/*
Copyright © 2023 Philipp Wolfer <phw@uploadedlobster.com>

Scotty is free software: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later version.

Scotty is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
Scotty. If not, see <https://www.gnu.org/licenses/>.
*/

package auth

import (
	"context"

	"golang.org/x/oauth2"
)

type OAuth2Strategy interface {
	Config() oauth2.Config

	AuthCodeURL(verifier string, state string) AuthUrl

	ExchangeToken(code CodeResponse, verifier string) (*oauth2.Token, error)
}

type AuthUrl struct {
	// The URL the user must visit to approve access
	Url string
	// Random state string passed on to the callback.
	// Leave empty if the service does not support state.
	State string
	// Parameter name of the code passed on to the callback (usually "code")
	Param string
}

type CodeResponse struct {
	Code  string
	State string
}

func NewStandardStrategy(conf oauth2.Config) OAuth2Strategy {
	return StandardStrategy{conf: conf}
}

type StandardStrategy struct {
	conf oauth2.Config
}

func (s StandardStrategy) Config() oauth2.Config {
	return s.conf
}

func (s StandardStrategy) AuthCodeURL(verifier string, state string) AuthUrl {
	url := s.conf.AuthCodeURL(state, oauth2.AccessTypeOffline, oauth2.S256ChallengeOption(verifier))
	return AuthUrl{
		Url:   url,
		State: state,
		Param: "code",
	}
}

func (s StandardStrategy) ExchangeToken(code CodeResponse, verifier string) (*oauth2.Token, error) {
	ctx := context.Background()
	return s.conf.Exchange(ctx, code.Code, oauth2.VerifierOption(verifier))
}