package main

import "context"

type (
	Ingester struct {
		writer  Queue
		reader  Queue
		process processFunc
	}
	processFunc func(context.Context, []byte) ([]byte, error)
)

func NewIngester(writer, reader Queue, process processFunc) Ingester {
	return Ingester{
		writer:  writer,
		reader:  reader,
		process: process,
	}
}

func (i Ingester) Process(ctx context.Context) error {
	ctx, can := context.WithCancel(ctx)
	defer can()

	for ctx.Err() == nil {
		reservation, read, err := i.reader.Syn(ctx)
		if err != nil {
			return err
		}
		processed, err := i.process(ctx, read)
		if err != nil {
			return err
		}
		if err := i.writer.Enqueue(ctx, processed); err != nil {
			return err
		}
		if err := i.reader.Ack(ctx, reservation); err != nil {
			return err
		}
	}

	return ctx.Err()
}