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package com.github.dnbn.submerge.api.parser;

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

import org.apache.commons.io.IOUtils;
import org.apache.commons.lang.StringUtils;

import com.github.dnbn.submerge.api.parser.exception.InvalidFileException;
import com.github.dnbn.submerge.api.parser.exception.InvalidSubException;
import com.github.dnbn.submerge.api.subtitle.common.TimedTextFile;
import com.github.dnbn.submerge.api.utils.FileUtils;

public abstract class BaseParser implements SubtitleParser {

	/**
	 * UTF-8 BOM Marker
	 */
	private static final char BOM_MARKER = '\ufeff';

	@Override
	public T parse(File file) {

		if (!file.isFile()) {
			throw new InvalidFileException("File " + file.getName() + " is invalid");
		}

		try (FileInputStream fis = new FileInputStream(file)) {
			return parse(fis, file.getName());
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

	@SuppressWarnings("unchecked")
	@Override
	public T parse(InputStream is, String fileName) {

		try {
			Type type = this.getClass().getGenericSuperclass();
			T sub = ((Class) ((ParameterizedType) type).getActualTypeArguments()[0]).newInstance();

			byte[] bytes = IOUtils.toByteArray(is);

			try (InputStream nis = new ByteArrayInputStream(bytes);
					InputStreamReader isr = new InputStreamReader(nis, FileUtils.guessEncoding(bytes));
					BufferedReader br = new BufferedReader(isr)) {

				skipBom(br);
				sub.setFileName(fileName);
				parse(br, sub);
			}

			return sub;

		} catch (IOException e) {
			throw new InvalidFileException(e);
		} catch (InstantiationException | IllegalAccessException e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * Parse the subtitle file into a ParsableSubtitle object
	 * 
	 * @param br: the buffered reader
	 * @param sub : the subtitle object to fill
	 * @throws IOException
	 * @throws InvalidSubException if an error has occured when parsing the subtitle file
	 */
	protected abstract void parse(BufferedReader br, T sub) throws IOException;

	/**
	 * Ignore blank spaces and return the first text line
	 * 
	 * @param br: the buffered reader
	 * @throws IOException
	 */
	protected static String readFirstTextLine(BufferedReader br) throws IOException {

		String line = null;
		while ((line = br.readLine()) != null) {
			if (!StringUtils.isEmpty(line.trim())) {
				break;
			}
		}
		return line;
	}

	/**
	 * Remove the byte order mark if exists
	 * 
	 * @param br: the buffered reader
	 * @throws IOException
	 */
	private static void skipBom(BufferedReader br) throws IOException {

		br.mark(4);
		if (BOM_MARKER != br.read()) {
			br.reset();
		}
	}

	/**
	 * Reset the reader at the previous mark if the current line is a new section
	 * 
	 * @param br: the reader
	 * @param line: the current line
	 * @throws IOException
	 */
	protected static void reset(BufferedReader br, String line) throws IOException {

		if (line != null && line.startsWith("[")) {
			br.reset();
		}
	}

	/**
	 * Mark the position in the reader and read the next text line
	 * 
	 * @param br: the buffered reader
	 * @return the next text line
	 * @throws IOException
	 */
	protected static String markAndRead(BufferedReader br) throws IOException {

		br.mark(32);
		return readFirstTextLine(br);
	}

}