LoggingWriter.java

package com.cadrlife.devsearch.agent.service;

import com.google.common.base.Preconditions;

import java.io.IOException;
import java.io.Writer;

public class LoggingWriter extends Writer {
    private static final String NEWLINE = System.getProperty("line.separator");
    private final StringBuilder builder = new StringBuilder();
    private final LogHook logHook;

    public static interface LogHook {
        void log(String msg);
    }
    
    public LoggingWriter(LogHook logHook) {
        Preconditions.checkNotNull(logHook);
        this.logHook = logHook;
    }
    
    private void logIfNeeded() {
        while (builder.length() > 0) {
            synchronized (builder) {
                final int newlineIndex = builder.indexOf(NEWLINE);
                if (newlineIndex < 0) {
                    return;
                }
                if (newlineIndex == 0) {
                    builder.delete(0, NEWLINE.length());
                    // Maybe don't need to do blank lines
                   logHook.log("");
                }
                
                final String msg = builder.substring(0, newlineIndex);
                builder.delete(0, newlineIndex + NEWLINE.length());
                logHook.log(msg);
            }
        }
    }



    @Override
    public void write(int c) throws IOException {
        synchronized (builder) {
            builder.append((char) c);
        }
        logIfNeeded();
    }

    @Override
    public void write(char[] cbuf) throws IOException {
        synchronized (builder) {
            builder.append(cbuf);
        }
        logIfNeeded();
    }

    @Override
    public void write(String str) throws IOException {
        synchronized (builder) {
            builder.append(str);
        }
        logIfNeeded();
    }

    @Override
    public void write(String str, int off, int len) throws IOException {
        synchronized (builder) {
            builder.append(str);
        }
        logIfNeeded();
    }

    @Override
    public Writer append(CharSequence csq) throws IOException {
        synchronized (builder) {
            builder.append(csq);
        }
        logIfNeeded();
        return this;
    }

    @Override
    public Writer append(CharSequence csq, int start, int end) throws IOException {
        synchronized (builder) {
            builder.append(csq, start, end);
        }
        logIfNeeded();
        return this;
    }

    @Override
    public Writer append(char c) throws IOException {
        synchronized (builder) {
            builder.append(c);
        }
        logIfNeeded();
        return this;
    }

    @Override
    public void write(char[] cbuf, int off, int len) throws IOException {
        synchronized (builder) {
            builder.append(cbuf, off, len);
        }
        logIfNeeded();
    }

    @Override
    public void flush() throws IOException {
        logIfNeeded();
    }

    @Override
    public void close() throws IOException {
        synchronized (builder) {
            if (builder.length() > 0 && builder.lastIndexOf(NEWLINE) < builder.length() - NEWLINE.length()) {
                builder.append(NEWLINE);
            }
            logIfNeeded();
        }
    }
}