import { promises as fs } from 'fs';
import { fileURLToPath } from 'url';
import { dirname, join } from 'path';
import xml2js from 'xml2js';

const __filename = fileURLToPath(import.meta.url);
const __dirname = dirname(__filename);

const LANGUAGES = ['en', 'zh-Hans', 'zh-Hant'];
const BASE_URL = 'mirror.starset.fans';

interface Update {
    id: string;
    date: string;
}

interface UpdateIndex {
    updates: Update[];
}

async function getYearlyIndices(lang: string): Promise<string[]> {
    const indexDir = join(__dirname, '..', 'data', lang, 'updates', 'index');
    try {
        const files = await fs.readdir(indexDir);
        return files.filter(file => file.match(/^\d{4}\.json$/));
    } catch (err) {
        console.error(`Error reading index directory for ${lang}:`, err);
        return [];
    }
}

async function generateUpdateUrls(lang: string) {
    const yearFiles = await getYearlyIndices(lang);
    const urls = [];
    
    for (const yearFile of yearFiles) {
        try {
            const content = await fs.readFile(
                join(__dirname, '..', 'data', lang, 'updates', 'index', yearFile),
                'utf-8'
            );
            const data = JSON.parse(content) as UpdateIndex;
            
            if (data.updates) {
                for (const update of data.updates) {
                    urls.push({
                        loc: `https://${BASE_URL}/updates/${update.id}`,
                        lastmod: update.date,
                        changefreq: 'monthly',
                        priority: '0.7'
                    });
                }
            }
        } catch (err) {
            console.error(`Error processing ${yearFile} for ${lang}:`, err);
        }
    }
    
    return urls;
}

async function mergeSitemaps() {
    const parser = new xml2js.Parser();
    const mainSitemapPath = join(__dirname, '..', 'dist', 'sitemap.xml');
    
    try {
        const mainSitemapContent = await fs.readFile(mainSitemapPath, 'utf-8');
        const mainSitemap = await parser.parseStringPromise(mainSitemapContent);
        
        // Filter out existing update URLs while maintaining order
        const existingUrls = mainSitemap.urlset.url.filter((url: any) => 
            !url.loc[0].includes('/updates/'));
        
        mainSitemap.urlset.url = existingUrls;
        
        // Add language-specific update URLs at the end
        for (const lang of LANGUAGES) {
            const updateUrls = await generateUpdateUrls(lang);
            mainSitemap.urlset.url.push(...updateUrls);
        }
        
        const builder = new xml2js.Builder();
        const newSitemap = builder.buildObject(mainSitemap);
        
        await fs.writeFile(mainSitemapPath, newSitemap);
        console.log('Successfully updated sitemap.xml in dist directory');
    } catch (err) {
        console.error('Error merging sitemaps:', err);
        if (err instanceof Error && 'code' in err && err.code === 'ENOENT') {
            console.error('Make sure the dist directory exists and contains sitemap.xml');
        }
        process.exit(1);
    }
}

// Run the script
mergeSitemaps();