package goblincave.gitea.nes;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;

import org.apache.commons.io.FilenameUtils;

import io.github.jacksonbrienen.jwfd.FileExtension;
import io.github.jacksonbrienen.jwfd.JWindowsFileDialog;

public class ATXtoAT3 {
	
	public static void main(String[] args) throws IOException {
		
		FileExtension atx = new FileExtension("ATX File", "atx");
		
		String[] selection = JWindowsFileDialog.showMultiDialog(null, "Select ATX files to process", atx, FileExtension.ALL);
		String output = JWindowsFileDialog.showDirectoryDialog(null, "Choose where to export AT3 files");
		
		if(selection == null)
			System.out.println("No files selected.");
		
		else {
			for(int i = 0; i < selection.length; i++) {
				
				String path = selection[i];
				File file1 = new File(path);
				System.out.println("Opening " + path);
				int start = 0x20; // findChunk("RIFF", file, 0x10);
				int end = findChunk("EOFC", file1, 0x10);
				File AT3 = trim(file1, start, end, output);
				
				System.out.println("Saving " + AT3.toPath());
			}
		}
		
		System.out.println(selection.length + " files exported.");
		
	}
	
	/**
	 * Trims input file up to start address and after end address, saving trimmed data to output path.
	 * 
	 * @param input
	 * @param start
	 * @param end
	 * @param output
	 * @return trimmed file
	 */
	private static File trim(File input, int start, int end, String output) {
		
		// input validation
		// start and end must be between 0 and file length
		// start must be less than end
		if(start < 0 || start > input.length() || end < 0 || end > input.length() || start >= end)
			return null;
		
		File trimmed = new File(output + "/" + FilenameUtils.removeExtension(input.getName()) + ".at3");
		
		try (
				FileInputStream in = new FileInputStream(input); 
				FileOutputStream out = new FileOutputStream(trimmed);
		) {
			in.skipNBytes(start);
			byte[] bytes = new byte[end - start];
			int readBytes = in.read(bytes);
			out.write(bytes, 0, readBytes);
		} catch (IOException e) {
			e.printStackTrace();
		}
		
		return trimmed;
		
	}

	/**
	 * Returns the first instance of the provided key in the file.
	 * 
	 * @param key
	 * @param file
	 * @param width - search address increment value. Smaller values are more thorough, but take longer to process. Adjust according to the conventions of a given file. If unsure, use a value of 1. 
	 * @return first match
	 */
	public static int findChunk(String key, File file, int width) throws IOException {
		
		int keyValue = asciiToInt(key);

		// find address of sequence in file
		try (RandomAccessFile RAF = new RandomAccessFile(file, "r")) {
			for(int a = 0; a + width < file.length(); a += width) {
				RAF.seek(a);
				if(RAF.readInt() == keyValue) {
					return a;
				}
			}
		}

		// returns -1 if not found
		return -1;
	}
	
	/**
	 * Converts the given ASCII sequence to an equivalent integer value.
	 */
	private static int asciiToInt(String key) {
		int value = 0;
		for(int i = 0; i < key.length(); i++)
			value += key.charAt(key.length() - 1 - i) * Math.pow(16, 2 * i);
		return value;
	}

}