// Copyright (C) 2009 Mihai Preda

package arity.calculator;

import android.content.Context;
import java.io.*;

abstract class FileHandler {
    private String fileName;
    private Context context;
    private int version;
    boolean fileNotFound;

    private DataInputStream openInput() throws IOException {
	try {
	    return new DataInputStream(new BufferedInputStream(context.openFileInput(fileName), 256));
	} catch (FileNotFoundException e) {
            fileNotFound = true;
	    return null;
	}
    }

    private DataOutputStream openOutput() throws IOException {
	return new DataOutputStream(new BufferedOutputStream(context.openFileOutput(fileName, 0), 256));
    }

    FileHandler(Context context, String fileName, int version) {
	this.context = context;
	this.fileName = fileName;
	this.version = version;
    }

    void load() {
	try {
	    DataInputStream is = openInput();
	    if (is != null) {
		int readVersion = is.readInt();
		if (readVersion != version) {
		    throw new IllegalStateException("invalid version " + readVersion);
		}
		doRead(is);
		is.close();
	    }
	} catch (IOException e) {
	    throw new RuntimeException("" + e);
	}
    }

    void save() {
	try {
            DataOutputStream os = openOutput();
            os.writeInt(version);
	    doWrite(os);
            os.close();
        } catch (IOException e) {
            throw new RuntimeException("" + e);
        }
    }

    abstract void doRead(DataInputStream is) throws IOException;
    abstract void doWrite(DataOutputStream os) throws IOException;
}