actually do some OAuth

auth/auth.go

@@ -1,18 +1,59 @@
 package auth
 
 import (
+	"crypto/rand"
+	"encoding/base64"
 	"fmt"
+	"net/http"
 
 	"astraltech.xyz/calendar/v2/webserver"
+	"golang.org/x/oauth2"
 )
 
+func generateState() (string, error) {
+	b := make([]byte, 32)
+	if _, err := rand.Read(b); err != nil {
+		return "", err
+	}
+	return base64.RawURLEncoding.EncodeToString(b), nil
+}
+
 func HandlePasswordAuth(authData webserver.PasswordAuthData) bool {
 	fmt.Printf("%s, %s\n", authData.Username, authData.Password)
 	return false
 }
 
 func HandleOAuth(authData webserver.OAuthAuthData) bool {
-	fmt.Printf("doing an OAuth")
+	state, err := generateState()
+	if err != nil {
+		http.Error(*authData.ResponseWriter, "Failed to generate state", http.StatusInternalServerError)
+		return false
+	}
+	verifier := oauth2.GenerateVerifier()
+
+	http.SetCookie(*authData.ResponseWriter, &http.Cookie{
+		Name:     "oauth_state",
+		Value:    state,
+		Path:     "/",
+		MaxAge:   300,
+		HttpOnly: true,
+		SameSite: http.SameSiteLaxMode,
+	})
+
+	http.SetCookie(*authData.ResponseWriter, &http.Cookie{
+		Name:     "pkce_verifier",
+		Value:    verifier,
+		Path:     "/",
+		HttpOnly: true,
+		SameSite: http.SameSiteLaxMode,
+	})
+
+	url := OAuthConfigs[0].AuthCodeURL(
+		state,
+		oauth2.S256ChallengeOption(verifier),
+	)
+	http.Redirect(*authData.ResponseWriter, authData.Request, url, http.StatusFound)
+
 	return false
 }