import {from, of} from 'rxjs'
import {map, tap} from 'rxjs/operators'
import readChunk from 'read-chunk'
import {getSize} from './get-size'

const chunkSize = Math.pow(2, 22)

const progress = (context: any) => from(getSize(context)())
    .pipe(map((size: any) => (context.position / size) * 100))
    .pipe(tap((progress: number) => context.onProgress(progress)))
    .toPromise()

export const getNext = (context: any) => async () => of(readChunk.sync(context.path, context.position, chunkSize))
    .pipe(tap((chunk: any) => context.position += chunk.length))
    .pipe(tap(() => context.onProgress && from(progress(context))))
    .toPromise()