sapper/lib/utils/create_app.js

const fs = require('fs');
const path = require('path');
const { dest, server_routes, dev } = require('../config.js');

module.exports = function create_app(src, dest, routes, options) {
	function create_client_main() {
		const template = fs.readFileSync('templates/main.js', 'utf-8');

		const code = `[${
			routes
				.filter(route => route.type === 'page')
				.map(route => {
					const params = route.dynamic.length === 0 ?
						'{}' :
						`{ ${route.dynamic.map((part, i) => `${part}: match[${i + 1}]`).join(', ') } }`;

					return `{ pattern: ${route.pattern}, params: match => (${params}), load: () => import(/* webpackChunkName: "${route.id}" */ '${src}/${route.file}') }`
				})
				.join(', ')
		}]`;

		const main = template
			.replace(/__app__/g, path.resolve(__dirname, '../../runtime/app.js'))
			.replace(/__routes__/g, code)
			.replace(/__dev__/g, String(dev));

		const file = path.resolve(dest, 'main.js');

		fs.writeFileSync(file, main);

		// need to fudge the mtime, because webpack is soft in the head
		const { atime, mtime } = fs.statSync(file);
		fs.utimesSync(file, atime.getTime() - 999999, mtime.getTime() - 999999);
	}

	function create_server_routes() {
		const imports = routes
			.map(route => {
				return route.type === 'page' ?
					`import ${route.id} from '${src}/${route.file}';` :
					`import * as ${route.id} from '${src}/${route.file}';`;
			})
			.join('\n');

		const exports = `export { ${routes.map(route => route.id)} };`;

		fs.writeFileSync(server_routes, `${imports}\n\n${exports}`);

		const { atime, mtime } = statSync(server_routes);
		fs.utimesSync(server_routes, atime.getTime() - 999999, mtime.getTime() - 999999);
	}

	// TODO in dev mode, watch files
	create_client_main();
	create_server_routes();
};