package worker

import (
	"context"
	"log/slog"
	"time"
)

const defaultTaskName = "batch worker"

// BatchRunner executes one batch and returns the number of processed records.
// Returning 0 stops the current drain cycle.
type BatchRunner func(ctx context.Context, limit int) (int, error)

func Run(ctx context.Context, runner BatchRunner, interval time.Duration, batchSize int, logger *slog.Logger, taskName string) {
	if runner == nil || interval <= 0 || batchSize <= 0 {
		return
	}
	if logger == nil {
		logger = slog.Default()
	}
	if taskName == "" {
		taskName = defaultTaskName
	}

	RunOnce(ctx, runner, batchSize, logger, taskName)

	ticker := time.NewTicker(interval)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			RunOnce(ctx, runner, batchSize, logger, taskName)
		}
	}
}

func RunOnce(ctx context.Context, runner BatchRunner, batchSize int, logger *slog.Logger, taskName string) {
	if runner == nil || batchSize <= 0 {
		return
	}
	if logger == nil {
		logger = slog.Default()
	}
	if taskName == "" {
		taskName = defaultTaskName
	}

	totalProcessed := 0
	for {
		processed, err := runner(ctx, batchSize)
		if err != nil {
			if ctx.Err() == nil {
				logger.Warn(taskName+" run failed", "error", err)
			}
			return
		}
		if processed <= 0 {
			break
		}
		totalProcessed += processed
	}

	if totalProcessed > 0 {
		logger.Info(taskName+" completed", "processed", totalProcessed)
	}
}