<?php

namespace App\Service\business;

use App\Service\common\UtilsService;

/**
 * 装修模板 JSON 的白名单校验
 *
 * 导入的 JSON 会被小程序当成 CSS 变量注入根节点，一份坏 JSON 能把线上小程序打成白屏，
 * 所以入库前必须过白名单：键名不在表里的丢弃，值必须是安全的短字符串。
 * 这里只允许「值」，不允许任何 CSS 语句片段（分号、url()、表达式一律拒绝）。
 */
class WxTemplateSchemaService
{
    private static mixed $_instance;

    /**
     * 允许的令牌键，分组 => 键名清单
     */
    public const TOKEN_SCHEMA = [
        'color' => [
            'primary', 'primary_soft', 'primary_strong', 'accent', 'bg', 'bg_soft',
            'surface', 'surface_soft', 'text', 'text_soft', 'text_muted', 'border',
            'price', 'success', 'warning', 'danger', 'mask',
        ],
        'font' => [
            'family', 'family_title', 'size_xs', 'size_sm', 'size_md', 'size_lg',
            'size_xl', 'size_title', 'weight_normal', 'weight_bold', 'line_height', 'letter_spacing',
        ],
        'radius' => ['none', 'sm', 'md', 'lg', 'xl', 'pill'],
        'shadow' => ['none', 'sm', 'md', 'lg'],
        'space' => ['xxs', 'xs', 'sm', 'md', 'lg', 'xl', 'page'],
        'motion' => ['fast', 'base', 'slow', 'easing', 'easing_in', 'easing_out'],
    ];

    /**
     * 允许的布局键与可选值
     */
    public const LAYOUT_SCHEMA = [
        'home' => [
            'hero' => ['banner', 'carousel', 'split', 'fullscreen'],
            'category' => ['grid', 'scroll', 'card', 'sidebar'],
            'product' => ['waterfall', 'list', 'grid', 'magazine'],
        ],
        'product' => [
            'gallery' => ['swiper', 'stack', 'fullbleed'],
            'price' => ['inline', 'card', 'sticky'],
            'action' => ['fixed', 'inline'],
        ],
        'list' => [
            'style' => ['card', 'table', 'timeline'],
        ],
        'mine' => [
            'header' => ['gradient', 'image', 'plain'],
            'menu' => ['grid', 'list'],
        ],
        'effect' => [
            'transition' => ['fade', 'slide', 'zoom', 'none'],
            'skeleton' => ['shimmer', 'pulse', 'none'],
        ],
    ];

    /**
     * 危险片段：出现即拒绝整个值
     */
    private const FORBIDDEN = ['<', '>', ';', '{', '}', 'url(', 'expression', 'javascript:', 'import'];

    public static function getInstance(): null|static
    {
        $name = get_called_class();
        if (!isset(self::$_instance[$name])) {
            self::$_instance[$name] = new static();
        }
        return self::$_instance[$name];
    }

    /**
     * 清洗令牌：只保留白名单键，值必须安全
     *
     * @param mixed $tokens 数组或 JSON 字符串
     * @param bool $strict true 时遇到非法值直接报错（导入场景），false 时静默丢弃
     */
    public function sanitizeTokens(mixed $tokens, bool $strict = false): array
    {
        $tokens = $this->toArray($tokens);
        $clean = [];
        foreach (self::TOKEN_SCHEMA as $group => $keys) {
            $source = $tokens[$group] ?? [];
            if (!is_array($source)) {
                continue;
            }
            foreach ($keys as $key) {
                if (!array_key_exists($key, $source)) {
                    continue;
                }
                $value = $source[$key];
                if (!$this->isSafeValue($value)) {
                    if ($strict) {
                        UtilsService::getInstance()->errorThrow("模板令牌 {$group}.{$key} 的值不合法");
                    }
                    continue;
                }
                $clean[$group][$key] = (string) $value;
            }
        }
        return $clean;
    }

    /**
     * 清洗布局：值必须是枚举里的选项，非法值退回该项的第一个选项
     */
    public function sanitizeLayout(mixed $layout, bool $strict = false): array
    {
        $layout = $this->toArray($layout);
        $clean = [];
        foreach (self::LAYOUT_SCHEMA as $page => $options) {
            $source = $layout[$page] ?? [];
            if (!is_array($source)) {
                continue;
            }
            foreach ($options as $key => $allowed) {
                if (!array_key_exists($key, $source)) {
                    continue;
                }
                $value = (string) $source[$key];
                if (!in_array($value, $allowed, true)) {
                    if ($strict) {
                        UtilsService::getInstance()->errorThrow("模板布局 {$page}.{$key} 只能是：" . implode('/', $allowed));
                    }
                    $value = $allowed[0];
                }
                $clean[$page][$key] = $value;
            }
        }
        return $clean;
    }

    /**
     * 小程序侧要的扁平 CSS 变量表：--color-primary 这种
     */
    public function toCssVariables(array $tokens): array
    {
        $vars = [];
        foreach ($tokens as $group => $items) {
            if (!is_array($items)) {
                continue;
            }
            foreach ($items as $key => $value) {
                $vars['--' . str_replace('_', '-', $group . '-' . $key)] = $value;
            }
        }
        return $vars;
    }

    private function isSafeValue(mixed $value): bool
    {
        if (is_int($value) || is_float($value)) {
            return true;
        }
        if (!is_string($value)) {
            return false;
        }
        $value = trim($value);
        if ($value === '' || mb_strlen($value) > 64) {
            return false;
        }
        foreach (self::FORBIDDEN as $needle) {
            if (stripos($value, $needle) !== false) {
                return false;
            }
        }
        return true;
    }

    private function toArray(mixed $value): array
    {
        if (is_string($value)) {
            $value = json_decode($value, true);
            if (!is_array($value)) {
                UtilsService::getInstance()->errorThrow('模板 JSON 解析失败');
            }
        }
        return is_array($value) ? $value : [];
    }
}