<?php
/**
 * Footer acknowledgment link.
 *
 * @package Acknowledgify
 */

namespace Acknowledgify\Includes;

// Exit if accessed directly.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Builds the footer acknowledgment markup.
 */
class Footer_Link {

	/**
	 * Build the acknowledgment markup for a placement.
	 *
	 * Returns an empty string when the feature is off, when the requested
	 * placement is not the one the site has chosen, or when there is nothing
	 * meaningful to render.
	 *
	 * Styling follows footer_style_mode and applies identically in all three
	 * placement modes. It used to be tied to Auto-insert, so a site that
	 * styled its link and then switched placement silently lost the styling.
	 *
	 * @param string $placement_selector The placement asking for the markup:
	 *                                   auto_insert, shortcode or php_snippet.
	 * @return string Safe markup, or '' when nothing should be output.
	 */
	public static function get_markup( $placement_selector ) {
		if ( 1 !== (int) Helper::get_setting( 'enable_footer_link', 0 ) ) {
			return '';
		}

		if ( Helper::get_setting( 'footer_placement_options' ) !== $placement_selector ) {
			return '';
		}

		/**
		 * Filters the footer acknowledgment text before tokens are resolved.
		 *
		 * The main use is a multilingual site that wants a different credit
		 * per language. WPML, Polylang and the rest translate content and
		 * registered strings, not a single site-wide option, so rather than
		 * ship an integration for each of them this filter lets a site vary
		 * the text however it likes in a few lines of its own code.
		 *
		 * The returned value is still passed through the tag allow-list below,
		 * so a filter cannot introduce markup that a user could not have typed.
		 *
		 * @param string $text               Stored link text, tokens unresolved.
		 * @param string $placement_selector auto_insert, shortcode or php_snippet.
		 */
		$text = (string) apply_filters(
			'acknowledgify_footer_link_text',
			(string) Helper::get_setting( 'footer_link_text' ),
			$placement_selector
		);

		// Tokens resolve before escaping. wp_kses() then runs over the result,
		// so a token cannot introduce markup the allow-list would reject.
		$link_text = wp_kses(
			Tokens::resolve( $text ),
			array(
				'strong' => array(),
				'em'     => array(),
				'b'      => array(),
				'i'      => array(),
				'u'      => array(),
				'span'   => array( 'class' => true ),
				'div'    => array( 'class' => true ),
			)
		);

		/**
		 * Filters the footer acknowledgment address before tokens are resolved.
		 *
		 * Companion to acknowledgify_footer_link_text, for sending each
		 * language to a different destination. The returned value still goes
		 * through esc_url(), so an unsafe scheme is rejected as usual.
		 *
		 * @param string $url                Stored link address, tokens unresolved.
		 * @param string $placement_selector auto_insert, shortcode or php_snippet.
		 */
		$url = (string) apply_filters(
			'acknowledgify_footer_link_url',
			(string) Helper::get_setting( 'footer_link_url' ),
			$placement_selector
		);

		$link_url = esc_url( Tokens::resolve( $url ) );

		// An anchor with no text is unusable and unreadable to a screen
		// reader, and one with no destination is not a link. Either means the
		// user has cleared the field, so render nothing at all.
		if ( '' === trim( wp_strip_all_tags( $link_text ) ) || '' === $link_url ) {
			return '';
		}

		$custom_class = (string) Helper::get_setting( 'footer_custom_class', '' );

		// ack-footer-link and any custom class are the stable hooks external
		// CSS targets, so they are emitted unconditionally in both style modes.
		$classes = trim( 'ack-footer-link ' . $custom_class );

		$attributes = array( 'class="' . esc_attr( $classes ) . '"' );

		/**
		 * Filters the rel attribute values on the footer acknowledgment link.
		 *
		 * Defaults to nofollow to qualify distributed credit links. Google's
		 * link-spam policy includes widely distributed footer links among its
		 * examples. This default is not a blanket compliance guarantee.
		 *
		 * Return an array of rel keywords, for example array( 'sponsored' )
		 * for a paid credit, or an empty array to output a followed link.
		 * noopener is always added afterwards and cannot be removed, because
		 * the link opens in a new tab.
		 *
		 * @param string[] $rel                Rel keywords. Default array( 'nofollow' ).
		 * @param string   $placement_selector auto_insert, shortcode or php_snippet.
		 */
		$rel = apply_filters( 'acknowledgify_footer_link_rel', array( 'nofollow' ), $placement_selector );

		// Keep only well-formed keywords, whatever a filter returned. A rel
		// keyword is a bare token, so anything else is discarded rather than
		// escaped into the attribute.
		$rel = array_filter(
			array_map( 'strtolower', array_filter( (array) $rel, 'is_string' ) ),
			static function ( $keyword ) {
				return (bool) preg_match( '/^[a-z][a-z0-9-]*$/', $keyword );
			}
		);

		$rel[] = 'noopener';
		$rel   = array_values( array_unique( $rel ) );

		$link_attributes = array(
			'href="' . $link_url . '"',
			'target="_blank"',
			'rel="' . esc_attr( implode( ' ', $rel ) ) . '"',
		);

		if ( 'plugin' === Helper::get_setting( 'footer_style_mode' ) ) {
			$text_color = Helper::get_setting( 'footer_text_color' );
			$font_size  = Helper::get_setting( 'footer_font_size' );
			$bg_color   = Helper::get_setting( 'footer_bg_color' );
			$alignment  = Helper::get_setting( 'footer_alignment' );

			$wrapper_styles = array(
				'color:' . $text_color,
				'font-size:' . $font_size,
			);

			// Both are optional; emit nothing when unset so the theme decides.
			if ( '' !== $bg_color ) {
				$wrapper_styles[] = 'background-color:' . $bg_color;
			}

			if ( 'inherit' !== $alignment ) {
				$wrapper_styles[] = 'text-align:' . $alignment;
			}

			$attributes[] = 'style="' . esc_attr( implode( '; ', $wrapper_styles ) . ';' ) . '"';

			/*
			 * Colour and size must also be set on the anchor. Themes style
			 * "a { color: ... }" directly, which beats a colour inherited from
			 * the wrapper, so setting it only on the wrapper meant the chosen
			 * colour never reached the visible link text.
			 */
			$link_attributes[] = 'style="' . esc_attr(
				'color:' . $text_color . '; font-size:' . $font_size . ';'
			) . '"';
		}

		/**
		 * Filters the wrapper element for the footer acknowledgment.
		 *
		 * Defaults to div, which is what every existing site renders. A block
		 * theme places wp_footer output after the footer template part and so
		 * outside the theme's layout container; if that is awkward, switching
		 * to span, or to the external style mode, usually resolves it.
		 *
		 * @param string $tag                Element name. Default 'div'.
		 * @param string $placement_selector auto_insert, shortcode or php_snippet.
		 */
		$tag = (string) apply_filters( 'acknowledgify_footer_wrapper_tag', 'div', $placement_selector );
		$tag = preg_replace( '/[^a-z0-9]/', '', strtolower( $tag ) );

		if ( '' === $tag ) {
			$tag = 'div';
		}

		$output = sprintf(
			'<%1$s %2$s><a %3$s>%4$s</a></%1$s>',
			$tag,
			implode( ' ', $attributes ),
			implode( ' ', $link_attributes ),
			$link_text
		);

		return wp_kses_post( $output );
	}

	/**
	 * Echo the acknowledgment markup for a placement.
	 *
	 * @param string $placement_selector auto_insert, shortcode or php_snippet.
	 * @return void
	 */
	public static function footer_output( $placement_selector ) {
		// Already passed through wp_kses_post() in get_markup().
		// phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
		echo self::get_markup( $placement_selector );
	}
}