/*******************************************************************************
 * Copyright (c) 2000, 2007 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
 *******************************************************************************/
package org.eclipse.che.ide.ext.java.jdt.templates.api;

import org.eclipse.che.ide.ext.java.jdt.text.Document;
import org.eclipse.che.ide.runtime.Assert;
import org.eclipse.che.ide.api.text.BadLocationException;
import org.eclipse.che.ide.api.text.Position;


/**
 * Instances of this class describe the context of a template as a region of a document. That region may be either specified by
 * its offset and length, or by a <code>Position</code> which may or may not be registered with the document.
 * <p>
 * Clients may instantiate and extend this class.
 * </p>
 *
 * @since 3.0
 */
public class DocumentTemplateContext extends TemplateContext {

    /** The text of the document. */
    protected final Document fDocument;

    /**
     * The region of the document described by this context. We store a position since clients may specify the document region as
     * (updateable) Positions.
     */
    private final Position fPosition;

    /** The original offset of this context. Will only be updated by the setter method. */
    private int fOriginalOffset;

    /** The original length of this context. Will only be updated by the setter method. */
    private int fOriginalLength;

    /**
     * Creates a document template context.
     *
     * @param type
     *         the context type
     * @param document
     *         the document this context applies to
     * @param offset
     *         the offset of the document region
     * @param length
     *         the length of the document region
     */
    public DocumentTemplateContext(TemplateContextType type, Document document, int offset, int length) {
        this(type, document, new Position(offset, length));
    }

    /**
     * Creates a document template context. The supplied <code>Position</code> will be queried to compute the <code>getStart</code>
     * and <code>getEnd</code> methods, which will therefore answer updated position data if it is registered with the document.
     *
     * @param type
     *         the context type
     * @param document
     *         the document this context applies to
     * @param position
     *         the position describing the area of the document which forms the template context
     * @since 3.1
     */
    public DocumentTemplateContext(TemplateContextType type, Document document, Position position) {
        super(type);

        Assert.isNotNull(document);
        Assert.isNotNull(position);
        Assert.isTrue(position.getOffset() <= document.getLength());

        fDocument = document;
        fPosition = position;
        fOriginalOffset = fPosition.getOffset();
        fOriginalLength = fPosition.getLength();
    }

    /**
     * Returns the document.
     *
     * @return the document
     */
    public Document getDocument() {
        return fDocument;
    }

    /**
     * Returns the completion offset within the string of the context.
     *
     * @return the completion offset within the string of the context
     */
    public int getCompletionOffset() {
        return fOriginalOffset;
    }

    /**
     * Sets the completion offset.
     *
     * @param newOffset
     *         the new completion offset
     */
    protected void setCompletionOffset(int newOffset) {
        fOriginalOffset = newOffset;
        fPosition.setOffset(newOffset);
    }

    /**
     * Returns the completion length within the string of the context.
     *
     * @return the completion length within the string of the context
     */
    public int getCompletionLength() {
        return fOriginalLength;
    }

    /**
     * Sets the completion length.
     *
     * @param newLength
     *         the new completion length
     */
    protected void setCompletionLength(int newLength) {
        fOriginalLength = newLength;
        fPosition.setLength(newLength);
    }

    /**
     * Returns the keyword which triggered template insertion.
     *
     * @return the keyword which triggered template insertion
     */
    public String getKey() {
        int offset = getStart();
        int length = getEnd() - offset;
        try {
            return fDocument.get(offset, length);
        } catch (BadLocationException e) {
            return ""; //$NON-NLS-1$
        }
    }

    /**
     * Returns the beginning offset of the keyword.
     *
     * @return the beginning offset of the keyword
     */
    public int getStart() {
        return fPosition.getOffset();
    }

    /**
     * Returns the end offset of the keyword.
     *
     * @return the end offset of the keyword
     */
    public int getEnd() {
        return fPosition.getOffset() + fPosition.getLength();
    }

    /*
     * @see org.eclipse.jface.text.templates.TemplateContext#canEvaluate(org.eclipse.jface.text.templates.Template)
     */
    public boolean canEvaluate(Template template) {
        return true;
    }

    /*
     * @see org.eclipse.jface.text.templates.TemplateContext#evaluate(org.eclipse.jface.text.templates.Template)
     */
    public TemplateBuffer evaluate(Template template) throws BadLocationException, TemplateException {
        if (!canEvaluate(template))
            return null;

        TemplateTranslator translator = new TemplateTranslator();
        TemplateBuffer buffer = translator.translate(template);

        getContextType().resolve(buffer, this);

        return buffer;
    }
}