import _googlePolyline from 'google-polyline';
import distance from 'gps-distance';

const {decode} = _googlePolyline;

// todo: what is p.delta?
// todo: what is p.type?
// todo: what is p.crdEncS?
// todo: what is p.crdEncF?
const parsePolyline = (ctx, p) => { // p = raw polyline
	const points = decode(p.crdEncYX);
	if (points.length === 0) {
		return null;
	}

	const res = points.map(([lat, lon]) => ({
		type: 'Feature',
		properties: {},
		geometry: {
			type: 'Point',
			coordinates: [lon, lat],
		},
	}));

	if (Array.isArray(p.ppLocRefL)) {
		for (let ref of p.ppLocRefL) {
			const p = res[ref.ppIdx];
			if (p && ref.location) {
				p.properties = ref.location;
			}
		}

		// Often there is one more point right next to each point at a station.
		// We filter them here if they are < 5m from each other.
		for (let i = 1; i < res.length; i++) {
			const p1 = res[i - 1].geometry.coordinates;
			const p2 = res[i].geometry.coordinates;
			const d = distance(p1[1], p1[0], p2[1], p2[0]);
			if (d >= 0.005) {
				continue;
			}
			const l1 = Object.keys(res[i - 1].properties).length;
			const l2 = Object.keys(res[i].properties).length;
			if (l1 === 0 && l2 > 0) {
				res.splice(i - 1, 1);
			} else if (l2 === 0 && l1 > 0) {
				res.splice(i, 1);
			}
		}
	}

	return {
		type: 'FeatureCollection',
		features: res,
	};
};

export {
	parsePolyline,
};