package auth

import (
	"sync"

	"golang.org/x/oauth2"
)

type TokenSource struct {
	client *Client
	token  *Token

	mu sync.Mutex
}

func (c *Client) TokenSource(token *Token) oauth2.TokenSource {
	return &TokenSource{
		client: c,
		token:  token,
	}
}

func (ts *TokenSource) Token() (*oauth2.Token, error) {
	ts.mu.Lock()
	defer ts.mu.Unlock()

	if ts.token.Valid() {
		return ts.token.Underlying(), nil
	}

	token, err := ts.client.RefreshToken(ts.token)
	if err != nil {
		return nil, err
	}

	ts.token = token
	return ts.token.Underlying(), nil
}