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/*
 * Copyright (c) 2009-2022 jMonkeyEngine
 * 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 'jMonkeyEngine' 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 THE COPYRIGHT OWNER OR
 * CONTRIBUTORS 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 jme3tools.shader;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * GLSL Preprocessor
 * 
 * @author Riccardo Balbo
 */
public class Preprocessor {

    public static InputStream apply(InputStream in) throws IOException {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        byte chunk[] = new byte[1024];
        int read;
        while ((read = in.read(chunk)) != -1) {
            bos.write(chunk, 0, read);
        }
        bos.close();
        in.close();

        String code = bos.toString("UTF-8");

        code = Preprocessor.forMacro(code);

        return new ByteArrayInputStream(code.getBytes("UTF-8"));
    }

    /**
     * #for i=0..100 ( #ifdef ENABLE_INPUT_$i $0 #endif ) 
     *      do something with $i
     * #endfor
     */
    private static final Pattern FOR_REGEX = Pattern.compile("([^=]+)=\\s*([0-9]+)\\s*\\.\\.\\s*([0-9]+)\\s*\\((.+)\\)");

    public static String forMacro(String code) {
        StringBuilder expandedCode = new StringBuilder();
        StringBuilder currentFor = null;
        String forDec = null;
        int skip = 0;
        String codel[] = code.split("\n");
        boolean captured = false;
        for (String l : codel) {
            if (!captured) {
                String ln = l.trim();
                if (ln.startsWith("#for")) {
                    if (skip == 0) {
                        forDec = ln;
                        currentFor = new StringBuilder();
                        skip++;
                        continue;
                    }
                    skip++;
                } else if (ln.startsWith("#endfor")) {
                    skip--;
                    if (skip == 0) {
                        forDec = forDec.substring("#for ".length()).trim();

                        Matcher matcher = FOR_REGEX.matcher(forDec);
                        if (matcher.matches()) {
                            String varN = "$" + matcher.group(1);
                            int start = Integer.parseInt(matcher.group(2));
                            int end = Integer.parseInt(matcher.group(3));
                            String inj = matcher.group(4);
                            if (inj.trim().isEmpty()) inj = "$0";
                            String inCode = currentFor.toString();
                            currentFor = null;
                            for (int i = start; i < end; i++) {
                                expandedCode.append("\n").append(inj.replace("$0", "\n" + inCode ).replace(varN, "" + i)).append("\n");
                            }
                            captured = true;
                            continue;
                        }
                    }
                }
            }
            if (currentFor != null) currentFor.append(l).append("\n");
            else expandedCode.append(l).append("\n");
        }
        code = expandedCode.toString();
        if (captured) code = forMacro(code);
        return code;
    }

}