/*
Copyright (c) 2013, Adam Retter
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
    * Neither the name of Adam Retter Consulting nor the
      names of its contributors may be used to endorse or promote products
      derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL Adam Retter BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.exist.extensions.exquery.modules.request;

import org.exist.dom.QName;
import org.exist.xquery.Cardinality;
import org.exist.xquery.FunctionSignature;
import org.exist.xquery.XPathException;
import org.exist.xquery.XQueryContext;
import org.exist.xquery.value.FunctionParameterSequenceType;
import org.exist.xquery.value.FunctionReturnSequenceType;
import org.exist.xquery.value.Sequence;
import org.exist.xquery.value.SequenceType;
import org.exist.xquery.value.StringValue;
import org.exist.xquery.value.Type;
import org.exist.xquery.value.ValueSequence;
import org.exquery.http.HttpRequest;

/**
 *
 * @author Adam Retter <adam.retter@googlemail.com>
 */
public class HeaderFunctions extends AbstractRequestModuleFunction {

    private final static QName qnHeaderNames = new QName("header-names", RequestModule.NAMESPACE_URI, RequestModule.PREFIX);
    private final static QName qnHeader = new QName("header", RequestModule.NAMESPACE_URI, RequestModule.PREFIX);
    
    public final static FunctionSignature FNS_HEADER_NAMES = new FunctionSignature(
        qnHeaderNames,
        "Gets the names of HTTP Headers available in the HTTP Request.",
        null,
        new FunctionReturnSequenceType(Type.STRING, Cardinality.ONE_OR_MORE, "The names of available HTTP Headers in the HTTP Request.")
    );
    
    public final static FunctionSignature FNS_HEADER = new FunctionSignature(
        qnHeader,
        "Gets the value of the named HTTP Header in the HTTP Request. If there is no such header, then an empty sequence is returned.",
        new SequenceType[] {
            new FunctionParameterSequenceType("header-name", Type.STRING, Cardinality.EXACTLY_ONE, "The name of the HTTP Header to retrieve the value of.")
        },
        new FunctionReturnSequenceType(Type.STRING, Cardinality.ZERO_OR_ONE, "The value of the named HTTP Header, or an empty sequence.")
    );
    
    public final static FunctionSignature FNS_HEADER_WITH_DEFAULT = new FunctionSignature(
        qnHeader,
        "Gets the value of the named HTTP Header in the HTTP Request.  If there is no such header in the HTTP Request, then the value specified in $default is returned instead.",
        new SequenceType[] {
            new FunctionParameterSequenceType("header-name", Type.STRING, Cardinality.EXACTLY_ONE, "The name of the HTTP Header to retrieve the value of."),
            new FunctionParameterSequenceType("default", Type.STRING, Cardinality.EXACTLY_ONE, "The default value to use if the named HTTP Header is not present in the request.")
        },
        new FunctionReturnSequenceType(Type.STRING, Cardinality.EXACTLY_ONE, "The value of the named HTTP Header, or the default value.")
    );
    
    public HeaderFunctions(final XQueryContext context, final FunctionSignature signature) {
        super(context, signature);
    }
    
    @Override
    public Sequence eval(final Sequence[] args, final HttpRequest request) throws XPathException {
        final Sequence result;
        
        if(isCalledAs(qnHeaderNames.getLocalPart())) {
            result = new ValueSequence();
            for(final String parameterName : request.getHeaderNames()) {
                result.add(new StringValue(parameterName));
            }
        } else if(isCalledAs(qnHeader.getLocalPart())) {
            final String headerName = args[0].getStringValue();
            
            if(getSignature().getArgumentCount() == 1) {
                result = getHeader(request, headerName, null);
            } else if(getSignature().getArgumentCount() == 2) {
                final Sequence defaultValues = args[1];
                result = getHeader(request, headerName, defaultValues);
            } else {
                throw new XPathException(this, "Unknown function call: " + getSignature());
            }   
        } else {
            throw new XPathException(this, "Unknown function call: " + getSignature());
        }
        
        return result;
    }
    
    private Sequence getHeader(final HttpRequest request, final String headerName, final Sequence defaultValues) throws XPathException {
        final Sequence result;
        final String headerValue = request.getHeader(headerName);
        if(headerValue == null) {
            if(defaultValues != null) {
                result = defaultValues;
            } else {
                result = Sequence.EMPTY_SEQUENCE;
            }
        } else {
            result = new StringValue(headerValue);
        }
        
        return result;
    }
}