<?php

namespace FluentForm\App\Services\Integrations\MailChimp;

/**
 * Super-simple, minimum abstraction MailChimp API v3 wrapper
 * MailChimp API v3: http://developer.mailchimp.com
 * This wrapper: https://github.com/drewm/mailchimp-api
 *
 * @author Drew McLellan <drew.mclellan@gmail.com>
 *
 * @version 2.4
 */
class MailChimp
{
    private $api_key;
    private $api_endpoint = 'https://<dc>.api.mailchimp.com/3.0';

    public const TIMEOUT = 10;

    /*  SSL Verification
        Read before disabling:
        http://snippets.webaware.com.au/howto/stop-turning-off-curlopt_ssl_verifypeer-and-fix-your-php-config/
    */
    public $verify_ssl = true;

    private $request_successful = false;
    private $last_error = '';
    private $last_response = [];
    private $last_request = [];

    /**
     * Create a new instance
     *
     * @param string $api_key      Your MailChimp API key
     * @param string $api_endpoint Optional custom API endpoint
     *
     * @throws \Exception
     */
    public function __construct($api_key, $api_endpoint = null)
    {
        $this->api_key = $api_key;

        if (null === $api_endpoint) {
            if (false === strpos($this->api_key, '-')) {
                throw new \Exception("Invalid Mailchimp API key `{$api_key}` supplied.");
            }
            list(, $data_center) = explode('-', $this->api_key);
            $this->api_endpoint = str_replace('<dc>', $data_center, $this->api_endpoint);
        } else {
            $this->api_endpoint = $api_endpoint;
        }

        $this->last_response = ['headers' => null, 'body' => null];
    }

    /**
     * @return string The url to the API endpoint
     */
    public function getApiEndpoint()
    {
        return $this->api_endpoint;
    }

    /**
     * Convert an email address into a 'subscriber hash' for identifying the subscriber in a method URL
     *
     * @param string $email The subscriber's email address
     *
     * @return string Hashed version of the input
     */
    public function subscriberHash($email)
    {
        return md5(strtolower($email));
    }

    /**
     * Was the last request successful?
     *
     * @return bool True for success, false for failure
     */
    public function success()
    {
        return $this->request_successful;
    }

    /**
     * Get the last error returned by either the network transport, or by the API.
     * If something didn't work, this should contain the string describing the problem.
     *
     * @return string|false describing the error
     */
    public function getLastError()
    {
        return $this->last_error ?: false;
    }

    /**
     * Get an array containing the HTTP headers and the body of the API response.
     *
     * @return array Assoc array with keys 'headers' and 'body'
     */
    public function getLastResponse()
    {
        return $this->last_response;
    }

    /**
     * Get an array containing the HTTP headers and the body of the API request.
     *
     * @return array Assoc array
     */
    public function getLastRequest()
    {
        return $this->last_request;
    }

    /**
     * Make an HTTP DELETE request - for deleting data
     *
     * @param string $method  URL of the API request method
     * @param array  $args    Assoc array of arguments (if any)
     * @param int    $timeout Timeout limit for request in seconds
     *
     * @return array|false Assoc array of API response, decoded from JSON
     */
    public function delete($method, $args = [], $timeout = self::TIMEOUT)
    {
        return $this->makeRequest('delete', $method, $args, $timeout);
    }

    /**
     * Make an HTTP GET request - for retrieving data
     *
     * @param string $method  URL of the API request method
     * @param array  $args    Assoc array of arguments (usually your data)
     * @param int    $timeout Timeout limit for request in seconds
     *
     * @return array|false Assoc array of API response, decoded from JSON
     */
    public function get($method, $args = [], $timeout = self::TIMEOUT)
    {
        return $this->makeRequest('get', $method, $args, $timeout);
    }

    /**
     * Make an HTTP PATCH request - for performing partial updates
     *
     * @param string $method  URL of the API request method
     * @param array  $args    Assoc array of arguments (usually your data)
     * @param int    $timeout Timeout limit for request in seconds
     *
     * @return array|false Assoc array of API response, decoded from JSON
     */
    public function patch($method, $args = [], $timeout = self::TIMEOUT)
    {
        return $this->makeRequest('patch', $method, $args, $timeout);
    }

    /**
     * Make an HTTP POST request - for creating and updating items
     *
     * @param string $method  URL of the API request method
     * @param array  $args    Assoc array of arguments (usually your data)
     * @param int    $timeout Timeout limit for request in seconds
     *
     * @return array|false Assoc array of API response, decoded from JSON
     */
    public function post($method, $args = [], $timeout = self::TIMEOUT)
    {
        return $this->makeRequest('post', $method, $args, $timeout);
    }

    /**
     * Make an HTTP PUT request - for creating new items
     *
     * @param string $method  URL of the API request method
     * @param array  $args    Assoc array of arguments (usually your data)
     * @param int    $timeout Timeout limit for request in seconds
     *
     * @return array|false Assoc array of API response, decoded from JSON
     *
     * @throws \Exception
     */
    public function put($method, $args = [], $timeout = self::TIMEOUT)
    {
        return $this->makeRequest('put', $method, $args, $timeout);
    }

    /**
     * Performs the underlying HTTP request. Not very exciting.
     *
     * @param string $http_verb The HTTP verb to use: get, post, put, patch, delete
     * @param string $method    The API method to be called
     * @param array  $args      Assoc array of parameters to be passed
     * @param int    $timeout
     *
     * @return array|false Assoc array of decoded result
     *
     * @throws \Exception
     */
    private function makeRequest($http_verb, $method, $args = [], $timeout = self::TIMEOUT)
    {
        if (! function_exists('curl_init') || ! function_exists('curl_setopt')) {
            throw new \Exception("cURL support is required, but can't be found.");
        }

        $url = $this->api_endpoint . '/' . $method;

        $response = $this->prepareStateForRequest($http_verb, $method, $url, $timeout);

        $httpHeader = [
            'Accept: application/vnd.api+json',
            'Content-Type: application/vnd.api+json',
            'Authorization: apikey ' . $this->api_key,
        ];

        if (isset($args['language'])) {
            $httpHeader[] = 'Accept-Language: ' . $args['language'];
        }

        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_HTTPHEADER, $httpHeader);
        curl_setopt($ch, CURLOPT_USERAGENT, 'DrewM/MailChimp-API/3.0 (github.com/drewm/mailchimp-api)');
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_VERBOSE, true);
        curl_setopt($ch, CURLOPT_HEADER, true);
        curl_setopt($ch, CURLOPT_TIMEOUT, $timeout);
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, $this->verify_ssl);
        curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_0);
        curl_setopt($ch, CURLOPT_ENCODING, '');
        curl_setopt($ch, CURLINFO_HEADER_OUT, true);

        switch ($http_verb) {
            case 'post':
                curl_setopt($ch, CURLOPT_POST, true);
                $this->attachRequestPayload($ch, $args);
                break;

            case 'get':
                $query = http_build_query($args, '', '&');
                curl_setopt($ch, CURLOPT_URL, $url . '?' . $query);
                break;

            case 'delete':
                curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'DELETE');
                break;

            case 'patch':
                curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'PATCH');
                $this->attachRequestPayload($ch, $args);
                break;

            case 'put':
                curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'PUT');
                $this->attachRequestPayload($ch, $args);
                break;
        }

        $responseContent = curl_exec($ch);
        $response['headers'] = curl_getinfo($ch);
        $response = $this->setResponseState($response, $responseContent, $ch);
        $formattedResponse = $this->formatResponse($response);

        curl_close($ch);

        $this->determineSuccess($response, $formattedResponse, $timeout);

        return $formattedResponse;
    }

    /**
     * @param string  $http_verb
     * @param string  $method
     * @param string  $url
     * @param integer $timeout
     */
    private function prepareStateForRequest($http_verb, $method, $url, $timeout)
    {
        $this->last_error = '';

        $this->request_successful = false;

        $this->last_response = [
            'headers'     => null, // array of details from curl_getinfo()
            'httpHeaders' => null, // array of HTTP headers
            'body'        => null, // content of the response
        ];

        $this->last_request = [
            'method'  => $http_verb,
            'path'    => $method,
            'url'     => $url,
            'body'    => '',
            'timeout' => $timeout,
        ];

        return $this->last_response;
    }

    /**
     * Get the HTTP headers as an array of header-name => header-value pairs.
     *
     * The "Link" header is parsed into an associative array based on the
     * rel names it contains. The original value is available under
     * the "_raw" key.
     *
     * @param string $headersAsString
     *
     * @return array
     */
    private function getHeadersAsArray($headersAsString)
    {
        $headers = [];

        foreach (explode("\r\n", $headersAsString) as $i => $line) {
            if (0 === $i) { // HTTP code
                continue;
            }

            $line = trim($line);
            if (empty($line)) {
                continue;
            }

            list($key, $value) = explode(': ', $line);

            if ('Link' == $key) {
                $value = array_merge(
                    ['_raw' => $value],
                    $this->getLinkHeaderAsArray($value)
                );
            }

            $headers[$key] = $value;
        }

        return $headers;
    }

    /**
     * Extract all rel => URL pairs from the provided Link header value
     *
     * Mailchimp only implements the URI reference and relation type from
     * RFC 5988, so the value of the header is something like this:
     *
     * 'https://us13.api.mailchimp.com/schema/3.0/Lists/Instance.json; rel="describedBy", <https://us13.admin.mailchimp.com/lists/members/?id=XXXX>; rel="dashboard"'
     *
     * @param string $linkHeaderAsString
     *
     * @return array
     */
    private function getLinkHeaderAsArray($linkHeaderAsString)
    {
        $urls = [];

        if (preg_match_all('/<(.*?)>\s*;\s*rel="(.*?)"\s*/', $linkHeaderAsString, $matches)) {
            foreach ($matches[2] as $i => $relName) {
                $urls[$relName] = $matches[1][$i];
            }
        }

        return $urls;
    }

    /**
     * Encode the data and attach it to the request
     *
     * @param resource $ch   cURL session handle, used by reference
     * @param array    $data Assoc array of data to attach
     */
    private function attachRequestPayload(&$ch, $data)
    {
        $encoded = json_encode($data);
        $this->last_request['body'] = $encoded;
        curl_setopt($ch, CURLOPT_POSTFIELDS, $encoded);
    }

    /**
     * Decode the response and format any error messages for debugging
     *
     * @param array $response The response from the curl request
     *
     * @return array|false The JSON decoded into an array
     */
    private function formatResponse($response)
    {
        $this->last_response = $response;

        if (! empty($response['body'])) {
            return json_decode($response['body'], true);
        }

        return false;
    }

    /**
     * Do post-request formatting and setting state from the response
     *
     * @param array  $response        The response from the curl request
     * @param string $responseContent The body of the response from the curl request
     *
     * * @return array    The modified response
     */
    private function setResponseState($response, $responseContent, $ch)
    {
        if (false === $responseContent) {
            $this->last_error = curl_error($ch);
        } else {
            $headerSize = $response['headers']['header_size'];

            $response['httpHeaders'] = $this->getHeadersAsArray(substr($responseContent, 0, $headerSize));
            $response['body'] = substr($responseContent, $headerSize);

            if (isset($response['headers']['request_header'])) {
                $this->last_request['headers'] = $response['headers']['request_header'];
            }
        }

        return $response;
    }

    /**
     * Check if the response was successful or a failure. If it failed, store the error.
     *
     * @param array       $response          The response from the curl request
     * @param array|false $formattedResponse The response body payload from the curl request
     * @param int         $timeout           The timeout supplied to the curl request.
     *
     * @return bool If the request was successful
     */
    private function determineSuccess($response, $formattedResponse, $timeout)
    {
        $status = $this->findHTTPStatus($response, $formattedResponse);

        if ($status >= 200 && $status <= 299) {
            $this->request_successful = true;
            return true;
        }

        if (isset($formattedResponse['detail'])) {
            $this->last_error = sprintf('%d: %s', $formattedResponse['status'], $formattedResponse['detail']);
            return false;
        }

        if ($timeout > 0 && $response['headers'] && $response['headers']['total_time'] >= $timeout) {
            $this->last_error = sprintf('Request timed out after %f seconds.', $response['headers']['total_time']);
            return false;
        }

        $this->last_error = 'Unknown error, call getLastResponse() to find out what happened.';
        return false;
    }

    /**
     * Find the HTTP status code from the headers or API response body
     *
     * @param array       $response          The response from the curl request
     * @param array|false $formattedResponse The response body payload from the curl request
     *
     * @return int HTTP status code
     */
    private function findHTTPStatus($response, $formattedResponse)
    {
        if (! empty($response['headers']) && isset($response['headers']['http_code'])) {
            return (int) $response['headers']['http_code'];
        }

        if (! empty($response['body']) && isset($formattedResponse['status'])) {
            return (int) $formattedResponse['status'];
        }

        return 418;
    }
}
