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() {
        // TODO: Record the chunk start time in chunkStatus.
        chunkStatus.setStartTimeMs(System.currentTimeMillis());
        double downloaded = 0.0;
        System.out.printf("[%s] Started — Chunk #%d (%.1f MB)%n",
                Thread.currentThread().getName(),
                chunkStatus.getChunkId(),
                chunkStatus.getChunkSizeMB());

        // TODO: Print a message that this chunk has started downloading.

        while (downloaded < chunkStatus.getChunkSizeMB()) {
            int delay = config.getMinStepDelayMs()
                    + random.nextInt(config.getMaxStepDelayMs() - config.getMinStepDelayMs() + 1);

            // TODO: Generate a random sleep delay between min and max delay.
            // TODO: Sleep for that delay.
            // TODO: Generate a random download amount for this step.
            // TODO: Increase downloaded, but do not go beyond chunk size.
            // TODO: Save the updated downloaded value into chunkStatus.
            // TODO: Optionally print step-by-step progress.
            try {
                Thread.sleep(delay);
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
                return;
            }
            double step = config.getMinStepDownloadMB()
                    + random.nextDouble() * (config.getMaxStepDownloadMB() - config.getMinStepDownloadMB());
            downloaded = Math.min(downloaded + step, chunkStatus.getChunkSizeMB());
            chunkStatus.setDownloadedMB(downloaded);
            System.out.printf("[%s] Chunk #%d → %.2f / %.1f MB (%.1f%%)%n",
                    Thread.currentThread().getName(),
                    chunkStatus.getChunkId(),
                    chunkStatus.getDownloadedMB(),
                    chunkStatus.getChunkSizeMB(),
                    chunkStatus.getProgressPercentage());
            }

        // TODO: Mark the chunk as completed.
        // TODO: Record the chunk end time in chunkStatus.
        // TODO: Print a message that this chunk has finished downloading.
    chunkStatus.setCompleted(true);
    chunkStatus.setEndTimeMs(System.currentTimeMillis());

        System.out.printf("[%s] Finished — Chunk #%d in %d ms%n",
                Thread.currentThread().getName(),
                chunkStatus.getChunkId(),
                chunkStatus.getDownloadDurationMs());
}

}