moltin/gomo

package gomo

import (
    "encoding/json"
    "errors"
    "fmt"
    "io/ioutil"
    "net/http"
)

var errUnableToAuthenticate = errors.New("Unable to authenticate")

// AuthResponse contains the response from the auth call
type authResponse struct {
    Expires     int    `json:"expires"`
    ExpiresIn   int    `json:"expires_in"`
    Identifier  string `json:"identifier"`
    TokenType   string `json:"token_type"`
    AccessToken string `json:"access_token"`
}

func (c Client) authURL() string {
    return fmt.Sprintf("%s/oauth/access_token", c.Endpoint)
}

// Authenticate makes a call to get the access token for the client's credentials
func (c *Client) Authenticate() error {
    var err error

    r, err := http.PostForm(c.authURL(), c.credentials.authFormValues())
    if err != nil {
        return err
    }

    if r.StatusCode != 200 {
        return errUnableToAuthenticate
    }

    return c.extractAccessTokenFromResponse(r)
}

func (c *Client) extractAccessTokenFromResponse(r *http.Response) error {

    defer r.Body.Close()

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

    ar := authResponse{}
    err = json.Unmarshal(b, &ar)
    if err != nil {
        return err
    }

    c.AccessToken = ar.AccessToken

    return nil
}