package poke;
import java.io.Closeable;
import java.io.IOException;
import java.io.Reader;

public class RingBuf implements Closeable {
    private static final int BUFSIZE = 64;
    private char[] ringBuf = new char[BUFSIZE];
    private int rbIdx = 0;

    Reader r;
    public RingBuf(Reader reader) {
        r = reader;
    }
    public int read() throws IOException {
        int ch;
        if ((ch = r.read()) == -1)
            return -1;
        ringBuf[rbIdx] = (char)ch;
        rbIdx = (rbIdx + 1) % BUFSIZE;
        return ch;
    }
    public boolean justRead(char[] needle) {
        int rbi = rbIdx;
        int i;
        for (i=needle.length-1; i >= 0; i--) {
            rbi = (rbi == 0) ? BUFSIZE - 1 : rbi - 1;
            if (ringBuf[rbi] != needle[i])
                return false;
        }
        return true;
    }
    public String readUntil(char[] terminator) throws IOException {
        StringBuilder sb = new StringBuilder();
        int c;
        while ((c = read()) != -1) {
            if (justRead(terminator))
                return sb.toString();
            sb.append((char)c);
        }
        return sb.toString();
    }
    public void close() throws IOException {
        r.close();
    }
}