import { Glob } from 'glob';
import * as fs from 'fs';

export class SitemapGenerator {
    private readonly SITEMAP_HEADER = `<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">`;

    private readonly SITEMAP_FOOTER = `
</urlset>`;

    private readonly baseUrl: string;
    private readonly srcDirectory: string;

    private sitemapContent = '';

    constructor(srcDirectory: string, baseUrl: string) {
        this.baseUrl = SitemapGenerator.withTrailingSlash(baseUrl);
        this.srcDirectory = SitemapGenerator.withTrailingSlash(srcDirectory);
    }

    private static withTrailingSlash(text: string) {
        if (!text.endsWith('/')) {
            return text + '/';
        }
        return text;
    }

    process(): void {
        new Glob(this.srcDirectory + '/**/index.html', (err: Error, res: string[]) => this.filesCallback(err, res));
    }

    private addToSitemap(file: string): void {
        let url = file.replace(this.srcDirectory, this.baseUrl);
        url = url.replace('/index.html', '');
        this.sitemapContent += `
    <url>
        <loc>${ url }</loc>
    </url>`;
    }

    private writeSitemapToFile(): void {
        fs.writeFile(this.srcDirectory + 'sitemap.xml', this.SITEMAP_HEADER + this.sitemapContent + this.SITEMAP_FOOTER, (err: NodeJS.ErrnoException | null) => {
            if (err) {
                console.log(err.message);
                return;
            }

            console.log(`sitemap.xml successfully created in '${ this.srcDirectory }'`);
        });
    }


    private filesCallback(err: Error, files: string[]): void {
        if (err) {
            console.log('Error', err);
            return;
        }

        files.sort((a, b) => {
            return a.length - b.length || a.localeCompare(b);
        });

        files.forEach(route => this.addToSitemap(route));

        this.writeSitemapToFile();
    }
}