Clojure - Pedestal - Oauth2 - Google sign-in example. inspired by: https://blog.knoldus.com/2014/04/05/google-sign-in-using-clojure/

oauth_google.clj

(ns oauth-google
  (:require
   [io.pedestal.interceptor :refer [interceptor]]
   [io.pedestal.interceptor.chain :refer [terminate]]
   [io.pedestal.http :as http]
   [io.pedestal.log :as log]
   [cheshire.core :as cheshire]
   [clj-http.client :as client-clj]
   [ring.util.response :as ring-resp]
   [ring.util.codec :as codec]))

(def google-red
  {:name  ::google-red
   :enter (fn [{{:keys [session form-params] :as request} :request
                response                                  :response
                datomic                                   :datomic
                config                                    :config
                :as                                       context}]
            (let [gcreds (->> config :oauth2-creds :google)
                  red (str "https://accounts.google.com/o/oauth2/auth?"
                           "scope=email%20profile&"
                           "redirect_uri=" (codec/url-encode (->> gcreds :redirect-uri)) "&"
                           "response_type=code&"
                           "client_id=" (codec/url-encode (->> gcreds :client-id)) "&"
                           "approval_prompt=force")]
              (assoc context :response (ring-resp/redirect red))))})

(defn google [q-params client-id client-secret redirect-uri]
  (let [access-token-response (->> {:form-params {:code          (->> q-params :code)
                                                  :client_id     client-id
                                                  :client_secret client-secret
                                                  :redirect_uri  redirect-uri
                                                  :grant_type    "authorization_code"}}
                                   (client-clj/post "https://accounts.google.com/o/oauth2/token"))
        access-token (get (->> access-token-response :body cheshire/parse-string) "access_token")
        user-details (->> access-token
                          (str "https://www.googleapis.com/oauth2/v1/userinfo?access_token=")
                          client-clj/get
                          :body
                          cheshire/parse-string)]
    user-details))

(def oauth2-google
  {:name  ::oauth2-google
   :enter (fn [{{:keys [session form-params query-params] :as request} :request
                response                                  :response
                datomic                                   :datomic
                config                                    :config
                :as                                       context}]
            (let [gcreds (->> config :oauth2-creds :google)]
              (clojure.pprint/pprint (google query-params
                                             (->> gcreds :client-id)
                                             (->> gcreds :client-secret)
                                             (->> gcreds :redirect-uri)))))})

(comment
  "You can't use this directly on repl, notice that client-id, redirect-uri and client-secret taken out from the context's config"
  "You need to have a running pedestal service"
  
  "res ex"
  {"verified_email" true,
   "id" "5264680293438599876546",
   "gender" "male",
   "email" "arifian.r@gmail.com",
   "given_name" "Arifian",
   "name" "Arifian Rahardianda",
   "locale" "en",
   "link" "https://plus.google.com/105468029343859983435",
   "picture"
   "https://lh5.googleusercontent.com/-r7Y25M7Ozn4/AAAAAAAAAAI/AAAAAAAAAPE/AuBdJkT4ktM/photo.jpg",
   "family_name" "Rahardianda"})

(def routes
  [["/google" :get [google-red] :route-name :google-red]
   ["/auth_google" :get [oauth2-google] :route-name :oauth2-google]])