/**
 * Copyright (C) 2011  JTalks.org Team
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */
package org.jtalks.jcommune.web.tags;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.Tag;
import javax.servlet.jsp.tagext.TagSupport;

import org.jtalks.common.service.security.SecurityContextFacade;
import org.springframework.security.access.PermissionEvaluator;
import org.springframework.security.core.Authentication;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

/**
 * An implementation of {@link Tag} that allows its body through if some 
 * authorizations are granted to the request's object.
 * Typical use case: <br>
 *  <code> 
 *  <jtalks:haspermission targetId="${topic.branch.id}" targetType="BRANCH"<br>
 *          permission="BranchPermission.DELETE_OWN_POSTS">
 *      <br>    Some jsp code<br>
 *  </jtalks:haspermission>
 *  </code>
 * 
 * @author Vyacheslav Mishcheryakov
 */
@SuppressWarnings("serial")
public class HasPermission extends TagSupport {

    private transient PermissionEvaluator aclEvaluator;
    private transient SecurityContextFacade securityContextFacade;
    
    /** Identifier of object to check permission */
    private Long targetId;
    
    /** Type of object (e.g. BRANCH) */
    private String targetType;
    
    /** Simple name of permission (enum value). See 
     * {@link org.jtalks.common.model.permissions.JtalksPermission} and its
     * subclasses
     */
    private String permission;
    
    /**
     * @param targetId the ID of object to check permission
     */
    public void setTargetId(Long targetId) {
        this.targetId = targetId;
    }

    /**
     * @param targetType type of targeted object
     */
    public void setTargetType(String targetType) {
        this.targetType = targetType;
    }

    /**
     * @param permission Simple name of permission (enum value)
     */
    public void setPermission(String permission) {
        this.permission = permission;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public int doStartTag() throws JspException {
        if (isAnyParameterMissed()) {
            throw new JspException("Some parameter is missed or empty");
        }

        Authentication authentication = securityContextFacade.getContext().getAuthentication();
        //Authentication can be null when request not goes through spring security filters
        if (authentication == null) {
            return Tag.SKIP_BODY;
        }
        
        if (aclEvaluator.hasPermission(authentication, targetId, targetType, permission)) {
            return Tag.EVAL_BODY_INCLUDE;
        }

        return Tag.SKIP_BODY;
    }
    
    /**
     * Checks if any required tag parameter is missed or blank
     * @return true if any required parameter is not specified.
     */
    private boolean isAnyParameterMissed() {
        boolean isTargetIdMissed = targetId == null;
        boolean isTargetTypeMissed = targetType == null || "".equals(targetType);
        boolean isPermissionMissed = permission == null || "".equals(permission);
        return  isTargetIdMissed || isTargetTypeMissed || isPermissionMissed;
    }

    /** 
     * Fetches all required beans from Spring context when page context is set.
     * This guaranteed that all services will be initialized before actual 
     * page rendering
     * 
     * @param pageContext page context to be set for this tag invocation
     *
     */
    @Override
    public void setPageContext(PageContext pageContext) {
        super.setPageContext(pageContext);
        WebApplicationContext ctx = WebApplicationContextUtils
                .getRequiredWebApplicationContext(pageContext.getServletContext());
        aclEvaluator = ctx.getBean(PermissionEvaluator.class);
        securityContextFacade = ctx.getBean(SecurityContextFacade.class);
    }
    
}