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basecamp3.go
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basecamp3.go
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package basecamp3
import (
"context"
"encoding/json"
"errors"
"fmt"
"io"
"io/ioutil"
"log"
"net/http"
"strconv"
"strings"
"time"
"golang.org/x/oauth2"
)
var Endpoint = oauth2.Endpoint{
AuthURL: "https://launchpad.37signals.com/authorization/new",
TokenURL: "https://launchpad.37signals.com/authorization/token",
}
const (
BasecampApiRootURL = "https://3.basecampapi.com"
)
type Basecamp struct {
client *http.Client
oauth *oauth2.Config
TokenPersitence func(w http.ResponseWriter, r *http.Request) ContextWithTokenPersistence
}
type ContextWithTokenPersistence interface {
context.Context
oauth2.TokenSource
SetToken(*oauth2.Token)
}
func (bc *Basecamp) getClient(tokensource oauth2.TokenSource) *http.Client {
if bc.client == nil {
// reset default client to prevent settings to be overwritten by other previously created http clients
http.DefaultClient = &http.Client{}
bc.client = oauth2.NewClient(context.Background(), tokensource)
}
return bc.client
}
func (bc *Basecamp) verified(ctx ContextWithTokenPersistence, code string) error {
tok, err := bc.oauth.Exchange(ctx, code, oauth2.SetAuthURLParam("type", "web_server"))
if err != nil {
return err
}
ctx.SetToken(tok)
bc.getClient(bc.oauth.TokenSource(ctx, tok))
return nil
}
func (bc *Basecamp) VerifyRequest(w http.ResponseWriter, r *http.Request) {
code := r.URL.Query().Get("code")
err := bc.verified(bc.TokenPersitence(w, r), code)
if err == nil {
fmt.Fprintf(w, "Auth successful")
} else {
fmt.Fprintf(w, "Auth error: %v", err)
}
}
func (bc *Basecamp) Authenticate(w http.ResponseWriter, r *http.Request) {
http.Redirect(w, r, bc.oauth.AuthCodeURL("state", oauth2.SetAuthURLParam("type", "web_server")), http.StatusTemporaryRedirect)
}
func (bc *Basecamp) ApiReverseProxy(w http.ResponseWriter, r *http.Request) {
path := strings.TrimPrefix(r.URL.Path, "/proxy")
url := BasecampApiRootURL + path
log.Printf("GET %s\n", url)
bc.proxyGet(bc.TokenPersitence(w, r), url, w)
}
func extractToken(client *http.Client) *oauth2.Token {
t, err := client.Transport.(*oauth2.Transport).Source.Token()
if err == nil {
return t
}
return nil
}
func (bc *Basecamp) get(ctx ContextWithTokenPersistence, url string) (*http.Response, error) {
req, err := http.NewRequest("GET", url, nil)
if err != nil {
return nil, err
}
req.Header.Set("User-Agent", "Balazsgrill's BC3 integration (https://github.com/balazsgrill/basecamp3)")
client := bc.getClient(ctx)
t := extractToken(client)
if t == nil {
// TODO redirect to auth
return nil, errors.New("not authenticated")
} else {
ctx.SetToken(t)
return client.Do(req)
}
}
func (bc *Basecamp) getWithRateLimit(ctx ContextWithTokenPersistence, url string) (*http.Response, error) {
resp, err := bc.get(ctx, url)
if err != nil {
return resp, err
}
if resp.StatusCode == 429 {
// API Rate limit
waits := resp.Header.Get("Retry-After")
wait, err := strconv.Atoi(waits)
if err != nil {
log.Printf("HTTP 429 received, but no walid Retry-After header was provided (%s)", waits)
}
time.Sleep(time.Duration(wait) * time.Second)
resp, err = bc.get(ctx, url)
if err != nil {
return resp, err
}
}
return resp, err
}
func (bc *Basecamp) jsonGet(ctx ContextWithTokenPersistence, url string, value interface{}) error {
resp, err := bc.getWithRateLimit(ctx, url)
if err != nil {
return err
}
defer resp.Body.Close()
data, _ := ioutil.ReadAll(resp.Body)
if resp.StatusCode != http.StatusOK {
return fmt.Errorf("HTTP %d: %s", resp.StatusCode, string(data))
}
return json.Unmarshal(data, value)
}
func (bc *Basecamp) proxyGet(ctx ContextWithTokenPersistence, url string, w http.ResponseWriter) {
resp, err := bc.get(ctx, url)
if err != nil {
w.WriteHeader(http.StatusBadGateway)
fmt.Fprint(w, err)
return
}
defer resp.Body.Close()
w.WriteHeader(resp.StatusCode)
io.Copy(w, resp.Body)
}
func New(clientID string, clientSecret string, redirectURL string) *Basecamp {
return &Basecamp{
oauth: &oauth2.Config{
ClientID: clientID,
ClientSecret: clientSecret,
RedirectURL: redirectURL,
Scopes: []string{},
Endpoint: Endpoint,
},
TokenPersitence: ReverseProxyRequestContext,
}
}
func NewByOauth(oauth *oauth2.Config) *Basecamp {
return &Basecamp{
oauth: oauth,
TokenPersitence: ReverseProxyRequestContext,
}
}
// ServeLocalhost configures and starts a HTTP server on localhost which can be used to authenticate and query BC.
// Capable of handling a single BC session, and assumes the redirect URL to be set as http://localhost:<port>/verify
func ServeLocalhost(port int, clientID string, clientSecret string) {
bc := New(clientID, clientSecret, fmt.Sprintf("http://localhost:%d/verify", port))
// handle route using handler function
http.HandleFunc("/verify", bc.VerifyRequest)
http.HandleFunc("/auth", bc.Authenticate)
http.HandleFunc("/proxy/", bc.ApiReverseProxy)
log.Printf("Listening on port %d", port)
http.ListenAndServe(fmt.Sprintf("localhost:%d", port), nil)
}