xValues.ts

import { MapDeltaStream } from '../delta-streams/streams/map'
import { Point } from './Points'
import { mapValues } from 'lodash'
import { deltaNone, deltaUnknown } from '../delta-streams/deltas/collection'
import mapDeltaStream from '../delta-streams/mapDeltaStream'

export default (points: MapDeltaStream<Point>): MapDeltaStream<number> => {
    const outSubject = mapDeltaStream<number>({})

    points.stream.subscribe(({ data, delta }) => {
        const { data: previousData } = outSubject.stream.value
        switch (delta.type) {
            case 'none': {
                outSubject.stream.next({ data: previousData, delta: deltaNone() })
                break
            }
            case 'unknown': {
                const xValues = mapValues(data, point => point.x)
                outSubject.stream.next({
                    data: xValues,
                    delta: deltaUnknown(xValues),
                })
                break
            }
            case 'swapped': {
                const { sourceKey, destinationKey } = delta
                outSubject.swap.next({ sourceKey, destinationKey })
                break
            }
            case 'removed': {
                outSubject.remove.next({ key: delta.key })
                break
            }
            case 'inserted': {
                outSubject.insert.next({ key: delta.key, value: data[delta.key].x })
                break
            }
            case 'mutated': {
                outSubject.mutate.next({ key: delta.key, value: data[delta.key].x })
                break
            }
            case 'renamed': {
                outSubject.rename.next({ key: delta.key, newKey: delta.newKey })
                break
            }
        }
    })

    return outSubject
}