/*******************************************************************************
 * Copyright (c) 2000, 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 * Port to the D programming language:
 *     Frank Benoit <benoit@tionex.de>
 *******************************************************************************/
module dwtx.jface.text.TextSelection;

import dwt.dwthelper.utils;


/**
 * Standard implementation of {@link dwtx.jface.text.ITextSelection}.
 * <p>
 * Makes advantage of the weak contract of correctness of its interface. If
 * generated from a selection provider, it only remembers its offset and length
 * and computes the remaining information on request.</p>
 */
public class TextSelection : ITextSelection {

    /** Internal empty text selection */
    private final static ITextSelection NULL= new TextSelection();

    /**
     * Returns a shared instance of an empty text selection.
     *
     * @return a shared instance of an empty text selection
     */
    public static ITextSelection emptySelection() {
        return NULL;
    }

    /** Document which delivers the data of the selection */
    private IDocument fDocument;
    /** Offset of the selection */
    private int fOffset;
    /** Length of the selection */
    private int fLength;


    /**
     * Creates an empty text selection.
     */
    private TextSelection() {
        this(null, -1, -1);
    }

    /**
     * Creates a text selection for the given range. This
     * selection object describes generically a text range and
     * is intended to be an argument for the <code>setSelection</code>
     * method of selection providers.
     *
     * @param offset the offset of the range
     * @param length the length of the range
     */
    public TextSelection(int offset, int length) {
        this(null, offset, length);
    }

    /**
     * Creates a text selection for the given range of the given document.
     * This selection object is created by selection providers in responds
     * <code>getSelection</code>.
     *
     * @param document the document whose text range is selected in a viewer
     * @param offset the offset of the selected range
     * @param length the length of the selected range
     */
    public TextSelection(IDocument document, int offset, int length) {
        fDocument= document;
        fOffset= offset;
        fLength= length;
    }

    /**
     *
     * Returns true if the offset and length are smaller than 0.
     * A selection of length 0, is a valid text selection as it
     * describes, e.g., the cursor position in a viewer.
     *
     * @return <code>true</code> if this selection is empty
     * @see dwtx.jface.viewers.ISelection#isEmpty()
     */
    public bool isEmpty() {
        return fOffset < 0 || fLength < 0;
    }

    /*
     * @see dwtx.jface.text.ITextSelection#getOffset()
     */
    public int getOffset() {
        return fOffset;
    }

    /*
     * @see dwtx.jface.text.ITextSelection#getLength()
     */
    public int getLength() {
        return fLength;
    }

    /*
     * @see dwtx.jface.text.ITextSelection#getStartLine()
     */
    public int getStartLine() {

        try {
            if (fDocument !is null)
                return fDocument.getLineOfOffset(fOffset);
        } catch (BadLocationException x) {
        }

        return -1;
    }

    /*
     * @see dwtx.jface.text.ITextSelection#getEndLine()
     */
    public int getEndLine() {
        try {
            if (fDocument !is null) {
                int endOffset= fOffset + fLength;
                if (fLength !is 0)
                    endOffset--;
                return fDocument.getLineOfOffset(endOffset);
            }
        } catch (BadLocationException x) {
        }

        return -1;
    }

    /*
     * @see dwtx.jface.text.ITextSelection#getText()
     */
    public String getText() {
        try {
            if (fDocument !is null)
                return fDocument.get(fOffset, fLength);
        } catch (BadLocationException x) {
        }

        return null;
    }

    /*
     * @see java.lang.Object#equals(Object)
     */
    public bool equals(Object obj) {
        if (obj is this)
            return true;

        if (obj is null || getClass() !is obj.getClass())
            return false;

        TextSelection s= (TextSelection) obj;
        bool sameRange= (s.fOffset is fOffset && s.fLength is fLength);
        if (sameRange) {

            if (s.fDocument is null && fDocument is null)
                return true;
            if (s.fDocument is null || fDocument is null)
                return false;

            try {
                String sContent= s.fDocument.get(fOffset, fLength);
                String content= fDocument.get(fOffset, fLength);
                return sContent.equals(content);
            } catch (BadLocationException x) {
            }
        }

        return false;
    }

    /*
     * @see java.lang.Object#hashCode()
     */
    public int hashCode() {
        int low= fDocument !is null ? fDocument.hashCode() : 0;
        return (fOffset << 24) | (fLength << 16) | low;
    }
}