package de.thedevstack.conversationsplus.services.filetransfer;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import de.thedevstack.conversationsplus.entities.DownloadableFile;
import de.thedevstack.conversationsplus.entities.Message;
import de.thedevstack.conversationsplus.entities.Transferable;
import de.thedevstack.conversationsplus.persistance.FileBackend;
import de.thedevstack.conversationsplus.utils.StreamUtil;

/**
 *
 */
public class FileTransferEntity implements Transferable {
    /**
     * Listeners to inform about a status change.
     */
    private final List<FileTransferStatusListener> statusListeners = new ArrayList<>();
    /**
     * The associated message.
     */
    private final Message message;
    /**
     * Number of attempts.
     */
    private int attempts = 0;
    /**
     * The status of the file transfer.
     */
    private FileTransferStatusEnum transferStatus;
    /**
     * Number of bytes transmitted.
     */
    private long transmitted = 0;
    /**
     * The associated file.
     */
    private DownloadableFile file;
    /**
     * The associated file as stream.
     */
    private InputStream fileInputStream;

    /**
     * Initializes the FileTransferEntity based on the associated message.
     * This initialization includes loading the file and associating this transferable to the message.
     * @param message the message in which the file to transfer is contained.
     */
    public FileTransferEntity(Message message) {
        this.message = message;
        this.message.setTransferable(this);
        this.file = FileBackend.getFile(message, false);
    }

    /**
     * Start something.
     * Empty implementation since documentation in interface is missing.
     * @return <code>false</code>
     */
    @Override
    public boolean start() {
        return false;
    }

    /**
     * Returns the global transferable status.
     *
     * @return {@value STATUS_FAILED} if #isFailed returns <code>true</code>, {@value STATUS_UPLOADING} otherwise
     */
    @Override
    public int getStatus() {
        int status = (isFailed()) ? STATUS_FAILED : STATUS_UPLOADING;
        return status;
    }

    /**
     * Returns the expected file size of the underlying file.
     * @return the expected file size or 0 if no file is associated.
     */
    @Override
    public long getFileSize() {
        return file == null ? 0 : file.getExpectedSize();
    }

    /**
     * Calculates the current progress in percent.
     *
     * @return the current progress in percent
     */
    @Override
    public int getProgress() {
        if (file == null) {
            return 0;
        }
        return (int) ((((double) transmitted) / file.getExpectedSize()) * 100);
    }

    /**
     * Cancels the file transfer and informs the listeners about cancellation.
     */
    @Override
    public void cancel() {
        this.transferStatus = FileTransferStatusEnum.CANCELED;

        this.close();

        for (FileTransferStatusListener listener : this.statusListeners) {
            listener.onCancel(this);
        }
    }

    /**
     * Starts an transfer attempt.
     */
    public void startAttempt() {
        this.attempts++;
        this.transferStatus = FileTransferStatusEnum.TRANSFERRING;
    }

    /**
     * Fails an file transfer and informs the listeners about failure.
     *
     * @param failureReason the reason of failure.
     */
    public void fail(FileTransferFailureReason failureReason) {
        this.transferStatus = FileTransferStatusEnum.FAILED;

        this.close();

        failureReason.setAttempt(this.attempts);
        for (FileTransferStatusListener listener : this.statusListeners) {
            listener.onFailure(this, failureReason);
        }
    }

    /**
     * Updates the progress by adding parameter value to current progress value.
     *
     * @param progress the number of newly transferred bytes
     */
    public void updateProgress(long progress) {
        if (0 == this.attempts) {
            this.startAttempt();
        }
        this.transmitted += progress;
    }

    /**
     * Set the status of the file transfer to FileTransferStatusEnum#TRANSFERRED and informs the listeners about success.
     */
    public void transferred() {
        this.transferStatus = FileTransferStatusEnum.TRANSFERRED;

        this.close();

        for (FileTransferStatusListener listener : this.statusListeners) {
            listener.onSuccess(this);
        }
    }

    /**
     * Closes the file input stream (if it is not yet closed) and removes association with message.
     */
    private void close() {
        StreamUtil.close(this.fileInputStream);
        this.getMessage().setTransferable(null);
    }

    /**
     * Whether the file is transferred or not.
     * @return <code>true</code> if the file is successfully transferred, <code>false</code> otherwise
     */
    public boolean isTransferred() {
        return FileTransferStatusEnum.TRANSFERRED == this.transferStatus;
    }

    /**
     * Whether the file transfer is canceled or not.
     * @return <code>true</code> if the file transfer was canceled, <code>false</code> otherwise
     */
    public boolean isCanceled() {
        return FileTransferStatusEnum.CANCELED == this.transferStatus;
    }

    /**
     * Whether the file transfer failed or not.
     * @return <code>true</code> if the file transfer failed, <code>false</code> otherwise
     */
    public boolean isFailed() {
        return FileTransferStatusEnum.FAILED == this.transferStatus;
    }

    public void setFileInputStream(InputStream fileInputStream) {
        this.fileInputStream = fileInputStream;
    }

    public InputStream getFileInputStream() {
        return fileInputStream;
    }

    public Message getMessage() {
        return message;
    }

    public DownloadableFile getFile() {
        return file;
    }

    public void addFileTransferStatusListener(FileTransferStatusListener... listeners) {
        this.statusListeners.addAll(Arrays.asList(listeners));
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        FileTransferEntity that = (FileTransferEntity) o;

        String uuid = message != null ? message.getUuid() : null;
        String thatUuid = that.message != null ? that.message.getUuid() : null;

        return uuid != null ? uuid.equals(thatUuid) : thatUuid == null;

    }

    @Override
    public int hashCode() {
        return message != null && message.getUuid() != null ? message.getUuid().hashCode() : 0;
    }
}