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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2020 Saxonica Limited
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

package net.sf.saxon.functions.hof;

import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.functions.AbstractFunction;
import net.sf.saxon.functions.SystemFunction;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.NodeInfo;
import net.sf.saxon.om.Sequence;
import net.sf.saxon.om.StructuredQName;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.iter.ManualIterator;
import net.sf.saxon.type.FunctionItemType;

/**
 * A Callable that wraps another Callable and a Dynamic Context, in effect acting as a closure that
 * executes the original callable with a saved context.
 */
public class SystemFunctionWithBoundContextItem extends AbstractFunction {

    private final SystemFunction target;
    private final Item contextItem;

    public SystemFunctionWithBoundContextItem(SystemFunction target, final XPathContext context)  {
        this.target = target;
        Item contextItem = context.getContextItem();
        if (contextItem instanceof NodeInfo && contextItem.isStreamed()) {
            contextItem = null; // causing an XPDY0002 when the function is actually called
        }
        this.contextItem = contextItem;
    }


    /**
     * Evaluate the expression
     *
     * @param context   the dynamic evaluation context
     * @param arguments the values of the arguments, supplied as SequenceIterators
     * @return the result of the evaluation, in the form of a SequenceIterator
     * @throws XPathException
     *          if a dynamic error occurs during the evaluation of the expression
     */
    @Override
    public Sequence call(XPathContext context, Sequence[] arguments) throws XPathException {
        XPathContext c2 = context.newMinorContext();
        c2.setCurrentIterator(new ManualIterator(contextItem));
        return target.call(c2, arguments);
    }

    /**
     * Get the arity of the function
     *
     * @return the number of arguments in the function signature
     */
    @Override
    public int getArity() {
        return target.getArity();
    }

    /**
     * Get the item type of the function item
     *
     * @return the function item's type
     */
    @Override
    public FunctionItemType getFunctionItemType() {
        return target.getFunctionItemType();
    }

    /**
     * Get the name of the function, or null if it is anonymous
     *
     * @return the function name, or null for an anonymous inline function
     */
    @Override
    public StructuredQName getFunctionName() {
        return target.getFunctionName();
    }

    /**
     * Get a description of this function for use in error messages. For named functions, the description
     * is the function name (as a lexical QName). For others, it might be, for example, "inline function",
     * or "partially-applied ends-with function".
     *
     * @return a description of the function for use in error messages
     */
    @Override
    public String getDescription() {
        return target.getDescription();
    }
}

// Copyright (c) 2018-2022 Saxonica Limited