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 >= .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,
}