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package prng.config;

import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Map;
import java.util.Properties;
import java.util.function.Supplier;
import java.util.prefs.BackingStoreException;
import java.util.prefs.Preferences;

/**
 * Loaded property configuration that knows from where it was loaded
 *
 * @author Simon Gretrix
 */
public class Props extends Properties {

  /** Serial version UID */
  private static final long serialVersionUID = 1L;

  /** Did this batch of properties load successfully? */
  private final boolean loadedOk;

  /** Where these properties came from */
  private final URI source;


  /**
   * Load preferences as properties
   *
   * @param prefSupplier source of preferences
   * @param src the nominal URI for these preferences
   */
  public Props(Supplier prefSupplier, URI src) {
    source = src;
    Preferences prefs = null;
    // Get the preferences using a privileged action.
    try {
      prefs = AccessController.doPrivileged(
          (PrivilegedAction) prefSupplier::get);
    } catch (SecurityException se) {
      Config.LOG.info("Unable to access preferences for \""
          + src.toASCIIString() + "\"", se);
    }

    // Start loading the properties
    if (prefs == null) {
      loadedOk = false;
      return;
    }

    boolean loadOk = true;
    try {
      // copy each preference into the properties
      for (String k : prefs.keys()) {
        String v = prefs.get(k, null);
        if (v != null) {
          setProperty(k, v);
        }
      }
    } catch (BackingStoreException bse) {
      loadOk = false;
      clear();
      Config.LOG.error("Failed to access preference storage.", bse);
    } finally {
      loadedOk = loadOk;
    }
  }


  /**
   * Load properties from the specified URL
   *
   * @param url the URL to load from
   */
  public Props(URL url) {
    boolean loadOk = true;
    Config.LOG.info("Loading configuration from {}", url.toExternalForm());
    try (InputStream in = url.openStream()) {
      load(in);
    } catch (IOException | IllegalArgumentException ioe) {
      // it went wrong :-(
      loadOk = false;
      clear();
      Config.LOG.error(
          "Failed to read configuration file " + url.toString(), ioe);
    } finally {
      loadedOk = loadOk;
    }

    // get URI from URL
    URI uri = null;
    try {
      uri = url.toURI();
    } catch (URISyntaxException e) {
      Config.LOG.warn("Unable to convert source URL \""
          + url.toExternalForm() + "\" to URI");
    } finally {
      source = uri;
    }
  }


  /**
   * Get where these properties were loaded from
   *
   * @return the source
   */
  public URI getSource() {
    return source;
  }


  /**
   * Set all key-value pairs on map that are set on this and not set on map.
   *
   * @param map the map which should inherit values from this
   */
  public void inherit(Map map) {
    for (Map.Entry e : entrySet()) {
      Object k = e.getKey();
      Object v = e.getValue();
      if ((k instanceof String) && (v instanceof String) && (!map.containsKey(k))) {
        map.put((String) k, (String) v);
      }
    }
  }


  /**
   * Did these properties load without error?
   *
   * @return true if loaded OK
   */
  public boolean isLoadedOk() {
    return loadedOk;
  }
}