sapper/lib/templates.js

const fs = require('fs');
const glob = require('glob');

const templates = glob.sync('*.html', { cwd: 'templates' })
	.map(file => {
		const template = fs.readFileSync(`templates/${file}`, 'utf-8');
		const status = file.replace('.html', '').toLowerCase();

		if (!/^[0-9x]{3}$/.test(status)) {
			throw new Error(`Bad template — should be a valid status code like 404.html, or a wildcard like 2xx.html`);
		}

		const specificity = (
			(status[0] === 'x' ? 0 : 4) +
			(status[1] === 'x' ? 0 : 2) +
			(status[2] === 'x' ? 0 : 1)
		);

		const pattern = new RegExp(`^${status.split('').map(d => d === 'x' ? '\\d' : d).join('')}$`);

		return {
			test: status => pattern.test(status),
			specificity,
			render(data) {
				return template.replace(/%sapper\.(\w+)%/g, (match, key) => {
					return key in data ? data[key] : '';
				});
			}
		}
	})
	.sort((a, b) => b.specificity - a.specificity);

exports.render = (status, data) => {
	const template = templates.find(template => template.test(status));
	if (template) return template.render(data);

	return `Missing template for status code ${status}`;
};

exports.onchange = fn => {
	// TODO in dev mode, keep this updated, and allow
	// webpack compiler etc to hook into it
};