Eu estou tentando fazer um aplicativo usando a API de calendário do Google. Estou seguindo as instruçõesAqui. Eu posso fazer o pedido para obter o código de autorização, mas não consigo formar um pedido válido para obter um token de acesso. Eu continuo recebendo a resposta{"error" : "invalid_request"}. Esta é a solicitação POST que estou fazendo:

POST /o/oauth2/token HTTP/1.1
Host: accounts.google.com
Content-Type: application/x-www-form-urlencoded

code=4/vxQqw9JMYEnXvI8A_93OV7kBSg6h.8r2yJUkMc18dshQV0ieZDAraZNwsbwI&
client_id=[my client id]&
client_secret=[my client secret]&
redirect_uri=http://localhost:8080/auth&
grant_type=authorization_code

Abaixo está a saída de chamar o url através de curl. Meu aplicativo real está escrito em Node.js, mas recebo a mesma resposta do curl, como faço no aplicativo. Eu procurei por aí e vi pessoas com problemas semelhantes, mas ainda não consigo descobrir o que estou fazendo de errado.

curl -v -k --header "Content-Type: application/x-www-form-urlencoded" --data-urlencode "code=4/vxQqw9JMYEnXvI8A_93OV7kBSg6h.8r2yJUkMc18dshQV0ieZDAraZNwsbwI&client_id=[my client id]&client_secret=[my client secret]&redirect_uri=http://localhost:8080/auth&grant_type=authorization_code" https://accounts.google.com/o/oauth2/token
* About to connect() to accounts.google.com port 443 (#0)
*   Trying 173.194.74.84... connected
* Connected to accounts.google.com (173.194.74.84) port 443 (#0)
* SSLv3, TLS handshake, Client hello (1):
* SSLv3, TLS handshake, Server hello (2):
* SSLv3, TLS handshake, CERT (11):
* SSLv3, TLS handshake, Server finished (14):
* SSLv3, TLS handshake, Client key exchange (16):
* SSLv3, TLS change cipher, Client hello (1):
* SSLv3, TLS handshake, Finished (20):
* SSLv3, TLS change cipher, Client hello (1):
* SSLv3, TLS handshake, Finished (20):
* SSL connection using RC4-SHA
* Server certificate:
*    subject: C=US; ST=California; L=Mountain View; O=Google Inc; CN=accounts.google.com
*    start date: 2011-07-21 00:00:00 GMT
*    expire date: 2013-07-18 23:59:59 GMT
*    common name: accounts.google.com (matched)
*    issuer: C=ZA; O=Thawte Consulting (Pty) Ltd.; CN=Thawte SGC CA
*    SSL certificate verify result: unable to get local issuer certificate (20), continuing anyway.
> POST /o/oauth2/token HTTP/1.1
> User-Agent: curl/7.21.3 (i386-apple-darwin8.11.1) libcurl/7.21.3 OpenSSL/0.9.7l zlib/1.2.5 libidn/1.17
> Host: accounts.google.com
> Accept: */*
> Content-Type: application/x-www-form-urlencoded
> Content-Length: 180
> 
< HTTP/1.1 400 Bad Request
< Cache-Control: no-cache, no-store, max-age=0, must-revalidate
< Pragma: no-cache
< Expires: Fri, 01 Jan 1990 00:00:00 GMT
< Date: Tue, 29 May 2012 12:43:49 GMT
< Content-Type: application/json
< X-Content-Type-Options: nosniff
< X-Frame-Options: SAMEORIGIN
< X-XSS-Protection: 1; mode=block
< Server: GSE
< Transfer-Encoding: chunked
< 
{
  "error" : "invalid_request"
* Connection #0 to host accounts.google.com left intact
* Closing connection #0
* SSLv3, TLS alert, Client hello (1):
}