import java.util.List;

public class ProgressMonitor implements Runnable {

    private final String fileName;
    private final int totalSizeMB;
    private final List<ChunkStatus> chunks;
    private final long monitorDelayMs;
    private final long startTimeMs;

    public ProgressMonitor(DownloadConfig config, List<ChunkStatus> chunks) {
        this.fileName = config.getFileName();
        this.totalSizeMB = config.getTotalSizeMB();
        this.chunks = chunks;
        this.monitorDelayMs = 500;
        this.startTimeMs = System.currentTimeMillis();
    }

    @Override
    public void run() {
        System.out.println("=== Download Progress ===");

        while (true) {
            double totalDownloadedMB = 0.0;
            int completedChunks = 0;

            for (ChunkStatus chunk : chunks) {
                totalDownloadedMB += chunk.getDownloadedMB();

                if (chunk.isCompleted()) {
                    completedChunks++;
                }
            }

            double percent = 0.0;
            if (totalSizeMB > 0) {
                percent = (totalDownloadedMB * 100.0) / totalSizeMB;
            }

            long elapsedMs = System.currentTimeMillis() - startTimeMs;
            double elapsedSec = elapsedMs / 1000.0;
            double speedMBps = (elapsedSec > 0) ? (totalDownloadedMB / elapsedSec) : 0.0;
            double remainingMB = totalSizeMB - totalDownloadedMB;
            double etaSec = (speedMBps > 0) ? (remainingMB / speedMBps) : 0.0;

            int barLength = 30;
            int filled = (int) (percent / 100.0 * barLength);
            StringBuilder bar = new StringBuilder("[");
            for (int i = 0; i < barLength; i++) {
                bar.append(i < filled ? "=" : " ");
            }
            bar.append("]");

            System.out.printf("\r%s %s %.1f/%.1f MB (%.1f%%) | Speed: %.1f MB/s | ETA: %.0fs | Chunks: %d/%d",
                    bar.toString(),
                    fileName,
                    totalDownloadedMB,
                    (double) totalSizeMB,
                    percent,
                    speedMBps,
                    etaSec,
                    completedChunks,
                    chunks.size()
            );

            if (completedChunks == chunks.size()) {
                System.out.println("Monitor: All chunks completed.");
                break;
            }

            try {
                Thread.sleep(monitorDelayMs);
            } catch (InterruptedException e) {
                System.out.println("Progress monitor interrupted.");
                return;
            }
        }
    }
}