Add Deluge widget

- Create semi-generic jsonrpc proxy handler
- Refactor NZBGet to use jsonrpc proxy handler

closes #190

src/utils/proxy/handlers/jsonrpc.js

@@ -0,0 +1,82 @@
+import { JSONRPCClient, JSONRPCErrorException } from "json-rpc-2.0";
+
+import { formatApiCall } from "utils/proxy/api-helpers";
+import { httpProxy } from "utils/proxy/http";
+import getServiceWidget from "utils/config/service-helpers";
+import createLogger from "utils/logger";
+import widgets from "widgets/widgets";
+
+const logger = createLogger("jsonrpcProxyHandler");
+
+export async function sendJsonRpcRequest(url, method, params, username, password) {
+  const headers = {
+    "content-type": "application/json",
+    "accept": "application/json"
+  }
+
+  if (username && password) {
+    const authorization = Buffer.from(`${username}:${password}`).toString("base64");
+    headers.authorization = `Basic ${authorization}`;
+  }
+
+  const client = new JSONRPCClient(async (rpcRequest) => {
+    const httpRequestParams = {
+      method: "POST",
+      headers,
+      body: JSON.stringify(rpcRequest)
+    };
+
+    // eslint-disable-next-line no-unused-vars
+    const [status, contentType, data] = await httpProxy(url, httpRequestParams);
+    const dataString = data.toString();
+    if (status === 200) {
+      const json = JSON.parse(dataString);
+
+      // in order to get access to the underlying error object in the JSON response
+      // you must set `result` equal to undefined
+      if (json.error && (json.result === null)) {
+        json.result = undefined;
+      }
+      return client.receive(json);
+    }
+
+    return Promise.reject(new Error(dataString));
+  });
+
+  try {
+    const response = await client.request(method, params);
+    return [200, "application/json", JSON.stringify(response)];
+  }
+  catch (e) {
+    if (e instanceof JSONRPCErrorException) {
+      return [200, "application/json", JSON.stringify({result: null, error: {code: e.code, message: e.message}})];
+    }
+
+    logger.warn("Error calling JSONPRC endpoint: %s.  %s", url, e);
+    return [500, "application/json", JSON.stringify({result: null, error: {code: 2, message: e.toString()}})];
+  }
+}
+
+export default async function jsonrpcProxyHandler(req, res) {
+  const { group, service, endpoint: method } = req.query;
+
+  if (group && service) {
+    const widget = await getServiceWidget(group, service);
+    const api = widgets?.[widget.type]?.api;
+
+    if (!api) {
+      return res.status(403).json({ error: "Service does not support API calls" });
+    }
+
+    if (widget) {
+      const url = formatApiCall(api, { ...widget });
+
+      // eslint-disable-next-line no-unused-vars
+      const [status, contentType, data] = await sendJsonRpcRequest(url, method, null, widget.username, widget.password);
+      res.status(status).end(data);
+    }
+  }
+
+  logger.debug("Invalid or missing proxy service type '%s' in group '%s'", service, group);
+  return res.status(400).json({ error: "Invalid proxy service type" });
+}