<?php
class AWeberCollection extends AWeberResponse implements ArrayAccess, Iterator, Countable {

    protected $pageSize = 100;
    protected $pageStart = 0;

    protected function _updatePageSize() {

        # grab the url, or prev and next url and pull ws.size from it
        $url = $this->url;
        if (array_key_exists('next_collection_link', $this->data)) {
            $url = $this->data['next_collection_link'];

        } elseif (array_key_exists('prev_collection_link', $this->data)) {
            $url = $this->data['prev_collection_link'];
        }

        # scan querystring for ws_size
        $url_parts = parse_url($url);

        # we have a query string
        if (array_key_exists('query', $url_parts)) {
            parse_str($url_parts['query'], $params);

            # we have a ws_size
            if (array_key_exists('ws_size', $params)) {

                # set pageSize
                $this->pageSize = $params['ws_size'];
                return;
            }
        }

        # we dont have one, just count the # of entries
        $this->pageSize = count($this->data['entries']);
    }

    public function __construct($response, $url, $adapter) {
        parent::__construct($response, $url, $adapter);
        $this->_updatePageSize();
    }

    /**
     * @var array Holds list of keys that are not publicly accessible
     */
    protected $_privateData = array(
        'entries',
        'start',
        'next_collection_link',
    );

    /**
     * getById
     *
     * Gets an entry object of this collection type with the given id
     * @param mixed $id     ID of the entry you are requesting
     * @access public
     * @return AWeberEntry
     */
    public function getById($id) {
        $data = $this->adapter->request('GET', "{$this->url}/{$id}");
        $url = "{$this->url}/{$id}";
        return new AWeberEntry($data, $url, $this->adapter);
    }

    /** getParentEntry
     *
     * Gets an entry's parent entry
     * Returns NULL if no parent entry
     */
    public function getParentEntry(){
        $url_parts = explode('/', $this->url);
        $size = count($url_parts);

        # Remove collection id and slash from end of url
        $url = substr($this->url, 0, -strlen($url_parts[$size-1])-1);

        try {
            $data = $this->adapter->request('GET', $url);
            return new AWeberEntry($data, $url, $this->adapter);
        } catch (Exception $e) {
            return NULL;
        }
    }

    /**
     * _type
     *
     * Interpret what type of resources are held in this collection by 
     * analyzing the URL
     *
     * @access protected
     * @return void
     */
    protected function _type() {
        $urlParts = explode('/', $this->url);
        $type = array_pop($urlParts);
        return $type;
    }

    /**
     * create
     *
     * Invoke the API method to CREATE a new entry resource.
     *
     * Note: Not all entry resources are eligible to be created, please
     *       refer to the AWeber API Reference Documentation at
     *       https://labs.aweber.com/docs/reference/1.0 for more
     *       details on which entry resources may be created and what
     *       attributes are required for creating resources.
     *
     * @access public
     * @param params mixed  associtative array of key/value pairs.
     * @return AWeberEntry(Resource) The new resource created
     */
    public function create($kv_pairs) {
        # Create Resource
        $params = array_merge(array('ws.op' => 'create'), $kv_pairs);
        $data = $this->adapter->request('POST', $this->url, $params, array('return' => 'headers'));

        # Return new Resource
        $url = $data['Location'];
        $resource_data = $this->adapter->request('GET', $url);
        return new AWeberEntry($resource_data, $url, $this->adapter);
    }

    /**
     * find
     *
     * Invoke the API 'find' operation on a collection to return a subset
     * of that collection.  Not all collections support the 'find' operation.
     * refer to https://labs.aweber.com/docs/reference/1.0 for more information.
     *
     * @param mixed $search_data   Associative array of key/value pairs used as search filters
     *                             * refer to https://labs.aweber.com/docs/reference/1.0 for a
     *                               complete list of valid search filters.
     *                             * filtering on attributes that require additional permissions to
     *                               display requires an app authorized with those additional permissions.
     * @access public
     * @return AWeberCollection 
     */
    public function find($search_data) {
        # invoke find operation
        $params = array_merge($search_data, array('ws.op' => 'find'));
        $data = $this->adapter->request('GET', $this->url, $params);

        # get total size
        $ts_params = array_merge($params, array('ws.show' => 'total_size'));
        $total_size = $this->adapter->request('GET', $this->url, $ts_params, array('return' => 'integer'));
        $data['total_size'] = $total_size;

        # return collection
        return $this->readResponse($data, $this->url);
    }

    /*
     * ArrayAccess Functions
     *
     * Allows this object to be accessed via bracket notation (ie $obj[$x])
     * http://php.net/manual/en/class.arrayaccess.php
     */

    public function offsetSet($offset, $value)  {}
    public function offsetUnset($offset)        {}
    public function offsetExists($offset) {

        if ($offset >=0 && $offset < $this->total_size) {
            return true;
        }
        return false;
    }
    protected function _fetchCollectionData($offset) {

        # we dont have a next page, we're done
        if (!array_key_exists('next_collection_link', $this->data)) {
            return null;
        }

        # snag query string args from collection
        $parsed = parse_url($this->data['next_collection_link']);

        # parse the query string to get params
        $pairs = explode('&', $parsed['query']);
        foreach ($pairs as $pair) {
            list($key, $val) = explode('=', $pair);
            $params[$key] = $val;
        }

        # calculate new args
        $limit = $params['ws.size'];
        $pagination_offset = intval($offset / $limit) * $limit;
        $params['ws.start'] = $pagination_offset;

        # fetch data, exclude query string
        $url_parts = explode('?', $this->url);
        $data = $this->adapter->request('GET', $url_parts[0], $params);
        $this->pageStart = $params['ws.start'];
        $this->pageSize = $params['ws.size'];

        $collection_data = array('entries', 'next_collection_link', 'prev_collection_link', 'ws.start');

        foreach ($collection_data as $item) {
            if (!array_key_exists($item, $this->data)) {
                continue;
            }
            if (!array_key_exists($item, $data)) {
                continue;
            }
            $this->data[$item] = $data[$item];
        }
    }

    public function offsetGet($offset) {

        if (!$this->offsetExists($offset)) {
            return null;
        }

        $limit = $this->pageSize;
        $pagination_offset = intval($offset / $limit) * $limit;

        # load collection page if needed
        if ($pagination_offset !== $this->pageStart) {
            $this->_fetchCollectionData($offset);
        }

        $entry = $this->data['entries'][$offset - $pagination_offset];

        # we have an entry, cast it to an AWeberEntry and return it
        $entry_url = $this->adapter->app->removeBaseUri($entry['self_link']);
        return new AWeberEntry($entry, $entry_url, $this->adapter);
    }

    /*
     * Iterator
     */
    protected $_iterationKey = 0;

    public function current() {
        return $this->offsetGet($this->_iterationKey);
    }

    public function key() {
        return $this->_iterationKey;
    }

    public function next() {
        $this->_iterationKey++;
    }

    public function rewind() {
        $this->_iterationKey = 0;
    }

    public function valid() {
        return $this->offsetExists($this->key());
    }

    /*
     * Countable interface methods
     * Allows PHP's count() and sizeOf() functions to act on this object
     * http://www.php.net/manual/en/class.countable.php
     */

    public function count() {
        return $this->total_size;
    }
}