnkeeper(routes)

	for _, route := range data {
		err := c.writeRoute(c.opts.Address+allRoutesPath, route)
		if err != nil {
			return err
		}
	}

	return nil
}

func (c *Client) DeleteAllIf(routes []*eskip.Route, cond eskip.RoutePredicate) error {
	return nil
}