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Chunk Template Engine for Java

There is a newer version: 3.6.2

package com.x5.template;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import com.x5.template.filters.FilterArgs;

public class CondLexer
{
    String conditional;
    CondTree parsed;

    public CondLexer(String conditional)
    {
        this.conditional = conditional;
    }

    public CondTree parse() throws InvalidExpressionException
    {
        if (parsed != null) {
            return parsed;
        }

        parsed = CondTree.buildBranch(lexLogicTokens());

        return parsed;
    }

    // pick apart high-level logic tokens && || ! () but treat entire
    // comparison tests as single token.
    private Iterator lexLogicTokens()
    {
        char c, d;
        int len = conditional.length();
        List tokens = new ArrayList();

        for (int i=0; i 0 && (c == '=' || c == '!')) {
                if (i+1 == len) {
                    return len;
                }
                d = s.charAt(i+1);
                if (d == '=' || d == '~') {
                    foundOperator = true;
                    i += 2;
                    continue;
                }
            }
            if (foundOperator) {
                // seeking RHS, ruled out tag, must be string constant or regex.
                if (c == '"' || c == '\'' || c == '/') {
                    String delim = Character.toString(c);
                    i = FilterArgs.nextUnescapedDelim(delim, s, i+1);
                    return (i > 0) ? i+1 : len;
                }
                // unquoted string :( assume next space/close-paren/&&/|| marks the end
                Matcher matcher = END_OF_UNQUOTED_STRING.matcher(s);
                if (matcher.find(i)) {
                    return matcher.start();
                } else {
                    return len;
                }
            }
            // falling through to here is okay... eg "if (true)" is permitted.
            // advance cursor to avoid infinite loop.
            i++;
        }
    }
}