<?php

class LinkedIn
{
    private $_config = array();
    private $_state = null;
    private $_access_token = null;
    private $_access_token_expires = null;
    private $_debug_info = null;
    private $_curl_handle = null;

    const API_BASE = 'https://api.linkedin.com/';
    const OAUTH_BASE = 'https://www.linkedin.com/oauth/';

    const SCOPE_BASIC_PROFILE = 'r_basicprofile'; // Name, photo, headline, and current positions
    const SCOPE_LITE_PROFILE = 'r_liteprofile'; // Name, photo, headline, and current positions
    const SCOPE_FULL_PROFILE = 'r_fullprofile'; // Full profile including experience, education, skills, and recommendations
    const SCOPE_EMAIL_ADDRESS = 'r_emailaddress'; // The primary email address you use for your LinkedIn account
    const SCOPE_NETWORK = 'r_network'; // Your 1st and 2nd degree connections
    const SCOPE_CONTACT_INFO = 'r_contactinfo'; // Address, phone number, and bound accounts
    const SCOPE_READ_WRITE_UPDATES = 'rw_nus'; // Retrieve and post updates to LinkedIn as you
    const SCOPE_READ_WRITE_GROUPS = 'rw_groups'; // Retrieve and post group discussions as you
    const SCOPE_WRITE_MESSAGES = 'w_messages'; // Send messages and invitations to connect as you
    const SCOPE_WRITE_SHARE = 'w_share'; // Share url to your contacts

    const HTTP_METHOD_GET = 'GET';
    const HTTP_METHOD_POST = 'POST';
    const HTTP_METHOD_PUT = 'PUT';
    const HTTP_METHOD_DELETE = 'DELETE';

    /**
     * @param array $config (api_key, api_secret, callback_url)
     * @throws \InvalidArgumentException
     * @throws \RuntimeException
     */
    public function __construct(array $config)
    {
        if (!isset($config['api_key']) || empty($config['api_key'])) {
            throw new \InvalidArgumentException('Invalid api key - make sure api_key is defined in the config array');
        }

        if (!isset($config['api_secret']) || empty($config['api_secret'])) {
            throw new \InvalidArgumentException('Invalid api secret - make sure api_secret is defined in the config array');
        }

        if (!isset($config['callback_url']) || empty($config['callback_url'])) {
            throw new \InvalidArgumentException('Invalid callback url - make sure callback_url is defined in the config array');
        }

        if (!extension_loaded('curl')) {
            throw new \RuntimeException('PHP CURL extension does not seem to be loaded');
        }

        $this->_config = $config;
    }

    /**
     * Get the login url, pass scope to request specific permissions
     *
     * @param array $scope - an array of requested permissions (can use scope constants defined in this class)
     * @param string $state - a unique identifier for this user, if none is passed, one is generated via uniqid
     * @return string $url
     */
    public function getLoginUrl(array $scope = array(), $state = null)
    {
        if (!empty($scope)) {
            $scope = implode('%20', $scope);
        }

        if (empty($state)) {
            $state = uniqid('', true);
        }
        $this->setState($state);

        $url = self::OAUTH_BASE . "v2/authorization?response_type=code&client_id={$this->_config['api_key']}&scope={$scope}&state={$state}&redirect_uri=" . urlencode($this->_config['callback_url']);


        return $url;
    }

    /**
     * Exchange the authorization code for an access token
     *
     * @param string $authorization_code
     * @throws \InvalidArgumentException
     * @throws \RuntimeException
     * @return string $access_token
     */
    public function getAccessToken($authorization_code = null)
    {
        if (!empty($this->_access_token)) {
            return $this->_access_token;
        }

        if (empty($authorization_code)) {
            throw new \InvalidArgumentException('Invalid authorization code. Pass in the "code" parameter from your callback url');
        }

        $params = array(
            'grant_type' => 'authorization_code',
            'code' => $authorization_code,
            'client_id' => $this->_config['api_key'],
            'client_secret' => $this->_config['api_secret'],
            'redirect_uri' => $this->_config['callback_url'],
        );

        /** Temp bug fix as per https://developer.linkedin.com/comment/28938#comment-28938 **/
        $tmp_params = http_build_query($params);

        $data = $this->_makeRequest( self::OAUTH_BASE .  'v2/accessToken?' . $tmp_params, array(), self::HTTP_METHOD_GET, array('x-li-format: json'));

        if (isset($data['error']) && !empty($data['error'])) {
            throw new \RuntimeException('Access Token Request Error: ' . $data['error'] . ' -- ' . $data['error_description']);
        }

        $this->_access_token = $data['access_token'];
        $this->_access_token_expires = $data['expires_in'];

        return $this->_access_token;
    }

    /**
     * This timestamp is "expires in". In other words, the token will expire in now() + expires_in
     *
     * @return int access token expiration time -
     */
    public function getAccessTokenExpiration()
    {
        return $this->_access_token_expires;
    }

    /**
     * Set the access token manually
     *
     * @param string $token
     * @throws \InvalidArgumentException
     * @return \LinkedIn\LinkedIn
     */
    public function setAccessToken($token)
    {
        $token = trim($token);
        if (empty($token)) {
            throw new \InvalidArgumentException('Invalid access token');
        }

        $this->_access_token = $token;

        return $this;
    }

    /**
     * Check if the access token has already been set.
     * If not we need to login or call setAccessToken
     *
     * @return boolean
     */
    public function hasAccessToken()
    {
        return !empty($this->_access_token);
    }

    /**
     * Set the state manually. State is a unique identifier for the user
     *
     * @param string $state
     * @throws \InvalidArgumentException
     * @return \LinkedIn\LinkedIn
     */
    public function setState($state)
    {
        $state = trim($state);
        if (empty($state)) {
            throw new \InvalidArgumentException('Invalid state. State should be a unique identifier for this user');
        }

        $this->_state = $state;

        return $this;
    }

    /**
     * Get state
     *
     * @return string
     */
    public function getState()
    {
        return $this->_state;
    }

    /**
     * POST to an authenciated API endpoint w/ payload
     *
     * @param string $endpoint
     * @param array $payload
     * @return array
     */
    public function post($endpoint, array $payload = array())
    {
        return $this->fetch($endpoint, $payload, self::HTTP_METHOD_POST);
    }

    /**
     * GET an authenticated API endpoind w/ payload
     *
     * @param string $endpoint
     * @param array $payload
     * @return array
     */
    public function get($endpoint, array $payload = array())
    {
        return $this->fetch($endpoint, $payload);
    }

    /**
     * PUT to an authenciated API endpoint w/ payload
     *
     * @param string $endpoint
     * @param array $payload
     * @return array
     */
    public function put($endpoint, array $payload = array())
    {
        return $this->fetch($endpoint, $payload, self::HTTP_METHOD_PUT);
    }

    /**
     * Make an authenticated API request to the specified endpoint
     * Headers are for additional headers to be sent along with the request.
     * Curl options are additional curl options that may need to be set
     *
     * @param string $endpoint
     * @param array $payload
     * @param string $method
     * @param array $headers
     * @param array $curl_options
     * @return array
     */
    public function fetch($endpoint, array $payload = array(), $method = 'GET', array $headers = array(), array $curl_options = array())
    {
        $concat = (stristr($endpoint,'?') ? '&' : '?');
        $endpoint = self::API_BASE . '/' . trim($endpoint, '/\\') . $concat;
        $headers[] = 'x-li-format: json';
        $headers[] = 'Authorization: Bearer ' . $this->getAccessToken();

        return $this->_makeRequest($endpoint, $payload, $method, $headers, $curl_options);
    }

    /**
     * Get debug info from the CURL request
     *
     * @return array
     */
    public function getDebugInfo()
    {
        return $this->_debug_info;
    }

    /**
     * Make a CURL request
     *
     * @param string $url
     * @param array $payload
     * @param string $method
     * @param array $headers
     * @param array $curl_options
     * @throws \RuntimeException
     * @return array
     */
    protected function _makeRequest($url, array $payload = array(), $method = 'GET', array $headers = array(), array $curl_options = array())
    {
        $ch = $this->_getCurlHandle();

        $options = array(
            CURLOPT_CUSTOMREQUEST => strtoupper($method),
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_URL => $url,
            CURLOPT_HTTPHEADER => $headers,
            CURLOPT_SSL_VERIFYPEER => false,
            CURLOPT_FOLLOWLOCATION => true
        );

        if (!empty($payload)) {
            if ($options[CURLOPT_CUSTOMREQUEST] == self::HTTP_METHOD_POST || $options[CURLOPT_CUSTOMREQUEST] == self::HTTP_METHOD_PUT) {
                $options[CURLOPT_POST] = true;
                $options[CURLOPT_POSTFIELDS] = json_encode($payload);
                $headers[] = 'Content-Length: ' . strlen($options[CURLOPT_POSTFIELDS]);
                $headers[] = 'Content-Type: application/x-www-form-urlencoded';
                $headers[] = 'Connection: Keep-Alive';
                $options[CURLOPT_HTTPHEADER] = $headers;
            } else {
                $options[CURLOPT_URL] .= '&' . http_build_query($payload, '&');
            }
        }

        if (!empty($curl_options)) {
            $options = array_replace($options, $curl_options);
        }

        if (isset($this->_config['curl_options']) && !empty($this->_config['curl_options'])) {
            $options = array_replace($options, $this->_config['curl_options']);
        }

        curl_setopt_array($ch, $options);
        $response = curl_exec($ch);
        $this->_debug_info = curl_getinfo($ch);

        if ($response === false) {
            throw new \RuntimeException('Request Error: ' . curl_error($ch));
        }

        $response = json_decode($response, true);
        if (isset($response['status']) && ($response['status'] < 200 || $response['status'] > 300)) {
            throw new \RuntimeException('Request Error: ' . $response['message'] . '. Raw Response: ' . print_r($response, true));
        }

        return $response;
    }

    protected function _getCurlHandle()
    {
        if (!$this->_curl_handle) {
            $this->_curl_handle = curl_init();
        }

        return $this->_curl_handle;
    }

    public function __destruct()
    {
        if ($this->_curl_handle) {
            curl_close($this->_curl_handle);
        }
    }

}