<?php
declare(strict_types=1);

namespace Zadex\Frontend;

defined('ABSPATH') || exit;

/**
 * Background declarations for values the JS CSS generator cannot reach: `background` fields inside a
 * repeater item (per-slide backgrounds of the slides widget, T183). Mirrors the `background` handler in
 * src/editor/core/css/handlers.ts (classic colour + image, or gradient) and returns an unescaped
 * declaration list (`background-color:#fff;background-image:url("…")`); callers esc_attr() it.
 */
final class InlineBackground
{
    /** @param mixed $value */
    public static function css($value): string
    {
        if (!is_array($value)) {
            return '';
        }
        $type = isset($value['type']) && is_string($value['type']) && $value['type'] !== '' ? $value['type'] : (isset($value['gradient']) ? 'gradient' : 'classic');
        $out = [];
        if ($type === 'gradient' && is_array($value['gradient'] ?? null)) {
            $gradient = self::gradient($value['gradient']);
            return $gradient !== '' ? 'background-image:' . $gradient : '';
        }
        $color = self::color($value['color'] ?? '');
        if ($color !== '') {
            $out[] = 'background-color:' . $color;
        }
        $url = isset($value['image']['url']) && is_string($value['image']['url']) ? self::url($value['image']['url']) : '';
        if ($type === 'classic' && $url !== '') {
            $out[] = 'background-image:url("' . $url . '")';
            foreach (['position' => 'background-position', 'size' => 'background-size', 'repeat' => 'background-repeat'] as $key => $prop) {
                $v = isset($value[$key]) && is_string($value[$key]) ? trim($value[$key]) : '';
                if ($v !== '' && preg_match('/^[a-z0-9%.\s-]+$/i', $v)) {
                    $out[] = $prop . ':' . $v;
                }
            }
        }
        return implode(';', $out);
    }

    /** Safe CSS colour (hex, rgb/hsl/color-mix functions, var(--x), named) or ''. */
    public static function color($value): string
    {
        if (!is_string($value)) {
            return '';
        }
        $value = trim($value);
        if ($value === '') {
            return '';
        }
        if (preg_match('/^#([0-9a-f]{3,4}|[0-9a-f]{6}|[0-9a-f]{8})$/i', $value)
            || preg_match('/^(rgba?|hsla?|color-mix)\([\w\s%.,\/#()-]+\)$/i', $value)
            || preg_match('/^var\(--[a-z0-9-]+\)$/i', $value)
            || preg_match('/^[a-z]+$/i', $value)) {
            return $value;
        }
        return '';
    }

    /** @param array<string, mixed> $g */
    private static function gradient(array $g): string
    {
        $stops = [];
        $list = is_array($g['stops'] ?? null) ? array_values(array_filter($g['stops'], 'is_array')) : [];
        $valid = array_values(array_filter($list, static fn(array $s): bool => self::color($s['color'] ?? '') !== ''));
        $n = count($valid);
        if ($n < 2) {
            return '';
        }
        foreach ($valid as $i => $s) {
            $pos = isset($s['position']) && is_numeric($s['position']) ? (float) $s['position'] + 0 : round(($i / ($n - 1)) * 100);
            $stops[] = self::color($s['color']) . ' ' . $pos . '%';
        }
        if (($g['type'] ?? 'linear') === 'radial') {
            return 'radial-gradient(circle, ' . implode(', ', $stops) . ')';
        }
        $angle = isset($g['angle']) && is_numeric($g['angle']) ? (float) $g['angle'] + 0 : 180;
        return 'linear-gradient(' . $angle . 'deg, ' . implode(', ', $stops) . ')';
    }

    private static function url(string $url): string
    {
        $url = function_exists('esc_url_raw') ? (string) esc_url_raw($url) : $url;
        return str_replace(['\\', '"', "\r", "\n"], ['\\\\', '\\"', '', ''], $url);
    }
}