<?php
/**
 * Design tokens: the scene's token tree becomes custom properties on one scope.
 *
 * Specified by `packages/core/src/tokens.js`.
 *
 * @package Aumframe
 */

namespace Aumframe\Css;

defined('ABSPATH') || exit;

final class Tokens
{
    /** `{color.brand}` is a reference to a token; anything else is a literal. */
    private const TOKEN_RE = '/^\{([a-zA-Z0-9_.-]+)\}$/';

    public static function path_to_var(string $path): string
    {
        return '--af-' . str_replace('.', '-', $path);
    }

    /** Turn a token reference into `var(--af-…)`; pass every other value through. */
    public static function resolve($value)
    {
        if (!is_string($value)) {
            return $value;
        }

        return preg_match(self::TOKEN_RE, $value, $m)
            ? 'var(' . self::path_to_var($m[1]) . ')'
            : $value;
    }

    public static function compile($tokens, string $scope = ':root'): string
    {
        $decls = [];
        self::walk($tokens, [], $decls);
        if (!$decls) {
            return '';
        }

        return $scope . '{' . implode('', $decls) . '}';
    }

    private static function walk($node, array $path, array &$out): void
    {
        if (!is_array($node)) {
            return;
        }
        foreach ($node as $key => $val) {
            $next = array_merge($path, [(string) $key]);
            /*
             * A nested table recurses; a leaf becomes one declaration. An empty table is
             * indistinguishable from an empty array after `json_decode(…, true)` and is
             * treated as a table, so it contributes nothing.
             */
            if (is_array($val) && ($val === [] || !Value::isList($val))) {
                self::walk($val, $next, $out);
                continue;
            }
            $out[] = self::path_to_var(implode('.', $next)) . ':' . Value::str($val) . ';';
        }
    }
}