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The latte-lang compiler project, which contains compiler and runtime required library.
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/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2016 KuiGang Wang
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package lt.compiler;

import lt.compiler.lexical.ElementStartNode;

import java.io.IOException;
import java.io.Reader;

/**
 * the entrance of scanners. it will read the first line of the file to determine which scanner to use.
 */
public class ScannerSwitcher implements Scanner {
        private final Scanner scanner;

        public ScannerSwitcher(String fileName, Reader reader, Properties properties, ErrorManager err) throws IOException, SyntaxException {
                PushLineBackReader plbr;
                if (reader instanceof PushLineBackReader) {
                        plbr = (PushLineBackReader) reader;
                } else {
                        plbr = new PushLineBackReader(reader);
                }

                String firstLine = plbr.readLine();
                plbr.push(firstLine);
                String text = firstLine.trim();
                if (text.startsWith("///")) {
                        text = text.substring(3).trim();
                } else {
                        text = "";
                }

                if (text.equals(":scanner-brace")) {
                        scanner = new BraceScanner(fileName, plbr, properties, err);

                } else if (text.equals("") || text.equals(":scanner-indent")) {
                        scanner = new IndentScanner(fileName, plbr, properties, err);

                } else {
                        err.SyntaxException("got " + text + " which is not a valid scanner select command", LineCol.SYNTHETIC_WITH_FILE(fileName));
                        err.info("assume it's :scanner-indent");
                        scanner = new IndentScanner(fileName, plbr, properties, err);
                }
        }

        @Override
        public ElementStartNode scan() throws IOException, SyntaxException {
                return scanner.scan();
        }
}