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[0] in function chmod in /var/www/hopeinstoughton_www/wp-content/plugins/simple-universal-google-analytics/main.php on line 8
[1] in function include_once in /var/www/hopeinstoughton_www/wp-settings.php on line 560
[2] in function require_once in /var/www/hopeinstoughton_www/wp-config.php on line 85
[3] in function require_once in /var/www/hopeinstoughton_www/wp-load.php on line 50
[4] in function require_once in /var/www/hopeinstoughton_www/wp-blog-header.php on line 13
[5] in function require in /var/www/hopeinstoughton_www/index.php on line 17

<?php


// https://www.cloudways.com/blog/add-facebook-login-in-php/

// ./composer.phar require  league/oauth2-facebook

use League\OAuth2\Client\Token\AccessToken;


class authenticate_facebook extends his_authenticate {
    public function __construct() {
        parent::__construct();
		
		$button = <<<'BLOCK'
<a href="/~/facebook-login" class="action-facebook _5h0c _5h0d" style="width: 400px; margin: 5px 0" role="button" tabindex="0">
<table class="uiGrid _51mz _5h0i _88va _5f0n" cellspacing="0" cellpadding="0"><tbody><tr class="_51mx"><td class="_51m-"><div class="_5h0j"><span class="_5h0k"><img class="img" src="https://static.xx.fbcdn.net/rsrc.php/v3/y3/r/U7MAWJlE6hZ.png" alt="" width="24" height="24"></span></div></td><td class="_51m- _51mw"><div class="_5h0s"><div class="_5h0o _8kto">Log in With Facebook</div></div></td></tr><tr class="_51mx"><td class="_51m-"><span class="_8jan"></span></td><td class="_51m-"></td></tr></tbody></table>
</a>
BLOCK;		
        $this->Name('Facebook')
            ->Head('')
            ->Button($button)
            ->onValueChange();
    }

    public function getValue($key = 'fb_client_id') {
        return $this->values[$key] ?? '';
    }
    
    protected function onValueChange() {
//<script  crossorigin="anonymous" src="https://connect.facebook.net/en_GB/sdk.js#xfbml=1&version=v17.0&appId={$id}&autoLogAppEvents=1" nonce="bFruQCAB"></script>
        $id = rawurlencode($this->getValue());	// async defer
		$head = <<<BLOCK
BLOCK;

		$head .= <<<'BLOCK'
<style type="text/css">
._5h0d ._5h0i {
	height: 40px;
}
._5h0i._88va {
	background-color: #1877f2;
}
._5h0c {
	background-color: transparent;
	cursor: pointer;
	display: inline-block;
	vertical-align: top;
}
._5f0n {
	table-layout: fixed;
	width: 100%;
  font-family: Helvetica, Arial, sans-serif;
  line-height: 1.28;
  -moz-text-size-adjust: none;	
}
._5h0i {
	border-radius: 4px;
	color: #fff;
}
._5h0d ._88va ._5h0k {
	margin: 8px 8px 8px 12px;
}
._5h0d ._8kto {
	font-weight: bold;
	padding-top: 1px;
}
._5h0c {
	cursor: pointer;
}
._5h0i {
	color: #fff;
}
._5h0d ._5h0o {
	font-size: 16px;
	margin-right: 12px;
}
._51mz {
	border-collapse: collapse;
	border-spacing: 0;
}
._5h0o {
	border: none;
	font-family: Helvetica, Arial, sans-serif;
	letter-spacing: .25px;
	overflow: hidden;
	text-align: center;
	text-overflow: clip;
	white-space: nowrap;
}
._5h0d ._5h0i td:first-child, ._5h0d ._xvp._5h0i td:last-child {
	width: 40px;
}
._5h0d ._88va ._5h0k {
	margin: 8px 8px 8px 12px;
}
._5h0d ._5h0k {
	height: 24px;
	margin: 8px;
}
._5h0d ._5h0k img {
	max-width: unset !important;
}
._5h0c ._5h0k {
	float: left;
}
._5h0c ._5h0j {
	white-space: nowrap;
}
._51mz ._51m-:first-child {
	padding-left: 0;
}
._51mx:last-child > ._51m- {
	padding-bottom: 0;
}
</style>
<script type="text/javascript">
function _fb_response(response) {
	if (response.status == 'connected') {
		document.location.href = '/~/facebook-auth' + 
			'?uid=' + encodeURIComponent( response.authResponse.userID) + 
			'&token=' + encodeURIComponent( response.authResponse.accessToken);
		
	}

}

jQuery(function() {
	let $form = jQuery('form.post-password-form');
	if ($form.length) {
		
		FB.getLoginStatus(function(response) {
			_fb_response(response);
		});
		jQuery('.action-facebook').on('click', function(e) {
			e.preventDefault()
			FB.login(function(response) {
					_fb_response(response);
				}, {
					scope: 'public_profile,email'
				}
			);
		});
	}
});
</script>
BLOCK;

        $text = <<<BLOCK
<div id="fb-root"></div>
BLOCK;
		$this->Head($head)
			 ->Body($text);
    }
    
    public function FieldDefinition() {
        return [
            [   
                'name' => 'fb_client_id',
                'caption' => 'App ID',
                'type' => 'string',
            ], [
                'name' => 'fb_secret',
                'caption' => 'Secret',
                'type' => 'string',
            ],
        ];
    }
	
	protected function _authorize($accessToken) {
		
		$fb = new \League\OAuth2\Client\Provider\Facebook([
			'clientId'          => $this->getValue('fb_client_id'),
			'clientSecret'      => $this->getValue('fb_secret'),
//			'redirectUri'       => 'https://example.com/callback-url',
			'graphApiVersion'   => 'v2.10',
		]);		

		try {
			$token = $fb->getLongLivedAccessToken($accessToken);
		} catch (Exception $e) {
			echo 'Failed to exchange the token: '.$e->getMessage();		// not a valid facebook login
			exit;
		}		
		$user = $fb->getResourceOwner($token);
		if (empty($user->getEmail())) {
			echo 'Fatal Error: You must have an email address associated with your facebook account';
			exit;
		}
		
		return [
			'id'        => $user->getId(),
			'email'     => $user->getEmail(),
			'name'      => $user->getName(),
			'picture'   => $user->getPictureUrl(),
		];
		
	}

	protected function _authorize_code($code) {
		
		$site = get_site_url();
		$fb = new \League\OAuth2\Client\Provider\Facebook([
			'clientId'          => $this->getValue('fb_client_id'),
			'clientSecret'      => $this->getValue('fb_secret'),
			'redirectUri'       => $site . '/~/facebook-auth',
			'graphApiVersion'   => 'v2.10',
		]);		

		try {
			$token = $fb->getAccessToken('authorization_code', [
				'code' => $code,
			]);

		} catch (Exception $e) {
			echo 'Failed to exchange the token: '.$e->getMessage();		// not a valid facebook login
			exit;
		}		
		$user = $fb->getResourceOwner($token);
		if (empty($user->getEmail())) {
			echo 'Fatal Error: You must have an email address associated with your facebook account';
			exit;
		}
		
		return [
			'id'        => $user->getId(),
			'email'     => $user->getEmail(),
			'name'      => $user->getName(),
			'picture'   => $user->getPictureUrl(),
		];
		
	}
	
	private function _generateLogin() {
		$site = get_site_url();

		$fb = new \League\OAuth2\Client\Provider\Facebook([
			'clientId'          => $this->getValue('fb_client_id'),
			'clientSecret'      => $this->getValue('fb_secret'),
//			'redirectUri'       => 'https://example.com/callback-url',
			'graphApiVersion'   => 'v2.10',
		]);		

		$permissions = ['email']; // Optional permissions
		
		$redirectUrl = rawurlencode($site . '/~/facebook-auth');
		$clientId = $this->getValue('fb_client_id');
		$loginUrl = "https://www.facebook.com/v18.0/dialog/oauth?client_id={$clientId}&redirect_uri={$redirectUrl}&scope=email";		// &state={"{st=state123abc,ds=123456789}"}
		header('Location: ' . $loginUrl);
	}
	
	
    public function onUrl($url) {
        if ($url == '/~/facebook-auth' && !$this->isPost) {
			session_start();
			if (isset($_GET['code'])) {
				$code = $_GET['code'];
				return $this->_authorize_code($code);
			} else {
				$token = $_GET['token'];
				return $this->_authorize($token);
			}
        } elseif ($url == '/~/facebook-login') {
			session_start();
			$this->_generateLogin();
			session_write_close();
			exit;
		}
        return NULL;                    // not intercepted
    }
	

}

return new authenticate_facebook;

/*
FB.login(function(response) {
  // handle the response
}, {scope: 'public_profile,email'});

 			FB.api('/v17.0/me', {fields: 'name,email'}, function(response2) {
				console.log('Successful login for: ', response2);
			});			

GET https://graph.facebook.com/v11.0/oauth/access_token?
  client_id={app-id} // Replace with your application’s ID
  &redirect_uri={"https://www.domain.com/login"}  // Must match the Redirect URI stated in the Authorization Request
  &code_verifier={code-verifier} // Replace with generated code verifier
  &code={authorization-code} // Replace with Authorization Code 

*/