<?php
/**
 * CSS Injector
 * Helper object for including dynamic styles into head of the document,
 * with possibilities of extending it.
 *
 * @copyright 2019-present Creative Themes
 * @license   http://www.gnu.org/copyleft/gpl.html GNU General Public License
 * @package Blocksy
 */

defined( 'ABSPATH' ) || die( "Don't run this file directly!" );

class Blocksy_Css_Injector {
	/**
	 * Temporary CSS attributes.
	 *
	 * @var array $attr Attributes.
	 */
	private $attr = array();

	/**
	 * Keyword that allows skiping a certain CSS rule from getting in the output.
	 */
	public static function get_skip_rule_keyword($suffix = '') {
		return 'CT_CSS_SKIP_RULE' . $suffix;
	}

	/**
	 * Injector constructor.
	 */
	public function __construct() {
		$this->additional_symbols = array( '-', '%', 'px', 's' );
	}

	/**
	 * Parse each temporary structure and transform it into actual CSS.
	 */
	public function build_css_structure() {
		// blocksy_print($this->attr);
		$content = '';

		if (count($this->attr)) {
			$content .= "\n" . $this->convert_to_css();
		}

		$content = $this->css_minify($content);

		return $content;
	}

	/**
	 * Add new line in CSS structure.
	 *
	 * @param string|array $key CSS class, id, tag.
	 * @param string|array $value CSS syntax.
	 */
	public function put($key, $value) {
		if (is_string($value) && trim($value) === '') {
			return;
		}

		if (is_array($key)) {
			$key = implode(",\n", $key);
		}

		if (! isset($this->attr[$key])) {
			$this->attr[$key] = [];
		}

		$rules = [];

		// Convert string to array.
		if ( ! is_array( $value ) ) {
			$rules = explode( ';', $value );
		} else {
			/**
			 * Support nested rules.
			 */
			foreach ( $value as $maybe_rule ) {
				$current_rules = explode( ';', $maybe_rule );

				foreach ( $current_rules as $current_rule ) {
					$rules[] = $current_rule;
				}
			}
		}

		foreach ( $rules as $line ) {
			$line = trim( $line );

			if ( $line ) {
				if ( ! in_array( $line, $this->attr[ $key ], true ) ) {
					$this->attr[ $key ][] = $line;
				}
			}
		}

		$this->attr[ $key ] = $this->remove_dublication(
			$this->attr[ $key ]
		);
	}

	/**
	 * Merge selectors that have the same CSS. This has the effect of increasing
	 * the weight of the selectors.
	 */
	private function merge_class_with_the_same_css() {
		return;

		$new_names = [];
		$used = [];

		foreach ( $this->attr as $key => $values ) {
			if ( isset( $used[ $key ] ) ) {
				continue;
			}

			foreach ( $this->attr as $sub_key => $sub_values ) {
				if ( $sub_key !== $key && $values === $sub_values ) {
					$used[ $sub_key ] = 1;
					$new_names[ $key ][] = $sub_key;
					$used[ $key ] = 1;
				}
			}
		}

		// Merge classes.
		foreach ( $new_names as $parent => $childs ) {
			$class_name = $parent . ",\n" . join( ",\n", $childs );
			$this->attr[ $class_name ] = $this->attr[ $parent ];

			// Remove CSS from main structure.
			if ( isset( $this->attr[ $parent ] ) ) {
				unset( $this->attr[ $parent ] );
			}

			// Remove all childs css.
			foreach ( $childs as $child_class ) {
				if ( isset( $this->attr[ $child_class ] ) ) {
					unset( $this->attr[ $child_class ] );
				}
			}
		}
	}

	/**
	 * Convert this->attr to a CSS string.
	 */
	private function convert_to_css() {
		$css = '';

		$this->merge_class_with_the_same_css();

		foreach ($this->attr as $key => $values) {
			$section = '';

			$section .= $key . " {\n";

			$content = '';

			foreach ($values as $line) {
				$line = trim( $line );

				if (! $this->is_empty_style($line)) {
					if (strpos($key, '@media') === false) {
						$line = str_replace(';', '', $line);
					}

					$content .= "    {$line}";

					if (strpos($key, '@media') === false) {
						$content .= ";\n";
					}
				}
			}

			// CSS is not empty.
			if ($content) {
				$section .= $content;
			} else {
				continue;
			}

			$section .= "}\n\n";
			$css .= $section;
		}

		// Erase structure.
		$this->attr = array();

		return $css;
	}

	/**
	 * Check if a CSS rule is empty.
	 *
	 * @param string $line Single rule.
	 */
	private function is_empty_style( $line ) {
		$parts = explode(':', $line);

		if (count($parts) <= 1) {
			return false;
		}

		if (! isset($parts[1])) {
			return true;
		}

		$parts[1] = str_replace($this->additional_symbols, '', $parts[1]);

		return strlen(trim($parts[1])) === 0;
	}

	/**
	 * Very rudimentary CSS minifier.
	 *
	 * @param string $minify CSS to be minified.
	 */
	private function css_minify( $minify ) {
		if (defined('WP_DEBUG') && WP_DEBUG) {
			// return $minify;
		}

		/* remove comments */
		$minify = preg_replace( '!/\*[^*]*\*+([^/][^*]*\*+)*/!', '', $minify );

		/* remove tabs, spaces, newlines, etc. */
		$minify = str_replace( array( "\r\n", "\r", "\n", "\t", '  ', '    ', '    ' ), '', $minify );
		/* remove space after colons */
		$minify = str_replace( ': ', ':', $minify );

		return $minify;
	}

	/**
	 * Remove dublications of CSS rules.
	 * Input: array( 'color: red', 'color: blue' )
	 * Output: array( 'color: blue' )
	 * Return the last rule.
	 *
	 * @param array $rules CSS Rules.
	 * @return array
	 */
	protected function remove_dublication( $rules ) {
		$result = array();
		$dublication = array();

		for ( $i = count( $rules ) - 1; $i >= 0; $i-- ) {
			$line = $rules[ $i ];

			if ( strpos( $line, self::get_skip_rule_keyword() ) !== false ) {
				continue;
			}

			$position = strpos( $line, ':' );
			$key = substr( $line, 0, $position );

			/**
			 * Skip redundant variables
			 * --a: var(--a)
			 */
			if (strpos($key, '--') === 0) {
				if (strpos(explode(':', $line)[1], $key) !== false) {
					continue;
				}
			}

			if ( ! in_array( $key, $dublication, true ) ) {
				$result[] = $line;
				$dublication[] = $key;
			}
		}

		krsort( $result );

		return $result;
	}
}