Add Transmission widget

- Update http.js to support writing request bodies
- Update http.js to support returning all response headers

resolves: #104

src/utils/proxies/transmission.js

@@ -0,0 +1,56 @@
+import { httpProxy } from "utils/http";
+import { formatApiCall } from "utils/api-helpers";
+
+import getServiceWidget from "utils/service-helpers";
+
+export default async function transmissionProxyHandler(req, res) {
+  const { group, service, endpoint } = req.query;
+
+  if (!group || !service) {
+    return res.status(400).json({ error: "Invalid proxy service type" });
+  }
+
+  const widget = await getServiceWidget(group, service);
+
+  if (!widget) {
+    return res.status(400).json({ error: "Invalid proxy service type" });
+  }
+
+  const url = new URL(formatApiCall(widget.type, { endpoint, ...widget }));
+  const csrfHeaderName = "x-transmission-session-id";
+
+  const method = "POST";
+  const body = JSON.stringify({
+    method: "torrent-get",
+    arguments: {
+      fields: ["percentDone", "status", "rateDownload", "rateUpload"]
+    }
+  });
+
+  const reqHeaders = {
+    "content-type": "application/json",
+  };
+
+  let [status, contentType, data, responseHeaders] = await httpProxy(url, {
+    method: method,
+    auth: `${widget.username}:${widget.password}`,
+    body: body,
+    headers: reqHeaders,
+  });
+
+  if (status === 409) {
+    // Transmission is rejecting the request, but returning a CSRF token
+    reqHeaders[csrfHeaderName] = responseHeaders[csrfHeaderName];
+
+    // retry the request, now with the CSRF token
+    [status, contentType, data] = await httpProxy(url, {
+      method: method,
+      auth: `${widget.username}:${widget.password}`,
+      body: body,
+      headers: reqHeaders,
+    });
+  }
+
+  if (contentType) res.setHeader("Content-Type", contentType);
+  return res.status(status).send(data);
+}