<?php

/**

 * WordPress Post Thumbnail Template Functions.

 *

 * Support for post thumbnails

 * Themes function.php must call add_theme_support( 'post-thumbnails' ) to use these.

 *

 * @package WordPress

 * @subpackage Template

 */

/**

 * Check if post has an image attached.

 *

 * @since 2.9.0

 *

 * @param int $post_id Optional. Post ID.

 * @return bool Whether post has an image attached.

 */

function has_post_thumbnail( $post_id = null ) {

	return (bool) get_post_thumbnail_id( $post_id );

}

/**

 * Retrieve Post Thumbnail ID.

 *

 * @since 2.9.0

 *

 * @param int $post_id Optional. Post ID.

 * @return int

 */

function get_post_thumbnail_id( $post_id = null ) {

	$post_id = ( null === $post_id ) ? get_the_ID() : $post_id;

	return get_post_meta( $post_id, '_thumbnail_id', true );

}

/**

 * Display Post Thumbnail.

 *

 * @since 2.9.0

 *

 * @param string|array $size Optional. Image size. Defaults to 'post-thumbnail', which theme sets using set_post_thumbnail_size( $width, $height, $crop_flag );.

 * @param string|array $attr Optional. Query string or array of attributes.

 */

function the_post_thumbnail( $size = 'post-thumbnail', $attr = '' ) {

	echo get_the_post_thumbnail( null, $size, $attr );

}

/**

 * Update cache for thumbnails in the current loop

 *

 * @since 3.2

 *

 * @param object $wp_query Optional. A WP_Query instance. Defaults to the $wp_query global.

 */

function update_post_thumbnail_cache( $wp_query = null ) {

	if ( ! $wp_query )

		$wp_query = $GLOBALS['wp_query'];

	if ( $wp_query->thumbnails_cached )

		return;

	$thumb_ids = array();

	foreach ( $wp_query->posts as $post ) {

		if ( $id = get_post_thumbnail_id( $post->ID ) )

			$thumb_ids[] = $id;

	}

	if ( ! empty ( $thumb_ids ) ) {

		_prime_post_caches( $thumb_ids, false, true );

	}

	$wp_query->thumbnails_cached = true;

}

/**

 * Retrieve Post Thumbnail.

 *

 * @since 2.9.0

 *

 * @param int $post_id Optional. Post ID.

 * @param string $size Optional. Image size. Defaults to 'post-thumbnail'.

 * @param string|array $attr Optional. Query string or array of attributes.

 */

function get_the_post_thumbnail( $post_id = null, $size = 'post-thumbnail', $attr = '' ) {

	$post_id = ( null === $post_id ) ? get_the_ID() : $post_id;

	$post_thumbnail_id = get_post_thumbnail_id( $post_id );

	/**

	 * Filter the post thumbnail size.

	 *

	 * @since 2.9.0

	 *

	 * @param string $size The post thumbnail size.

	 */

	$size = apply_filters( 'post_thumbnail_size', $size );

	if ( $post_thumbnail_id ) {

		/**

		 * Fires before fetching the post thumbnail HTML.

		 *

		 * Provides "just in time" filtering of all filters in wp_get_attachment_image().

		 *

		 * @since 2.9.0

		 *

		 * @param string $post_id           The post ID.

		 * @param string $post_thumbnail_id The post thumbnail ID.

		 * @param string $size              The post thumbnail size.

		 */

		do_action( 'begin_fetch_post_thumbnail_html', $post_id, $post_thumbnail_id, $size );

		if ( in_the_loop() )

			update_post_thumbnail_cache();

		$html = wp_get_attachment_image( $post_thumbnail_id, $size, false, $attr );

		/**

		 * Fires after fetching the post thumbnail HTML.

		 *

		 * @since 2.9.0

		 *

		 * @param string $post_id           The post ID.

		 * @param string $post_thumbnail_id The post thumbnail ID.

		 * @param string $size              The post thumbnail size.

		 */

		do_action( 'end_fetch_post_thumbnail_html', $post_id, $post_thumbnail_id, $size );

	} else {

		$html = '';

	}

	/**

	 * Filter the post thumbnail HTML.

	 *

	 * @since 2.9.0

	 *

	 * @param string $html              The post thumbnail HTML.

	 * @param string $post_id           The post ID.

	 * @param string $post_thumbnail_id The post thumbnail ID.

	 * @param string $size              The post thumbnail size.

	 * @param string $attr              Query string of attributes.

	 */

	return apply_filters( 'post_thumbnail_html', $html, $post_id, $post_thumbnail_id, $size, $attr );

}