<?php

function get_img( $args = array() ) {
	$defaults = [
		'img_ID' => get_post_thumbnail_id( $GLOBALS['post'] ),
		'size'   => null,
		'before' => '<div class="lazy-wrapper">',
		'after'  => '</div>',
	];

	$args = wp_parse_args( $args, $defaults );

	$uploads_dir  = wp_upload_dir();
	$full_img_url = wp_get_attachment_image_url( $args['img_ID'], 'full' );

	list( $full_width, $full_height ) = getimagesize( $full_img_url );

	$svg_placeholder_url  = preg_replace( '/\.(jpe?g|png|gif|bmp)$/i', '.svg', $full_img_url );
	$svg_placeholder_path = str_replace( $uploads_dir['baseurl'], $uploads_dir['basedir'], $svg_placeholder_url );

	$svg_content = get_file_content( $svg_placeholder_url );
	$svg_content = str_replace( '#', '%23', $svg_content ); // fix Data-URI SVG not working in Firefox: # in the content needs to be escaped as %23.

	$img_placeholder_size = empty( $args['size'] ) ? [ $full_width / 15, $full_height / 15 ] : [ $args['size'][0] / 15, $args['size'][1] / 15 ];
	$img_placeholder_url  = wp_get_attachment_image_url( $args['img_ID'], $img_placeholder_size );

	$placeholder = file_exists( $svg_placeholder_path ) ? 'data:image/svg+xml;utf8,' . $svg_content : $img_placeholder_url;
	$data_src    = empty( $args['size'] ) ? $full_img_url : wp_get_attachment_image_url( $args['img_ID'], [ $args['size'][0], $args['size'][1] ] );

	$retina_img_url = $full_width >= $args['size'][0] * 2 && ! empty( $args['size'] ) ? wp_get_attachment_image_url( $args['img_ID'], [ $args['size'][0] * 2, $args['size'][1] * 2 ] ) : '';
	$data_srcset    = ! empty( $retina_img_url ) ? "data-srcset='$retina_img_url 2x'" : '';

	$alt = get_post_meta( $args['img_ID'], '_wp_attachment_image_alt', true );

	$img_width  = empty( $args['size'] ) ? $full_width : $args['size'][0];
	$img_height = empty( $args['size'] ) ? $full_height : $args['size'][1];

	$img = $args['before'] . "<img class='lazy' src='$placeholder' data-src='$data_src' $data_srcset alt='$alt' width='$img_width', height='$img_height' />" . $args['after'];

	return $img;
}