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package org.apache.jasper.compiler;

import java.util.*;
import javax.servlet.jsp.tagext.FunctionInfo;
import org.apache.jasper.JasperException;

/**
 * This class generates functions mappers for the EL expressions in the page.
 * Instead of a global mapper, a mapper is used for ecah call to EL
 * evaluator, thus avoiding the prefix overlapping and redefinition
 * issues.
 *
 * @author Kin-man Chung
 */

public class ELFunctionMapper {
    private int currFunc = 0;
    StringBuilder ds;  // Contains codes to initialize the functions mappers.
    StringBuilder ss;  // Contains declarations of the functions mappers.

    /**
     * Creates the functions mappers for all EL expressions in the JSP page.
     *
     * @param compiler Current compiler, mainly for accessing error dispatcher.
     * @param page The current compilation unit.
     */
    public static void map(Compiler compiler, Node.Nodes page) 
		throws JasperException {

	ELFunctionMapper map = new ELFunctionMapper();
	map.ds = new StringBuilder();
	map.ss = new StringBuilder();

	page.visit(map.new ELFunctionVisitor());

	// Append the declarations to the root node
	String ds = map.ds.toString();
	if (ds.length() > 0) {
	    Node root = page.getRoot();
	    new Node.Declaration(map.ss.toString(), null, root);
	    new Node.Declaration("static {\n" + ds + "}\n", null, root);
	}
    }

    /**
     * A visitor for the page.  The places where EL is allowed are scanned
     * for functions, and if found functions mappers are created.
     */
    class ELFunctionVisitor extends Node.Visitor {
	
	/**
	 * Use a global name map to facilitate reuse of function maps.
	 * The key used is prefix:function:uri.
	 */
	private HashMap<String, String> gMap = new HashMap<String, String>();

	public void visit(Node.ParamAction n) throws JasperException {
	    doMap(n.getValue());
	    visitBody(n);
	}

	public void visit(Node.IncludeAction n) throws JasperException {
	    doMap(n.getPage());
	    visitBody(n);
	}

	public void visit(Node.ForwardAction n) throws JasperException {
	    doMap(n.getPage());
	    visitBody(n);
	}

        public void visit(Node.SetProperty n) throws JasperException {
	    doMap(n.getValue());
	    visitBody(n);
	}

        public void visit(Node.UseBean n) throws JasperException {
	    doMap(n.getBeanName());
	    visitBody(n);
	}

        public void visit(Node.PlugIn n) throws JasperException {
	    doMap(n.getHeight());
	    doMap(n.getWidth());
	    visitBody(n);
	}

        public void visit(Node.JspElement n) throws JasperException {

	    Node.JspAttribute[] attrs = n.getJspAttributes();
	    for (int i = 0; attrs != null && i < attrs.length; i++) {
		doMap(attrs[i]);
	    }
	    doMap(n.getNameAttribute());
	    visitBody(n);
	}

        public void visit(Node.UninterpretedTag n) throws JasperException {

	    Node.JspAttribute[] attrs = n.getJspAttributes();
	    for (int i = 0; attrs != null && i < attrs.length; i++) {
		doMap(attrs[i]);
	    }
	    visitBody(n);
	}

        public void visit(Node.CustomTag n) throws JasperException {
	    Node.JspAttribute[] attrs = n.getJspAttributes();
	    for (int i = 0; attrs != null && i < attrs.length; i++) {
		doMap(attrs[i]);
	    }
	    visitBody(n);
	}

        public void visit(Node.ELExpression n) throws JasperException {
	    doMap(n.getEL());
	}

	private void doMap(Node.JspAttribute attr) 
		throws JasperException {
	    if (attr != null) {
		doMap(attr.getEL());
	    }
	}

        /**
         * Creates function mappers, if needed, from ELNodes
         */
	private void doMap(ELNode.Nodes el) 
		throws JasperException {

            // Only care about functions in ELNode's
	    class Fvisitor extends ELNode.Visitor {
		ArrayList<ELNode.Function> funcs =
                        new ArrayList<ELNode.Function>();
		Set<String> keys = new HashSet<String>();
		public void visit(ELNode.Function n) throws JasperException {
                    if (n.getUri() == null) {
                        // Can be a lambda expresion call
                        return;
                    }
		    String key = n.getPrefix() + ":" + n.getName();
		    if (! keys.contains(key)) {
			keys.add(key);
			funcs.add(n);
		    }
		}
	    }

	    if (el == null) {
		return;
	    }

	    // First locate all unique functions in this EL
	    Fvisitor fv = new Fvisitor();
	    el.visit(fv);
	    ArrayList<ELNode.Function> functions = fv.funcs;

	    if (functions.size() == 0) {
		return;
	    }

	    // Reuse a previous map if possible
	    String decName = matchMap(functions);
	    if (decName != null) {
		el.setMapName(decName);
		return;
	    }
	
	    // Generate declaration for the map statically
	    decName = getMapName();
	    ss.append("static private org.apache.jasper.runtime.ProtectedFunctionMapper " + decName + ";\n");

	    ds.append("  " + decName + "= ");
	    ds.append("org.apache.jasper.runtime.ProtectedFunctionMapper");

	    // Special case if there is only one function in the map
	    String funcMethod = null;
	    if (functions.size() == 1) {
		funcMethod = ".getMapForFunction";
	    } else {
		ds.append(".getInstance();\n");
		funcMethod = "  " + decName + ".mapFunction";
	    }

            // Setup arguments for either getMapForFunction or mapFunction
	    for (int i = 0; i < functions.size(); i++) {
		ELNode.Function f = (ELNode.Function)functions.get(i);
		FunctionInfo funcInfo = f.getFunctionInfo();
		String key = f.getPrefix()+ ":" + f.getName();
		ds.append(funcMethod + "(\"" + key + "\", " +
			funcInfo.getFunctionClass() + ".class, " +
			'\"' + f.getMethodName() + "\", " +
			"new Class[] {");
		String params[] = f.getParameters();
		for (int k = 0; k < params.length; k++) {
		    if (k != 0) {
			ds.append(", ");
		    }
		    int iArray = params[k].indexOf('[');
		    if (iArray < 0) {
			ds.append(params[k] + ".class");
		    }
		    else {
			String baseType = params[k].substring(0, iArray);
			ds.append("java.lang.reflect.Array.newInstance(");
			ds.append(baseType);
			ds.append(".class,");

			// Count the number of array dimension
			int aCount = 0;
			for (int jj = iArray; jj < params[k].length(); jj++ ) {
			    if (params[k].charAt(jj) == '[') {
				aCount++;
			    }
			}
			if (aCount == 1) {
			    ds.append("0).getClass()");
			} else {
			    ds.append("new int[" + aCount + "]).getClass()");
			}
		    }
		}
		ds.append("});\n");
		// Put the current name in the global function map
		gMap.put(f.getPrefix() + ':' + f.getName() + ':' + f.getUri(),
			 decName);
	    }
	    el.setMapName(decName);
	}

        /**
         * Find the name of the function mapper for an EL.  Reuse a
         * previously generated one if possible.
         * @param functions An ArrayList of ELNode.Function instances that
         *                  represents the functions in an EL
         * @return A previous generated function mapper name that can be used
         *         by this EL; null if none found.
         */
	private String matchMap(ArrayList<ELNode.Function> functions) {

	    String mapName = null;
	    for (int i = 0; i < functions.size(); i++) {
		ELNode.Function f = functions.get(i);
		String temName = gMap.get(f.getPrefix() + ':' +
					f.getName() + ':' + f.getUri());
		if (temName == null) {
		    return null;
		}
		if (mapName == null) {
		    mapName = temName;
		} else if (!temName.equals(mapName)) {
		    // If not all in the previous match, then no match.
		    return null;
		}
	    }
	    return mapName;
	}

        /*
         * @return An unique name for a function mapper.
         */
	private String getMapName() {
	    return "_jspx_fnmap_" + currFunc++;
	}
    }
}

