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/*************************************************************************
 *
 * ADOBE CONFIDENTIAL
 * __________________
 *
 *  Copyright 2013 Adobe Systems Incorporated
 *  All Rights Reserved.
 *
 * NOTICE:  All information contained herein is, and remains
 * the property of Adobe Systems Incorporated and its suppliers,
 * if any.  The intellectual and technical concepts contained
 * herein are proprietary to Adobe Systems Incorporated and its
 * suppliers and are protected by trade secret or copyright law.
 * Dissemination of this information or reproduction of this material
 * is strictly forbidden unless prior written permission is obtained
 * from Adobe Systems Incorporated.
 **************************************************************************/
package com.adobe.granite.ui.components;

import java.util.Locale;

import javax.annotation.CheckForNull;
import javax.annotation.Nonnull;
import javax.servlet.ServletRequest;
import javax.servlet.ServletRequestWrapper;
import javax.servlet.jsp.PageContext;

import org.apache.sling.api.SlingHttpServletRequest;

/**
 * A helper to deal with EL easier.
 */
public class ExpressionHelper {
    private ExpressionResolver resolver;

    @Nonnull
    private SlingHttpServletRequest request;

    @SuppressWarnings("null")
    public ExpressionHelper(@Nonnull ExpressionResolver resolver, @Nonnull PageContext pageContext) {
        this(resolver, toSlingRequest(pageContext.getRequest()));
    }

    public ExpressionHelper(@Nonnull ExpressionResolver resolver, @Nonnull SlingHttpServletRequest servletRequest) {
        this.resolver = resolver;
        this.request = servletRequest;
    }

    /**
     * Resolves the given expression as string. Request's locale will be used.
     *
     * @param expression
     *            the expression to be resolved
     * @return the resolved expression as a string, or {@code null} when expression
     *         is {@code}
     */
    public String getString(@CheckForNull String expression) {
        return get(expression, String.class);
    }

    /**
     * Resolves the given expression as string, with the given locale.
     *
     * @param expression
     *            the expression to be resolved
     * @param locale
     *            the locale
     * @return the resolved expression as a string, or {@code null} when expression
     *         is {@code}
     */
    public String getString(@CheckForNull String expression, @Nonnull Locale locale) {
        return get(expression, locale, String.class);
    }

    /**
     * Resolves the given expression as boolean. Request's locale will be used.
     *
     * @param expression
     *            the expression to be resolved
     * @return the resolved expression as a boolean, or {@code null} when expression
     *         is {@code}
     */
    public boolean getBoolean(@CheckForNull String expression) {
        Boolean result = get(expression, Boolean.class);
        if (result == null) {
            return false;
        } else {
            return result;
        }
    }

    /**
     * Resolves the given expression as boolean, with the given locale.
     *
     * @param expression
     *            the expression to be resolved
     * @param locale
     *            the locale
     * @return the resolved expression as a boolean, or {@code null} when expression
     *         is {@code}
     */
    public boolean getBoolean(@CheckForNull String expression, @Nonnull Locale locale) {
        Boolean result = get(expression, locale, Boolean.class);
        if (result == null) {
            return false;
        } else {
            return result;
        }
    }

    /**
     * Resolves the given expression. Request's locale will be used.
     *
     * @param expression
     *            the expression to be resolved
     * @param expectedType
     *            the expected type of the resolved expression
     * @param 
     *            the type of the resolved expression
     * @return the resolved expression, or {@code null} when expression is {@code}
     */
    @SuppressWarnings("null")
    public  T get(@CheckForNull String expression, @Nonnull Class expectedType) {
        return get(expression, request.getLocale(), expectedType);
    }

    /**
     * Resolves the given expression, with the given locale.
     *
     * @param expression
     *            the expression to be resolved
     * @param locale
     *            the locale
     * @param expectedType
     *            the expected type of the resolved expression
     * @param 
     *            the type of the resolved expression
     * @return the resolved expression, or {@code null} when expression is {@code}
     */
    public  T get(@CheckForNull String expression, @Nonnull Locale locale, @Nonnull Class expectedType) {
        if (expression == null) {
            return null;
        }

        return resolver.resolve(expression, locale, expectedType, request);
    }

    @SuppressWarnings("null")
    @Nonnull
    private static SlingHttpServletRequest toSlingRequest(@Nonnull ServletRequest req) {
        while (!(req instanceof SlingHttpServletRequest)) {
            if (req instanceof ServletRequestWrapper) {
                req = ((ServletRequestWrapper) req).getRequest();
            } else {
                throw new IllegalStateException("request wrong class");
            }
        }

        return (SlingHttpServletRequest) req;
    }
}