Refactor DataWriter once more to group a file

The input and output file are closely related, do not burden others with
tracking which output and input need to be matched.

1 files changed, 79 insertions, 37 deletions

diff --git a/src/io/DataWriter.java b/src/io/DataWriter.java
index 841b27d..d762fee 100644
--- a/src/io/DataWriter.java
+++ b/src/io/DataWriter.java
@@ -26,12 +26,12 @@ public class DataWriter implements ResultListener {
     /**
      * The writer for the tweet stream.
      */
-    private final OutputStream m_tweetWriter;
+    private final Store m_tweet;
 
     /**
      * the writer for the profile stream.
      */
-    private final OutputStream m_profileWriter;
+    private final Store m_profile;
 
     /**
      * the buffer of tweet ids that already exist.
@@ -55,67 +55,50 @@ public class DataWriter implements ResultListener {
      */
     public DataWriter(final String profilesName, final String tweetsName)
             throws IOException {
-        m_profileIdSet = readIds(profilesName);
-        m_profileWriter = getFileWriter(profilesName);
+        m_profile = getStore(profilesName);
+        m_profileIdSet = readIds(m_profile);
 
-        m_tweetIdSet = readIds(tweetsName);
-        m_tweetWriter = getFileWriter(tweetsName);
+        m_tweet = getStore(profilesName);
+        m_tweetIdSet = readIds(m_tweet);
     }
 
     /**
-     * Given a filename, return a suitable input stream.
+     * For a given filename, get an instance that provides I/O.
      *
-     * @param tweetsName File name.
-     * @return A stream from which JSON objects can be read (one per line).
-     * @throws IOException
+     * @param filename File to read/write.
+     * @return A Store instance providing read and write access.
+     * @throws IOException if the target file cannot be read or written.
      */
-    protected InputStream getFileReader(String tweetsName)
-            throws IOException {
-        return new FileInputStream(tweetsName);
-    }
-
-    /**
-     * Given a filename, return a suitable output stream.
-     *
-     * @param tweetsName File name.
-     * @return A stream to which JSON objects can be written (one per line).
-     * @throws IOException
-     */
-    protected OutputStream getFileWriter(String tweetsName)
-            throws IOException {
-        return new FileOutputStream(tweetsName, true);
+    protected Store getStore(String filename) throws IOException {
+        return new SimpleFileStore(filename);
     }
 
     public void close() {
-        try {
-            m_tweetWriter.close();
-            m_profileWriter.close();
-        } catch (IOException ex) {
-            getLogger().log(Level.SEVERE, null, ex);
-        }
+        m_tweet.close();
+        m_profile.close();
     }
 
     @Override
     public void profileGenerated(JSONObject obj) {
-        writeObject(obj, m_profileWriter, m_profileIdSet);
+        writeObject(obj, m_profile.getOutputStream(), m_profileIdSet);
     }
 
     @Override
     public void tweetGenerated(JSONObject obj) {
-        writeObject(obj, m_tweetWriter, m_tweetIdSet);
+        writeObject(obj, m_tweet.getOutputStream(), m_tweetIdSet);
     }
 
     /**
      * Read the current existing tweetName and profileName filenames and fill
      * the existing id set.
      *
-     * @param filename The file to parse.
+     * @param is An input stream that provides JSON objects.
      * @return The set of ids, may be empty if the fill does not exist.
      */
-    private Set readIds(String filename) throws IOException {
+    private Set<Long> readIds(Store store) throws IOException {
         Set<Long> idSet = new HashSet<>();
         try {
-            InputStream is = getFileReader(filename);
+            InputStream is = store.getInputStream();
             Scanner reader = new Scanner(is);
             // parse each line into a JSONObject, read the id and add it to
             // the set of ids.
@@ -127,7 +110,7 @@ public class DataWriter implements ResultListener {
         } catch (FileNotFoundException ex) {
             // ignore, file will be created if necessary.
         } catch (JSONException ex) {
-            getLogger().log(Level.WARNING, filename
+            getLogger().log(Level.WARNING, store.getFileName()
                     + ": File is only partially processed", ex);
         }
         return idSet;
@@ -162,4 +145,63 @@ public class DataWriter implements ResultListener {
     private Logger getLogger() {
         return Logger.getLogger(getClass().getName());
     }
+
+    abstract class Store {
+
+        private final String filename;
+        protected OutputStream os;
+
+        Store(String filename) {
+            this.filename = filename;
+        }
+
+        /**
+         * @return The file name associated with this store.
+         */
+        public String getFileName() {
+            return filename;
+        }
+
+        /**
+         * Properly closes a file, flushing any buffers.
+         */
+        public void close() {
+            try {
+                os.close();
+            } catch (IOException ex) {
+                Logger.getLogger(getClass().getName()).log(Level.WARNING,
+                        "Could not close " + getFileName(), ex);
+            }
+        }
+
+        /**
+         * Returns a previously opened writable file stream.
+         *
+         * @return A stream to which JSON objects can be written (one per line).
+         */
+        public OutputStream getOutputStream() {
+            return os;
+        }
+
+        /**
+         * Opens a new input stream for the file.
+         *
+         * @return A stream from which JSON objects can be read (one per line).
+         * @throws IOException if no input file can be retrieved.
+         */
+        abstract public InputStream getInputStream() throws IOException;
+    }
+
+    class SimpleFileStore extends Store {
+
+        SimpleFileStore(String filename) throws FileNotFoundException {
+            super(filename);
+            os = new FileOutputStream(getFileName(), true);
+        }
+
+        @Override
+        public InputStream getInputStream() throws FileNotFoundException {
+            return new FileInputStream(getFileName());
+        }
+    }
 }