1 files changed, 125 insertions, 0 deletions
diff --git a/json/src/com/jetbrains/jsonSchema/remote/JsonSchemaRemoteContentProvider.java b/json/src/com/jetbrains/jsonSchema/remote/JsonSchemaRemoteContentProvider.java
new file mode 100644
index 00000000..dad1766b
--- /dev/null
+++ b/json/src/com/jetbrains/jsonSchema/remote/JsonSchemaRemoteContentProvider.java
@@ -0,0 +1,125 @@
+// Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package com.jetbrains.jsonSchema.remote;
+
+import com.intellij.json.JsonFileType;
+import com.intellij.openapi.fileTypes.FileType;
+import com.intellij.openapi.vfs.VirtualFile;
+import com.intellij.openapi.vfs.impl.http.DefaultRemoteContentProvider;
+import com.intellij.util.Url;
+import com.intellij.util.containers.ContainerUtil;
+import com.intellij.util.io.HttpRequests;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.URLConnection;
+import java.nio.file.Files;
+import java.time.Duration;
+import java.util.List;
+
+public class JsonSchemaRemoteContentProvider extends DefaultRemoteContentProvider {
+  private static final int DEFAULT_CONNECT_TIMEOUT = 10000;
+  private static final long UPDATE_DELAY = Duration.ofHours(4).toMillis();
+  static final String STORE_URL_PREFIX_HTTP = "http://json.schemastore.org";
+  static final String STORE_URL_PREFIX_HTTPS = "https://schemastore.azurewebsites.net";
+  private static final String SCHEMA_URL_PREFIX = "http://json-schema.org/";
+  private static final String ETAG_HEADER = "ETag";
+  private static final String LAST_MODIFIED_HEADER = "Last-Modified";
+
+  private long myLastUpdateTime = 0;
+
+  @Override
+  public boolean canProvideContent(@NotNull Url url) {
+    String externalForm = url.toExternalForm();
+    return externalForm.startsWith(STORE_URL_PREFIX_HTTP)
+           || externalForm.startsWith(STORE_URL_PREFIX_HTTPS)
+           || externalForm.startsWith(SCHEMA_URL_PREFIX)
+           || externalForm.endsWith(".json");
+  }
+
+  @Override
+  protected void saveAdditionalData(@NotNull HttpRequests.Request request, @NotNull File file) throws IOException {
+    URLConnection connection = request.getConnection();
+    if (saveTag(file, connection, ETAG_HEADER)) return;
+    saveTag(file, connection, LAST_MODIFIED_HEADER);
+  }
+
+  @Nullable
+  @Override
+  protected FileType adjustFileType(@Nullable FileType type, @NotNull Url url) {
+    if (type == null && url.toExternalForm().startsWith(SCHEMA_URL_PREFIX)) {
+      // json-schema.org doesn't provide a mime-type for schemas
+      return JsonFileType.INSTANCE;
+    }
+    return super.adjustFileType(type, url);
+  }
+
+  private static boolean saveTag(@NotNull File file, @NotNull URLConnection connection, @NotNull String header) throws IOException {
+    String tag = connection.getHeaderField(header);
+    if (tag != null) {
+      String path = file.getAbsolutePath();
+      if (!path.endsWith(".json")) path += ".json";
+      File tagFile = new File(path + "." + header);
+      saveToFile(tagFile, tag);
+      return true;
+    }
+    return false;
+  }
+
+  private static void saveToFile(@NotNull File tagFile, @NotNull String headerValue) throws IOException {
+    if (!tagFile.exists()) if (!tagFile.createNewFile()) return;
+    Files.write(tagFile.toPath(), ContainerUtil.createMaybeSingletonList(headerValue));
+  }
+
+  @Override
+  public boolean isUpToDate(@NotNull Url url, @NotNull VirtualFile local) {
+    long now = System.currentTimeMillis();
+    // don't update more frequently than once in 4 hours
+    if (now - myLastUpdateTime < UPDATE_DELAY) {
+      return true;
+    }
+
+    myLastUpdateTime = now;
+    String path = local.getPath();
+
+    if (now - new File(path).lastModified() < UPDATE_DELAY) {
+      return true;
+    }
+
+    if (checkUpToDate(url, path, ETAG_HEADER)) return true;
+    if (checkUpToDate(url, path, LAST_MODIFIED_HEADER)) return true;
+
+    return false;
+  }
+
+  private boolean checkUpToDate(@NotNull Url url, @NotNull String path, @NotNull String header) {
+    File file = new File(path + "." + header);
+    try {
+      return isUpToDate(url, file, header);
+    }
+    catch (IOException e) {
+      // in case of an error, don't bother with update for the next UPDATE_DELAY milliseconds
+      //noinspection ResultOfMethodCallIgnored
+      new File(path).setLastModified(System.currentTimeMillis());
+      return true;
+    }
+  }
+
+  @Override
+  protected int getDefaultConnectionTimeout() {
+    return DEFAULT_CONNECT_TIMEOUT;
+  }
+
+  private boolean isUpToDate(@NotNull Url url, @NotNull File file, @NotNull String header) throws IOException {
+    List<String> strings = file.exists() ? Files.readAllLines(file.toPath()) : ContainerUtil.emptyList();
+
+    String currentTag = strings.size() > 0 ? strings.get(0) : null;
+    if (currentTag == null) return false;
+
+    String remoteTag = connect(url, HttpRequests.head(url.toExternalForm()),
+                               r -> r.getConnection().getHeaderField(header));
+
+    return currentTag.equals(remoteTag);
+  }
+}