import Supercluster from 'supercluster'

export function createClusterIndex(options = {}) {
  const index = new Supercluster(options)
  const state = { features: Object.freeze([]) }

  return {
    load(features) {
      const list = Object.freeze([...(features ?? [])])
      index.load(list)
      state.features = list
    },
    query(view) {
      if (!view || state.features.length === 0) return []
      const { west, south, east, north, zoom } = view
      return index.getClusters(
        [west, south, east, north],
        Math.floor(zoom ?? 14),
      ).map((feature) => {
        if (!feature.properties?.cluster) return feature
        return {
          ...feature,
          properties: {
            ...feature.properties,
            expansionZoom: index.getClusterExpansionZoom(feature.properties.cluster_id),
          },
        }
      })
    },
  }
}
