Add FreshRSS widget (#1377)

* feat: add FreshRSS widget

* refactor: revert credentialed.js

* refactor: custom proxy handler for FreshRSS

* refactor: cache the token as long as possible

During installation, the salt is generated and remains constant unless
the user re-installs the FreshRSS instance.

src/widgets/freshrss/proxy.js

@@ -0,0 +1,97 @@
+import cache from "memory-cache";
+
+import { httpProxy } from "utils/proxy/http";
+import { formatApiCall } from "utils/proxy/api-helpers";
+import getServiceWidget from "utils/config/service-helpers";
+import createLogger from "utils/logger";
+import widgets from "widgets/widgets";
+
+const proxyName = "freshrssProxyHandler";
+const sessionTokenCacheKey = `${proxyName}__sessionToken`;
+const logger = createLogger(proxyName);
+
+async function login(widget, service) {
+  const endpoint = "accounts/ClientLogin";
+  const api = widgets?.[widget.type]?.api
+  const loginUrl = new URL(formatApiCall(api, { endpoint, ...widget }));
+  const headers = { "Content-Type": "application/x-www-form-urlencoded" };
+
+  const [, , data,] = await httpProxy(loginUrl, {
+    method: "POST",
+    body: new URLSearchParams({
+      Email: widget.username,
+      Passwd: widget.password
+    }).toString(),
+    headers,
+  });
+
+  try {
+    const [, token] = data.toString().split("\n").find(line => line.startsWith("Auth=")).split("=")
+    cache.put(`${sessionTokenCacheKey}.${service}`, token);
+    return { token };
+  } catch (e) {
+    logger.error("Unable to login to FreshRSS API: %s", e);
+  }
+
+  return { token: false };
+}
+
+async function apiCall(widget, endpoint, service) {
+  const key = `${sessionTokenCacheKey}.${service}`;
+  const headers = {
+    "Authorization": `GoogleLogin auth=${cache.get(key)}`,
+  }
+  const url = new URL(formatApiCall(widgets[widget.type].api, { endpoint, ...widget }));
+  const method = "GET";
+
+  let [status, contentType, data, responseHeaders] = await httpProxy(url, {
+    method,
+    headers,
+  });
+
+  if (status === 401) {
+    logger.debug("FreshRSS API rejected the request, attempting to obtain new session token");
+    const { token } = await login(widget, service);
+    headers.Authorization = `GoogleLogin auth=${token}`;
+
+    // retry the request, now with the new session token
+    [status, contentType, data, responseHeaders] = await httpProxy(url, {
+      method,
+      headers,
+    });
+  }
+
+  if (status !== 200) {
+    logger.error("Error getting data from FreshRSS: %s status %d. Data: %s", url, status, data);
+    return { status, contentType, data: null, responseHeaders };
+  }
+
+  return { status, contentType, data: JSON.parse(data.toString()), responseHeaders };
+}
+
+export default async function freshrssProxyHandler(req, res) {
+  const { group, service } = req.query;
+
+  if (!group || !service) {
+    logger.debug("Invalid or missing service '%s' or group '%s'", service, group);
+    return res.status(400).json({ error: "Invalid proxy service type" });
+  }
+
+  const widget = await getServiceWidget(group, service);
+  if (!widget) {
+    logger.debug("Invalid or missing widget for service '%s' in group '%s'", service, group);
+    return res.status(400).json({ error: "Invalid proxy service type" });
+  }
+
+  if (!cache.get(`${sessionTokenCacheKey}.${service}`)) {
+    await login(widget, service);
+  }
+
+  const { data: subscriptionData } = await apiCall(widget, "reader/api/0/subscription/list", service);
+  const { data: unreadCountData } = await apiCall(widget, "reader/api/0/unread-count", service);
+
+  return res.status(200).send({
+    subscriptions: subscriptionData?.subscriptions.length,
+    unread: unreadCountData?.max
+  });
+}