ExternalUtils: Check coala binary before execution

Fixes #13

com.coala.core/src/com/coala/core/utils/DialogUtils.java

@@ -0,0 +1,33 @@
+package com.coala.core.utils;
+
+import org.eclipse.jface.dialogs.MessageDialog;
+
+import java.io.IOException;
+import java.net.URI;
+import java.net.URISyntaxException;
+
+public class DialogUtils {
+  /**
+   * Dialog asking the user to install the coala framework.
+   * If the user answers in affirmative the coala website is opened
+   * in the default web browser.
+   */
+  public static void installcoalaDialog() {
+    URI coalaWebsite = null;
+    try {
+      coalaWebsite = new URI("http://coala-analyzer.org");
+    } catch (URISyntaxException ex) {
+      ex.printStackTrace();
+    }
+    boolean ret = MessageDialog.openQuestion(null, "coala is not installed",
+        "The coala framework is required to run code analysis. "
+            + "Do you want to know how to install coala?");
+    if (ret) {
+      try {
+        java.awt.Desktop.getDesktop().browse(coalaWebsite);
+      } catch (IOException ex) {
+        ex.printStackTrace();
+      }
+    }
+  }
+}

com.coala.core/src/com/coala/core/utils/ExternalUtils.java

@@ -17,9 +17,11 @@
 import org.json.JSONArray;
 import org.json.JSONObject;
 
+import java.io.BufferedReader;
 import java.io.ByteArrayOutputStream;
 import java.io.File;
 import java.io.IOException;
+import java.io.InputStreamReader;
 import java.util.Iterator;
 
 public class ExternalUtils {
@@ -40,6 +42,10 @@ public class ExternalUtils {
    */
   public static void runBearOnFile(final IFile file, String bear)
       throws ExecuteException, IOException, InterruptedException {
+    if (!checkPrerequisite("coala")) {
+      DialogUtils.installcoalaDialog();
+      return;
+    }
     String path = file.getRawLocation().toOSString();
     CommandLine cmdLine = new CommandLine("coala-json");
     cmdLine.addArgument("-f" + path);
@@ -88,6 +94,10 @@ public void onProcessFailed(ExecuteException executeException) {
    */
   public static void runcoafile(final String path, final IProject project)
       throws ExecuteException, IOException {
+    if (!checkPrerequisite("coala")) {
+      DialogUtils.installcoalaDialog();
+      return;
+    }
     File cwd = new File(path);
     CommandLine cmdLine = new CommandLine("coala-json");
     final ByteArrayOutputStream stdout = new ByteArrayOutputStream();
@@ -209,6 +219,39 @@ public static void processJsonAndMark(String json, IProject project) throws IOEx
     }
   }
 
+  /**
+   * Searches for the given binary in the PATH environmental variable.
+   * 
+   * @param binary
+   *          The executable that needs to be checked
+   * @return True is the binary is present, false otherwise
+   */
+  private static boolean checkPrerequisite(String binary) {
+    ProcessBuilder pb = new ProcessBuilder(isWindows() ? "where" : "which", binary);
+    boolean foundBinary = false;
+    try {
+      Process proc = pb.start();
+      int errCode = proc.waitFor();
+      if (errCode == 0) {
+        try (BufferedReader reader = new BufferedReader(
+            new InputStreamReader(proc.getInputStream()))) {
+          foundBinary = true;
+        }
+      } else {
+        System.out.println(binary + " not in PATH");
+      }
+    } catch (IOException ex) {
+      System.out.println("Something went wrong while searching for " + binary);
+    } catch (InterruptedException ex) {
+      System.out.println("Something went wrong while searching for " + binary);
+    }
+    return foundBinary;
+  }
+
+  private static boolean isWindows() {
+    return System.getProperty("os.name").toLowerCase().contains("windows");
+  }
+
   /**
    * Creates a problem marker.
    *