cauth/handlers.go

package cauth

import (
	"context"
	"crypto/rand"
	"encoding/base64"
	"fmt"
	"log"
	"net/http"
	"time"

	"github.com/coreos/go-oidc/v3/oidc"
	"golang.org/x/oauth2"
)

type Handlers struct {
	oauth2Config *oauth2.Config
	session      SessionStorer
	verifier     *oidc.IDTokenVerifier
}

func NewHandler(oauth2Config *oauth2.Config, session SessionStorer, verifier *oidc.IDTokenVerifier) (*Handlers, error) {
	return &Handlers{
		oauth2Config: oauth2Config,
		session:      session,
		verifier:     verifier,
	}, nil
}

type UserClaims struct {
	Email    string `json:"email"`
	Verified bool   `json:"email_verified"`
	Name     string `json:"given_name"`
	Username string `json:"cognito:username"`
	Picture  string `json:"picture"`
}

func generateState() (string, error) {
	b := make([]byte, 16)
	_, err := rand.Read(b)
	if err != nil {
		return "", err
	}
	return base64.URLEncoding.EncodeToString(b), nil
}

func (h *Handlers) SignIn(w http.ResponseWriter, r *http.Request) {
	state, err := generateState()
	if err != nil {
		log.Println("Failed to generate state")
		http.Error(w, "Something went wrong", http.StatusInternalServerError)
		return
	}

	session, err := h.session.Get(r)
	if err != nil {
		http.Error(w, "Failed to get session", http.StatusInternalServerError)
		return
	}
	session.Values["state"] = state
	err = session.Save(r, w)
	if err != nil {
		http.Error(w, "Failed to save session", http.StatusInternalServerError)
		return
	}

	http.Redirect(w, r, h.oauth2Config.AuthCodeURL(state, oauth2.AccessTypeOffline), http.StatusFound)
}

// CallbackHandler handles the OAuth2 callback from Cognito
func (h *Handlers) CallbackHandler(w http.ResponseWriter, r *http.Request) {
	ctx := context.Background()

	session, err := h.session.Get(r)
	if err != nil {
		http.Error(w, "Failed to get session", http.StatusInternalServerError)
		return
	}

	state, ok := session.Values["state"].(string)
	if !ok || state != r.URL.Query().Get("state") {
		http.Error(w, "Invalid state parameter", http.StatusBadRequest)
		return
	}

	code := r.URL.Query().Get("code")
	if code == "" {
		http.Error(w, "Code not found", http.StatusBadRequest)
		return
	}

	oauth2Token, err := h.oauth2Config.Exchange(ctx, code)
	if err != nil {
		log.Printf("Failed to exchange token: %v", err)
		http.Error(w, "Failed to exchange token", http.StatusInternalServerError)
		return
	}

	rawIDToken, ok := oauth2Token.Extra("id_token").(string)
	if !ok {
		http.Error(w, "No id_token field in oauth2 token", http.StatusInternalServerError)
		return
	}

	idToken, err := h.verifier.Verify(ctx, rawIDToken)
	if err != nil {
		log.Printf("Failed to verify ID Token: %v", err)
		http.Error(w, "Failed to verify ID Token", http.StatusInternalServerError)
		return
	}

	var claims UserClaims

	if err := idToken.Claims(&claims); err != nil {
		log.Printf("Failed to parse claims: %v", err)
		http.Error(w, "Failed to parse claims", http.StatusInternalServerError)
		return
	}

	session.Values["access_token"] = oauth2Token.AccessToken
	session.Values["user_info"] = claims

	fmt.Println(claims)
	session.Options.MaxAge = int(oauth2Token.Expiry.Sub(time.Now()).Seconds())
	err = session.Save(r, w)
	if err != nil {
		log.Printf("Failed to save session: %v", err)
		http.Error(w, "Failed to save session", http.StatusInternalServerError)
		return
	}

	http.Redirect(w, r, "/", http.StatusFound)
}

// LogoutHandler clears the session and logs the user out
func (h *Handlers) LogoutHandler(w http.ResponseWriter, r *http.Request) {
	session, err := h.session.Get(r)
	if err != nil {
		http.Error(w, "Failed to get session", http.StatusInternalServerError)
		return
	}

	session.Options.MaxAge = -1
	err = session.Save(r, w)
	if err != nil {
		log.Printf("Failed to clear session: %v", err)
		http.Error(w, "Failed to clear session", http.StatusInternalServerError)
		return
	}

	http.Redirect(w, r, "/", http.StatusSeeOther)
}