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/*************************************************************************
* ADOBE CONFIDENTIAL
* ___________________
*
* Copyright 2013 Adobe
* All Rights Reserved.
*
* NOTICE: All information contained herein is, and remains
* the property of Adobe and its suppliers, if any. The intellectual
* and technical concepts contained herein are proprietary to Adobe
* and its suppliers and are protected by all applicable intellectual
* property laws, including trade secret and copyright laws.
* Dissemination of this information or reproduction of this material
* is strictly forbidden unless prior written permission is obtained
* from Adobe.
**************************************************************************/
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;
    }
}