package org.simantics.scl.rest;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

import javax.ws.rs.WebApplicationException;
import javax.ws.rs.ext.WriterInterceptor;
import javax.ws.rs.ext.WriterInterceptorContext;

import org.simantics.scl.runtime.function.Function1;
import org.simantics.scl.runtime.tuple.Tuple0;

public class WriteProgressInterceptor implements WriterInterceptor {

    private Function1<Long, Tuple0> callback;
    
    public WriteProgressInterceptor(Function1<Long, Tuple0> callback) {
        this.callback = callback;
    }

    @Override
    public void aroundWriteTo(WriterInterceptorContext context) throws IOException, WebApplicationException {

        final OutputStream os = context.getOutputStream();

        context.setOutputStream(new FilterOutputStream(os) {
            private long count;
            
            @Override public void write(byte[] b, int off, int len) throws IOException {
                out.write(b, off, len);
                count += len;
                callback.apply(count);
            }

            @Override
            public void write(int b) throws IOException {
                out.write(b);
                count++;
                callback.apply(count);
            }
        });

        context.proceed();
    }

}