import * as ReactDOMServer from 'react-dom/server';
import cookie from 'cookie';
import config from 'config';

// import our main App component
import App from '../../src/App';

import { getLinks } from '../sape';
import { StaticRouter } from 'react-router-dom/server';
import { VisitorProvider } from '../../src/ui/VisitorContext';

import path from 'path';
import fs from 'fs';

// convert a Unicode string to a string in which
// each 16-bit unit occupies only one byte
function toBinary(string) {
    const codeUnits = new Uint16Array(string.length);
    for (let i = 0; i < codeUnits.length; i++) {
        codeUnits[i] = string.charCodeAt(i);
    }
    return Buffer.from(String.fromCharCode(...new Uint8Array(codeUnits.buffer))).toString('base64');
}

const STATIC_ROOT = config.get('service.static_root') || path.resolve(__dirname, 'public');

const serverRenderer = async (req, res) => {

    // point to the html file created by CRA's build tool
    const filePath = path.resolve(STATIC_ROOT, 'index.html');

    // links
    const cookies = cookie.parse(req.headers.cookie || '');

    const links = await getLinks(req.originalUrl, cookies['sape_cookie']);
    fs.readFile(filePath, 'utf8', (err, htmlData) => {
        if (err) {
            console.error('err', err);
            return res.status(404).end();
        }

        const routerContext = {};

        const props = {
            footer: links.join(' ')
        };

        const marker = '<div id="app">';
        const data = htmlData.split(marker);
        const propsData = `<script>window.__PROPS__="${toBinary(JSON.stringify(props))}";</script>${marker}`;
        let didError = false;
        const { pipe } = ReactDOMServer.renderToPipeableStream(
            <VisitorProvider>
                <StaticRouter location={req.baseUrl} context={routerContext}>
                    <App {...props} />
                </StaticRouter>
            </VisitorProvider>
            , {
                onShellReady() {
                    res.statusCode = didError ? 500 : 200;
                    res.setHeader('Content-type', 'text/html');
                    res.write(data[0]);
                    res.write(propsData);
                    pipe(res, { end: false });
                },
                onShellError() {
                    didError = true;
                    res.statusCode = 500;
                    res.setHeader('Content-type', 'text/html');
                    res.send(
                      '<h1>Something went wrong :(</h1>'
                    );
                    res.end();
                  },
                onAllReady() {
                    if (!didError) {
                        res.write(data[1]);
                    }
                    res.end();
                },
                onError(err) {
                    didError = true;
                    console.log(err);
                }
            });
    });
};

export default serverRenderer;