<?php

declare(strict_types=1);

namespace Sarcio\WordPress;

/**
 * Style rules the assistant keeps for the site: each one a selector, one CSS
 * property and its value, stored as data and never as CSS text. A rule is
 * accepted only when its selector fits a narrow character set and WordPress's
 * own safecss_filter_attr() keeps its declaration unchanged, and the
 * stylesheet is built from the rules here and printed with
 * wp_add_inline_style().
 */
final class StyleRules
{
    public const OPTION = 'sarcio_style_rules';
    public const HANDLE = 'sarcio-style-rules';
    public const MAX_RULES = 200;
    public const MAX_SELECTOR = 200;
    public const MAX_VALUE = 200;

    public const PROPERTIES = [
        'background-color', 'border', 'border-bottom', 'border-color', 'border-left', 'border-radius', 'border-right',
        'border-style', 'border-top', 'border-width', 'color', 'column-gap', 'display', 'font-family', 'font-size',
        'font-style', 'font-weight', 'gap', 'height', 'letter-spacing', 'line-height', 'margin', 'margin-bottom',
        'margin-left', 'margin-right', 'margin-top', 'max-height', 'max-width', 'min-height', 'min-width', 'padding',
        'padding-bottom', 'padding-left', 'padding-right', 'padding-top', 'row-gap', 'text-align', 'text-decoration',
        'text-indent', 'text-transform', 'vertical-align', 'width', 'word-spacing',
    ];

    private const SELECTOR = '/^[A-Za-z0-9\-_.# >+~:\[\]="\'(),*]+$/';
    private const REFUSED = ['url(', 'expression', '@import', 'javascript:', '/*', '*/', '</', '\\', '{', '}', ';', '<', '>', '@', '!'];

    public function register(): void
    {
        add_action('wp_enqueue_scripts', [$this, 'enqueue'], 100);
    }

    public function enqueue(): void
    {
        $css = self::css(self::all());
        if ($css === '') {
            return;
        }
        wp_register_style(self::HANDLE, false, [], SARCIO_WP_VERSION);
        wp_enqueue_style(self::HANDLE);
        wp_add_inline_style(self::HANDLE, wp_strip_all_tags($css));
    }

    /** @return array<string,array{selector:string,property:string,value:string}> */
    public static function all(mixed $stored = null): array
    {
        $stored ??= get_option(self::OPTION, []);
        $out = [];
        foreach (is_array($stored) ? $stored : [] as $rule) {
            if (!is_array($rule)) {
                continue;
            }
            $clean = self::check((string) ($rule['selector'] ?? ''), (string) ($rule['property'] ?? ''), (string) ($rule['value'] ?? ''));
            if (is_array($clean)) {
                $out[self::id($clean['selector'], $clean['property'])] = $clean;
            }
        }
        return $out;
    }

    public static function id(string $selector, string $property): string
    {
        return substr(md5($selector . '|' . $property), 0, 12);
    }

    /**
     * The rule as it would be stored, or why it is refused.
     *
     * @return array{selector:string,property:string,value:string}|string
     */
    public static function check(string $selector, string $property, string $value): array|string
    {
        $selector = trim(preg_replace('~\s+~', ' ', $selector) ?? '');
        $property = strtolower(trim($property));
        $value = trim($value);
        if ($selector === '' || strlen($selector) > self::MAX_SELECTOR || !preg_match(self::SELECTOR, $selector)) {
            return __('That selector is not one the assistant can style.', 'sarcio');
        }
        if (!in_array($property, self::PROPERTIES, true)) {
            return __('That property is not one the assistant can set.', 'sarcio');
        }
        if ($value === '' || strlen($value) > self::MAX_VALUE) {
            return __('That value is empty or too long.', 'sarcio');
        }
        if (self::refused($selector, ['url(', 'expression', 'javascript:']) || self::refused($value, self::REFUSED)) {
            return __('That rule carries something a style rule cannot.', 'sarcio');
        }
        if (substr_count($selector, '(') !== substr_count($selector, ')') || substr_count($selector, '[') !== substr_count($selector, ']')) {
            return __('That selector is not one the assistant can style.', 'sarcio');
        }
        $declaration = $property . ': ' . $value;
        if (!function_exists('safecss_filter_attr') || safecss_filter_attr($declaration) !== $declaration) {
            return __('WordPress does not accept that value for this property.', 'sarcio');
        }
        return ['property' => $property, 'selector' => $selector, 'value' => $value];
    }

    /** @param array<int,string> $needles */
    private static function refused(string $text, array $needles): bool
    {
        $lower = strtolower($text);
        foreach ($needles as $needle) {
            if (str_contains($lower, $needle)) {
                return true;
            }
        }
        return false;
    }

    /** @param array<string,array{selector:string,property:string,value:string}> $rules */
    public static function css(array $rules): string
    {
        $bySelector = [];
        foreach ($rules as $rule) {
            $bySelector[$rule['selector']][] = $rule['property'] . ': ' . $rule['value'];
        }
        $css = '';
        foreach ($bySelector as $selector => $declarations) {
            $css .= $selector . ' { ' . implode('; ', $declarations) . "; }\n";
        }
        return str_contains($css, '</') ? '' : $css;
    }
}