feat(interceptor): XHR/fetch wrap to detect Train responses

src/interceptor.js

@@ -0,0 +1,92 @@
+/**
+ * Wraps XHR and fetch to listen for the request Torn sends when the
+ * user clicks "Train". When such a request is detected, the response
+ * is parsed via `parseTrainResponse`, the new attribute value is
+ * compared against the previous one, and `onTrain({attr, delta, ts})`
+ * is invoked.
+ *
+ * `parseTrainResponse(text, url)` is intentionally permissive and
+ * returns `{ newValue, attr } | null`. The default implementation
+ * tries JSON first, then a regex fallback.
+ */
+export function startRequestInterceptor({ prevValue, currentAttr, onTrain, onParseFail }) {
+  let lastValue = prevValue;
+  let warnedFor = null;
+
+  const handle = (text, url) => {
+    const parsed = parseTrainResponse(text, url);
+    if (!parsed) {
+      if (warnedFor !== url) {
+        warnedFor = url;
+        onParseFail && onParseFail(url);
+      }
+      return;
+    }
+    if (parsed.attr !== currentAttr) return;
+    const delta = parsed.newValue - lastValue;
+    lastValue = parsed.newValue;
+    if (delta > 0) onTrain({ attr: parsed.attr, delta, ts: Date.now() });
+  };
+
+  wrapXhr(handle);
+  wrapFetch(handle);
+
+  return {
+    updatePrevValue(v) { lastValue = v; },
+  };
+}
+
+function parseTrainResponse(text, url) {
+  // Try JSON
+  try {
+    const j = JSON.parse(text);
+    // Torn historically returns an HTML fragment; if it's JSON, look
+    // for a known shape. This is a placeholder — adjust after manual
+    // verification.
+    if (j && typeof j === 'object' && 'newValue' in j && 'attr' in j) {
+      return { newValue: Number(j.newValue), attr: String(j.attr) };
+    }
+  } catch { /* not JSON */ }
+
+  // Fallback: scan text for a number formatted like an attribute.
+  const m = text.match(/(\d{1,3}(?:,\d{3})+|\d{4,})/);
+  if (m) {
+    const newValue = parseInt(m[1].replace(/,/g, ''), 10);
+    if (Number.isFinite(newValue) && newValue > 0) {
+      // Without a confirmed attr, fall back to whatever currentAttr
+      // the caller passed in.
+      return { newValue, attr: null };
+    }
+  }
+  return null;
+}
+
+function wrapXhr(handle) {
+  const origOpen = XMLHttpRequest.prototype.open;
+  const origSend = XMLHttpRequest.prototype.send;
+  XMLHttpRequest.prototype.open = function (method, url) {
+    this.__tatUrl = String(url);
+    return origOpen.apply(this, arguments);
+  };
+  XMLHttpRequest.prototype.send = function () {
+    this.addEventListener('load', () => {
+      try { handle(this.responseText, this.__tatUrl); } catch { /* noop */ }
+    });
+    return origSend.apply(this, arguments);
+  };
+}
+
+function wrapFetch(handle) {
+  const origFetch = window.fetch;
+  if (origFetch.__tatWrapped) return;
+  window.fetch = async function (...args) {
+    const url = typeof args[0] === 'string' ? args[0] : args[0]?.url || '';
+    const res = await origFetch.apply(this, args);
+    try {
+      const text = await res.clone().text();
+      handle(text, String(url));
+    } catch { /* noop */ }
+    return res;
+  };
+  window.fetch.__tatWrapped = true;
+}