// Educational simplification:
// each worker writes only to its own ChunkStatus,
// and the monitor only reads chunk states.
// volatile is used here to make progress updates more visible across threads.

/**
 * Represents the state and download progress of a single file chunk.
 * Each worker thread updates its own ChunkStatus, while the monitor thread reads it.
 */
public class ChunkStatus {
    private final int chunkId;
    private final double chunkSizeMB;
    private volatile double downloadedMB;
    private volatile boolean completed;
    private volatile long startTimeMs;
    private volatile long endTimeMs;

    /**
     * Initializes a chunk with its unique ID and total allocated size.
     * Progress-related fields are initialized to default values.
     */
    public ChunkStatus(int chunkId, double chunkSizeMB) {
        this.chunkId = chunkId;
        this.chunkSizeMB = chunkSizeMB;
        this.downloadedMB = 0.0;
        this.completed = false;
        this.startTimeMs = 0;
        this.endTimeMs = 0;
    }

    // Getters and Setters
    public int getChunkId() {
        return chunkId;
    }

    public double getChunkSizeMB() {
        return chunkSizeMB;
    }

    public double getDownloadedMB() {
        return downloadedMB;
    }

    public void setDownloadedMB(double downloadedMB) {
        // Guard to prevent downloaded size exceeding actual chunk size
        if (downloadedMB >= this.chunkSizeMB) {
            this.downloadedMB = this.chunkSizeMB;
        } else {
            this.downloadedMB = downloadedMB;
        }
    }

    public boolean isCompleted() {
        return completed;
    }

    public void setCompleted(boolean completed) {
        this.completed = completed;
    }

    public long getStartTimeMs() {
        return startTimeMs;
    }

    public void setStartTimeMs(long startTimeMs) {
        this.startTimeMs = startTimeMs;
    }

    public long getEndTimeMs() {
        return endTimeMs;
    }

    public void setEndTimeMs(long endTimeMs) {
        this.endTimeMs = endTimeMs;
    }

    /**
     * Helper method to calculate the duration of this specific chunk's download.
     * Returns 0 if the chunk hasn't started or finished yet.
     */
    public long getDownloadDurationMs() {
        if (startTimeMs > 0 && endTimeMs > startTimeMs) {
            return endTimeMs - startTimeMs;
        } else if (startTimeMs > 0 && !completed) {
            return System.currentTimeMillis() - startTimeMs;
        }
        return 0;
    }

    /**
     * Helper method to calculate the download percentage of this chunk.
     */
    public double getProgressPercentage() {
        if (chunkSizeMB == 0) return 100.0;
        return (downloadedMB / chunkSizeMB) * 100.0;
    }

    @Override
    public String toString() {
        return String.format("Chunk #%d: %.1f/%.1f MB (%.1f%%)%s",
                chunkId,
                downloadedMB,
                chunkSizeMB,
                getProgressPercentage(),
                completed ? " [Completed]" : ""
        );
    }

    public void setStartTime(long startTime) {
        this.startTimeMs = startTime;
    }
}