<?php

// guarantee use of https
wp_oembed_remove_provider( '#https?://(www\.)?slideshare\.net/.*#i' );
wp_oembed_add_provider( '#https?://(www\.)?slideshare\.net/.*#i', 'https://www.slideshare.net/api/oembed/2', true );

/*
 * Slideshare shortcode format:
 * Old style (still compatible): [slideshare id=5342235&doc=camprock-101002163655-phpapp01&w=300&h=200]
 * New style: [slideshare id=5342235&w=300&h=200&fb=0&mw=0&mh=0&sc=no]
 *
 * Legend:
 *	id    = Document ID provided by Slideshare
 *	w     = Width of iFrame     (int)
 *	h     = Height of iFrame    (int)
 *	fb    = iFrame frameborder  (int)
 *	mw    = iFrame marginwidth  (int)
 *	mh    = iFrame marginheight (int)
 *	sc    = iFrame Scrollbar    (yes/no)
 *	pro   = Slideshare Pro      (yes/no)
 *	style = Inline CSS          (string)
 **/

add_shortcode( 'slideshare', 'slideshare_shortcode' );

function slideshare_shortcode( $atts ) {
	global $content_width;

	$params = shortcode_new_to_old_params( $atts );
	parse_str( $params, $arguments );

	if ( empty( $arguments ) ) {
		return '<!-- SlideShare error: no arguments -->';
	}

	$attr = shortcode_atts(
		array(
			'id'    => '',
			'w'     => '',
			'h'     => '',
			'fb'    => '',
			'mw'    => '',
			'mh'    => '',
			'sc'    => '',
			'pro'   => '',
			'style' => '',
		), $arguments
	);

	// check that the Slideshare ID contains letters, numbers and query strings
	$pattern = '/[^-_a-zA-Z0-9?=&]/';
	if ( empty( $attr['id'] ) || preg_match( $pattern, $attr['id'] ) ) {
		return '<!-- SlideShare error: id is missing or has illegal characters -->';
	}

	// check the width/height
	$w = $attr['w'];
	if ( empty( $w ) && ! empty( $content_width ) ) {
		$w = intval( $content_width );
	} elseif ( ! ( $w = intval( $w ) ) || $w < 300 || $w > 1600 ) {
		$w = 425;
	} else {
		$w = intval( $w );
	}

	$h = ceil( $w * 348 / 425 ); // Note: user-supplied height is ignored.

	if ( isset( $attr['pro'] ) && $attr['pro'] ) {
		$source = 'https://www.slideshare.net/slidesharepro/' . $attr['id'];
	} else {
		$source = 'https://www.slideshare.net/slideshow/embed_code/' . $attr['id'];
	}

	if ( isset( $rel ) ) {
		$source = add_query_arg( 'rel', intval( $rel ), $source );
	}

	if ( isset( $startSlide ) ) {
		$source = add_query_arg( 'startSlide', intval( $startSlide ), $source );
	}

	$player = sprintf( "<iframe src='%s' width='%d' height='%d'", esc_url( $source ), $w, $h );

	// check the frameborder
	if ( ! empty( $attr['fb'] ) || '0' === $attr['fb'] ) {
		$player .= " frameborder='" . intval( $attr['fb'] ) . "'";
	}

	// check the margin width; if not empty, cast as int
	if ( ! empty( $attr['mw'] ) || '0' === $attr['mw'] ) {
		$player .= " marginwidth='" . intval( $attr['mw'] ) . "'";
	}

	// check the margin height, if not empty, cast as int
	if ( ! empty( $attr['mh'] ) || '0' === $attr['mh'] ) {
		$player .= " marginheight='" . intval( $attr['mh'] ) . "'";
	}

	if ( ! empty( $attr['style'] ) ) {
		$player .= " style='" . esc_attr( $attr['style'] ) . "'";
	}

	// check the scrollbar; cast as a lowercase string for comparison
	if ( ! empty( $attr['sc'] ) ) {
		$sc = strtolower( $attr['sc'] );

		if ( in_array( $sc, array( 'yes', 'no' ) ) ) {
			$player .= " scrolling='" . $sc . "'";
		}
	}

	$player .= ' allowfullscreen webkitallowfullscreen mozallowfullscreen></iframe>';

	return $player;
}