make location of gnuplot configurable

pdb-plotting/src/main/java/org/lucares/recommind/logs/Gnuplot.java

@@ -6,10 +6,18 @@ import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
 import java.util.Collection;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import com.google.common.io.Files;
 
 public class Gnuplot {
 
+	private static final Logger LOGGER = LoggerFactory.getLogger(Gnuplot.class);
+	private static final Logger METRICS_LOGGER = LoggerFactory.getLogger("org.lucares.metrics.gnuplot");
+
+	private static final String ENV_GNUPLOT_HOME = "GNUPLOT_HOME";
+	private static final String PROPERTY_GNUPLOT_HOME = "gnuplot.home";
 	private final Path tmpDirectory;
 
 	public Gnuplot(final Path tmpDirectory) {
@@ -22,18 +30,54 @@ public class Gnuplot {
 		final GnuplotFileGenerator generator = new GnuplotFileGenerator();
 
 		final String gnuplotFileContent = generator.generate(settings, dataSeries);
-		System.out.println(gnuplotFileContent);
+		LOGGER.debug(gnuplotFileContent);
 
 		final File gnuplotFile = File.createTempFile("gnuplot", ".dem", tmpDirectory.toFile());
 		Files.write(gnuplotFileContent, gnuplotFile, StandardCharsets.UTF_8);
 
 		final long start = System.nanoTime();
 
-		final ProcessBuilder processBuilder = new ProcessBuilder("gnuplot", gnuplotFile.getAbsolutePath());
-		processBuilder.inheritIO();
-		final Process process = processBuilder.start();
-		process.waitFor();
+		try {
+			final ProcessBuilder processBuilder = new ProcessBuilder(gnuplotBinary(), gnuplotFile.getAbsolutePath());
+			processBuilder.inheritIO();
+			final Process process = processBuilder.start();
+			process.waitFor();
+		} catch (final IOException e) {
+			if (e.getMessage().contains("No such file or directory")) {
+				throw new IOException("Did not find gnuplot. Add it to the 'PATH' or create an environment variable '"
+						+ ENV_GNUPLOT_HOME + "' or add the java property '" + PROPERTY_GNUPLOT_HOME + "': "
+						+ e.getMessage(), e);
+			} else {
+				throw e;
+			}
+		}
 
-		System.out.println("gnuplot: " + (System.nanoTime() - start) / 1_000_000.0 + "ms");
+		METRICS_LOGGER.debug("gnuplot: {}ms", (System.nanoTime() - start) / 1_000_000.0);
+	}
+
+	private String gnuplotBinary() {
+
+		if (System.getProperty(PROPERTY_GNUPLOT_HOME) != null) {
+
+			if (isWindows()) {
+				return System.getProperty(PROPERTY_GNUPLOT_HOME) + "\\bin\\+gnuplot.exe";
+			} else {
+				return System.getProperty(PROPERTY_GNUPLOT_HOME) + "/bin/gnuplot";
+			}
+		}
+		if (System.getenv(ENV_GNUPLOT_HOME) != null) {
+
+			if (isWindows()) {
+				return System.getenv(ENV_GNUPLOT_HOME) + "\\bin\\+gnuplot.exe";
+			} else {
+				return System.getenv(ENV_GNUPLOT_HOME) + "/bin/gnuplot";
+			}
+		}
+
+		return "gnuplot";
+	}
+
+	private boolean isWindows() {
+		return System.getProperty("os.name").toLowerCase().startsWith("windows");
 	}
 }

pdb-plotting/src/main/java/org/lucares/recommind/logs/Plotter.java

@@ -108,7 +108,7 @@ public class Plotter {
 			Thread.currentThread().interrupt();
 			throw new IllegalStateException("Plotting was interrupted.");
 		} catch (final IOException e) {
-			throw new InternalPlottingException("Plotting failed.", e);
+			throw new InternalPlottingException("Plotting failed: " + e.getMessage(), e);
 		} finally {
 			FileUtils.delete(tmpDir);
 		}