package org.limewire.core.api.library;

import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.io.File;
import java.io.IOException;
import java.net.URI;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;


/**
 * A Transferable that returns a javaFileListFlavor, built up from
 * a list of 'FileTransfer' and 'LazyFileTransfer' items.  The lazy
 * items will be retrieved only when the data of the transfer is requested
 * (in response to a getTransferData call).
 */
public class FileTransferable implements Transferable {
    
    private final List<File> files;
    
    private final List<? extends File> lazyFiles;
    
    /**
     * Holds the data flavor used on linux desktops for file drags.
     */
    public static final DataFlavor URIFlavor = createURIFlavor();
    
    public static final List<? extends File> EMPTY_FILE_TRANSFER_LiST =
        Collections.emptyList();
    
    public static final List<File> EMPTY_FILE_LIST = Collections.emptyList();
    
    static DataFlavor createURIFlavor() {
        try {
            return new DataFlavor("text/uri-list;class=java.lang.String");
        } catch (ClassNotFoundException cnfe) {
            return null;
        }
    }
    
    public FileTransferable(List<File> files) {
        this(files, EMPTY_FILE_TRANSFER_LiST);
    }
    
    public FileTransferable(List<File> realFiles,
            List<? extends File> lazyFiles) {
        if (realFiles == null) { 
            throw new NullPointerException("realFiles must not be null");
        }
        if (lazyFiles == null) {
            throw new NullPointerException("lazyFiles must not be empty");
        }
        // copy, given list might not me mutable
        this.files = new ArrayList<File>(realFiles);
        this.lazyFiles = new ArrayList<File>(lazyFiles);
    }

    private List<File> getFiles() {
        if (!lazyFiles.isEmpty()) {
            for (File transfer : lazyFiles) {
                File f = transfer;
                if (f != null)
                    files.add(f);
            }
            lazyFiles.clear();
        }
        return files;
    }
    
    public Object getTransferData(DataFlavor flavor) 
      throws UnsupportedFlavorException, IOException {
        if (flavor.equals(DataFlavor.javaFileListFlavor)) {
            return getFiles();
        } else if (URIFlavor.equals(flavor)) {
            StringBuilder sb = new StringBuilder();
            String lineSep = System.getProperty("line.separator");
            for (File file : getFiles()) {
                URI uri = file.toURI();
                if (sb.length() > 0) {
                    sb.append(lineSep);
                }
                sb.append(uri.toString());
            }
            return sb.toString();
        }
        else {
            throw new UnsupportedFlavorException(flavor);
        }
    }

    public DataFlavor[] getTransferDataFlavors() {
//        if(OSUtils.isWindows()) {
            return new DataFlavor[] { DataFlavor.javaFileListFlavor };
//        } else {
//            return new DataFlavor[] { DataFlavor.javaFileListFlavor, URIFlavor };
//        }
    }

    public boolean isDataFlavorSupported(DataFlavor flavor) {
        return flavor.equals(DataFlavor.javaFileListFlavor)
            || flavor.equals(URIFlavor);
    }
}