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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 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.expr.parser;

import net.sf.saxon.expr.Container;
import net.sf.saxon.expr.Expression;
import net.sf.saxon.expr.StaticContext;
import net.sf.saxon.expr.flwor.Clause;
import net.sf.saxon.om.StructuredQName;

/**
 *  A code injector can be used to add code to the expression tree (for example, diagnostic tracing code)
 *  during the process of parsing and tree construction
 */
public interface CodeInjector {

     /**
     * Wrap an expression in a diagnostic expression.
     *
     * @param exp         the expression to be wrapped
     * @param env         the static context
     * @param construct   integer constant identifying the kind of construct
     * @param qName       the name of the construct (if applicable)
     * @return a replacement for the original expression (or the original expression unchanged). Normally
      * the new expression will collect or output some diagnostic information and then invoke the original
      * expression. However this is not required; the new expression could be a complete replacement for the
      * original.
     */

    public Expression inject(Expression exp, StaticContext env, int construct, StructuredQName qName);

    /**
     * Insert a tracing clause into the pipeline of clauses that evaluates a FLWOR expression
     * @param target the clause whose execution is being traced
     * @param env the static context of the containing FLWOR expression
     * @param container the container of the FLWOR expression (providing location information)
     */

    public Clause injectClause(Clause target, StaticContext env, Container container);
}