functions.php

<?php

$format    = null;
$fullitems = false;

add_action('init', 'set_api_permalink_structure', 0);
add_action('init', 'set_globals', 0);
add_action('template_redirect', 'handle_api_path');

function set_api_permalink_structure() {

	global $wp_rewrite;
	$wp_rewrite->set_permalink_structure('/%category%/%postname%/');
	$wp_rewrite->flush_rules();
}

function set_globals() {

	global $format;
	$format = strtoupper($_GET['format']);
	if ('JSON' !== $format && 'XML' !== $format) {
		$format = null;
	}

	global $fullitems;
	$fullitems = false;
		if ('1' === $_GET['fullitems'] || 'true' === $_GET['fullitems']) {
		$fullitems = true;
	}
}

function handle_api_path() {

	if (is_404()) {
		$current_path  = rtrim(parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH), '/');
		$category_base = get_option('category_base');
		if ('' === $category_base) $category_base = 'category';

		if (check_if_api_root($current_path, $category_base)) {
			global $wp_query;
			$wp_query->is_404 = false;
			$wp_query->is_archive = true;
			status_header(200);
		} else {
			$current_post = check_if_valid_item_path($current_path, $category_base);
			if (is_object($current_post)) {
				global $query_string;
				query_posts($query_string . "&p=$current_post->ID");
				global $wp_query;
				$wp_query->is_404 = false;
				$wp_query->is_single = true;
				status_header(200);
			}
		}
	}
}

function check_if_api_root($current_path, $api_base) {

	$api_root_path = parse_url(site_url($api_base), PHP_URL_PATH);
	return ($current_path === $api_root_path);
}

function check_if_valid_item_path($current_path, $api_base) {

	$path_chunks = explode('/', $current_path);
	$api_index   = -1;
	foreach ($path_chunks as $index => $chunk) {
		if ($api_base === $chunk) {
			$api_index = $index;
			break;
		}
	}

	if (-1 === $api_index) return false;

	$chunks_max_index = count($path_chunks) - 1;
	$item_output = null;
	for ($index = $api_index + 1; $index < $chunks_max_index; $index++) {
		$item_output = check_api_chunks_relation($path_chunks[$index], $path_chunks[$index + 1], $api_index + 1 === $index);
		if (!$item_output) return $item_output;
	}

	return $item_output;
}

function check_api_chunks_relation($parent_chunk, $child_chunk, $is_first_resource) {
	$parent_resource = get_category_by_slug($parent_chunk);
	$child_resource  = get_category_by_slug($child_chunk);

	if (!$parent_resource || ($is_first_resource && 0 != $parent_resource->parent)) return false;

	if (!$child_resource) {
		$child_item = get_posts(array('name' => $child_chunk, 'category' => $parent_chunk));
		if (0 === count($child_item)) return false;
		return $child_item[0];
	}

	if ($child_resource->parent !== $parent_resource->cat_ID) return false;

	return true;
}

function the_current_data($parent_ID) {

	echo get_current_data($parent_ID);
}

function get_current_data($parent_ID = 0) {

	if ('' == $parent_ID) $parent_ID = 0;

	$categories = prepare_categories_data(get_categories(array(
		'parent'     => $parent_ID,
		'hide_empty' => 0,
		'exclude'    => 1
	)));

	global $fullitems;
	$data = array('resources' => $categories, 'items' => array());
	if (have_posts()) {
		while (have_posts()) {
			the_post();
			$data['items'][] = prepare_post_data($fullitems);
		}
	}

	return format_current_data($data);
}

function the_current_post() {

	echo get_current_post();
}

function get_current_post() {

	$data = array('items' => array());
	if (have_posts()) {
		while (have_posts()) {
			the_post();
			$data['items'][] = prepare_post_data(true);
		}
	}

	return format_current_data($data);
}

function prepare_categories_data($categories) {

	$categories_output = array();
	foreach($categories as $category) {
		$id = $category->cat_ID;
		$categories_output[] = array(
			'ID'          => $id,
			'parent'      => $category->parent,
			'name'        => $category->name,
			'slug'        => $category->slug,
			'description' => $category->description,
			'count'       => $category->count,
			'link'        => get_category_link($id)
		);
	}

	return $categories_output;
}

function prepare_post_data($fullitems) {

	$id      = get_the_ID();
	$title   = get_the_title();
	$link    = get_permalink();
	$slug    = basename($link);
	$excerpt = get_the_excerpt();

	if ($fullitems) {
		$content = get_the_content();
		$post_output = array(
			'ID'            => $id,
			'link'          => $link,
			'slug'          => $slug,
			'title'         => $title,
			'author'        => get_the_author(),
			'date'          => mysql2date('c', get_the_date()),
			'tags'          => implode(', ', wp_get_post_tags($id, array('fields' => 'names'))),
			'categories'    => implode(', ', wp_get_post_categories($id, array('fields' => 'names'))),
			'excerpt'       => $excerpt,
			'content'       => strip_tags($content),
			'html-content'  => apply_filters('the_content', $content),
			'custom-fields' => prepare_post_customs(),
			'attachments'   => prepare_post_attachments(),
			'comments'      => prepare_post_comments(),
		);
	} else {
		$post_output = array(
			'ID'      => $id,
			'link'    => $link,
			'slug'    => $slug,
			'title'   => $title,
			'excerpt' => $excerpt
		);
	}

	return $post_output;
}

function prepare_post_customs() {

	$customs_output = array();
	foreach (get_post_custom() as $key => $value) {
		if('_' != $key{0}) {
			$customs_output[] = array('key' => $key, 'values' => $value);
		}
	}

	return $customs_output;
}

function prepare_post_attachments() {

	$attachments = get_children(array(
		'post_type'   => 'attachment',
		'post_parent' => get_the_ID()
	));

	$attachments_output = array();
	foreach($attachments as $attachment) {
		$id = $attachment->ID;
		$content = $attachment->post_content;

		$useful_data = array(
			'ID'               => $id,
			'title'            => $attachment->post_title,
			'caption'          => $attachment->post_excerpt,
			'description'      => strip_tags($content),
			'html-description' => apply_filters('the_content', $content),
			'mime-type'        => get_post_mime_type($id),
			'link'             => wp_get_attachment_url($id),
		);

		$image_metadata = wp_get_attachment_metadata($id);
		if (!empty($image_metadata)) {
			$useful_data['width']  = $image_metadata['width'];
			$useful_data['height'] = $image_metadata['height'];
			foreach ($image_metadata['sizes'] as $size => $value) {
				$src = wp_get_attachment_image_src($id, $size);
				$value['link'] = $src[0];
				unset($value['file']);

				$useful_data['sizes'][$size] = $value;
			}
		}

		$attachments_output[] = $useful_data;
	}

	return $attachments_output;
}

function prepare_post_comments() {

	$comments = get_approved_comments(get_the_ID());

	$comments_ouput = array();
	foreach($comments as $comment) {
		$content = $comment->comment_content;
		$comments_ouput[] = array(
			'ID'           => $comment->comment_ID,
			'author'       => $comment->comment_author,
			'author-email' => $comment->comment_author_email,
			'date'         => mysql2date('c', get_the_date()),
			'content'      => strip_tags($content),
			'html-content' => apply_filters('the_content', $content),
		);
	}

	return $comments_ouput;
}

function format_current_data($data) {

	global $format;
	switch ($format) {
		case "XML":
			return get_current_data_as_XML($data);
			break;
		case "JSON":
			return get_current_data_as_JSON($data);
			break;
		default:
			add_action('wp_enqueue_scripts', 'load_api_html_styles');
			add_filter('body_class', 'add_api_html_body_class');
			return $data;
	}
}

function load_api_html_styles() {

	wp_enqueue_style('api-html-style', get_template_directory_uri() . '/style.api.html.css');
}

function add_api_html_body_class($classes) {

	$classes[] = 'apipress-html';
	return $classes;
}

function get_current_data_as_XML($data) {

	$xml_output = new SimpleXMLElement('<?xml version="1.0"?><root></root>');
	$data = add_xml_cdata($data);
	get_xml_from_array($data, $xml_output);
	return $xml_output->asXML();
}

function add_xml_cdata($data, $ancestor = 'ancestor') {

	$cdata_keys = array(
		'name', 'title', 'author', 'tags', 'categories', 'excerpt', 'content', 'html-content',
		'key', 'values', 'caption', 'description', 'html-description');

	foreach($data as $key => $value) {
		if (is_array($value)) {
			$value = add_xml_cdata($value, $key);
		} else {
			if ((is_numeric($key) && in_array($ancestor, $cdata_keys)) || in_array($key, $cdata_keys)) {
				$value = '<![CDATA[' . $value . ']]>';
			}
		}

		$data[$key] = $value;
	}

	return $data;
}

function get_xml_from_array($array, &$xml, $subnode_name = 'subnode') {

	foreach ($array as $key => $value) {
		if (is_array($value)) {
			if (!is_numeric($key)) {
				$subnode = $xml->addChild("$key");
				get_xml_from_array($value, $subnode, get_xml_collections_subnodes_names($key));
			} else {
				$subnode = $xml->addChild("$subnode_name");
				$subnode->addAttribute("key", "$key");
				get_xml_from_array($value, $subnode);
			}
		} else {
			if (!is_numeric($key)) {
				$xml->addChild("$key", htmlspecialchars("$value"));
			} else {
				$subnode = $xml->addChild("$subnode_name", htmlspecialchars("$value"));
				$subnode->addAttribute("key", "$key");
			}
		}
	}
}

function get_xml_collections_subnodes_names($collection_name) {

	switch ($collection_name) {
		case "resources":
			$subnode_name = 'resource';
			break;
		case "items":
			$subnode_name = 'item';
			break;
		case "custom-fields":
			$subnode_name = 'custom-field';
			break;
		case "values":
			$subnode_name = 'value';
			break;
		case "attachments":
			$subnode_name = 'attachment';
			break;
		case "comments":
			$subnode_name = 'comment';
			break;
	}

	return $subnode_name;
}

function get_current_data_as_JSON($data) {

	return json_encode($data);
}

?>