import type { ChunkBuilder } from "@tsplus/stdlib/collections/Chunk"

/**
 * Returns a new channel, which is the same as this one, except that all the
 * outputs are collected and bundled into a tuple together with the terminal
 * value of this channel.
 *
 * As the channel returned from this channel collects all of this channel's
 * output into an in- memory chunk, it is not safe to call this method on
 * channels that output a large or unbounded number of values.
 *
 * @tsplus getter effect/core/stream/Channel doneCollect
 */
export function doneCollect<Env, InErr, InElem, InDone, OutErr, OutElem, OutDone>(
  self: Channel<Env, InErr, InElem, InDone, OutErr, OutElem, OutDone>
): Channel<
  Env,
  InErr,
  InElem,
  InDone,
  OutErr,
  never,
  readonly [Chunk<OutElem>, OutDone]
> {
  return Channel.suspend(() => {
    const builder = Chunk.builder<OutElem>()
    return (self >> reader<Env, OutErr, OutElem, OutDone>(builder)).flatMap((z) =>
      Channel.sync([builder.build(), z])
    )
  })
}

function reader<Env, OutErr, OutElem, OutDone>(
  builder: ChunkBuilder<OutElem>
): Channel<Env, OutErr, OutElem, OutDone, OutErr, never, OutDone> {
  return Channel.readWith(
    (outElem) =>
      Channel.sync(() => {
        builder.append(outElem)
      }).flatMap(() => reader<Env, OutErr, OutElem, OutDone>(builder)),
    (outErr) => Channel.fail(outErr),
    (outDone) => Channel.succeed(outDone)
  )
}