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// Copyright 2014 Gary Burd
//
// 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 main
import (
"encoding/json"
"flag"
"fmt"
"io/ioutil"
"log"
"net/http"
"net/url"
"text/template"
"github.com/gomodule/oauth1/examples/session"
"github.com/gomodule/oauth1/oauth"
)
// Session state keys.
const (
tempCredKey = "tempCred"
tokenCredKey = "tokenCred"
)
var oauthClient = oauth.Client{
TemporaryCredentialRequestURI: "https://api.discogs.com/oauth/request_token",
ResourceOwnerAuthorizationURI: "https://www.discogs.com/oauth/authorize",
TokenRequestURI: "https://api.discogs.com/oauth/access_token",
Header: http.Header{"User-Agent": {"ExampleDiscogsClient/1.0"}},
}
var credPath = flag.String("config", "config.json", "Path to configuration file containing the application's credentials.")
func readCredentials() error {
b, err := ioutil.ReadFile(*credPath)
if err != nil {
return err
}
return json.Unmarshal(b, &oauthClient.Credentials)
}
// serveLogin gets the OAuth temp credentials and redirects the user to the
// Discogs' authorization page.
func serveLogin(w http.ResponseWriter, r *http.Request) {
callback := "http://" + r.Host + "/callback"
tempCred, err := oauthClient.RequestTemporaryCredentials(nil, callback, nil)
if err != nil {
http.Error(w, "Error getting temp cred, "+err.Error(), 500)
return
}
s := session.Get(r)
s[tempCredKey] = tempCred
if err := session.Save(w, r, s); err != nil {
http.Error(w, "Error saving session , "+err.Error(), 500)
return
}
http.Redirect(w, r, oauthClient.AuthorizationURL(tempCred, nil), 302)
}
// serveOAuthCallback handles callbacks from the OAuth server.
func serveOAuthCallback(w http.ResponseWriter, r *http.Request) {
s := session.Get(r)
tempCred, _ := s[tempCredKey].(*oauth.Credentials)
if tempCred == nil || tempCred.Token != r.FormValue("oauth_token") {
http.Error(w, "Unknown oauth_token.", 500)
return
}
tokenCred, _, err := oauthClient.RequestToken(nil, tempCred, r.FormValue("oauth_verifier"))
if err != nil {
http.Error(w, "Error getting request token, "+err.Error(), 500)
return
}
delete(s, tempCredKey)
s[tokenCredKey] = tokenCred
if err := session.Save(w, r, s); err != nil {
http.Error(w, "Error saving session , "+err.Error(), 500)
return
}
http.Redirect(w, r, "/", 302)
}
// serveLogout clears the token credentials
func serveLogout(w http.ResponseWriter, r *http.Request) {
s := session.Get(r)
delete(s, tokenCredKey)
if err := session.Save(w, r, s); err != nil {
http.Error(w, "Error saving session , "+err.Error(), 500)
return
}
http.Redirect(w, r, "/", 302)
}
// authHandler reads the auth cookie and invokes a handler with the result.
type authHandler struct {
handler func(w http.ResponseWriter, r *http.Request, c *oauth.Credentials)
optional bool
}
func (h *authHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
cred, _ := session.Get(r)[tokenCredKey].(*oauth.Credentials)
if cred == nil && !h.optional {
http.Error(w, "Not logged in.", 403)
return
}
h.handler(w, r, cred)
}
// getJSON gets a resource from the Discogs API server and decodes the result as JSON.
func getJSON(cred *oauth.Credentials, endpoint string, form url.Values, v interface{}) error {
resp, err := oauthClient.Get(nil, cred, "https://api.discogs.com"+endpoint, form)
if err != nil {
return err
}
defer resp.Body.Close()
if resp.StatusCode != 200 {
return fmt.Errorf("server returned status %d", resp.StatusCode)
}
return json.NewDecoder(resp.Body).Decode(v)
}
// respond responds to a request by executing the html template t with data.
func respond(w http.ResponseWriter, t *template.Template, data interface{}) {
w.Header().Set("Content-Type", "text/html; charset=utf-8")
if err := t.Execute(w, data); err != nil {
log.Print(err)
}
}
func serveHome(w http.ResponseWriter, r *http.Request, cred *oauth.Credentials) {
if r.URL.Path != "/" {
http.NotFound(w, r)
return
}
if cred == nil {
data := struct{ Host string }{r.Host}
respond(w, homeLoggedOutTmpl, &data)
} else {
var data struct {
Username string
}
if err := getJSON(cred, "/oauth/identity", nil, &data); err != nil {
http.Error(w, err.Error(), 500)
return
}
respond(w, homeTmpl, &data)
}
}
var httpAddr = flag.String("addr", ":8080", "HTTP server address")
func main() {
flag.Parse()
if err := readCredentials(); err != nil {
log.Fatalf("Error reading configuration, %v", err)
}
http.Handle("/", &authHandler{handler: serveHome, optional: true})
http.HandleFunc("/login", serveLogin)
http.HandleFunc("/logout", serveLogout)
http.HandleFunc("/callback", serveOAuthCallback)
if err := http.ListenAndServe(*httpAddr, nil); err != nil {
log.Fatalf("Error listening, %v", err)
}
}
var (
homeLoggedOutTmpl = template.Must(template.New("loggedout").Parse(
`<html>
<body>
<a href="/login">login</a>
</body>
</html>`))
homeTmpl = template.Must(template.New("home").Parse(
`<html>
<body>
<p>Welcome {{.Username}}!
</body></html>`))
)
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