connectors/file/src/main/java/org/apache/edgent/connectors/file/runtime/TextFileWriter.java

/*
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
*/

package org.apache.edgent.connectors.file.runtime;

import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.file.Path;

import org.apache.edgent.function.Consumer;
import org.apache.edgent.function.Supplier;
import org.slf4j.Logger;

public class TextFileWriter implements Consumer<String>, AutoCloseable {
    private static final long serialVersionUID = 1L;
    static final Logger trace = FileConnector.getTrace();
    private volatile String encoding = "UTF-8";
    private volatile Charset charset;
    private final Supplier<String> basePathname;
    private final Supplier<IFileWriterPolicy<String>> policyFn;
    private volatile boolean initialized;
    private volatile IFileWriterPolicy<String> policy;
    private StringWriterFile activeFile;
    
    private String getEncoding() {
        return encoding;
    }

    public TextFileWriter(Supplier<String> basePathname, Supplier<IFileWriterPolicy<String>> policy) {
        this.basePathname = basePathname;
        this.policyFn = policy;
        charset = Charset.forName(getEncoding());
    }
    
    private IFileWriterPolicy<String> getPolicy() {
        if (policy == null) {
            policy = policyFn.get();
        }
        return policy;
    }
    
    private void initialize() {
        getPolicy().initialize(basePathname.get(),
                                () -> flushActiveFile(),
                                () -> closeActiveFile());
        initialized = true;
        trace.info("writer policy: {}", getPolicy());
    }
    
    private synchronized void flushActiveFile() {
        if (activeFile != null) {
            try {
                activeFile.flush();
            } catch (IOException e) {
                trace.trace("flush of {} failed", activeFile.path(), e);
            }
        }
    }

    @Override
    public void accept(String line) {
        if (!initialized)
            initialize();
        writeLine(line);
    }
    
    private void writeLine(String line) {
        // prevent async time based cycle or flush while writing the tuple
        synchronized(this) {
            try {
                if (activeFile == null) {
                    newActiveFile();
                }
                int nbytes = activeFile.write(line);
                getPolicy().wrote(line, nbytes);
            }
            catch (IOException e) {
                trace.error("Error writing tuple {} of length {} to {}",
                        activeFile.tupleCnt(), line.length(), activeFile.path(), e);
            }
        }
        if (getPolicy().shouldCycle()) {
            closeActiveFile();
        }
        else if (getPolicy().shouldFlush()) {
            flushActiveFile();
        }
    }
    
    private synchronized void newActiveFile() throws IOException {
        Path path = getPolicy().getNextActiveFilePath();
        activeFile = new StringWriterFile(path, charset);
    }

    /**
     * close, finalize, and apply retention policy
     */
    private synchronized void closeActiveFile() {
        StringWriterFile activeFile = this.activeFile;
        try {
            this.activeFile = null;
            if (activeFile != null) {
                activeFile.close();
                getPolicy().closeActiveFile(activeFile.path());
                activeFile = null;
            }
        }
        catch (IOException e) {
            trace.error("error closing active file '{}'", activeFile.path(), e);
        }
    }

    @Override
    public void close() throws Exception {
        closeActiveFile();
        getPolicy().close();
    }
}