<?php
/**
 * Dynamic Style Generator
 *
 * Generates and manages page-specific dynamic styles with minification.
 * Collects block styles and outputs them as optimized CSS files.
 *
 * @since      1.0.0
 * @package    Acumenpopup
 * @subpackage Acumenpopup/includes/Core
 */

namespace Acumenpopup\Core;

// Exit if accessed directly.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Class Dynamic_Style
 *
 * Manages dynamic CSS generation for blocks (Singleton).
 *
 * @since   1.0.0
 * @package Acumenpopup
 */
class Dynamic_Style {

	/**
	 * The single instance of the class.
	 *
	 * @since  1.0.0
	 * @access private
	 * @var    Dynamic_Style|null
	 */
	private static $instance = null;

	/**
	 * Stores all collected dynamic styles.
	 *
	 * @since  1.0.0
	 * @access private
	 * @var    array
	 */
	private static $styles = array();

	/**
	 * The directory path for storing CSS files.
	 *
	 * @since  1.0.0
	 * @access private
	 * @var    string
	 */
	private $css_dir;

	/**
	 * The URL for the CSS directory.
	 *
	 * @since  1.0.0
	 * @access private
	 * @var    string
	 */
	private $css_url;

	/**
	 * Private constructor to prevent direct instantiation.
	 *
	 * @since  1.0.0
	 * @access private
	 */
	private function __construct() {
		$this->setup_directories();
		$this->init_hooks();
	}

	/**
	 * Get the single instance of the Dynamic_Style class.
	 *
	 * @since  1.0.0
	 * @access public
	 *
	 * @return Dynamic_Style The single instance.
	 */
	public static function get_instance() {
		if ( is_null( self::$instance ) ) {
			self::$instance = new self();
		}

		return self::$instance;
	}

	/**
	 * Setup CSS directories for storing generated files.
	 *
	 * Creates the directory structure if it doesn't exist.
	 *
	 * @since  1.0.0
	 * @access private
	 *
	 * @return void
	 */
	private function setup_directories() {
		$upload_dir    = wp_upload_dir();
		$this->css_dir = trailingslashit( $upload_dir['basedir'] ) . 'acumenpopup/css';
		$this->css_url = trailingslashit( $upload_dir['baseurl'] ) . 'acumenpopup/css';

		if ( ! file_exists( $this->css_dir ) ) {
			wp_mkdir_p( $this->css_dir );
		}
	}

	/**
	 * Initialize WordPress hooks.
	 *
	 * @since  1.0.0
	 * @access private
	 *
	 * @return void
	 */
	private function init_hooks() {
		add_filter( 'render_block', array( $this, 'collect_dynamic_styles' ), 10, 2 );
		add_action( 'wp_footer', array( $this, 'generate_css_file' ), 10 );
		add_action( 'wp_enqueue_scripts', array( $this, 'enqueue_dynamic_styles' ) );
	}

	/**
	 * Collect dynamic styles from rendered blocks.
	 *
	 * Filters each block during rendering to collect any blockStyle attributes.
	 *
	 * @since  1.0.0
	 * @access public
	 *
	 * @param string $block_content The block content.
	 * @param array  $block         The block data including attributes.
	 *
	 * @return string The unmodified block content.
	 */
	public function collect_dynamic_styles( $block_content, $block ) {
		// Only process Acumenpopup blocks.
		if ( ! isset( $block['blockName'] ) || false === strpos( $block['blockName'], 'acumenpopup/' ) ) {
			return $block_content;
		}

		/**
		 * Action hook for rendering Acumenpopup blocks.
		 *
		 * Allows other components to hook into block rendering.
		 *
		 * @since 1.0.0
		 *
		 * @param array $block The block data.
		 */
		do_action( 'acumenpopup_render_block', $block );

		// Collect block styles.
		if ( isset( $block['attrs']['blockStyle'] ) && ! empty( $block['attrs']['blockStyle'] ) ) {
			$block_id = isset( $block['attrs']['blockId'] )
				? sanitize_key( $block['attrs']['blockId'] )
				: 'acumenpopup-block-' . md5( maybe_serialize( $block['attrs'] ) );

			self::$styles[ $block_id ] = $this->sanitize_custom_css( $block['attrs']['blockStyle'] );
		}

		return $block_content;
	}

	/**
	 * Securely sanitize custom CSS by stripping HTML and dangerous vectors.
	 *
	 * @since  1.0.0
	 * @access private
	 *
	 * @param string $css Unsanitized CSS string.
	 *
	 * @return string Sanitized CSS string.
	 */
	private function sanitize_custom_css( $css ) {
		// Validate UTF-8 encoding
		$css = wp_check_invalid_utf8( $css );

		if ( empty( $css ) ) {
			return '';
		}

		// Normalize whitespace to prevent obfuscation tricks
		$css = preg_replace( '/\s+/', ' ', $css );

		// Remove CSS comments (can hide payloads: /* expression */background:url() */)
		$css = preg_replace( '!/\*.*?\*/!s', '', $css );

		// Remove backslash escapes used to bypass keyword filters (e.g. \65 xpression)
		$css = preg_replace( '/\\\\[0-9a-fA-F]{0,6}\s?/', '', $css );

		// Block dangerous CSS functions and protocols
		// Covers: expression(), url(), javascript:, vbscript:, data:, behavior
		if ( preg_match(
			'/expression\s*\(
			| url\s*\(
			| javascript\s*:
			| vbscript\s*:
			| data\s*:
			| @import
			| behavior\s*:
			| -moz-binding\s*:
			| content\s*:/ix',
			$css
		) ) {
			return '';
		}

		// Block HTML tags that could escape the <style> context
		if ( preg_match( '/<\s*\/?\s*(script|style|link|meta|object|embed|iframe)/i', $css ) ) {
			return '';
		}

		// Trim and return
		return trim( $css );
	}

	/**
	 * Generate the CSS file with collected styles.
	 *
	 * Writes minified CSS to a page-specific file in wp-content/uploads.
	 *
	 * @since  1.0.0
	 * @access public
	 *
	 * @return void
	 */
	public function generate_css_file() {
		if ( empty( self::$styles ) ) {
			return;
		}

		$page_id      = get_queried_object_id();
		$css_filename = 'acumenpopup-dynamic-styles-' . absint( $page_id ) . '.min.css';
		$css_file     = trailingslashit( $this->css_dir ) . $css_filename;

		// Combine all styles.
		$css_content = implode( '', self::$styles );

		// Add header comment and minify.
		$css_content = sprintf(
			"/* Acumenpopup Dynamic Styles - Page ID: %d - Generated: %s */\n%s",
			absint( $page_id ),
			esc_html( current_time( 'mysql' ) ),
			$this->minify_css( $css_content )
		);

		// Initialize filesystem.
		$this->init_filesystem();

		global $wp_filesystem;

		// Only write if content has changed.
		$existing_content = '';
		if ( file_exists( $css_file ) && $wp_filesystem ) {
			$existing_content = $wp_filesystem->get_contents( $css_file );
		}

		if ( $existing_content !== $css_content && $wp_filesystem ) {
			$wp_filesystem->put_contents( $css_file, $css_content, FS_CHMOD_FILE );
		}

		// Clear the styles array after generating.
		self::$styles = array();
	}

	/**
	 * Enqueue the generated dynamic styles.
	 *
	 * @since  1.0.0
	 * @access public
	 *
	 * @return void
	 */
	public function enqueue_dynamic_styles() {
		$page_id       = get_queried_object_id();
		$css_filename  = 'acumenpopup-dynamic-styles-' . absint( $page_id ) . '.min.css';
		$css_file_path = trailingslashit( $this->css_dir ) . $css_filename;
		$css_file_url  = trailingslashit( $this->css_url ) . $css_filename;

		if ( file_exists( $css_file_path ) ) {
			wp_enqueue_style(
				'acumenpopup-dynamic-styles-' . absint( $page_id ),
				esc_url( $css_file_url ),
				array(),
				filemtime( $css_file_path )
			);
		}
	}

	/**
	 * Minify CSS content.
	 *
	 * Removes comments, unnecessary whitespace, and optimizes the CSS.
	 *
	 * @since  1.0.0
	 * @access private
	 *
	 * @param string $css The CSS content to minify.
	 *
	 * @return string The minified CSS.
	 */
	private function minify_css( $css ) {
		// Remove comments.
		$css = preg_replace( '!/\*[^*]*\*+([^/][^*]*\*+)*/!', '', $css );

		// Remove space after colons.
		$css = str_replace( ': ', ':', $css );

		// Remove whitespace.
		$css = str_replace(
			array( "\r\n", "\r", "\n", "\t", '  ', '    ', '    ' ),
			'',
			$css
		);

		return $css;
	}

	/**
	 * Initialize the WordPress filesystem.
	 *
	 * @since  1.0.0
	 * @access private
	 *
	 * @return void
	 */
	private function init_filesystem() {
		global $wp_filesystem;

		if ( empty( $wp_filesystem ) ) {
			require_once ABSPATH . '/wp-admin/includes/file.php';
			WP_Filesystem();
		}
	}

	/**
	 * Clean up generated CSS files.
	 *
	 * Removes all generated CSS files and directories.
	 * Called during plugin uninstall.
	 *
	 * @since  1.0.0
	 * @access public
	 *
	 * @return void
	 */
	public static function cleanup_files() {
		$upload_dir = wp_upload_dir();
		$css_dir    = trailingslashit( $upload_dir['basedir'] ) . 'acumenpopup/css';

		if ( ! file_exists( $css_dir ) ) {
			return;
		}

		global $wp_filesystem;

		if ( empty( $wp_filesystem ) ) {
			require_once ABSPATH . '/wp-admin/includes/file.php';
			WP_Filesystem();
		}

		if ( ! $wp_filesystem ) {
			return;
		}

		// Delete all files in CSS directory.
		$files = glob( $css_dir . '/*' );
		if ( is_array( $files ) ) {
			foreach ( $files as $file ) {
				if ( is_file( $file ) ) {
					$wp_filesystem->delete( $file );
				}
			}
		}

		// Remove the CSS directory.
		$wp_filesystem->rmdir( $css_dir );

		// Remove parent directory if empty.
		$parent_dir = dirname( $css_dir );
		if ( file_exists( $parent_dir ) ) {
			$remaining_files = glob( $parent_dir . '/*' );
			if ( empty( $remaining_files ) ) {
				$wp_filesystem->rmdir( $parent_dir );
			}
		}
	}

	/**
	 * Prevent cloning of the instance.
	 *
	 * @since  1.0.0
	 * @access public
	 *
	 * @return void
	 */
	public function __clone() {
		_doing_it_wrong(
			__FUNCTION__,
			esc_html__( 'Cloning is forbidden.', 'acumen-popup' ),
			'1.0.0'
		);
	}

	/**
	 * Prevent unserializing of the instance.
	 *
	 * @since  1.0.0
	 * @access public
	 *
	 * @return void
	 */
	public function __wakeup() {
		_doing_it_wrong(
			__FUNCTION__,
			esc_html__( 'Unserializing is forbidden.', 'acumen-popup' ),
			'1.0.0'
		);
	}
}