<?php

namespace App\Services\Email;

use App\Exceptions\InvalidTemplateVariableException;
use App\Models\Template;
use App\Support\MailPlaceholders;

/**
 * Render Template subject/message: chỉ thay thế placeholder dạng {{key}} đã khai báo
 * trong metadata.variables. Không eval(), không compile Blade/PHP.
 */
class EmailTemplateRenderer
{
    private const PLACEHOLDER_PATTERN = MailPlaceholders::PATTERN;

    /**
     * @return array{subject: string, html: string}
     */
    public function render(Template $template, array $data): array
    {
        $variables = $template->variables();

        $this->assertKnownVariables($template->scenario ?? $template->name ?? 'unknown', (string) $template->subject, $variables);
        $this->assertKnownVariables($template->scenario ?? $template->name ?? 'unknown', (string) $template->message, $variables);

        return [
            'subject' => $this->replace((string) $template->subject, $variables, $data),
            'html'    => $this->replace((string) $template->message, $variables, $data),
        ];
    }

    private function assertKnownVariables(string $scenario, string $content, array $variables): void
    {
        $used = MailPlaceholders::extract($content);
        $invalid = array_values(array_diff($used, array_keys($variables)));

        if ($invalid !== []) {
            throw new InvalidTemplateVariableException($scenario, $invalid);
        }
    }

    private function replace(string $content, array $variables, array $data): string
    {
        $examples = array_map(fn (array $definition) => $definition['example'] ?? '', $variables);
        $content = MailPlaceholders::resolveConditionals($content, [...$examples, ...$data]);

        return preg_replace_callback(self::PLACEHOLDER_PATTERN, function (array $match) use ($variables, $data) {
            $key = $match[1];
            if (!isset($variables[$key]) && !array_key_exists($key, $data)) {
                return $match[0];
            }
            $definition = $variables[$key] ?? [];
            $value = $data[$key] ?? $definition['example'] ?? '';

            return $this->formatValue((string) $value, $definition['type'] ?? 'string');
        }, $content) ?? $content;
    }

    private function formatValue(string $value, string $type): string
    {
        return match ($type) {
            // html: nội dung tin cậy do Email Builder sinh ra sẵn (đã được builder escape khi build).
            'html' => $value,
            'url'  => filter_var($value, FILTER_VALIDATE_URL) ? htmlspecialchars($value, ENT_QUOTES, 'UTF-8') : '',
            default => htmlspecialchars($value, ENT_QUOTES, 'UTF-8'),
        };
    }
}