/*******************************************************************************
 * 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
 *******************************************************************************/
package org.eclipse.che.ide.ext.java.jdt.templates.api;

import org.eclipse.che.ide.api.text.BadLocationException;

import java.util.HashMap;
import java.util.Map;

/**
 * Provides the context for a <code>Template</code> being resolved. Keeps track of resolved variables.
 * <p>
 * Clients may extend this class.
 * </p>
 *
 * @since 3.0
 */
public abstract class TemplateContext {

    /** The context type of this context */
    private final TemplateContextType fContextType;

    /** Additional variables. */
    private final Map fVariables = new HashMap();

    /** A flag to indicate that the context should not be modified. */
    private boolean fReadOnly;

    /**
     * Creates a template context of a particular context type.
     *
     * @param contextType
     *         the context type of this context
     */
    protected TemplateContext(TemplateContextType contextType) {
        fContextType = contextType;
        fReadOnly = true;
    }

    /**
     * Returns the context type of this context.
     *
     * @return the context type of this context
     */
    public TemplateContextType getContextType() {
        return fContextType;
    }

    /**
     * Sets or clears the read-only flag.
     *
     * @param readOnly
     *         the new read-only state
     */
    public void setReadOnly(boolean readOnly) {
        fReadOnly = readOnly;
    }

    /**
     * Returns <code>true</code> if the receiver is read-only, <code>false</code> otherwise.
     *
     * @return <code>true</code> if the receiver is read-only, <code>false</code> otherwise
     */
    public boolean isReadOnly() {
        return fReadOnly;
    }

    /**
     * Defines the value of a variable.
     *
     * @param name
     *         the name of the variable
     * @param value
     *         the value of the variable, <code>null</code> to un-define a variable
     */
    public void setVariable(String name, String value) {
        fVariables.put(name, value);
    }

    /**
     * Returns the value of a defined variable.
     *
     * @param name
     *         the name of the variable
     * @return returns the value of the variable, <code>null</code> if the variable was not defined
     */
    public String getVariable(String name) {
        return (String)fVariables.get(name);
    }

    /**
     * Evaluates the template in this context and returns a template buffer.
     * <p>
     * Evaluation means translating the template into a <code>TemplateBuffer</code>, resolving the defined variables in this
     * context and possibly formatting the resolved buffer.
     * </p>
     *
     * @param template
     *         the template to evaluate
     * @return returns the buffer with the evaluated template or <code>null</code> if the buffer could not be created
     * @throws BadLocationException
     *         if evaluation fails due to concurrently changed documents etc.
     * @throws TemplateException
     *         if the template specification is not valid
     */
    public abstract TemplateBuffer evaluate(Template template) throws BadLocationException, TemplateException;

    /**
     * Tests if the specified template can be evaluated in this context.
     * <p>
     * Examples are templates defined for a different context (e.g. a javadoc template cannot be evaluated in Java context).
     * </p>
     *
     * @param template
     *         the <code>Template</code> to check
     * @return <code>true</code> if <code>template</code> can be evaluated in this context, <code>false</code> otherwise
     */
    public abstract boolean canEvaluate(Template template);

}