import java.util.Random;

/**
 * Simulates downloading a single chunk of a file.
 *
 * <p>This class is intentionally provided as a skeleton for students.
 * The main multithreading and simulation logic should be completed
 * in the run() method.</p>
 */
public class DownloadWorker implements Runnable {

    private final ChunkStatus chunkStatus;
    private final DownloadConfig config;
    private final Random random;

    public DownloadWorker(ChunkStatus chunkStatus, DownloadConfig config) {
        this.chunkStatus = chunkStatus;
        this.config = config;
        this.random = new Random();
    }

    @Override
    public void run() {
        long startTime = System.currentTimeMillis();
        chunkStatus.setStartTime(startTime);

        double downloaded = 0.0;

        System.out.println("Chunk \"" + chunkStatus.getChunkId() + "\" started downloading.");

        while (downloaded < chunkStatus.getChunkSizeMB()) {

            try {
                //Generate a random sleep delay between min and max delay.
                int minDelay = config.getMinDelayMs();
                int maxDelay = config.getMaxDelayMs();
                int randomDelay = random.nextInt((maxDelay - minDelay) + 1) + minDelay;

                //Sleep for that delay.
                Thread.sleep(randomDelay);

                //Generate a random download amount for this step.
                double minStep = config.getMinStepDelayMs();
                double maxStep = config.getMaxStepDelayMs();
                double randomStep = (maxStep + minStep)*random.nextDouble() + minStep;

                //Increase downloaded, but do not go beyond chunk size.
                downloaded += randomStep;
                if (downloaded > chunkStatus.getChunkSizeMB()) {
                    downloaded = chunkStatus.getChunkSizeMB();
                }

                //Save the updated downloaded value into chunkStatus.
                chunkStatus.setDownloadedMB(downloaded);

                //print step-by-step progress.
                System.out.printf("Chunk #%d: Downloaded %.2f / %.2f MB%n",
                        chunkStatus.getChunkId(), downloaded, chunkStatus.getChunkSizeMB());

            } catch (InterruptedException e) {
                System.out.println("Chunk \"" + chunkStatus.getChunkId() + "\" was interrupted!");
                return;
            }
        }

        //Mark the chunk as completed.
        chunkStatus.setCompleted(true);

        //Record the chunk end time in chunkStatus.
        long endTime = System.currentTimeMillis();
        chunkStatus.setEndTimeMs(endTime);

        //Print a message that this chunk has finished downloading.
        System.out.println("Chunk \"" + chunkStatus.getChunkId() + "\" has finished downloading.");
    }

}