inventory-plus-plus/internal/server/middleware/auth.go

package middleware

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io"
	"time"

	"ruben/inventory2/internal/consts"
	"ruben/inventory2/internal/domains/accounts"
	"ruben/inventory2/internal/domains/authentication"
	"ruben/inventory2/internal/logging"
	"ruben/inventory2/internal/server/cookies"
	"ruben/inventory2/internal/server/response"

	"github.com/gin-gonic/gin"
)

type (
	Auth struct {
		log         *logging.Logger
		auth        *authentication.Authenticator
		newLoginURL LoginURLProviderFunc
		accts       *accounts.Store
	}

	Identity struct {
		AccessToken string
		Claims      authentication.AccessTokenClaims
		User        accounts.OAuthUser
		Account     *accounts.Account
	}

	LoginURLProviderFunc = func(ctx context.Context, auth *authentication.Authenticator, targetURI string) (string, error)

	AuthorizationAssertions = response.HandlerFunc
)

func NewAuth(
	logger *logging.Logger,
	auth *authentication.Authenticator,
	newLoginURL LoginURLProviderFunc,
	accts *accounts.Store,
) *Auth {
	return &Auth{
		log:         logger,
		auth:        auth,
		newLoginURL: newLoginURL,
		accts:       accts,
	}
}

func (a *Auth) AddIdentity(fn response.HandlerFunc) response.HandlerFunc {
	return func(c *gin.Context) (response.Response, error) {
		c, err := a.AddIdentityToRequest(c)
		if err != nil {
			return nil, err
		}

		return fn(c)
	}
}

func (a *Auth) AddIdentityToRequest(c *gin.Context) (*gin.Context, error) {
	r := c.Request

	ck, err := r.Cookie("access_token")
	if err != nil {
		return c, nil
	}

	ctx := r.Context()

	accessToken := ck.Value

	claims, expiration, err := a.auth.GetAccessTokenClaimsAndExpiration(ctx, accessToken)
	if err != nil {
		if errors.Is(err, consts.ErrNotFound) {
			return c, nil
		}

		return c, response.Errorf("failed to load authentication details: %w", err)
	}

	if expiration.Before(time.Now()) {
		return c, nil
	}

	user, acct, err := a.accts.GetUserAndAccountByAccessToken(ctx, accessToken)
	if err != nil {
		return c, response.Errorf("failed to load user and account defails: %w", err)
	}

	c.Request = r.WithContext(SetIdentity(ctx, Identity{
		AccessToken: accessToken,
		Claims:      claims,
		User:        user,
		Account:     acct,
	}))

	return c, nil
}

// TODO: after getting auth, consider making http handler functions take 'claims', etc, as function arguments
//	- then consider doing the same with authorizationAssertions

// auth middleware to verify access_token cookie and set custom claims in the request context
func (a *Auth) AuthenticateAndAddIdentity(f response.HandlerFunc, assertions ...AuthorizationAssertions) response.HandlerFunc {
	return func(c *gin.Context) (response.Response, error) {
		c, res, err := a.AuthenticateAndAddIdentityToRequest(c, assertions...)
		if res != nil || err != nil {
			return res, nil
		}

		return f(c)
	}
}

func (a *Auth) AuthenticateAndAddIdentityToRequest(c *gin.Context, assertions ...AuthorizationAssertions) (*gin.Context, response.Response, error) {
	r := c.Request
	ck, err := r.Cookie("access_token")
	if err != nil {
		return c, response.TemporaryRedirect("/").
			JSON("no access_token cookie provided"), nil
	}

	ctx := r.Context()

	accessToken := ck.Value

	claims, expiration, err := a.auth.GetAccessTokenClaimsAndExpiration(ctx, accessToken)
	if err != nil {
		if errors.Is(err, consts.ErrNotFound) {
			u, err := a.newLoginURL(ctx, a.auth, r.URL.String())
			if err != nil {
				return c, nil, response.Errorf("failed to generate login url: %w", err)
			}

			return c, response.TemporaryRedirect(u), nil
		}

		return c, nil, response.Errorf("failed to authenticate: %w", err)
	}

	now := time.Now()

	// refresh tokens, when the access token is "old enough"

	// id token lifetime is 48 hours, allowing a person to use the app everyday comfortably, with wiggle room, without having to log in.
	const idTokenLifetime = 48 * time.Hour
	if refreshFloor := expiration.Add(-(idTokenLifetime / 4)); refreshFloor.Before(now) {
		accessToken, expiration, err = a.auth.RefreshAccessToken(ctx, accessToken)
		if err != nil {
			a.log.Warn("failed to refresh access token", "error", err)
			return c, response.TemporaryRedirect("/").
				Body(io.NopCloser(bytes.NewBuffer([]byte(fmt.Sprintf("failed to refresh access token: %v", err))))).
				Cookie(cookies.Expired("access_token")), nil
		}

		// 'redirect' to same url, to set the new access_token cookie
		return c, response.TemporaryRedirect(r.URL.String()).
			Cookie(cookies.AccessToken(accessToken, expiration)), nil
	}

	// add identity info to request context

	user, acct, err := a.accts.GetUserAndAccountByAccessToken(ctx, accessToken)
	if err != nil {
		return c, nil, response.Errorf("failed to authorize: %w", err)
	}

	for _, as := range assertions {
		if res, err := as(c); res != nil || err != nil {
			return c, res, err
		}
	}

	r = r.WithContext(SetIdentity(ctx, Identity{
		AccessToken: accessToken,
		Claims:      claims,
		User:        user,
		Account:     acct,
	}))
	c.Request = r

	return c, nil, nil
}

type identityKey struct{}

// stores identity in request context
func SetIdentity(ctx context.Context, id Identity) context.Context {
	return context.WithValue(ctx, identityKey{}, id)
}

// get identity from request context
func GetIdentity(ctx context.Context) Identity {
	id, _ := ctx.Value(identityKey{}).(Identity)
	return id
}