<?php
/**
 * ConvertKit API
 *
 * @class Opt_In_ConvertKit_Api
 **/
class Opt_In_ConvertKit_Api {
	
	private $_api_key;
	private $_api_secret;
	private $_endpoint = 'https://api.convertkit.com/v3/';
	
	/**
	 * Constructs class with required data
	 *
	 * Opt_In_ConvertKit_Api constructor.
	 * @param $api_key
	 */
	function __construct( $api_key, $api_secret = '' ) {
		$this->_api_key = $api_key;
		$this->_api_secret = $api_secret;
	}
	
	/**
	 * Sends request to the endpoint url with the provided $action
	 *
	 * @param string $verb
	 * @param string $action rest action
	 * @param array $args
	 * @return object|WP_Error
	 */
	private function _request( $verb = "GET", $action, $args = array() ){
		$url = trailingslashit( $this->_endpoint )  . $action;
		
		$_args = array(
			"method" => $verb,
			"headers" =>  array(
				'X-Auth-Token' => 'api-key '. $this->_api_key,
				'Content-Type' => 'application/json;charset=utf-8'
			)
		);

		if( "GET" === $verb ){
			$url .= ( "?" . http_build_query( $args ) );
		}else{
			$_args['body'] = json_encode( $args['body'] );
		}

		$res = wp_remote_request( $url, $_args );
		
		if ( !is_wp_error( $res ) && is_array( $res ) ) {

			if( $res['response']['code'] <= 204 )
				return json_decode(  wp_remote_retrieve_body( $res ) );

			$err = new WP_Error();
			$err->add($res['response']['code'], $res['response']['message'] );
			return  $err;
		}

		return  $res;
	}

	/**
	 * Sends rest GET request
	 *
	 * @param $action
	 * @param array $args
	 * @return array|mixed|object|WP_Error
	 */
	private function _get( $action, $args = array() ){
		return $this->_request( "GET", $action, $args );
	}

	/**
	 * Sends rest POST request
	 *
	 * @param $action
	 * @param array $args
	 * @return array|mixed|object|WP_Error
	 */
	private function _post( $action, $args = array()  ){
		return $this->_request( "POST", $action, $args );
	}

	/**
	 * Retrieves ConvertKit forms as array of objects
	 *
	 * @return array|WP_Error
	 */
	public function get_forms(){
		return $this->_get( "forms", array(
			'api_key' => $this->_api_key
		) )->forms;
	}
	
	/**
	 * Retrieves ConvertKit form's custom fields as array of objects
	 *
	 * @return array|WP_Error
	 */
	public function get_form_custom_fields(){
		return $this->_get( "custom_fields", array(
			'api_key' => $this->_api_key
		) )->custom_fields;
	}
	
	/**
	 * Add new custom fields to subscription
	 *
	 * @param $field_data
	 * @return array|mixed|object|WP_Error
	 */
	public function create_custom_fields( $field_data ){
		$res =  $this->_post("custom_fields", array(
			"body" =>  $field_data
		));

		return empty( $res ) ? __("Successfully added custom field", Opt_In::TEXT_DOMAIN) : $res;
	}

	/**
	 * Add new subscriber
	 *
	 * @param $form_id
	 * @param $data
	 * @return array|mixed|object|WP_Error
	 */
	public function subscribe( $form_id, $data ){
		$res =  $this->_post("forms/". $form_id ."/subscribe", array(
			"body" =>  $data
		));

		return empty( $res ) ? __("Successful subscription", Opt_In::TEXT_DOMAIN) : $res;
	}

	/**
	 * Verify if an email is already a subscriber.
	 *
	 * @param (string) $email
	 *
	 * @return (object) Returns data of existing subscriber if exist otherwise false.
	 **/
	function is_subscriber( $email ) {
		$url = 'subscribers';
		$args = array(
			'api_key' => $this->_api_key,
			'api_secret' => $this->_api_secret,
			'email_address' => $email,
		);

		$res = $this->_get( $url, $args );

		return ! is_wp_error( $res ) && ! empty( $res->subscribers ) ? array_shift( $res->subscribers ) : false;
	}
}