#30: Fix imports lookup in WebStorm 2017

Workaround, see comments in:

- #30
- https://intellij-support.jetbrains.com/hc/en-us/community/posts/115000163684-Resource-roots-in-WebStorm

Author: kshchepanovskyi

src/main/java/io/protostuff/jetbrains/plugin/reference/file/FilePathReferenceProvider.java

@@ -41,9 +41,9 @@
 import org.jetbrains.annotations.Nullable;
 
 /**
- * Copied from IntelliJ IDEA source code.
+ * File path references provider.
  *
- * @author cdr
+ * @author Kostiantyn Shchepanovskyi
  */
 @SuppressWarnings("checkstyle:JavadocMethod")
 public class FilePathReferenceProvider extends PsiReferenceProvider {
@@ -63,6 +63,7 @@ public FilePathReferenceProvider() {
     public FilePathReferenceProvider(boolean endingSlashNotAllowed) {
         myEndingSlashNotAllowed = endingSlashNotAllowed;
         sourceRootsProviders.add(new AllSourceRootsProvider());
+        sourceRootsProviders.add(new WebCoreResourcePathRootsProvider());
         sourceRootsProviders.add(new CustomIncludePathRootsProvider());
         sourceRootsProviders.add(new LibrariesAndSdkClassesRootsProvider());
     }

src/main/java/io/protostuff/jetbrains/plugin/reference/file/WebCoreResourcePathRootsProvider.java

@@ -0,0 +1,74 @@
+package io.protostuff.jetbrains.plugin.reference.file;
+
+import com.google.common.base.Strings;
+import com.intellij.openapi.diagnostic.Logger;
+import com.intellij.openapi.module.Module;
+import com.intellij.openapi.project.Project;
+import com.intellij.openapi.vfs.LocalFileSystem;
+import com.intellij.openapi.vfs.VirtualFile;
+import com.intellij.util.containers.MultiMap;
+import java.lang.reflect.Method;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * A workaround for getting resource roots in WebStorm 2017.1.
+ *
+ * https://github.com/protostuff/protobuf-jetbrains-plugin/issues/30
+ * https://intellij-support.jetbrains.com/hc/en-us/community/posts/115000163684-Resource-roots-in-WebStorm
+ *
+ * @author Kostiantyn Shchepanovskyi
+ */
+class WebCoreResourcePathRootsProvider implements FilePathReferenceProvider.SourceRootsProvider {
+
+    private static final Logger LOGGER = Logger.getInstance(WebCoreResourcePathRootsProvider.class);
+
+    private static final Method GET_INSTANCE;
+    private static final Method GET_RESOURCE_ROOTS;
+
+    public static final String CLASS_NAME = "com.intellij.webcore.resourceRoots.WebResourcesPathsConfiguration";
+
+    static {
+        Method getInstance = null;
+        Method getResourceRoots = null;
+        try {
+            Class<?> clazz = Class.forName(CLASS_NAME);
+            getInstance = clazz.getMethod("getInstance", Project.class);
+            getResourceRoots = clazz.getMethod("getResourceRoots");
+        } catch (Exception e) {
+            LOGGER.info("Could not load class " + CLASS_NAME);
+        }
+        GET_INSTANCE = getInstance;
+        GET_RESOURCE_ROOTS = getResourceRoots;
+    }
+
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public VirtualFile[] getSourceRoots(Module module) {
+        try {
+            if (GET_INSTANCE != null && GET_RESOURCE_ROOTS != null) {
+                List<VirtualFile> result = new ArrayList<>();
+                Object configurationInstance = GET_INSTANCE.invoke(null, module.getProject());
+                MultiMap<String, String> resourceRoots = (MultiMap<String, String>) GET_RESOURCE_ROOTS.invoke(configurationInstance);
+                for (Map.Entry<String, Collection<String>> entry : resourceRoots.entrySet()) {
+                    for (String uri : entry.getValue()) {
+                        if (!Strings.isNullOrEmpty(uri) && uri.startsWith("file://")) {
+                            String path = uri.substring(7);
+                            VirtualFile file = LocalFileSystem.getInstance().findFileByPath(path);
+                            if (file != null && file.isDirectory()) {
+                                result.add(file);
+                            }
+                        }
+                    }
+                }
+                return result.toArray(new VirtualFile[0]);
+            }
+        } catch (Exception e) {
+            LOGGER.error("Could not get source roots for WebCore IDE", e);
+        }
+        return new VirtualFile[0];
+    }
+}