package io.github.lonamiwebs.overgram.utils;

import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Iterator;

public class CharacterIterator implements Iterator<Character>, Iterable<Character>, AutoCloseable {

    private static final int BUFFER_SIZE = 4096;

    private final InputStreamReader reader;
    private final char[] buffer;
    private int index;
    private int length;

    public CharacterIterator(final InputStreamReader reader) {
        this.reader = reader;
        buffer = new char[BUFFER_SIZE];
        index = 0;
        readNext();
    }

    @Override
    public Iterator<Character> iterator() {
        return this;
    }

    @Override
    public boolean hasNext() {
        if (index == BUFFER_SIZE) {
            readNext();
            index = 0;
        }
        return index < length;
    }

    @Override
    public Character next() {
        if (index == BUFFER_SIZE) {
            readNext();
            index = 0;
        }
        return buffer[index++];
    }

    @Override
    public void close() {
        try {
            reader.close();
        } catch (Exception ignored) {
        }
    }

    private void readNext() {
        try {
            length = reader.read(buffer);
        } catch (IOException ignored) {
            length = -1;
        }
    }
}