package worker

import (
	"context"
)

type (

	// A simple worker to deal with list.
	ChanProcessor[T any] interface {
		Query(context.Context) (<-chan T, error)
		Process(context.Context, T) error
	}

	ListProcessor[T any] interface {
		Query(context.Context) ([]T, error)
		Process(context.Context, T) error
	}

	chanProcessorWorker[T any] struct {
		chanProcessor ChanProcessor[T]
		scheduler     *Scheduler
	}

	listProcessorWorker[T any] struct {
		listProcessor ListProcessor[T]
		scheduler     *Scheduler
	}
)

func NewWorkerFromListProcessor[T any](
	listProcessor ListProcessor[T],
	scheduler *Scheduler,
) Worker {
	return &listProcessorWorker[T]{
		listProcessor: listProcessor,
		scheduler:     scheduler,
	}
}

func NewWorkerFromChanProcessor[T any](
	listProcessor ChanProcessor[T],
	scheduler *Scheduler,
) Worker {
	return &chanProcessorWorker[T]{
		chanProcessor: listProcessor,
		scheduler:     scheduler,
	}
}

func (l *listProcessorWorker[T]) Start(ctx context.Context) error {
	for {
		values, err := l.listProcessor.Query(ctx)
		if err != nil {
			return err
		}

		select {
		case <-ctx.Done():
			return ctx.Err()
		default:
		}

		if len(values) == 0 {
			return nil
		}

		for _, v := range values {
			select {
			case <-ctx.Done():
				return ctx.Err()
			default:
			}

			if err := l.listProcessor.Process(ctx, v); err != nil {
				return err
			}
		}
	}
}

func (l *chanProcessorWorker[T]) Start(ctx context.Context) error {
	c, err := l.chanProcessor.Query(ctx)
	if err != nil {
		return err
	}

	for {
		select {
		case <-ctx.Done():
			return ctx.Err()
		case v, ok := <-c:
			if !ok {
				return nil
			}

			if err := l.chanProcessor.Process(ctx, v); err != nil {
				return err
			}
		}
	}
}