import sun.reflect.generics.reflectiveObjects.NotImplementedException;

import java.io.*;
import java.nio.CharBuffer;
import java.text.ParseException;
import java.util.InputMismatchException;
import java.util.Objects;

public final class Scanner {

    // Internal buffer used to hold input
    private CharBuffer buf1;
    private CharBuffer buf2;

    // Size of internal character buffer
    // 50M chars, or ~100MB of memory allocated by CharBuffer buf
    private static final int BUFFER_SIZE = 50 * 1024 * 1024;

    // The index into the buffer currently held by the Scanner
    private int position;

    // The input source
    private Reader source;
    private String lineSeparator;

    private Boolean isAtEndOfReader = false;
    private Boolean firstMethodCall = false;

    private Scanner(Reader source) {
        assert source != null : "source should not be null";
        this.source = source;
        buf1 = CharBuffer.allocate(BUFFER_SIZE);
        buf2 = CharBuffer.allocate(BUFFER_SIZE);
        firstMethodCall = true;
        isAtEndOfReader = false;
        lineSeparator = System.lineSeparator();
    }

    public Scanner(InputStream source) {
        this(new InputStreamReader(source));
    }
    public Scanner(String source) {
        this(new StringReader(source));
    }

    public boolean hasNextLine() throws IOException {
        if (firstMethodCall)
            updateBuffers();
        if (isAtEndOfReader)
            return false;
        throw new NotImplementedException();
    }

    public String nextLine() throws IOException {
        if (firstMethodCall)
            updateBuffers();
        if (isAtEndOfReader)
            throw new InputMismatchException("Unexpected end of input");
        throw new NotImplementedException();
    }

    public boolean hasNextInt() throws IOException {
        if (firstMethodCall)
            updateBuffers();
        if (isAtEndOfReader)
            return false;
        char nextChar = buf.charAt(position);
        if (nextChar >= '0' && nextChar <= '9') {
            return true;
        }
        return false;
    }

    public int nextInt() throws ParseException, IOException {
        if (firstMethodCall)
            updateBuffers();
        if (isAtEndOfReader)
            throw new InputMismatchException("Unexpected end of input");
        StringBuilder intStringBuilder = new StringBuilder();
        while (true) {
            char nextChar = buf.charAt(position);

            if (isAtEndOfReader)
            {
                String intString = intStringBuilder.toString();
                if (Objects.equals(intString, ""))
                    throw new InputMismatchException("Unexpected end of input");
                return Integer.parseInt(intString);
            }
            if (nextChar == ' ') {
                String intString = intStringBuilder.toString();
                return Integer.parseInt(intString);
            }

            if (nextChar < '0' || nextChar > '9') {
                throw new InputMismatchException("Unsupported char");
            }

            intStringBuilder.append(nextChar);

            position++;

            if (position == BUFFER_SIZE) {
                updateBuffers();
            }
        }
    }

    private void updateBuffers() throws IOException {
        int charsRead = source.read(buf1);
        if (charsRead == 0) {
            isAtEndOfReader = true;
        }

        position = 0;
    }

}