<?php
/**
 * Generates the :root stylesheet from the stored tokens.
 *
 * @package TokenForge
 */

namespace TokenForge;

defined( 'ABSPATH' ) || exit;

/**
 * Compiles tokens into a static CSS file under uploads/tokenforge/.
 */
class Css_Generator {

	const HANDLE      = 'tokenforge';
	const FILE_NAME   = 'tokenforge.css';
	const FULL_FILE   = 'tokenforge-full.css';
	const SHOP_FILE   = 'tokenforge-shop.css'; // WooCommerce shop pages (loads only where the shop appears)
	const OPTION_META = 'tokenforge_css_meta';

	/** @var Css_Generator|null */
	private static $instance = null;

	/**
	 * Singleton.
	 *
	 * @return Css_Generator
	 */
	public static function get_instance() {
		if ( null === self::$instance ) {
			self::$instance = new self();
		}
		return self::$instance;
	}

	/**
	 * Absolute directory for generated files.
	 *
	 * @return string
	 */
	public function dir() {
		$up = wp_get_upload_dir();
		/**
		 * Directory the stylesheet is written to (e.g. a scratch folder in tests).
		 *
		 * @param string $dir Absolute path.
		 */
		return apply_filters( 'tokenforge_css_dir', trailingslashit( $up['basedir'] ) . 'tokenforge' );
	}

	/**
	 * Public URL for generated files.
	 *
	 * @return string
	 */
	public function url() {
		$up = wp_get_upload_dir();
		return trailingslashit( $up['baseurl'] ) . 'tokenforge';
	}

	/**
	 * Full path to the generated stylesheet.
	 *
	 * @return string
	 */
	public function css_path() {
		return trailingslashit( $this->dir() ) . self::FILE_NAME;
	}

	/**
	 * Full URL to the generated stylesheet (cache-busted).
	 *
	 * @return string
	 */
	public function css_url() {
		$meta = get_option( self::OPTION_META, array() );
		$ver  = isset( $meta['mtime'] ) ? $meta['mtime'] : TOKENFORGE_VERSION;
		return add_query_arg( 'ver', $ver, trailingslashit( $this->url() ) . self::FILE_NAME );
	}

	/**
	 * Path of the stylesheet with every utility class (written only while
	 * unused classes are left out of the main one; the builder canvas uses it).
	 *
	 * @return string
	 */
	public function full_css_path() {
		return trailingslashit( $this->dir() ) . self::FULL_FILE;
	}

	/**
	 * URL of the stylesheet with every utility class (cache-busted).
	 *
	 * @return string
	 */
	public function full_css_url() {
		return add_query_arg( 'ver', $this->version(), trailingslashit( $this->url() ) . self::FULL_FILE );
	}

	/**
	 * Full path to the shop pages stylesheet (only written while WooCommerce's shop page styles are on).
	 *
	 * @return string
	 */
	public function shop_css_path() {
		return trailingslashit( $this->dir() ) . self::SHOP_FILE;
	}

	/**
	 * URL of the shop pages stylesheet (cache-busted like the main one).
	 *
	 * @return string
	 */
	public function shop_css_url() {
		return add_query_arg( 'ver', $this->version(), trailingslashit( $this->url() ) . self::SHOP_FILE );
	}

	/**
	 * The shop pages stylesheet: '' when there is nothing to write.
	 *
	 * @return string
	 */
	public function build_shop_css() {
		$css = Woo::build_shop();
		if ( '' === trim( $css ) ) {
			return '';
		}
		return '/* Generated by TokenForge ' . TOKENFORGE_VERSION . ' on ' . gmdate( 'Y-m-d H:i:s' ) . " UTC: WooCommerce shop pages. Do not edit directly. */\n" . $css;
	}

	/**
	 * Current stylesheet version (changes on every regenerate).
	 *
	 * @return string
	 */
	public function version() {
		$meta = get_option( self::OPTION_META, array() );
		return isset( $meta['mtime'] ) ? (string) $meta['mtime'] : TOKENFORGE_VERSION;
	}

	/**
	 * CSS for the block editor: the file, or a layer-free build when layers are on
	 * (the editor's style scoping doesn't reliably handle @layer).
	 *
	 * @return string
	 */
	public function editor_css() {
		// The shop pages part too: Cart, Checkout and product blocks can be edited there.
		return $this->build_css( false, true ) . Woo::build_shop();
	}

	/**
	 * Are any cascade layers switched on?
	 *
	 * @return bool
	 */
	public function uses_layers() {
		$s = Settings::get_instance()->get_settings();
		foreach ( self::LAYERS as $layer ) {
			if ( ! empty( $s[ 'layer_' . $layer ] ) ) {
				return true;
			}
		}
		return false;
	}

	/** Cascade layers, lowest priority first. */
	const LAYERS = array( 'defaults', 'base', 'buttons', 'cards', 'icons', 'content' );

	/**
	 * Build the CSS text from enabled tokens.
	 *
	 * @param bool $allow_layers Wrap the opted-in low-priority parts in @layer
	 *                           (false for the block editor, whose style
	 *                           scoping doesn't reliably handle @layer).
	 * @param bool $for_editor   For the block editor (every utility class, no root font size).
	 * @param bool $full         Every utility class, even ones the site does not use.
	 * @return string
	 */
	public function build_css( $allow_layers = true, $for_editor = false, $full = false ) {
		$tokens = Settings::get_instance()->all_variables();
		$lines  = array();
		foreach ( $tokens as $t ) {
			if ( empty( $t['enabled'] ) || '' === $t['value'] ) {
				continue;
			}
			$lines[] = sprintf( "\t--%s: %s;", $t['name'], $t['value'] );
		}
		$header  = "/* Generated by TokenForge " . TOKENFORGE_VERSION . " on " . gmdate( 'Y-m-d H:i:s' ) . " UTC. Do not edit directly. */\n";
		$body    = ":root {\n" . implode( "\n", $lines ) . "\n}\n";

		// Append the base-styles/components layer, then the utility-class layer
		// (utilities last so a class always wins over a base element style).
		$defaults   = Defaults::build();   // reset first
		$components = Components::build( $for_editor );
		$scheme     = Scheme::build();
		$extras     = Extras::build();
		$overlays   = Overlays::build();
		$motion     = Motion::build( $for_editor );
		$content    = Content::build();
		$width      = Width::build();
		$fw         = Framework::build( $full || $for_editor );
		$woo        = Woo::build(); // '' unless WooCommerce is active
		// Site-wide blockquotes cascade with the base styles (same layer choice).
		$components['css'] .= isset( $content['base'] ) ? $content['base'] : '';
		$parts = array(
			'defaults' => $defaults['css'],
			'base'     => $components['css'],
			'buttons'  => isset( $components['buttons'] ) ? $components['buttons'] : '',
			'cards'    => isset( $components['cards'] ) ? $components['cards'] : '',
			'icons'    => isset( $extras['icons'] ) ? $extras['icons'] : '',
			'content'  => $content['css'],
		);

		// Optional cascade layers: layered rules lose to ALL unlayered CSS (theme,
		// builder, custom), so these parts become trivially overridable. Tokens,
		// scheme, effects and utilities stay unlayered so they keep winning.
		$s     = Settings::get_instance()->get_settings();
		$order = '';
		if ( $allow_layers && $this->uses_layers() ) {
			$order = '@layer ' . implode( ', ', array_map( function ( $l ) {
				return 'tokenforge.' . $l;
			}, self::LAYERS ) ) . ";\n";
			foreach ( $parts as $layer => $css ) {
				if ( ! empty( $s[ 'layer_' . $layer ] ) && '' !== trim( $css ) ) {
					$parts[ $layer ] = "\n@layer tokenforge.$layer {" . $css . "}\n";
				}
			}
		}

		// Root font size: unlayered (beats Bricks' @layer 62.5%); never in the
		// block editor, whose rem base is the editor's own.
		$root = $for_editor ? '' : Defaults::root_css();

		// Developer SCSS (tokenforge_global_scss filter) last and unlayered, so it wins over everything generated.
		$scss = Scss::css();
		$scss = '' !== $scss ? "
/* --- Developer SCSS --- */
" . $scss . "
" : '';

		return $header . $order . Fonts::css() . ( isset( $defaults['reset'] ) ? $defaults['reset'] : '' ) . $parts['defaults'] . $body . $root . $parts['base'] . $parts['buttons'] . $parts['cards'] . $woo . $scheme['css'] . $extras['css'] . $parts['icons'] . Attributes::build( ! $full && ! $for_editor ) . $overlays['css'] . $motion['css'] . $width['css'] . $parts['content'] . $fw['css'] . $scss;
	}

	/**
	 * Write the stylesheet, then let the builder sync pick up the change.
	 *
	 * @return bool True when the stylesheet was written.
	 */
	public function rebuild() {
		$ok = $this->generate();
		do_action( 'tokenforge_tokens_saved' );
		return $ok;
	}

	/**
	 * Write a file so a visitor never reads half of it: write beside it, then rename over it.
	 * A failure leaves the old file as it was.
	 *
	 * @param string $path    Target file.
	 * @param string $content Content.
	 * @return bool True on success.
	 */
	private function write_file( $path, $content ) {
		$tmp = $path . '.tmp-' . bin2hex( random_bytes( 6 ) );
		// phpcs:disable WordPress.WP.AlternativeFunctions, WordPress.PHP.NoSilencedErrors
		// Windows refuses to rename over a file that is open: copy over it then.
		$ok = mb_strlen( $content, '8bit' ) === file_put_contents( $tmp, $content ) && ( @rename( $tmp, $path ) || @copy( $tmp, $path ) );
		// phpcs:enable
		if ( file_exists( $tmp ) ) {
			wp_delete_file( $tmp );
		}
		return $ok;
	}

	/**
	 * Write the stylesheet to disk.
	 *
	 * @return bool True on success.
	 */
	public function generate() {
		$dir = $this->dir();
		if ( ! wp_mkdir_p( $dir ) ) {
			return false;
		}
		// Keep the directory tidy / discourage listing.
		$index = trailingslashit( $dir ) . 'index.php';
		if ( ! file_exists( $index ) ) {
			file_put_contents( $index, "<?php // Silence is golden.\n" ); // phpcs:ignore WordPress.WP.AlternativeFunctions
		}
		$ok = $this->write_file( $this->css_path(), $this->build_css() );
		// Unused utility classes left out: the builder canvas gets every class from a second file.
		if ( Class_Usage::active() ) {
			$ok = $ok && $this->write_file( $this->full_css_path(), $this->build_css( true, false, true ) );
		} elseif ( file_exists( $this->full_css_path() ) ) {
			wp_delete_file( $this->full_css_path() );
		}
		// The shop pages sheet: written while it has something in it, removed otherwise.
		$shop = $this->build_shop_css();
		if ( '' !== $shop ) {
			$ok = $ok && $this->write_file( $this->shop_css_path(), $shop );
		} elseif ( file_exists( $this->shop_css_path() ) ) {
			wp_delete_file( $this->shop_css_path() );
		}
		if ( $ok ) {
			update_option(
				self::OPTION_META,
				array(
					'mtime'   => (string) round( microtime( true ) * 1000 ), // ms: two saves in one second still differ (hot reload)
					'version' => TOKENFORGE_VERSION,
					'woo'     => Woo::active(), // rebuild when WooCommerce is switched on or off
					'gs'      => Woo::uses_global_styles(), // or when a block theme comes or goes
					'split'   => Woo::split(), // or when a builder whose shop widgets can't be seen comes or goes
				)
			);
		}
		return $ok;
	}
}