<?php

declare(strict_types=1);

namespace app\common\library\docs;

use Webman\Http\Request;

/**
 * 按请求语言读取 docs 目录下的 Markdown 文件（英文缺失时回退中文）。
 */
final class MarkdownDocReader
{
    /**
     * @param array{relative:string,filename:string,ascii_fallback?:string} $zh
     * @param array{relative:string,filename:string,ascii_fallback?:string} $en
     * @return array{path:string,filename:string,ascii_fallback:string,lang:string}
     */
    public static function resolve(Request $request, array $zh, array $en): array
    {
        $lang = self::resolveLang($request);
        $useEn = $lang === 'en';
        $spec = $useEn ? $en : $zh;
        $base = rtrim(base_path(), DIRECTORY_SEPARATOR . '/');
        $path = $base . DIRECTORY_SEPARATOR . str_replace(['/', '\\'], DIRECTORY_SEPARATOR, $spec['relative']);
        if ($useEn && !is_file($path)) {
            $spec = $zh;
            $path = $base . DIRECTORY_SEPARATOR . str_replace(['/', '\\'], DIRECTORY_SEPARATOR, $zh['relative']);
            $lang = 'zh-cn';
        }
        $filename = strval($spec['filename'] ?? 'document.md');
        $asciiFallback = strval($spec['ascii_fallback'] ?? $filename);

        return [
            'path' => $path,
            'filename' => $filename,
            'ascii_fallback' => $asciiFallback,
            'lang' => $lang,
        ];
    }

    public static function resolveLang(Request $request): string
    {
        $thinkRaw = $request->header('think-lang', '');
        $thinkLang = is_string($thinkRaw) ? trim($thinkRaw) : '';
        if ($thinkLang === '' && is_array($thinkRaw) && isset($thinkRaw[0]) && is_string($thinkRaw[0])) {
            $thinkLang = trim($thinkRaw[0]);
        }

        $queryRaw = $request->get('lang');
        if ($queryRaw === null || $queryRaw === '') {
            $queryRaw = $request->post('lang');
        }
        $queryLang = is_string($queryRaw) ? trim($queryRaw) : (is_scalar($queryRaw) ? trim(strval($queryRaw)) : '');

        $headerRaw = $request->header('lang', '');
        $headerLang = is_string($headerRaw) ? trim($headerRaw) : '';

        $normalize = static function (string $raw): string {
            $s = str_replace('_', '-', strtolower(trim($raw)));
            if ($s === 'zh') {
                return 'zh-cn';
            }
            return $s;
        };

        foreach ([$thinkLang, $headerLang, $queryLang] as $candidate) {
            if ($candidate === '') {
                continue;
            }
            $normalized = $normalize($candidate);
            if ($normalized === 'en') {
                return 'en';
            }
            if ($normalized === 'zh-cn') {
                return 'zh-cn';
            }
        }

        return 'zh-cn';
    }
}