const {HttpError} = require('../server/HttpError');
const {RequestHandler} = require('../server/RequestHandler');
const {VirtualSequenceDiagram} = require('../../lib/sequence-diagram');

function beginTimer() {
	return process.hrtime();
}

function endTimer(timer) {
	const delay = process.hrtime(timer);
	return delay[0] * 1e9 + delay[1];
}

const NUM_MATCH = '[0-9]+(?:\\.[0-9]+)?';
const MATCH_RENDER = new RegExp(
	'^/render/' +
	`(?:(?:w(${NUM_MATCH}))?(?:h(${NUM_MATCH}))?/|z(${NUM_MATCH})/)?` +
	'(?:(uri|b64)/)?' +
	'(.*?)' +
	'(?:\\.(svg))?$',
	'i'
);

function getNumeric(v, name) {
	if(!v) {
		return null;
	}
	const n = Number.parseFloat(v);
	if(Number.isNaN(n)) {
		throw new HttpError(400, 'Invalid value for ' + name);
	}
	return n;
}

function readEncoded(str, encoding) {
	switch(encoding) {
	case 'b64':
		return Buffer
			.from(decodeURIComponent(str), 'base64')
			.toString('utf8');
	case 'uri':
		return str.split('/').map(decodeURIComponent).join('\n');
	default:
		throw new HttpError(400, 'Unknown encoding');
	}
}

function handleRender(req, res, {match, pickEncoding, log, writeEncoded}) {
	res.setHeader('Access-Control-Allow-Origin', '*');

	const encoding = pickEncoding();
	const size = {
		height: getNumeric(match[2], 'height'),
		width: getNumeric(match[1], 'width'),
		zoom: getNumeric(match[3], 'zoom'),
	};
	const code = readEncoded(match[5], (match[4] || 'uri').toLowerCase());
	const format = (match[6] || 'svg').toLowerCase();

	const timer = beginTimer();
	const svg = VirtualSequenceDiagram.render(code, {size});
	const delay = endTimer(timer);
	log('RENDER (' + (delay / 1e6).toFixed(3) + 'ms)');

	switch(format) {
	case 'svg':
		res.setHeader('Content-Type', 'image/svg+xml; charset=utf-8');
		writeEncoded(encoding, svg);
		break;
	default:
		throw new HttpError(400, 'Unsupported image format');
	}
}

const render = new RequestHandler('GET', MATCH_RENDER, handleRender);
render.info = 'Rendering sequence diagrams at /render/';

module.exports = {render};