com.github.jknack.amd4j.WhiteMinifier.java Source code

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Here is the source code for com.github.jknack.amd4j.WhiteMinifier.java

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/**
 * Copyright (c) 2013 Edgar Espina
 *
 * This file is part of amd4j (https://github.com/jknack/amd4j)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.github.jknack.amd4j;

import static org.apache.commons.io.FilenameUtils.removeExtension;

import org.mozilla.javascript.Parser;
import org.mozilla.javascript.ast.AstRoot;

/**
 * Remove comments, spaces and new lines from a JavaScript file.
 *
 * @author edgar.espina
 * @since 0.2.0
 */
public class WhiteMinifier extends Minifier {

    @Override
    public CharSequence minify(final Config config, final CharSequence input) {
        Parser parser = new Parser();
        String fname = removeExtension(config.getName()) + ".js";
        AstRoot tree = parser.parse(input.toString(), fname, 1);

        return strip(tree.toSource());
    }

    /**
     * Remove spaces and lines.
     *
     * @param source JavaScript code without comments.
     * @return The new source code.
     */
    private CharSequence strip(final String source) {
        StringBuilder buffer = new StringBuilder();
        int i = 0;
        while (i < source.length()) {
            char ch = source.charAt(i);
            if (ch == '\'' || ch == '"') {
                String literal = stringLiteral(source, ch, i);
                buffer.append(literal);
                i += literal.length() - 1;
            } else if (ch == '/') {
                String regex = regex(source, i);
                buffer.append(regex);
                i += regex.length() - 1;
            } else if (Character.isWhitespace(ch)) {
                if (i + 1 < source.length() && Character.isJavaIdentifierStart(source.charAt(i + 1))) {
                    // keep white between keywords or identifiers.
                    buffer.append(' ');
                }
            } else {
                buffer.append(ch);
            }
            i++;
        }
        return buffer;
    }

    /**
     * Extract a string literal from source.
     *
     * @param source The javascript source.
     * @param str The string char.
     * @param start The start position.
     * @return A string literal.
     */
    private String stringLiteral(final String source, final char str, final int start) {
        int i = start + 1;
        while (i < source.length()) {
            char ch = source.charAt(i);
            if (ch == str && source.charAt(i - 1) != '\\') {
                break;
            }
            i++;
        }
        return source.substring(start, i + 1);
    }

    /**
     * Extract a regex literal from source.
     *
     * @param source The javascript source.
     * @param start The start position.
     * @return A regex literal.
     */
    private String regex(final String source, final int start) {
        int i = start + 1;
        while (i < source.length()) {
            char ch = source.charAt(i);
            if (ch == '/' && source.charAt(i - 1) != '\\') {
                break;
            }
            i++;
        }
        return source.substring(start, i + 1);
    }
}